List of scientific errors

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Despite Walking with... being a documentary series, several paleontological inaccuracies appear throughout some of the shows. However, most of the errors are caused by newer and more recent discoveries. Here's a list of them.

A scaly *Velociraptor*, an example of scientific inaccuracy in the Walking with series

Walking with Dinosaurs Pilot[]

Eustreptospondylus was somewhat too lizard-like and resembled old reconstructions of dinosaurs.
Cetiosaurus had many errors, such as a far too long neck and a misshaped head. It can be noted that it vaguely resembles the Jurassic Park Mamenchisaurus.

Walking with Dinosaurs[]

New Blood[]

In the beginning, the narrator states that there was no grass in the Cretaceous. However, some putative grass microfossils have been recovered from the Albian stage of the Cretaceous, although they might instead represent basal relatives to true grasses. Regardless, true grasses are known to have existed during the Late Cretaceous thanks to phytoliths from the Indian Lameta Formation, dating to the Maastrichtian stage. Despite grasses having been around in the Late Cretaceous period, they weren't as widespread as they are today, and, to date, little evidence exists of their presence in North America at the time.
There is slight shrink wrapping on the heads of the Coelophysis, Postosuchus, and Plateosaurus. In reality, the skull openings likely were not externally visible.
There is no conclusive evidence that Coelophysis was cannibalistic. This behavior in the program was based on a fossil of Coelophysis with jumbled-up bones in its stomach cavity, but these turned out to be from species of small crocodylomorphs, rather than juvenile Coelophysis like previously speculated. However, this was discovered after the program's release. Moreover, this behavior is not implausible, given that cannibalism is not rare in theropods.
Coelophysis may have had feathers, but this is still highly debated. A recent study on thermoregulation in Triassic ornithodirans confirmed that Coelophysis would likely have a body completely covered in feathers, as much as any other smaller ornithodirans at the time. However, another study that aimed to calculate the body heat generated in comparison to body size of different animals showed that this correlation isn't always present and might have been highly variable in animals, including extinct ones. When translated to ornithodirans, it would ideally not be detrimental for smaller species to endure with a largely featherless skin covering and for larger species to endure with dense feathers on their bodies, as the differences in thermoregulation in response to size differences wouldn't be as obvious. This can be exemplified by fossil formations where small scaly dinosaurs coexist with equally small feathered dinosaurs, such as Psittacosaurus, which lived alongside several feathered theropods and even large feathered dinosaurs like Yutyrannus, implying size and distribution of filamentous integument aren't entirely dependent on each other. In the case of Triassic ornithodirans like Coelophysis, the presence or lack of filamentous integument may be complicated to ascertain. However, given it is usually accepted that dense filamentous covering is a basal trait in dinosaurs (given the feathered basal ornithischians and small theropods are known), it's fair to assume Coelophysis was probably covered in feathers purely due to phylogenetic relationships.
It would be impossible for Coelophysis to pronate its hands, with the hands instead being held with palms facing inwards in the real animal.
Coelophysis is known to have been sexually dimorphic, with two distinct body morphs, a gracile morph that likely represents females and a more robust morph that likely represents males, being known from the vast amount of specimens of the animal. However, all the Coelophysis individuals in the program are depicted with identical body proportions.
Coelophysis didn't evolve until 4 million years after the program's setting.
Dinosaurs probably evolved 23 million years before the setting instead of 10, as indicated by the recently discovered Nyasasaurus, which was found to be 243 million years old. However, whether Nyasasaurus is classified as a true dinosaur or a close relative is still debated.
Placerias may not have been as common as depicted in the program, as Placerias remains are generally concentrated in a single area of the Chinle Formation, the Placerias Quarry, with finds of the animal outside the quarry being much rarer. The narrator does state that Placerias are supposed to be rare, despite the numbers shown in the program.
Placerias may have had some hair coverage, though this is still debated. No definitive proof exists of the existence of hair-like filaments in non-cynodont synapsids, but it is certainly possible dicynodonts could have had them. If so, it doesn't seem likely that the skin would be covered in a dense pelt of hair, with more recent evidence seeming to support more naked hairless skin for the group.
It is stated in the program that Placerias is "the last of its kind" and "an endangered species." However, dicynodonts actually persisted after the extinction of Placerias, with species such as Lisowicia being known from later Triassic rocks than Placerias. However, it was the last dicynodont known from North America.
Placerias is called a reptile in the program, when it was actually a synapsid.
Archosaurs generally don't mark their territories with urine, unlike the male Postosuchus in the program. It's likely that, just like their crocodilian relatives, Postosuchus didn't mark their territory at all, maintaining and defending their hunting ground from intruders. However, crocodilians may excrete water from their cloaca in a similar manner to what is seen in the program. It is important to note that the diversity of extant archosaur behavior may not be reflective of the possible variety of ways extinct archosaurs behaved, so this behavior is not necessarily impossible, although it remains unlikely.
Postosuchus is now known to not have walked in a quadrupedal posture. It is instead believed to be bipedal. However, this theory was still debated when the series was made.
Postosuchus measured 13-16 feet (4-5 meters) long, not 19 feet (6 meters) as said in the program.
Thrinaxodon was long extinct by the time the program takes place, being from the Early Triassic rather than the Late Triassic. It also lived in South Africa and Antarctica, not North America. However, an unnamed species of cynodont is known only from teeth in the Chinle Formation, so the reconstruction of this cynodont was therefore based primarily on Thrinaxodon. Other cynodonts, like Arctotraversodon and Boreogomphodon, lived 220 million years ago in what is now North America, but these species were most likely herbivorous and don't match the morphology of the cynodont seen in the program. An undescribed species of dromatheriid is known from that time in North America as well. A possible replacement would be the recently described Kataigidodon, which lived in the same time and place in which the program was set, making this creature the first undisputed cynodont to be described from the Chinle Formation.
Plateosaurus couldn't move in a quadrupedal stance and was an obligate biped. However, this discovery was made after the program's release.
Plateosaurus lived in Europe, not North America. Despite the continents all being connected during this time, it most likely wouldn't have traveled such long distances. Recent studies on thermoregulation in Triassic ornithodirans support the presence of large sauropodomorphs like Plateosaurus in cooler regions, which explains why Triassic sauropodomorphs are largely absent from regions around the same latitude as the Chinle Formation. However, sauropodomorph footprints are known from the Chinle Formation, suggesting that at least some species of sauropodomorphs did live in the area, although these cannot be assigned to Plateosaurus itself.
Plateosaurus didn't evolve until 6 million years after the program's setting.
Peteinosaurus lived in Europe, not North America. Despite the continents all being connected and the narration stating that it is "an exotic hunter from far and wide," there isn't any indication that it traveled such long distances. Some species of Triassic pterosaurs did exist in North America, but they were part of the Dimorphodontidae family, such as Caelestiventus, or the Eudimorphodontidae family, like Arcticodactylus, and lived 208-201 million years ago, after the setting of the program.
The head of the Peteinosaurus is a little bit smaller than it would have been in life.
Although pycnofibres are present on the Peteinosaurus animatronic, they would very likely be much denser on the real animal.
When the Peteinosaurus is shown on the ground, its wings are seen to fold in from the sides. However, in the real animal, the wings would have folded in from the back, with the metacarpals rotating and causing the front digits to point backward. The tips of the wings are also too pointed, with the real animal likely having more rounded wingtips in life, although the extent of this roundness is still a matter of debate.

Time of the Titans[]

Diplodocus held its neck in a slightly higher position than shown in the series.
Diplodocus was probably not the longest of all sauropods as stated in the program. There were other sauropods longer than Diplodocus, such as Supersaurus.
There is no evidence for an ovipositor in Diplodocus. It was pure speculation by the creators of the series, who based it off of those of turtles. It is most likely that large sauropods preferred to lay their eggs while laying on the ground, with their cloaca close to the ground. The ovipositor hypothesis was an attempt at trying to go around the believed problem of having sauropods squatting to lay their eggs, but, in reality, sauropods, even the largest ones, could lay down on the ground just fine.
There is slight shrink wrapping on the heads of the Diplodocus, Allosaurus, Stegosaurus, Brachiosaurus, Ornitholestes, and the unidentified ornithopods. In reality, the skull openings would likely not be externally visible.
Sauropods like Diplodocus are believed to have had more soft tissue around their necks than shown in the series.
The nostrils of the Diplodocus and Brachiosaurus are located towards the back of the skull. However, it is now believed that the animals' nostrils were actually located much farther forwards on the skull.
The feet of the Diplodocus and Brachiosaurus are more elephant-like, whereas the feet of the real animals had metacarpals that were positioned like pillars in a semicircle, creating a hollow back of the hand that was ideal for supporting the animals' large mass.
The large claw on the front feet of Diplodocus is missing from the model, as are the three large claws on the hind feet.
Ornitholestes didn't have a nasal crest like the one depicted in the program. It was thought to have had one during the production of the series, however, due to the holotype specimen possessing a broken nasal bone that was pushed upwards, giving the illusion of a head crest.
Ornitholestes was likely covered in feathers based on its phylogenetic position, which did appear in the companion book. However, the model does have some primitive feathers displayed on some portions of the body in the form of quills.
The head of the Ornitholestes model is slightly too large compared to the rest of the body.
The lower jaw of Ornitholestes slightly turns down, which is not seen on the skull of the program's model.
Ornitholestes is now thought to have had sickle claws and retractable second toes like those of dromaeosaurids due to its recent classification as a maniraptoromorph.
It would be impossible for Ornitholestes, Allosaurus, and the unidentified ornithopods to pronate their hands, with the hands instead being held with palms facing inwards in the real animals.
Anurognathus was a micro nightjar-like insectivore, with no indication that it behaved like a modern oxpecker. Its anatomy in the program is also very inconsistent with the real animal, with the model having an elongated neck, deep skull, small wings that fold in from the sides, too pointed wingtips, and a too-thin coat of pycnofibres.
Anurognathus is only known from Germany, not North America. A possible replacement would be one of the other small pterosaurs known from the Morrison Formation, such as Mesadactylus and Kepodactylus. This error was fixed in The Complete Guide To Prehistoric Life.
The head design of the Allosaurus model is inaccurate. The crests are placed right above the eyes, when they were actually further down the skull, the small ridges in front of the crests are completely missing, and the snout turns down at the end, whereas the snout remains straight at the end in the real animal. Although this is still debated, it is also likely that, like many non-avian theropods, Allosaurus would have had immobile, lizard-like lips that would have covered its teeth when its mouth was closed. These errors were mostly corrected in The Ballad of Big Al, although the lip issue still remains.
Allosaurus was likely to have been a solitary hunter as opposed to the hunting pairs seen in the program, although pair hunting behavior isn't necessarily implausible for the real animal. It is also possible that Allosaurus may have temporarily hunted in groups to bring down large prey while remaining mostly solitary otherwise, similar to modern Komodo dragons.
Allosaurus is said to have been the top predator of its age. In reality, the top predator of the Late Jurassic Morrison Formation was the much larger Torvosaurus.
Allosaurus is now thought to have delivered a muscle-driven bite to prey. In the program, however, the Allosaurus is shown killing a baby Diplodocus by biting its neck like a Tyrannosaurus would.
The Brachiosaurus model is based on Giraffatitan, which was originally classified as an African species of Brachiosaurus, due to it being much more complete. Because of this, the Brachiosaurus model is slightly inaccurate. In reality, Brachiosaurus would have had a longer and deeper torso, a longer and taller tail, and would have carried more of its mass on its forelimbs.
Brachiosaurus weighed between 28 and 58 tons, not 70 tons as mentioned in the program.
The raised bump on the head of the Brachiosaurus model is somewhat too thin. In reality, the bump would likely have had more soft tissue around it.
Brachiosaurus is stated to be "the largest land animal that has ever existed," and it is later suggested that "life would never again be this large." However, several somphospondylan species, such as Apatosaurus, Barosaurus, Mamenchisaurus and Maraapunisaurus, reached even larger dimensions than those of Brachiosaurus. Moreover, contrary to what was stated at the end of the program, large-bodied sauropods persisted into the Cretaceous period.
Stegosaurus could not change the colors of its plates by flushing blood into them, as preserved integument impressions of Hesperosaurus have shown that stegosaur plates were covered in a horny sheath rather than skin.
The scales of Stegosaurus were polygonal in shape with large oval tubercles interrupting them. These tubercles are not present on the skin of the model in the program.
Stegosaurus is depicted as only having four digits on its front feet. However, the real animal actually had five digits on its front feet.
The plates of the Stegosaurus in the program are far larger than those of any known specimen of the animal.
Since the discovery of Sophie, a relatively complete Stegosaurus, it is now known that Stegosaurus had a slightly longer neck and tail with more downturned spikes and a shorter torso and back legs, reducing the curve in the animal's back.
There is some debate regarding the presence and extent of cheek coverings in ornithischian dinosaurs like Stegosaurus and the unidentified ornithopods seen in the program. Paleontologists originally believed that cheeks were present in most ornithischians, as a covering over the sides of the mouth would help keep plant material contained within the jaws as the animal chewed, the cheek teeth of many ornithischians were inset, with an overhanging maxilla and large dentary, suggesting that a cheek-like soft tissue structure might have stretched between the lower and upper jaws, and small foramina along many ornithischian jaw bone margins may be evidence of neurovascular structures that nourished cheek structures and supplied them with blood. However, a study in 2018 found that, rather than a more mammal-like arrangement of muscle fibers directed straight down from an attachment ridge on the upper jaw to the lower jaw, ornithischians probably had a forward-extending fan of muscle attached to the lower jaw at one end and the rest of the cranium at the other underneath the flaring cheek bone instead, indicating that truly muscular cheeks covering the entire extent of the back part of the mouth are unlikely. However, thinner, non-muscular cheek analogues are not ruled out for these animals. While the 2018 study is still heavily debated among paleontologists, the cheeks of the real Stegosaurus would likely be thinner, pushed further back, and shaped differently than the cheeks depicted on the program's model.
It is possible that small ornithopods like those seen in this program may have possessed a feathery coat over at least some parts of their bodies, although this remains unconfirmed.
The environment in the program is depicted as forested with some plains, while the actual environment of the Morrison Formation was far more arid, much like the Serengeti plains. However, this does not mean that the type of environment depicted in the program did not exist in the Morrison, as the formation was very intercut between arid areas and regions with lush vegetation. This error was mostly corrected in The Ballad of Big Al, which showed the Morrison fauna existing in a more arid environment.

Cruel Sea[]

The program is set in the Oxford Clay, a formation which dates from the Callovian to the Oxfordian (166-157 million years ago), not in the Tithonian (149 million years ago). Therefore, a large portion of the cast, with Rhamphorhynchus being an exception, are misplaced in time.
The narration in the program states that Ophthalmosaurus possessed "long, toothless snouts." However, fully grown Ophthalmosaurus specimens show that they did possess teeth. Interestingly, these teeth are present in the Ophthalmosaurus model used in the program, meaning that this error was likely a narration mistake. This error is fixed in the US version, where this narration is not present.
There is no evidence that adult Ophthalmosaurus ate young individuals of their species. However, given how common cannibalism is in reptiles, this behavior is not implausible.
Liopleurodon wasn't even half as big as it was in the series. It wasn't 25 meters long and 150 tonnes in weight, but was instead around 6.4 meters long and 1-1.7 tons in weight, being more than three times smaller than an orca. This gargantuan size may have originated from very fragmentary remains, such as the " Monster of Aramberri", which has been considered to be a 15 meter long subadult Liopleurodon in the past, or from large sauropod vertebrae found in the Oxford Clay which were once considered to belong to a pliosaur. These ideas have been considered unlikely, which led to the downsizing of the animal to only around 20 feet long.
Liopleurodon lived from the Callovian to the Kimmeridgian and was extinct by the Tithonian. A possible replacement would be the larger Pliosaurus, which lived at the time during which the program was set.
There is slight shrink wrapping on the heads of the Liopleurodon and Eustreptospondylus. In reality, the skull openings would likely not be externally visible.
Long-necked plesiosauroids and short-necked pliosaurs, such as Cryptoclidus and Liopleurodon respectively, are now thought to have flukes on their tails, not smooth lizard-like tails like in the series. However, the known specimens that possess these flukes are not assigned to either genus and this discovery came long after the series aired.
Cryptoclidus couldn't go on land like turtles or pinnipeds, as they were so adapted for aquatic life that doing so would be more equivalent to a whale or shark going on land, beaching itself and eventually dying.
Cryptoclidus did not get as big as 8 tons, with the real animal probably only weighing around one ton or less.
Cryptoclidus lived in the Callovian and Oxfordian and was extinct by the Tithonian. A possible replacement would be either Colymbosaurus or Kimmerosaurus, which lived at the time during which the program was set.
The head of the Cryptoclidus seen in the program is slightly too large compared to the rest of its body.
Rhamphorhynchus lacks many skeletal features required for a skim-feeder. Therefore it is believed to have not fished that way, most likely diving underwater to hunt fish instead.
Rhamphorhynchus had a shorter, thicker neck and longer wings that folded in from behind when walking. The tips of the wings are also too pointed, with the real animal likely having more rounded wingtips in life, although the extent of this roundness is still a matter of debate.
Rhamphorhynchus, like all pterosaurs, is believed to have possessed skin covered in a coat of pycnofibres over most of its body, a feature not present in the reconstruction of the species seen in the program.
The tail veins of the Rhamphorhynchus seen in the program should be slightly more asymmetrical.
The tips of the jaws of the Rhamphorhynchus seen in the program seem to be hard, keratinized structures, when, in reality, the tips were soft tissue structures.
Eustreptospondylus lived in the Oxfordian, not the Tithonian. A possible replacement would be Juratyrant, a five-meter-long relative of the Cretaceous Tyrannosaurus which lived at the time during which the program was set.
The skull design of the Eustreptospondylus model is inaccurate. The head is far too short and wide, there are crests above the eyes, which the real animal is believed to have lacked, and the snout is straight at the end, whereas the snout had a slight downturn in the real animal. Although this is still debated, it is also likely that, like many non-avian theropods, Eustreptospondylus would have had immobile, lizard-like lips that would have covered its teeth when its mouth was closed.
It would be impossible for Eustreptospondylus to pronate its hands, with the hands instead being held with palms facing inwards in the real animal.
The Eustreptospondylus seen in the program are slightly too small. They are stated to be 5 meters in length, which is close to the 4.6-meter length of the holotype specimen. However, the holotype is a juvenile, meaning that it is likely that Eustreptospondylus could have reached larger sizes than depicted in the program, with a believed adult length of 6 meters.

Giant of the Skies[]

The species of Ornithocheirus depicted in the program, O. mesembrinus, is now believed to be classified as its own genus, Tropeognathus. Though always recognized as its own species, there was a debate at the time about lumping it into the genus Ornithocheirus, the series's conclusion, or splitting it into Tropeognathus, as currently believed.
Tropeognathus had a wingspan of only 8.2-8.7 m (27.1–28.5 ft), so it was not as large as depicted in the series.
There is no evidence that Tropeognathus traveled the globe, as fossils of this genus have only been discovered in Brazil. This inaccuracy was likely based on Ornithocheirus being believed to have been known from both Europe and Brazil prior to the re-description of O. mesembrinus as Tropeognathus mesembrinus. As the two genera are now only known from Europe and Brazil respectively, it's unlikely that either genus engaged in lengthy, cross-continental migrations
Tropeognathus is depicted as possessing sexual dimorphism in the program, with only males possessing crests on their beaks while females had no beak crests. Although these differences were believed to constitute different sexes when the program was released, it is now thought that these different morphs represent different genera rather than different sexes, meaning that both sexes of Tropeognathus would likely have possessed crests on their beaks. However, this doesn't preclude other forms of sexual dimorphism from being present in this genus in life.
Tropeognathus is shown as moving in an extremely cumbersome manner on the ground. In reality, pterosaurs were likely far more agile on land than depicted in the program, with fossilized trackways of some species indicating that they were able to run on all fours. However, due to the much longer forelimb length relative to hind-limb length in ornithocheirid pterosaurs like Tropeognathus, they were likely less fast-moving or agile than other pterosaurs. Some studies have suggested that ornithocheirids may have been able to move quickly for at least short periods on land by making hopping, take-off-like movements, but their primary movement speed on land was likely much slower than that of other pterosaur families.
When on the ground, the wings of the Tropeognathus and Tupandactylus are seen to fold in from the sides. However, in the real animals, the wings would have folded in from the back, with the metacarpals rotating and causing the front digits to point backward. The tips of the wings are also too pointed, with the real animals likely having more rounded wingtips in life, although the extent of this roundness is still a matter of debate.
Tropeognathus is depicted as being able to feed by skimming its beak through the water in the program. Although this was believed to be accurate at the time of the program's release, as it was hypothesized that the crests on the pterosaur's beak could help the animal cut through the water more effectively, more recent research has indicated that this feeding method would not have been practical for this genus, as it is both too energetically costly for an animal weighing over one kilogram and the real animal lacked any kind of specialized beak anatomy necessary for this feeding method. In actuality, Tropeognathus likely fed by simply plunging its jaws into the water to snatch up fish.
Tropeognathus is stated to be unable to fly in the rain, as its pycnofibres would get too waterlogged to allow it to fly. Although this was believed to be accurate at the time of the program's release, more recent research has found evidence of pterosaurs being able to swim, such as pterosaur trace fossils left on what would have been the seafloor at the time, indicating that pterosaurs were capable of flight even if their pycnofibres became wet.
There is slight shrink wrapping on the heads of the Tropeognathus, Utahraptor, Iguanodon, Plesiopleurodon, and possibly Dakotadon, although too few remains of Dakotadon have been found to determine if this is really the case. In reality, the skull openings likely were not externally visible.
The species of Tapejara depicted in the program, T. navigens, along with a second former species of Tapejara (T. imperator), is now believed to be classified as its own genus, Tupandactylus, leaving T. wellnhofferi as the sole valid species of the genus Tapejara.
Tupandactylus might have been herbivores/frugivores in a similar fashion to toucans instead of coast-dwelling foragers as the series seems to imply (though, like toucans, it may still have had a taste for some meat).
Tupandactylus is depicted with ornithocheirid-like limb proportions, with massive forelimbs and short hind-limbs, offering them a cumbersome terrestrial gait. In reality, these pterosaurs, like their azhdarchid relatives, had longer hind limbs and shorter wings (albeit still obviously much larger than their hind-limbs), allowing them to be effective terrestrial foragers and potentially enabling them to run on the ground.
The crest of the Tupandactylus model is depicted with large ridges on its surface. These ridges are absent in preserved skulls of the two species of Tupandactylus and the single species of Tapejara.
The head of the Tupandactylus model is depicted as too small relative to the proportions of the rest of the body and is not as deep as it would have been in the real animal.
Tupandactylus is depicted as living on the coast in the program. In reality, several lines of evidence indicate that tapejarids like Tupandactylus were more likely to have lived further inland. For instance, tapejarid fossils are usually found in geologic formations that contain either land-based or marginal marine depositional environments and carbon and oxygen isotope analyses of their bones have indicated that they may have obtained their water from freshwater regions like rivers and lakes far away from a marine environment, although the high amounts of oxygen-18 in the bones could also possibly result from consumption of seawater. Moreover, tapejarids like Tupandactylus are believed to have had a diet of fruits and seeds, which typically grow inland away from the coast, providing further evidence that these animals likely lived further inland and not in coastal regions.
Although sexual dimorphism may have been present in tapejarids like Tupandactylus, there currently isn't any evidence of sexual dimorphism in the tapejarid fossil record, suggesting that both male and female Tupandactylus may have had large crests.
Tupandactylus navigens is now thought to have had a slightly different head crest shape than the one depicted in the program, being sharper and pointed further forward compared to the crest on the program's model.
Tropeognathus and Tupandactylus, like all pterosaurs, are believed to have possessed skin covered in a coat of pycnofibers. Although pycnofibers are present on the animatronics used in close-up shots of these genera, they are far less dense and widespread than they should be.
Tropeognathus and Tupandactylus both lived in the Aptian-Albian stages of the Cretaceous and thus wouldn't have evolved yet by the program's Barremian setting. This inaccuracy is likely due to the lumping of multiple pterosaur genera leading to the misconception that genera like Ornithocheirus and Tapejara lived over a longer period of time than they really did.
Iguanodon is depicted as living in both North America and Europe in the program. This is due to the lumping of many iguanodontid remains into Iguanodon proper at the time, with many of these remains being split into new genera and species over the years. While the European Iguanodon depicted in the program is most likely still considered to be Iguanodon proper, although it could potentially have been based on other since-split European iguanodontids, such as Mantellisaurus and Barilium, the North American Iguanodon depicted in the program is now classified as the separate genus Dakotadon.
Iguanodon is now known to have been far more robustly built than it appears in the program, with the forelimbs in particular being much more robust in real life relative to the thinner forelimbs seen in the Iguanodon model in the program.
When moving quadrupedally, the body of the Iguanodon model in the program appears to slope downwards. However, the real animal would have had a more horizontal body posture in life. This issue is likely also present in the Dakotadon model seen in the program, although too few remains of Dakotadon have been found to determine if this is really the case.
The narration in this program states that Iguanodon was the first herbivorous dinosaur to have back teeth for grinding vegetation prior to swallowing. While these back teeth are a feature present in Iguanodon, the genus wasn't the first herbivorous dinosaur to evolve this feature, as chewing behavior had already evolved in earlier ornithopods and was even present in the heterodontosaurids, a much older ornithischian group unrelated to Iguanodon.
Polacanthus is depicted as living in both North America and Europe. This is due to the lumping of the North American nodosaurid genus Hoplitosaurus into Polacanthus at the time the program aired. However,Hoplitosaurus has since been determined to be a separate genus from Polacanthus, with many of the similarities between the two genera used to justify their synonymy being found to actually be present in many ankylosaur genera, suggesting that Polacanthus was a genus solely confined to Europe. This error was corrected in the US version, where the American animal is identified as Gastonia instead.
The head of the Polacanthus model seen in the program is relatively elongated and lacks a beak. While the skull of the real Polacanthus is poorly known, inferences made from that of its close relative Gastonia indicate that the real animal would have had a shorter, more triangular head in life and would have possessed a beak-like many other ornithischian dinosaurs.
The back of the Polacanthus model depicted in the program is likely far more arched than it would have been in life, with the real animal having a flatter, more horizontally-positioned back.
The legs of the Polacanthus model depicted in the program are likely too long relative to the rest of the body.
There is some debate regarding the presence and extent of cheek coverings in ornithischian dinosaurs like Iguanodon, Dakotadon, and Polacanthus. Paleontologists originally believed that cheeks were present in most ornithischians, as a covering over the sides of the mouth would help keep plant material contained within the jaws as the animal chewed, the cheek teeth of many ornithischians were inset, with an overhanging maxilla and large dentary, suggesting that a cheek-like soft tissue structure might have stretched between the lower and upper jaws, and small foramina along many ornithischian jaw bone margins may be evidence of neurovascular structures that nourished cheek structures and supplied them with blood. However, a study in 2018 found that, rather than a more mammal-like arrangement of muscle fibers directed straight down from an attachment ridge on the upper jaw to the lower jaw, ornithischians probably had a forward-extending fan of muscle attached to the lower jaw at one end and the rest of the cranium at the other underneath the flaring cheek bone instead, indicating that truly muscular cheeks covering the entire extent of the back part of the mouth are unlikely. However, thinner, non-muscular cheek analogues are not ruled out for these animals. While the 2018 study is still heavily debated among paleontologists, the cheeks of the real animals would likely be thinner, pushed further back, and shaped differently than the cheeks depicted on their models in the program.
Utahraptor isn't known from Europe, instead only being known from North America. The inaccurate placement of this dinosaur in Europe is most likely due to the now inaccurate idea that Iguanodon and Polacanthus lived in both North America and Europe, leading to the producers hypothesizing that Utahraptor may have lived on both continents as well. Although other dromaeosaurs are known to have lived in Early Cretaceous Europe, such as Nuthetes and Dromaeosauroides, these genera lived in the Berriasian stage, not the Barremian stage depicted in the program. Another dromaeosaur, Ornithodesmus, existed in Europe during the Barremian, but it was too small to plausibly replace the Utahraptor in the program. Undescribed remains of large European dromaeosaurids from the Barremian are known, however, suggesting that a large dromaeosaur may have indeed lived in Europe during the time the program takes place. Another possible replacement would be the recently-described Vectiraptor, a dromaeosaur that is known from the Barremian of Europe and coexisted with both Iguanodon and Polacanthus.
Utahraptor measured 20-23 feet (6-7 meters) in length at full size, not 16 feet (5 meters) as said in the program.
Utahraptor is now known to have been far more robustly built than its portrayal in the program, with a short torso, large neural spines to anchor large back muscles, and a shorter but more maneuverable tail. The head of the Utahraptor model seen in the program is also smaller and less robust than it would have been in the real animal and lacks the more forward-angled teeth at the front of the lower jaw that were present in the real animal.
Utahraptor more than likely had feathers running from head, to toe, to tail, although the tip of the snout was likely naked. It even had feathers on its arms, making them wing-like, and a feathered tail fan. This error is seen across all dromaeosaurs in the Walking with... Series.
It would be impossible for Utahraptor to pronate its hands, with the hands instead being held with palms facing inwards in the real animal. The hands of the model are occasionally seen to be facing palm-inward in some shots, but they are still rotated slightly too far back relative to the real animal.
Utahraptor lived 139-134.6 million years ago and would've been extinct by 127 million years ago.
Utahraptor is depicted as hunting in a coordinated pack in the program. While this behavior isn't implausible, coordinated pack hunting at the level depicted in the program is a more mammalian behavior not seen in most of the modern descendants of dinosaurs (birds and crocodiles), making it unlikely to have been part of the behavior of the real animal. However, it is possible that dromaeosaurs may have temporarily hunted in groups to bring down large prey while remaining mostly solitary otherwise, similar to modern Komodo dragons.
In shots featuring the animatronic Utahraptor, the tongue of the animal is seen to be somewhat mobile. However, the more crocodilian-like hyoid bone, which serves as a support for the tongue, seen in theropods like Utahraptor relative to the more complex hyoid bone seen in mammals and some ornithischian dinosaurs, indicates that the tongue of the real animal would have been largely immobile in life. However, it is possible that dromaeosaurs like Utahraptor may have had somewhat more mobile tongues than other non-avian theropods, as some modern birds, their avian descendants, are able to move their tongues in a complex manner. However, more study is needed to determine if this increase in tongue mobility started in dromaeosaurs or if it only occurred later on in avian evolution.
The Iberomesornis model in the program is depicted with some traits more coherent with modern birds rather than more primitive paravians like the real animal, such as bare and scaly legs and feet instead of owl-like feathered legs and feet and a tail-fan made up of rectrices rather than just having two elongated rectrices extending from the tail or a short tuft of feathers around the tail. However, more recent research has indicated that some enantiornithines may have had more complex tail-feathering, including tail-fans, than previously realized, with this research suggesting that retrical tail-fans may have been the ancestral condition of enantiornithines. This indicates that the tail-fan of the Iberomesornis model in the program may not be an inaccuracy, although it has yet to be determined if a tail-fan or a similar complex tail-feather structure was actually present in Iberomesornis itself, as no feather impressions of the genus have been found. Additionally, enantiornithine tail fans do not have musculature associated with them, so the animal would not have been able to flick its tail feathers like a modern bird. Moreover, additional research has also revealed that some enantiornithines appear to have possessed at least somewhat bare and scaly legs and feet, although it is yet again unclear if this also applies to Iberomesornis itself, again due to a lack of feather impressions for this genus.
Iberomesornis lived in the Aptian stage of the Cretaceous and thus wouldn't have evolved yet by the program's Barremian setting.
Iberomesornis is depicted as nesting in trees. Enantiornithines are notorious for being superprecocial, like modern day megapodes, and evidence from genera like Gobipteryx and Neuquenornis indicates that they buried their eggs in the ground.
Plesiopleurodon lived in the lower Cenomanian stage of the Cretaceous and thus wouldn't have evolved yet by the program's Barremian setting. In the US version, it is identified as Liopleurodon instead, creating an even bigger mistake, as this genus went extinct 155 million years ago during the Late Jurassic.
Short-necked pliosaurs such as Plesiopleurodon are now thought to have had flukes on their tails, not smooth lizard-like tails like in the series. However, the known specimens that possess these flukes are not assigned to Plesiopleurodon and this discovery came long after the series aired.
As the Plesiopleurodon model used in the program is reused from the Liopleurodon model from Cruel Sea, it is likely far larger than the real animal would have been in life. However, as Plesiopleurodon is currently only known from a single skull and a few cervical vertebrae, it is unclear as to how large the real animal may have grown in life.
The unidentified pterosaur seen in the program is depicted with several inaccuracies common to pterosaurs in the series, such as lacking fur-like pycnofibers and having far too pointed wingtips. However, due to its unidentified nature, it is unclear if any other inaccuracies are present in the model relative to a particular real life animal.
The narration states that the first simple flowers began to appear in the Early Cretaceous period. While evidence from the fossil record does indicate that flowering plants began to diversify in the Early Cretaceous period, including during the Barremian stage setting of the program, molecular dating analyses have suggested that the original diversification of flowering plants may have occurred much earlier in either the Triassic or Early Jurassic periods. Moreover, the Chinese plant genus Nanjinganthus, which has been dated to the Early Jurassic, possesses some angiosperm-like characteristics and features, leading some researchers to suggest that it represents the earliest known flowering plant, potentially pushing back the origin of flowering plants by 50 million years. However, this assertion has been disputed, with other researchers arguing that the flowering plant features observed in Nanjinganthus are actually misinterpreted fragmented conifer cones. Therefore, while the oldest undisputed flowering plants did indeed first appear in the Early Cretaceous period like the program states, more research is still needed to determine whether or not this was their true origin point.

Spirits of the Ice Forest[]

Despite the program claiming to take place in Antarctica, it features the exclusively Australian Leaellynasaura, Koolasuchus, and Steropodon, indicating that the program should most likely take place in Australia instead of Antarctica. Muttaburrasaurus is also only known from Australia, but it is shown as migratory in the program, indicating that it is not always present in the region in which the program is set, although this is still speculative. The "Polar Allosaur" is also based off a singular bone found in Australia, although the program again states that it is "a summer visitor from warmer lands to the north." Moreover, debates regarding the true identity of this bone makes it impossible to determine if the animal was also exclusive to Australia as of yet, although it would only be known from Australia if the later identification of the animal as Australovenator by Walking With Dinosaurs media is taken into account. Although the pterosaurs seen in this program remain unidentified, they are at least partially based on the also exclusively Australian genus Aussiedraco, as a jawbone that would later be referred to this genus was referred to as part of the justification for including pterosaurs in this program in the book Walking with Dinosaurs: The Evidence, although these animals are again referred to as migratory despite this behavior again being speculative for this genus. This error was partially corrected by the companion book, which states that the program takes place in the Australian-Antarctic rift valley instead, although this still doesn't fully address the location inaccuracies stemming from the presence of the many exclusively Australian animals in the program.
Leaellynasaura lived 113-110 million years ago and would've been extinct by 106 million years ago.
Leaellynasaura may have had feathers to keep itself warm in the cold climate of Cretaceous Australia, although no definitive evidence has been found for their presence in this genus as of yet. The presence of feathers in the Middle Jurassic basal neornithischian Kulindadromeus suggests that a feathery integument was ancestral to ornithischians and may have even been ancestral to dinosaurs as a whole, suggesting that feathers may have been present in at least some form on Leaellynasaura. However, recent studies regarding the thermoregulatory abilities of dinosaurs and the existence of dinosaurs without a dense feathery integument that are known to have inhabited cold climates indicate that the presence of feathers may not necessarily be required for survival in colder latitudes.
The tail of the Leaellynasaura seen in the program is potentially significantly shorter than that of the real animal, with two articulated body fossil specimens referred to the genus in 2009 showing that Leaellynasaura possessed a tail made up of over 70 individual vertebrae, indicating that the animal's tail was up to three times the length of the rest of its entire body. Moreover, the tail specimens lack ossified tendons, which support and increase the rigidity of the tails of other ornithischian dinosaurs, with only the posterior half of the tail having increased rigidity due to expanded vertebral processes, suggesting that the animal's tail may have been far more flexible than depicted in the program. However, the referral of these specimens to Leaellynasaura has proved controversial in recent years, as a study published in 2013 found that the specimens couldn't be confidently referred to Leaellynasaura after a reassessment of the stratigraphy of the site from which they originated. Later work in 2017 has since reassigned these specimens to Leaellynasaura, but there is still debate as to their referral among paleontologists, meaning that the portrayal of Leaellynasaura with a shorter tail in the program may or may not be an inaccuracy when compared with the real animal.
It is possible that Leaellynasaura may have had smaller eyes relative to the size of its head than depicted in the program, as more recent studies have indicated that the Leaellynasaura specimen preserving large eye orbits and enlarged optic lobes in the brain case may belong to a juvenile. As juvenile vertebrates tend to have proportionally larger heads and eyes when compared to adults of the same species, it is possible that the enlarged orbits seen in this specimen are simply the result of age rather than an adaptation for sight in low-light conditions like in the program, although such an adaptation is far from implausible given the long and dark winter months of the environment in which the animal likely lived if it didn't migrate. Moreover, a study in 2017 using synchrotron scans to reconstruct the animal's internal skull anatomy did suggest that Leaellynasaura had good vision, meaning that the adaptation depicted in the program may not be an inaccuracy even if the eye size of the model is now contested. Leaellynasaura also likely had ridges above its eyes like those of other related small ornithischians.
There is some debate regarding the presence and extent of cheek coverings in ornithischian dinosaurs like Leaellynasaura and Muttaburrasaurus. Paleontologists originally believed that cheeks were present in most ornithischians, as a covering over the sides of the mouth would help keep plant material contained within the jaws as the animal chewed, the cheek teeth of many ornithischians were inset, with an overhanging maxilla and large dentary, suggesting that a cheek-like soft tissue structure might have stretched between the lower and upper jaws, and small foramina along many ornithischian jaw bone margins may be evidence of neurovascular structures that nourished cheek structures and supplied them with blood. However, a study in 2018 found that, rather than a more mammal-like arrangement of muscle fibers directed straight down from an attachment ridge on the upper jaw to the lower jaw, ornithischians probably had a forward-extending fan of muscle attached to the lower jaw at one end and the rest of the cranium at the other underneath the flaring cheek bone instead, indicating that truly muscular cheeks covering the entire extent of the back part of the mouth are unlikely. However, thinner, non-muscular cheek analogues are not ruled out for these animals. While the 2018 study was performed on more derived ornithischians than Leaellynasaura and is still heavily debated among paleontologists, the cheeks of both the real Leaellynasaura and Muttaburrasaurus would likely be thinner, pushed further back, and shaped differently than the cheeks depicted on their models in the program.
There is slight shrink wrapping on the heads of the Leaellynasaura, Muttaburrasaurus, and the "Polar Allosaur". In reality, the skull openings likely were not externally visible.
The neck and body of the Leaellynasaura model are likely thinner than those of the real animal.
The head of the Leaellynasaura appears to be a little too short when compared with that of the real animal, which had a more elongated skull. This shortened skull may be due to the animal originally being classified as a hypsilophodontid, with these animals tending to have shorter skulls than Leaellynasaura, with Leaellynasaura having since been classified as a member of the family Elasmaria in 2019.
The external ear opening on the Leaellynasaura model is likely slightly too high up on the skull.
The extent of social structure amongst the Leaellynasaura clans depicted in the program appears far more similar to mammalian social structures rather than reptilian ones, although the existence of such a social structure in Leaellynasaura is not necessarily implausible.
Muttaburrasaurus is portrayed as being slightly too robust and should be wholly bipedal rather than being capable of switching from walking bipedally to walking quadrupedally. These errors are likely the result of the animal originally being classified as an iguanodontid before a later study in 1996 reclassified it as a more basal member of the clade Rhabdodontomorpha.
There is no evidence Muttaburrasaurus were migratory. This is not an implausible piece of speculation, as fossils of this genus have been found in New South Wales and Queensland, potentially indicating that these animals could travel great distances, although this remains unconfirmed. Regardless, there is no evidence of their presence in Antarctica or even southern Australia, meaning that they likely didn't coexist with many of the other animals depicted in this program.
Muttaburrasaurus did not have thumb spikes like the ones depicted on the model in the program. This error is likely the result of the animal originally being classified as an iguanodontid before a later study in 1996 reclassified it as a more basal member of the clade Rhabdodontomorpha.
There is no evidence to suggest that Muttaburrasaurus possessed an inflatable nasal resonating chamber that could be used to communicate between individuals. However, this is not an implausible piece of speculation, as the skull of the animal does possess an inflated bony nasal bulla that appears to be hollow and some specimens that may represent a second species appear to have slightly differently shaped nasal bulla structures from those of more definitive specimens of the species M. langdoni, suggesting the possibility of sexually dimorphic display structures in this genus.
The ankle bone thought to belong to an allosauroid during production, on which the "Polar Allosaur" is based, is now believed to belong to a group of theropods known as the megaraptorids, whose classification is disputed. Its depiction as a dwarf allosaurid in the program is due to the ankle bone originally being described as a late-surviving species of Allosaurus ("A. robustus") that had evolved a smaller body size over time to withstand the colder climate of Australia, with this classification being due to similarities between the ankle bone and that of Allosaurus. However, the exact assignment of this ankle bone quickly became controversial. It was later identified as an ornithomimid, but was then reclassified again as an abelisaurid. It later reverted back to being identified as an allosaurid again, although not Allosaurus itself, before eventually being reclassified yet again to its current identification as the remains of a megaraptorid.
The "allosaur" ankle bone came from a fossil bed that dates to the early Albian, not the late Albian, where the program is said to be set. The likely megaraptorid Rapator lived in the late Albian and could thus serve as a possible replacement, but it lived in New South Wales, not Victoria, meaning that, while it would have coexisted with Muttaburrasaurus, it would not have coexisted with Leaellynasaura or Koolasuchus.
Later Walking with Dinosaurs media, such as the old BBC Nature website, identify the "Polar Allosaur" as Australovenator, a genus of megaraptorid theropod known from the Cenomanian Winton Formation of Australia to which the "allosaur" ankle bone has been assigned in more recent studies. If this is the case, the model seen in the program has many physical inaccuracies when compared with the real animal, with the real animal having a more gracile skull with smaller teeth and relatively long, flexible arms. Moreover, Australovenator is too young to be featured in the program, being known from around 95 million years ago, whereas the program is set 106 million years ago.

If the "Polar Allosaur" depicted in the program is classified as Australovenator, its method of hunting depicted in the program is inaccurate, with the real animal likely using its flexible arms and hind feet more than its mouth to capture or injure prey items.

Steropodon is live-acted by a modern coatimundi in the program when, in reality, it was a monotreme with an appearance likely more akin to that of the modern platypus.
Steropodon may have possessed a platypus-like bill in reality, as the potentially closely-related Teinolophos has been suggested to have had a similar bill-like structure, although this remains debated. An electrosensitive or mechanosensitive bill structure like this might have helped Steropodon navigate in the winter darkness of the polar Australian forests, providing further support for the presence of this structure, although more fossil remains would need to be found to confirm or deny its presence on the real animal
Steropodon lived in New South Wales, not Victoria, meaning that it wouldn't have coexisted with Leaellynasaura. A possible replacement would be Kryoryctes, which did coexist with Leaellynasaura in the Eumeralla Formation.
Steropodon lived from 100-96.6 million years ago, making it slightly too young to appear in this program, which is set 106 million years ago.
Koolasuchus lived in the Aptian and was extinct by the Albian. Its disappearance is theorized in the program to have occurred because the temperature warmed up enough for their habitats to have been compromised by crocodylomorphs colonizing the area and outcompeting them. However, there is no conclusive evidence to say that this was definitely the case. The fact temnospondyls and crocodylomorphs are known to have coexisted at earlier times during the Mesozoic suggests Koolasuchus probably did not disappear solely as a result of their arrival, although climatic partitioning between the two groups probably did allow Koolasuchus to persist as long as it did in its isolated environment.
Koolasuchus is depicted as walking on land somewhat like a salamander, which tend to use their hind-limbs when walking more than a temnospondyl amphibian like Koolasuchus would. In real life, Koolasuchus would likely have used its fore-limbs as a source of propulsion when on land due to its larger head shifting its center of mass more frontwards.
The narration in this program describes Koolasuchus as "hibernating" during the winter months. Being an amphibian, the real Koolasuchus wouldn't technically have undergone hibernation per se but instead may have entered brumation, a state of torpor and inactivity during the winter which can occur in ectothermic animals like amphibians.
The unidentified pterosaurs seen in this program are depicted with several inaccuracies common to pterosaurs in the series, such as lacking fur-like pycnofibers and having far too pointed wingtips. However, due to their unidentified nature, it is mostly unclear if any other inaccuracies are present in the model relative to a particular real life animal.
There is no evidence that pterosaurs like the ones depicted in this program were migratory, although this isn't implausible speculation. This inaccuracy may have been due to the inclusion of a jawbone originally believed to belong to Ornithocheirus that has since been referred to the genus Aussiedraco as part of the justification for including pterosaurs in this program, as indicated in the book Walking with Dinosaurs: The Evidence, which paleontologists at the time may have seen as evidence of the supposed global migrations of the genus Ornithocheirus like those depicted in Giant of the Skies.
The pterosaurs seen in this program appear to be shrunken-down versions of the Ornithocheirus model from Giant of the Skies. If they are partially based on Aussiedraco like Walking with Dinosaurs: The Evidence suggests, they would look slightly different from Ornithocheirus, as, despite both belonging to the clade Ornithocheirae, Aussiedraco has since been classified as part of the clade Targaryendraconia.
The narration of this program describes the Tuatara as "surviving from a time long before the dinosaurs" and that it will "remain long after them." The tuatara is the only living member of the order Rhynchocephalia, which originated in the Middle Triassic, whereas dinosaurs themselves originated in the Late Triassic, meaning that rhynchocephalians were not around "long before the dinosaurs." Moreover, in real life, while the tuatara is indeed alive today, it actually first definitively appeared in the Miocene, long after the dinosaurs went extinct, meaning that the modern tuatara would not have been around 106 million years ago during the time in which the program is set. However, there were other rhynchocephalians that lived in the Cretaceous, though Cretaceous-aged fossils of these animals have yet to be found in either Australia or Antarctica. Despite this, the discovery of jaws similar to those of the modern tuatara from a site in New Zealand dating to around 19 million years ago does suggest that the lineage leading to the tuatara was likely present in the region since at least 80-60 million years ago, when New Zealand separated from Gondwana, suggesting that it wouldn't be implausible for a tuatara-like animal to be present in either Australia or Antarctica around 106 million years ago, just not the tuatara itself.
The Cretaceous rhynchocephalian depicted in this program is live-acted by a modern tuatara. However, rhynchocephalians were an extremely diverse group of reptiles, possessing a variety of body and skull shapes even during their decline in the Cretaceous, meaning that there is no evidence to suggest that a hypothetical Cretaceous rhynchocephalian in either Australia or Antarctica would exactly resemble the modern tuatara.
There is currently no evidence to suggest that Giant Wetas were present in either Cretaceous Australia or Antarctica at the time in which the program is set. While there are specimens that may belong to the weta lineage found in Queensland that date back to the Early Jurassic (190 million years ago), these specimens have only been identified as members of the order Orthoptera, which includes grasshoppers, crickets, locusts, katydids, wetas, and their relatives, meaning that their identity as wetas specifically has not yet been confirmed. However, their presence in the region at this time is not implausible speculation, particularly if the Queensland remains turn out to represent true wetas.
It is unclear if any prehistoric weta species would share the ability of some modern weta species to allow their bodies to freeze during the winter, enabling them to withstand temperatures of up to -10°C, although the presence of this behavior in a hypothetical Cretaceous weta is not implausible speculation.
At the end of the program, the narration states that the climate in the South Pole would eventually get colder, causing the extinction of the animals that lived there during the Cretaceous. However, this is actually the opposite of what occurred, with the South Pole actually becoming progressively warmer through the rest of the Cretaceous until it began to freeze following the Eocene.

Death of a Dynasty[]

The ecosystem of Maastrichtian Montana was actually still thriving before the asteroid collision, with many lush swamps and forests, rather than being a volcanic wasteland like it is depicted in the program. However, at least some volcanic ash-field regions would still be present in Hell Creek, with volcanoes being present nearby as a result of mountain-building events to the west of the formation.
The program's narration claims that non-avian dinosaurs were living on a poisoned planet and rapidly decreasing in abundance before the impact of the asteroid wiped out what little remained. However, this has become a matter of great debate. Research at the time the series was in production supported the claim that non-avian dinosaurs were undergoing a gradual decline, dropping in diversity during the Maastrichtian when the program is set and declining particularly rapidly in the latest Maastrichtian of North America. However, more recent studies have argued that the data supporting a gradual decline was biased due to mostly originating from the Hell Creek Formation, indicating that a relatively small region of western North America shouldn't be used as a representative of conditions across the entirety of the planet. With other latest Maastrichtian localities from around the world taken into account, dinosaur diversity during this time has been suggested to have been severely underestimated, although caution should still be taken with dinosaur diversity curves due to artifacts caused by the geological record's biases, such as the amount of rock that can preserve fossils that is actually preserved, can easily obscure evolutionary trends. Other studies have continued to support the idea of a gradual decline in dinosaur diversity though, while still other studies have indicated that non-avian dinosaurs didn't decline in the long-term overall, but specific groups, such as North American ceratopsians and hadrosaurids, did actually decrease in diversity over the last 15 million years of the Cretaceous. Other statistical analyses have contradicted this, indicating that non-avian dinosaurs declined in diversity overall, with the exceptions of the hadrosaurids and ceratopsians, which continued to diversify throughout the Late Cretaceous, while still others argued for an overall increase in diversity across all groups at this time. More recent ecological niche modeling studies have suggested that the seeming decline in North American dinosaur diversity during the latest Cretaceous is actually an artifact, being explained by a reduction in the presence of fossiliferous rocks that could actually preserve fossils due to the presence of the proto-Rocky Mountains and drops in sea-level, concluding that diversity had been underestimated in the past. Therefore, whether or not dinosaurs were actually declining at the end of the Late Cretaceous is still an ongoing debate that remains far from a definitive answer like that provided in the program.
The narration states that the canopy of Maastrichtian Montana was mostly filled with broad-leaved trees instead of conifers. However, fossil evidence indicates that coniferous plants were actually still the main components of the canopy of Maastrichtian Montana, with broad-leaved trees being present but mostly relegated to the secondary canopy.
In the US version, the program is indicated to take place in Maastrichtian Idaho, although none of the creatures depicted in the program have currently been found in that state.
It would be impossible for Tyrannosaurus, Dromaeosaurus, and the unidentified neornithischian to pronate their hands, with the hands instead being held with palms facing inwards in the real animals.
The body of the Tyrannosaurus model in the program is not as robust as that of the real animal, while its legs are far slimmer than they would have been in life. The model's neck and tail are shorter and less muscular than those of the real animal and its feet are also much smaller than they would have been in life.
The skull of the Tyrannosaurus model in the program is smaller proportional to the rest of the body than it would have been in life. It is also slightly too blocky in shape with a shorter snout than the real animal would have had. The bosses above the eyes and ridge along the top of the skull are also absent, with the model only possessing ridges above the eyes and a slight ridge extending towards the snout.
The nostrils of the Tyrannosaurus model are located too high up on the snout when compared with the real animal.
The teeth of the Tyrannosaurus model in the program appear to all be the same size and shape, contrary to the heterodont tooth condition seen in the real animal, with the teeth in the front of the jaw being smaller than those further back. Although this is still debated, it is also likely that, like many non-avian theropods, Tyrannosaurus would have had immobile, lizard-like lips that would have covered its teeth when its mouth was closed.
The tongue of the Tyrannosaurus model is seen to be somewhat mobile. However, the more crocodilian-like hyoid bone, which serves as a support for the tongue, seen in theropods like Tyrannosaurus relative to the more complex hyoid bone seen in mammals and some ornithischian dinosaurs, indicates that the tongue of the real animal would have been largely immobile in life.
There is slight shrink wrapping on the heads of the Tyrannosaurus, Dromaeosaurus, Edmontosaurus, Quetzalcoatlus, Triceratops, and the unidentified theropod carcass. In reality, the skull openings would likely not be externally visible. In the carcass's case, this shrink wrapping may also simply be due to decomposition.
Tyrannosaurus is said to have weighed five tons in the program. While this is a reasonable weight for this genus, the real animal likely weighed around 6.6-9.8 tons on average.
The program's narration describes female Tyrannosaurus as being larger than males of the genus. This claim was based on the existence of two distinct body morphs in Tyrannosaurus, with one being more robust and one being more gracile, with paleontologists suggesting that these morphs were due to sexual dimorphism and that the robust morph represented females due to the angle between the ischium and the tail vertebrae being greater than that of the gracile morph, potentially providing more space for laying eggs. Moreover, it was also suggested that the first chevrons underneath the tail was shorter and placed further back in the robust morph, similar to those of crocodiles, which researchers believed was also indicative of creating a wider space for females to lay eggs effectively. However, the existence of this sexually dimorphic difference in crocodilian chevrons was later disproven, followed by these bones being found to have no significant variation amongst Tyrannosaurus specimens. The angle of the ischium has also since been found to not show significant variation between Tyrannosaurus specimens, with several other suggested sexually dimorphic features in this genus being found to be similarly uninformative. Therefore, it is currently impossible to determine whether sexual dimorphism was present within Tyrannosaurus without the discovery and research of further specimens, although the existence of such dimorphism is not implausible speculation.
Tyrannosaurus may have had some form of feathering on its body. However, the integument of this genus is still debated. Based on fossil evidence, it is believed that Tyrannosaurus was likely mostly covered in scaly skin, although small and/or sparse feathering could be present on some portions of the body. It is also possible that juvenile Tyrannosaurus would have feathery integument, although this remains unconfirmed.
The scales on the Tyrannosaurus model are very large and noticeable, with some areas also possessing skin folds. Based on skin impressions, the real animal possessed small scales across most of its body, with the animal likely appearing somewhat smooth from afar. However, it is possible that some larger scales were present on the animal's head and face.
Tyrannosaurus has been theorized to have used low-frequency sounds rather than the full-throated roaring in the series. It may have used closed mouth calls to communicate over long distances. This is a speculative approach based on the assumption that these dinosaurs would have lacked the complex vocal structures of modern birds, and therefore, would have produced relatively simpler sounds similar to those produced by extant crocodilian, turtle, and lepidosaur species that lack a complex vocal apparatus, as well as birds that lack a syrinx, or at least a developed one. However, not much is known about the vocal apparatus of non-avialan dinosaurs and there is little information on the evolution of the syrinx (the vocal organ for modern birds) before the origin of the Ornithurae clade. Therefore it is unknown how complex the vocal organs of non-avialan dinosaurs could have been, regardless if they had a sort of proto-syrinx or developed a different organ to produce complex sounds. Moreover, even in modern reptiles that lack a syrinx or complex vocal folds, vocalizations can prove to be quite varied, ranging from squeaks, hisses, grunts, bellows, and even loud roars, like in crocodilians. A preserved larynx has been found in a specimen of the ankylosaurid Pinacosaurus, with its specialized anatomy suggesting that at least some dinosaurs may have been able to produce loud and explosive calls similar to those of modern birds. However, it is currently unknown if this feature applies to Tyrannosaurus.
Tyrannosaurus is depicted as an ambush predator in the program. While this is indeed a likely hunting strategy for the real animal, it has also been suggested that Tyrannosaurus hunted by stalking its prey over long distances before using a final burst of speed to take down its prey.
Recent studies have suggested that Tyrannosaurus likely removed flesh from carcasses similar to modern crocodiles, shaking their heads from side to side to tear off bits of meat rather than simply quickly retracting their heads to pull off meat like in the program.
It has been suggested that, due to the presence of deep, unhealed Tyrannosaurus bite mark grooves in the frills of Triceratops specimens, the overall lack of flesh on the frill of a Triceratops, and the presence of Tyrannosaurus bite marks on the ball and socket joint in the neck of some Triceratops specimens, Tyrannosaurus may have bit the frills of dead Triceratops in order to rip off their heads and access their prey's large neck muscles. However, the Triceratops carcass in the program still has its head attached to its body, although this may be a result of the Triceratops being a smaller individual or due to it being intended as a mating gift rather than purely for feeding.
Tyrannosaurus is shown to stand up from a sitting position by rising and shifting the back right leg to gain balance with no input from the animal's arms in the program. However, there is some evidence that the real animal would have likely used its arms as leverage to help it rise from a sitting position, with a sandstone block from New Mexico potentially preserving traces of parallel forearm prints alongside a possible single-toed left footprint potentially belonging to Tyrannosaurus, suggesting that the animal may have stood from a sitting position by stepping forward with its left foot while pushing down with its arms to push it upward.
Tyrannosaurus is depicted as engaging in parental care in the program. While this behavior isn't implausible, given the inferred behavior of other theropod dinosaurs, such as oviraptorids, and the observed behavior of many modern birds and crocodilians, there is currently no evidence for this behavior in Tyrannosaurus in the fossil record. A juvenile specimen of Gorgosaurus, a relative of Tyrannosaurus, has been found with the legs and bits of the tails of hatchling oviraptorids in its stomach, which, when combined with evidence of older tyrannosaurids hunting larger dinosaurs, indicates that juvenile tyrannosaurids had to feed themselves and that juvenile and adult tyrannosaurids were likely hunting different organisms in different ecological niches to avoid competition with one another, suggesting that, if parental care was present in tyrannosaurids, it likely didn't last into later juvenile growth stages. Moreover, a subadult Tyrannosaurus bone has been discovered with tooth marks from a larger Tyrannosaurus, suggesting that juvenile tyrannosaurids could sometimes also serve as food sources for adults.
The head of the juvenile Tyrannosaurus model is somewhat too blocky and robust when compared to the thiner and longer heads of juveniles of the real animal. Moreover, the body and legs of the juvenile model are a little bulkier than those of a real juvenile Tyrannosaurus. However, some of these comparisons may be complicated based on whether or not "Nanotyrannus" specimens are considered to represent juvenile Tyrannosaurus, which is still a matter of considerable debate.
The skull of the Dromaeosaurus model is too blocky and stout and the body is too skinny when compared with that of the real animal.
Dromaeosaurus more than likely had feathers running from head, to toe, to tail, although the tip of the snout was likely naked. It even had feathers on its arms, making them wing-like, and a feathered tail fan. This error is seen across all dromaeosaurs in the Walking with... Series.
Dromaeosaurus is depicted as hunting in a coordinated pack in the program. While this behavior isn't implausible, coordinated pack hunting at the level depicted in the program is a more mammalian behavior not seen in most of the modern descendants of dinosaurs (birds and crocodiles), making it unlikely to have been part of the behavior of the real animal. However, it is possible that dromaeosaurs may have temporarily hunted in groups to bring down large prey while remaining mostly solitary otherwise, similar to modern Komodo dragons.
Dromaeosaurus lived during the Campanian of Canada, not the Maastrichtian of Montana where the program is set. This error may be due to fragments of bone and teeth of dromaeosaurids that were originally believed to belong to Dromaeosaurus being found in the Hell Creek Formation of Montana, with these fragments since being identified as material of the separate genus Acheroraptor. Two possible replacements would be the dromaeosaurid genera Acheroraptor and Dakotaraptor, which lived during the Maastrichtian of Montana, but these had yet to be described during the production of the program. However, the description paper for Dakotaraptor indicates that Dromaeosaurus material is known from younger rocks dating to the Maastrichtian, although this material has yet to be found in Hell Creek.
Dromaeosaurus is depicted as hunting Torosaurus under the cover of darkness in the program. While this behavior isn't necessarily impossible, more recent studies of the eye orbit and inner ear structure of dromaeosaurids, including Dromaeosaurus itself, has suggested that, despite its good sense of hearing that might help it to hunt at night, the real animal would not have had especially good vision under low-light conditions, meaning that the real animal would be much more suited to hunting during the daytime.
Dinilysia was already extinct by the Maastrichtian, having lived 85 million years ago during the Coniacian. It also only lived in South America, while the program takes place in North America. A good replacement would likely be Cerberophis, which lived in the Hell Creek Formation at the time during which the program is set. Cerberophis is now believed to be a basal member of the derived snake group, but it was believed to be an indeterminate member of the boa family at time the series was in production, likely explaining the decision for the snake to be live-acted with a modern red-tailed boa in the program.
Dinilysia is shown to possess pit organs that enable it to detect body heat. However, it is unlikely that this or any other known Cretaceous snake genus possessed these organs, as infrared sensing organs appear to have convergently evolved independently in modern boas, pythons, and pit vipers, meaning that a common ancestor of all three of these lineages likely didn't possess these infrared sensing organs. This error may have been due to the previous identification of Cerberophis as an indeterminate boa, which would have indicated that a member of a family known to possess infrared sending organs would have been present in Hell Creek at the time the program is set.
"Anatotitan" is no longer considered its own genus, with it now being identified as a species of Edmontosaurus, E. annectens.
Edmontosaurus, like all hadrosaurs, didn't have thumb spikes like their iguanodontid cousins.
The skull of the Edmontosaurus model is too long and flat when compared with that of the real animal. Moreover, the model's snout is shown to have a spatulate shape, while the snout of the real animal would have had a beak-like rhamphotheca on the upper jaw that would have instead formed a more downturned, shovel-shaped snout.
The neck of the Edmontosaurus model appears to be far thinner than it would have been in life.
Edmontosaurus annectens may have possessed a small, fleshy, comb-like crest on its head in life, as such a crest has been found to be present in the slightly older species E. regalis, although the presence of this crest in E. annectens is unconfirmed.
The forelimbs and hands of the Edmontosaurus model are slightly too robust in proportion to the rest of the body when compared to the real animal, which had much more slim front libs relative to its hind-limbs.
The hands of the Edmontosaurus model are noticeably inaccurate when compared with the hands of the real animal. The model shows two distinct hoof-like structures on each hand, with the second digit projecting out from higher up on the hand than the fifth digit, the third and fourth digits being separated and both possessing nails, and an extra digit seemingly present. In reality, the second, third, and fourth digits were fused together inside of a fleshy structure with a single hoof-like nail at the tip, with the second digit partly projecting outward from the hoof-like structure beneath the outward projection of the fifth digit further up the hand and the first digit being completely absent.
The row of midline feature scales associated with the tip of each vertebra's neural spine that ran from the base of the neck to the tail in the real Edmontosaurus is missing from the model seen in the program.
Torosaurus is said to be very common in Montana right before the asteroid impact in the program, which is implied to be set in the Hell Creek Formation. While recent evidence from both Montana and Canada indicates that Torosaurus would likely have been present in the late Maastrichtian stage of the Cretaceous, its remains are still rather rare in the Hell Creek Formation when compared with those of Triceratops, suggesting that it was far less common in Montana than it is depicted in the program.
There are only four digits visible on the front feet of the Torosaurus and Triceratops models. However, ceratopsians like Torosaurus and Triceratops often had five digits on their front feet, with the fifth digit often not contacting the ground.
The frill of the Torosaurus model has very straight edges on all sides. This was actually more of a variable feature in the real animal, with some specimens possessing triangular epiparietal bones on the edges of their frills while others possess more smooth edged frills. The top of the frill also appears to be slightly too rounded, with some specimens of this animal showing a slight concavity at the top of the frill instead, although this is also a variable feature in this animal.
There is currently no evidence that Torosaurus could not change the colors of the skin on its frill by flushing blood into it, although this isn't necessarily unreasonable speculation.
The nose horn of the Torosaurus model may be slightly too small, as the size and shape of this horn has been found to be variable amongst Torosaurus specimens. Moreover, the brow horns of the Torosaurus model may be a little too straight, as, despite having similarly noticeable variability amongst different specimens, many have been found to have slightly curved forwards.
The brow horns of the Torosaurus and Triceratops models are placed slightly too far back behind their eyes, with the real animals' brow horns projecting from directly above their eye orbits. This error is also present in the juvenile Torosaurus model.
The skull of the Torosaurus model is slightly too short when compared with that of the real animal.
It is possible that Torosaurus and Triceratops possessed bristles down their tails similar to those present in the basal ceratopsian Psittacosaurus, although there is currently no confirmed fossil evidence of these structures in these animals.
The models of Torosaurus and Triceratops are depicted with wrinkly, elephantine skin. While skin impressions from Torosaurus are not yet known, skin impressions from Triceratops suggest that the real animals were likely covered in large, sub-circular or polygonal scales surrounded by many smaller, non-overlapping, polygonal scales.
The frills of the juvenile Torosaurus model are likely extended too far backwards compared to those of real juveniles, as, while no skull elements from juvenile Torosaurus are known, skulls from juveniles of the closely related Triceratops indicate that the frills likely didn't become elongated until the animal reached roughly 75% of its adult body size. It is also possible that, like Triceratops, the frills of juvenile Torosaurus would have had a more scalloped look due to the presence of epoccipitals around their edges, although whether they were actually present on juveniles of the real animal remains unknown.
The nostrils of the Triceratops model are slightly too high up on the skull and too close to the nasal horn when compared to those of the real animal.
It is possible that the brow horns of the Triceratops model should be slightly more recurved based off of skulls of juveniles of the real animal, although this is dependent on how young the individual in the program is intended to be.
Deinosuchus was extinct by the time the program is set, being from the Campanian (82-73 million years ago) rather than the Maastrichtian. There were crocodilians present in Montana during this time period, such as Borealosuchus and Brachychampsa, but both were too small to fill the role of the large crocodilian shown in the program. The crocodylomorph could likely best be replaced by Thoracosaurus, which is believed to have reached lengths of up to 8 meters and is possibly present in the Hell Creek Formation where the program is set, although the remains assigned to it from Hell Creek may belong to a different species that was just similar in appearance to Thoracosaurus.
Deinosuchus is described as being a "1-tonne crocodile". In reality, Deinosuchus likely weighed from 2.3 metric tons up to potentially around 8.5 metric tons. Moreover, Deinosuchus has since been classified as an alligatoroid, not a crocodile.
The jaws of the Deinosuchus model in the program are far too thin and lack the laterally expanded region around the nasal openings that was present in the real animal.
The tip of the snout of the Deinosuchus model depicts interlocking upper and lower jaw teeth, with all of the teeth from the lower jaw visible with the mouth closed, similarly to modern crocodiles. However, Deinosuchus has since been classified as an alligatoroid, with the real animal only having the fourth tooth back from the front of the lower jaw visible with the mouth closed while all other lower jaw teeth were hidden.
Due to the Quetzalcoatlus model being a modified version of the Tropeognathus model from Giant of the Skies, it only shares a faint resemblance to the real animal. The program's design has a much smaller head than the real animal and depicts the animal's head crest as being a tiny conical notch at the back of the head behind the eyes rather than a more rectangular crest positioned further down the head than the eyes. The real animal's skull was also noticeably deeper at the back before thinning out to a sharp tip at the front, with these proportions being absent from the model in the program. The real animal's neck was much longer than the program's design and the model's body is also proportionally larger relative to the head and neck than it would have been in life.
The Quetzalcoatlus model seen in the program is depicted with several inaccuracies common to pterosaurs in the series, such as lacking fur-like pycnofibers and having far too pointed wingtips, although the extent of roundness in pterosaur wingtips is still a matter of debate.
When the Quetzalcoatlus is shown on the ground, its wings are seen to fold in from the sides. However, in the real animal, the wings would have folded in from the back, with the metacarpals rotating and causing the front digits to point backward.
The Quetzalcoatlus model appears to be too small relative to the rest of its environment while on the ground, with the real animal potentially having a wingspan of up to ten meters in length. The narration describes Quetzalcoatlus as being a "thirteen metere giant," but this measurement is likely slightly oversized, with the real animal likely being around three meters (9.8 feet) high at the shoulder with a ten foot wingspan.
Quetzalcoatlus is depicted walking very slowly and hunched over while on the ground, whereas the real animal would have stood much more upright and was capable of walking somewhat quickly while on the ground.
The Quetzalcoatlus model is depicted with teeth in its beak in the program, which the real animal completely lacked.
The presence of Quetzalcoatlus in the Hell Creek Formation like in the program is still debated. One of the only pieces of pterosaur material known from Hell Creek is a single neck vertebra belonging to an indeterminate azhdarchid pterosaur that has been suggested to belong to Quetzalcoatlus, although its referral to the genus remains unconfirmed.
Quetzalcoatlus is depicted as feeding on fish through dip feeding, dipping its head into bodies of water to pluck out fish. While this was believed to be accurate at the time the series was made, the necks of azhdarchids like Quetzalcoatlus were far too stiff for dip feeding to be possible, being unable to bend their head underneath and behind the body. Moreover, they also lacked the necessary stress-reducing specializations of the lower jaw and neck for skim feeding behavior to be possible. In reality, azhdarchids like Quetzalcoatlus were more likely to have fed terrestrially, as can be determined by the distribution of their fossils, the presence of trackways showing they were skilled walkers on the ground, the length of their limbs, and their skull and neck anatomy, likely feeding on smaller vertebrates while walking around on the ground for long periods of time.
The narration claims that pterosaurs have been in decline "for the last 20 million years" and that Quetzalcoatlus was among "the only ones left," suggesting that pterosaurs were being rapidly outcompeted by birds at the end of the Cretaceous. However, while this was believed at the time the series was in production, more recent studies have indicated that pterosaurs were not actually declining towards the end of the Cretaceous, with Maastrichtian-aged pterosaur remains from North America and Morocco indicating that both pteranodontid and nyctosaurid pterosaurs were also present at the very end of the Cretaceous instead of solely azhdarchids like had been previously thought, with the Moroccan pterosaurs in particular still being notably diverse, with all three families being represented within the seven currently known Moroccan pterosaur species and displaying multiple different morphologies and ecological niches, indicating that the idea of their decline was simply due to the biases of the fossil record rather than an actual decline in pterosaur diversity at the end of the Cretaceous. However, pterosaurs did decrease in overall diversity by this time, with the notable extinction of several groups by the middle of the Cretaceous. Moreover, it is no longer believed that birds simply outcompeted pterosaurs and filled in their ecological niches, with the presence of many smaller pterosaurs alongside larger taxa in Morocco indicating that small birds hadn't filled in the niches occupied by small pterosaurs in the Jurassic and Early Cretaceous during the Late Cretaceous like had previously been believed, with their previous absence from the fossil record likely being due to sampling bias. It has also been suggested that pterosaurs had extended their size range in the Late Cretaceous rather than solely being large in size, meaning that the niches previously occupied by smaller pterosaur species were actually being taken over by the smaller juveniles of larger species through ontogenetic niche partitioning rather than birds.
Didelphodon was not badger or Tasmanian devil-like in appearance. In reality, based on a currently undescribed specimen, it had a head like a Tasmanian Devil and a body like an otter. This error was due to the animal only being known from teeth with a morphology similar to that of the Tasmanian devil at the time of the program's production.
The narration describes Didelphodon as being a marsupial. In reality, Didelphodon is classified as a metatherian, being part of a more inclusive group including marsupials and various extinct marsupial-like mammal lineages.
The program's narration describes Didelphodon as weighing ten kilograms, claiming that "this is about as big as Cretaceous mammals get." In reality, Didelphodon was lighter than claimed in the program, weighing around 5.2 kilograms as an adult. Moreover, other Cretaceous mammals are known to have exceeded this weight, such as Repenomamus giganticus, which has been estimated to have an adult weight of around 12-14 kilograms.
There has been some debate regarding the ecology of Didelphodon, with some studies suggesting that the family including Didelphodon, the Stagodontidae, was actually semi-aquatic based on isolated bones and feet assigned to the family found in aquatic deposits. However, these remains are only referred to the family due to their size, meaning that they can't actually be assigned to Didelphodon due to a lack of identifiable material. Moreover, it has been suggested that features of the foot bones indicated evidence of greater foot mobility, which would be useful for paddling in an aquatic environment. However, it has instead be argued that these features show that the feet were more rigid, making them better suited for digging. However, Didelphodon has also been found to group with known semi-aquatic mammal species in terms of locomotion, although this is again based on the isolated material that only has a questionable association with Didelphodon. Therefore, it is possible that Didelphodon would have been semi-aquatic and wouldn't have scurried about furiously for terrestrial prey like in the program, but this remains unconfirmed.
Ankylosaurus was not as tall and bulky in reality as it appeared in the series, with the real animal appearing flatter and holding itself closer down to the ground.
The skull of the Ankylosaurus model is far more rounded than it would have been in life, with the real animal having a flatter, more triangular skull. The model's skull is also missing the tile-like polygonal bony plates called caputegulae that would have covered most of the top of the skull, making the skull appear far more smooth than it would have in life, and has much smaller and more conical horns on the back of the skull with blunter tips than the real animal would have had, although recent studies suggest that the more blunted tips of the horns are possibly representative of older Ankylosaurus individuals.
The osteoderms of Ankylosaurus would likely have arranged with relatively larger spaces between osteoderms and fewer rows of osteoderms down the back in life when compared with the model in the program. The osteoderms of the model are also far more narrow than they would have been in life and the bony cervical half-rings on the neck are also absent.
The knobs on the tail club of the Ankylosaurus model project slightly too far sideways when compared to the club of the real animal, with the model's club seeming to more closely resemble that of Euoplocephalus or Anodontosaurus.
While it is likely that Ankylosaurus could have used its tail club as a predator defense structure, studies of the tail club of the ankylosaurid Zuul suggest that, based on characteristic osteoderm injuries, these clubs may have evolved for the purposes of sexual selection and intraspecific combat, with individuals of the same species slamming them into the sides of their rivals during competition for resources like territory or mates, rather than specifically for predator defense like the narration in this program suggests.
There is some debate regarding the presence and extent of cheek coverings in ornithischian dinosaurs like Edmontosaurus, Torosaurus, Triceratops, Ankylosaurus, and the unidentified neornithischian. Paleontologists originally believed that cheeks were present in most ornithischians, as a covering over the sides of the mouth would help keep plant material contained within the jaws as the animal chewed, the cheek teeth of many ornithischians were inset, with an overhanging maxilla and large dentary, suggesting that a cheek-like soft tissue structure might have stretched between the lower and upper jaws, and small foramina along many ornithischian jaw bone margins may be evidence of neurovascular structures that nourished cheek structures and supplied them with blood. However, a study in 2018 found that, rather than a more mammal-like arrangement of muscle fibers directed straight down from an attachment ridge on the upper jaw to the lower jaw, ornithischians probably had a forward-extending fan of muscle attached to the lower jaw at one end and the rest of the cranium at the other underneath the flaring cheek bone instead, indicating that truly muscular cheeks covering the entire extent of the back part of the mouth are unlikely. However, thinner, non-muscular cheek analogues are not ruled out for these animals. While the 2018 study is still heavily debated among paleontologists, the cheeks of the real animals would likely be thinner, pushed further back, and shaped differently than the cheeks depicted on their models in the program.
The eyes of smaller neornithischians are more pronounced than depicted in the program, instead resembling the eyes of eagles.
The body of the unidentified neornithischian is likely too thin relative to the bodies of real small neornithischians.
It is possible that small ornithopods like the unidentified neornithischian in the program may have possessed a feathery coat over at least some parts of their bodies, although this remains unconfirmed.
In the US version, the unidentified neornithischians are identified as Hypsilophodon, which actually lived in the Early Cretaceous of England, not the Late Cretaceous of North America.
Despite being known from the Hell Creek Formation, where the program takes place, the remains of Purgatorius known from this formation have more recently been dated to the Paleocene section of the formation, living less than 200,000 years after the K-PG boundary, meaning that Purgatorius may not have been present at the time during which the program is set. However, the presence of multiple species of Purgatorius so close to the K-PG boundary has been suggested to indicate that the genus might have originated during the Late Cretaceous, although more fossil material of this genus is needed to confirm its presence in the Late Cretaceous.
The program indicates that the asteroid that caused the extinction of the non-avian dinosaurs hit the planet 65.5 million years ago. However, more recent studies of potassium and uranium isotopes indicate that the asteroid actually hit the Earth around 66.043 million years ago instead.
The program seems to imply that volcanism was the main driver for non-avian dinosaur extinction, causing a decrease in diversity during the Maastrichtian which allowed the asteroid to wipe out what little remained. However, more recent research has indicated that the asteroid impact was actually the major driver of the extinction, with an analysis of the timing of volcanism in the Deccan Traps volcanic region of India in comparison to global temperature changes recorded in sedimentary rocks indicating that the main outgassing events occurred prior to the asteroid impact, with the K-PG mass extinction thus only coinciding with the asteroid's impact. This finding has continued to be debated in recent years, but it is also possible that a combination of the asteroid impact and volcanism was responsible for the extinction of the non-avian dinosaurs, with the seismic effects of the asteroid impact potentially providing further massive eruptions of the Deccan Traps.
The impact of the asteroid would have actually caused two visible flashes, one when the asteroid compressed the air around it upon entering the atmosphere and one when it actually impacted the planet, rather than the single flash depicted in the program.
The seismic activity shown in the aftermath of the asteroid impact in the program appears to be a slight tremor lasting for only a few moments. However, the asteroid impact actually resulted in a far more destructive greater than eleven Richter magnitude mega-quake occurring for several minutes soon after the impact, with the quake having far greater magnitude than any earthquake ever recorded by humanity.
The sonic boom and powerful winds following the asteroid impact are depicted as quickly following the flash of the impact in the program, when they actually took a few hours to reach the Hell Creek Formation from the Yucatan Peninsula.

The Ballad of Big Al[]

Big Al is a member of the recently described species Allosaurus jimmadseni, which lived in the Kimmeridgian, not the Tithonian.
Big Al is depicted as being 9 meters long, however, further examination of his fossils has shown he was actually 7.5 meters long when he died.
Othnielia should now be known as Nanosaurus, as more complete remains of Nanosaurus have since been found that show that Othnielia is its junior synonym.
Same issues with Ornitholestes, Diplodocus, Brachiosaurus, Stegosaurus and Anurognathus as seen above.
No definitive Allosaurus specimen has been found to be longer than 10 metres like the female shown in the film, when the other allosaurs eat the sick Diplodocus. However, there are some fragmentary remains suggesting they could have grown up to 12 metres which is slightly smaller than how the female Allosaurus is depicted as, additionally, most Allosaurus fossil specimens haven't reached skeletal maturity yet, and therefore they probably had the potential of growing to 10-13 meters in length in the oldest specimens. The so-called Saurophaganax would serve as a potential more accurate replacement, but despite the remains suggesting that Saurophaganax might have been bigger than Allosaurus, many scientists suggest instead that Saurophaganax is just a more mature Allosaurus or a different species of Allosaurus altogether. It grew bigger than 10 metres, it was closely related and it did live in the same place the show was set in, but it died out 5 million years before the time in which the program was set.

Walking with Beasts[]

New Dawn[]

The notion that mammals from the Paleocene and the early Eocene were all tiny creatures living under the oppressive domain of giant birds and other surviving archosaurs, such as the land-dwelling crocodylomorph Boverisuchus, is incorrect. We know that the first mammalian megafauna appeared a few million years after the K-Pg extinction, starting with pantodonts like Pantolambda and Bemalambda, as well as mesonychids (carnivorous ungulates) like Dissacus, all of these emerging during the early Paleocene (66-60 mya). Although birds, crocodylomorphs, turtles, and squamates were also diversifying and taking a very important part in the ecosystem, even as megafaunal creatures, the mammals took up the role of dominant land vertebrates much faster than them, and by the time of the show (49 mya) mammals were already dominating the landscape, by comparison. This however does specifically apply to Europe, where Gastornis and ratites are the largest land animals for most of the Eocene, a situation compared to Pleistocene Madagascar and its elephant birds.
Gastornis was an herbivore, in reality, lacking the hooked beak and strong, sharp talons that are characteristics of a predatory lifestyle, and calcium isotopes in the bones of specimens revealed that its dietary habits were similar to those of both herbivorous dinosaurs and mammals.
Eurotamandua is depicted as an actual tamandua, when it was a rather bizarre mammal of possible pholidotan affinities.
Ambulocetus was depicted as living in Germany, when in reality it was only found in Pakistan. However, the program does say that it might have migrated from its original home.
Ambulocetus had straight limbs, unlike the sprawled legs of the one in the program.
Ambulocetus is depicted as amphibious. However, recent research suggests that it was probably fully aquatic. However, it is likely that it would still go to land to give birth to their young. Either way, if moving on land, they would likely have moved in a clumsy fashion, like seals.
The primate Godinotia was a strepsirrhine, like a lemur, and would probably have resembled a modern lemur in life (as they are the most basal of primates) in contrast to the monkey-like reconstruction seen in the show.

Whale Killer[]

Basilosaurus swam in a serpentine way and had weak muscles so it couldn't swim fast for long.
Andrewsarchus is depicted just like a mesonychid, when it was a more entelodont-like artiodactyl in real life. However, this is a very common and big mistake as most drawings/paintings of Andrewsarchus depict it like a mesonychid. Only a few correct drawings exist. Pachyaena' was a very large mesonychid that inhabited the Eocene period in Asia, however, it lived in the Early Eocene, not in the Late Eocene like in the show (the same goes to Andrewsarchus which went extinct in the Middle Eocene). Mongolonyx was also a large mesonychid, this one lived in the Late Eocene, however it was in Mongolia, not in Pakistan, like in the show. In any case, we can agree that mesonychids were around in Asia, at the time, and probably were significant land predators in those regions.
Andrewsarchus lived about 41 million years ago, rather than 36 million years ago, when the program takes place.
Embolotherium possibly had a large, bulbous nose instead of the crest seen in the program, this is thought because of the nostril openings extending to the top of the crest, however, there is no evidence of this.
Dorudon was most likely not a social animal. However, the gatherings seen in the show might be exclusive to the breeding sanctuaries, where, outside of that circumstance, Dorudon retains a non-social lifestyle.

Land of Giants[]

Indricotherium should now be known as a synonym to Paraceratherium since the name Paraceratherium was the first name given to the animal. However, the show does refer to the animals as "indricotheres" rather than specifically stating the name Indricotherium, which, in that case, would be correct.
Although not directly stated, it is heavily implied that Paraceratherium was the largest land mammal, when in reality, Palaeoloxodon namadicus was the largest land mammal ever found.
Hyaenodon is said to have bone-crushing jaws. In real life, they were for shearing rather than crushing. It's still likely that they were capable of crushing some bone, though.
Hyaenodon had a slightly longer muzzle than is shown in the series.
Hyaenodon is said to be the size of a rhino, when in reality, the largest species, H. gigas, was more about the size of a bear.
Cynodictis is depicted walking on its toes, similar to wolves and dogs. In reality, Cynodictis walked on its feet, similar to bears and humans.
Cynodictis lived during the Late Eocene and Early Oligocene and died out by the time the program takes place. However, other species of bear dogs probably did exist during the same time and place.
Entelodon had already gone extinct 28 million years ago, rather than 25 million years ago.

Next of Kin[]

It may feel unlikely that Australopithecus afarensis could scare off large chalicotheres, unless the ones seen in the program were quite skittish in nature (something that can hardly be determined with mere fossils).
Dinofelis was actually more adapted to hunt grazing animals. However, in the show, they are shown hunting early hominids. Although not impossible, there were other felids likely more adapted to hunting hominids and their more forest-dwelling kin, such as pantherines.
The trunk of the Deinotherium is depicted as being rather short, when compared to modern elephants. Although that is suggestive that they had trouble in feeding or drinking, some interpretations favor the short-trunked interpretation, mostly due to the fact that Deinotherium diverged from modern elephants pretty early in proboscidean evolution, so structurally their trunks were possibly rather primitive and more tapir-like rather than elephant-like. The muscle attachment sites on the skull are also coherent with a more developed area around the mouth area, rather than around the nasal area, and that is suggestive of a rather more tapir-like trunk. In this interpretation, the action of eating and drinking would likely be achieved without the strong aid of the trunk, maybe developing a stance like giraffes during drinking or even entering the water sources entirely to drink, as a few animals do, including even modern elephants in the occasion.

Sabre-Tooth[]

Smilodon living in social groups is a controversial theory at best, but all experts agree that the lion pride idea is extremely unlikely, since male and female Smilodon are not known to have had sexual dimorphism, in sharp contrast to lions, where the two sexes are very differently built and also because both sexes appear to have been active hunters. It is possible that their social structure was more like that of modern-day wolves, with males and females providing a similar role in the pack order, if they were indeed social.
This program displays the now outdated hypothesis that North American carnivores like Smilodon outcompeted native South American carnivores like terror birds and sparassodonts. In reality, all of these species became extinct over one million years before carnivorans (barring procyonids, which were already present in the Miocene as bear-like omnivores) arrived, and Titanis at least co-existed with North American carnivores for two million years.
When the brothers take over the pride after they killed the cubs, they should've also kicked out the younger females, since they weren't old enough to breed and were other mouths to feed.
Macrauchenia is shown to be very nimble and deer-like, when it was actually more heavily built like a camel. It also probably had a shorter trunk than what is shown in the film. It would most likely either have had a trunk like those of Saiga antelope or not have had a trunk at all, but rather a moose-like snout.
Smilodon is currently thought to be a bulky predator that was built to ambush and wrestle its prey to the ground, and was ill-equipped for high-speed chases and quick, sharp turns like modern big cats, so the Macrauchenia chase scene is inaccurate.
Phorusrhacos probably did not have wing claws just like the seriema, its closest living relative.
Phorusrhacos was probably stockier and had a shorter neck than is shown in the series, and the most currently accepted estimates give it a height of just 1.6 meters tall.
Phorusrhacos lived in the Miocene, from 20-13 million year ago, not in the Pleistocene a mere 1 million years ago. Psilopterus material has been attributed to the Pleistocene, but the validity of this dating is dubious and hard to ascertain. Psilopterus was also too small to be a feasible replacement to the Phorusrhacos in the program. Titanis has also been attributed to Pleistocene strata and was big enough to fit a similar role to the terror birds from the program. However, the exact dating of the known material is inconclusive on whether or not it would have been found in the Pleistocene, and, if so, it would probably only live in the earliest stages of the epoch. Titanis also lived in North America instead of South America.
There is no evidence that Megatherium ate carrion to supplement its diet, but it is far from impossible, as some herbivores today have been recorded eating meat and some paleontologists do believe Megatherium was partly carnivorous, though that carnivory claim has little basis to it, given carbon isotope analysis strongly suggest Megatherium was a obligate herbivore. That said, it's not impossible that meat-eating was a very occasional behaviour to gain extra nutrients in their diet, as observed in other herbivores, including modern day sloths. To corroborate this idea, a study from 2021 found evidence for omnivory in Mylodon, another type of ground sloth, so it's possible that Megatherium ate meat on occasion too.

Mammoth Journey[]

Male Woolly Mammoth skulls did not have tusks that curve over another. Only Columbian mammoths are known to have this feature. However, this feature may have been rarely possible in some individuals.
The Neanderthal may not have been the last survivor of the genus Homo, besides humans: the Denisovans, may have went extinct around the same time as Neanderthals or long after.
The Cave Lion's model is reused from that of the Smilodon, minus the sabres. Cave paintings reveal that the real animal actually had much longer, tufted tails, a primitive to nonexistent mane, and bright yellow fur instead of white. It would've been a larger and whiter version of the modern lion.
The Neanderthal species had died out 40,000 years ago, 10,000 years before the time that the program takes place.

Walking with Cavemen[]

Lucy was not killed by being hit with a stick. It's been determined that she probably died from falling out of a tree. However, the reasons for the fall may still be uncertain.
During a brief moment when going underwater, a Basilosaurus can be seen. However, it says that this is happening during 8 million years ago, whereas Basilosaurus only lived until 36 million years ago. However, it is possible that this creature was supposed to represent another extinct whale species.
Homo naledi has been believed to have been a possible ancestor of our species instead of Homo habilis, when it was initially described. However H. naledi was described in 2015, more than a decade after Walking with Cavemen aired, so they could not have known about this species. However, this conclusion has since been proven unlikely, because it was since determined that Homo naledi lived from 335 to 236 thousand years B.C., which means they were too young to be our ancestors. Homo habilis is more primitive and probably evolved to Homo sapiens and Homo naledi separately.
Some paleoanthropologists do not recognize Homo ergaster and Homo erectus as separate species. Even if they were separate, some believe H. erectus did survive and evolved into the highly controversial Homo floresiensis. Currently, Homo ergaster is still a valid species, as well as Homo erectus, and further research is required to reach a conclusion to this systematic problem. The consensus does support Homo ergaster and Homo erectus as different species, with Homo floresiensis possibly being a much earlier offshoot.
Some paleoanthropologists believe the African Homo heidelbergensis is merely an archaic form of modern humans. However, this is debated and may not be true, as phylogenetic evidence seems to support a more Neanderthal affinity to the Heidelberg men.

Walking with Monsters[]

Water Dwellers[]

The species of long-tailed Anomalocaris from Cambrian Stage 3 Chengjiang, didn't reach 2 metres long, and that is even not being actual Anomalocaris. This appearance is based on specimen ELRC 20001. In 1995, it was described as a whole specimen of a new Anomalocaris species, "Anomalocaris saron". However, Anomalocaris saron is now thought not to actually belong to the genus Anomalocaris, and in 2021 got its own genus, Houcaris. ELRC 20001 was unrelated to Houcaris and got its own genus and species in 2022, Innovatiocaris maotianshanensis. The total length of Innovatiocaris is 15 cm, or only 7 cm without the tail. The frontal appendage of Houcaris is much larger, and the body length not including the tail may have exceeded 50 cm, however as mentioned above, Houcaris and Innovatiocaris are unrelated, and since Houcaris is known only from its frontal appendage, body shape of Houcaris is completely unknown. In fact, no species of Anomalocaris got that big. The closest was a larger species from the later Burgess Shale in British Columbia, Anomalocaris canadensis, which was about 40 cm long (including appendages about 65 cm long). An unnamed species of Anomalocaris close to A. canadensis (JS-1880) is known from Chenjiang, however it was much smaller than A. canadensis in Burgess.
"Anomalocaris" saron didn't feed on trilobites, rather more soft-bodied creatures.
"Anomalocaris" saron wasn't the first-ever apex predator, nor was it the apex predator of its time and place. The larger Omnidens, estimated to be 1.5 metres in length based on its mouthparts, was probably the largest Cambrian animal known, although its ecology was pretty different. While Anomalocaris was a nektonic predator, Omnidens was most likely a benthic predator if it has a similar anatomy to Pambdelurion. Anomalocaris canadensis, however, was the apex predator of the later Burgess Shale from the Miaolingian, though it did not surpass Omnidens in size.
In the confrontation between two Anomalocaris, the loser supposedly gets wounded by having its rigid armor split. However, this was based on a now invalid theory, and it is now known that the only relevant armor on the animal was the tripartite carapace on the head. The cuticle of Anomalocaris is sometimes believed to have been soft and flexible.
The Silurian segment of the program actually doesn't take place in the Silurian. The segment's setting is 418 million years ago in the Early Devonian, while the Silurian actually lasted from 443.8–419.2 million years ago.
Brontoscorpio was found in England, not Wales. However, given the geographical proximity of the two places (even during the Silurian) it's still considerable that Brontoscorpio inhabited Wales.
Brontoscorpio may have actually molted underwater due to its size.
Pterygotus was not the largest arthropod of all time, nor did it reach the sizes mentioned. However, the true holder of the title, Jaekelopterus rhenaniae, could attain closer proportions. It was once regarded as possible that the two genera could be lumped, but that hypothesis was long disregarded even before the program's release.
According to the program, scorpions like Brontoscorpio "have no memory at all". However, this may not be true, as most animals have at least some memory.
Cephalaspis was not ancestral to tetrapods. At the Late Silurian, the most likely replacement would be the already fully jawed Psarolepis.
In the Devonian segment, angelfish can be spotted. One can be seen in the background both when the segment starts and when the Hynerpeton is chased by the Stethacanthus. However, there were no teleosts in the Paleozoic era, much less in the Devonian. However it is still possible to be a primitive actinopterin, a clade of bony fish that includes (beyond teleosts) the holostei and the chondrostei (the latter already present at the Devonian). However, the fish appearing in the shots were likely a mistake.
Stethacanthus was likely an ocean-going animal and it wasn't a true shark.
Hyneria was smaller than depicted in the program, attaining lengths of 2.5-3.7 metres, as opposed to 5 metres.

Reptile's Beginnings[]

The Mesothelae spider in the program was based on Megarachne, which during the show's production was thought to be the largest spider ever to live. However, as production was wrapping up, another specimen of Megarachne was discovered that led to the realization that it was actually a eurypterid, leading to the animal in the program being referred to as a speculative species of giant mesothelae spider (an actual group of extant spiders that existed back in the Carboniferous, but its members only vaguely resembled the one from the program and were nowhere near as large).
Proterogyrinus was not an amphibian, though it may have lived an amphibious lifestyle. It was possibly a reptiliomorph.
There is no evidence suggesting that Arthropleura had powerful jaws, given the fact that its mouthparts have never been preserved along with the rest of the animal.
Arthropleura is now known to be a true millipede rather than a distant relative of them.
Arthropleura's ability to rear up is purely speculative, and it might not have been possible in real life.
Petrolacosaurus is incorrectly shown evolving into the synapsid Edaphosaurus, when in fact, it was an early diapsid, and could therefore not have been the ancestor of any synapsids. The most basal synapsid, Protoclepsydrops, would have been a more suitable candidate. However Edaphosaurus were already present 300 million years ago, so their ancestors would still be Edaphosaurus.
The Dimetrodon hatchlings are shown with their back sails fully erect, when they probably wouldn't have grown them yet.
The skin texture of Edaphosaurus and Dimetrodon may be slightly off. It is hypothesized they had scutes on their skin, similar but different to the ones on crocodilians. It's possible they lacked the scales of lepidosaurian reptiles.
There is no evidence that Dimetrodon were cannibals, however, this is not impossible.
There is no evidence that Dimetrodon eggs would take 7 months to hatch, but we do not have any information on Dimetrodon reproduction whatsoever, so any reconstruction of their reproductive habits will always be speculative until potential future discoveries prove otherwise.
Dimetrodon is depicted as living in a desert-like environment, when in fact, Dimetrodon is known to have lived in a swamp-like environment. However, it is still possible that some populations lived in slightly more arid environments than the average.
The tops of some Dimetrodon's neural spines could have been exposed bone rather than covered with a full sail, though that is debated.
In the programme, Dimetrodon and Edaphosaurus are described as "mammal-like reptiles". However, they were not reptiles, as synapsids form a distinct clade within Amniota, which also contains "reptiles".

Clash of Titans[]

Gorgonops and Rhinesuchus are only known from South Africa, yet in Clash of Titans, they are portrayed living with Scutosaurus, which was only found in Siberia. However, the gorgonopsid featured in the program was more likely an Inostrancevia, as it lived at the same time and place as Scutosaurus. Moreover, although the Rhinesuchus in the program is only referred to as a labyrinthodont, a rather wide-ranging term that has been traditionally used to describe more primitive amphibian or amphibian-like tetrapodomorphs, including ichthyostegalians, temnospondyls, etc., the term labyrinthodont has since been disused, as it is ultimately nearly synonymous with the Stegocephalia clade as a whole, and conveniently removes amniotes, lissamphibians, and lepospondyls out of its definition. A more accurate replacement for it could be Konzhukovia, which lived in Russia at the same time in which the first part of the program was set and was a labyrinthodont just like Rhinesuchus.
It is possible that gorgonopsids had hair. However, correlations with the MSX2, a gene that is believed to be correlated with the manifestation of the parietal foramen and the distribution of hair in mammals, has been used to determine which extinct synapsids might have been covered in hair. According to studies done in regards to the manifestation of this gene, the mutations that activate the formation of parietal foramen, may be accompanied by the loss of extensive hair distribution, and that correlation has been made in extinct synapsids. Gorgonopsids, therocephalians, and non-probainognathian cynodonts (which include Thrinaxodon and cynognathians) had parietal foramen, suggesting they didn't have an extensive hairy integument.
Euparkeria is not an ancestor of the dinosaurs due to it being more basal than the crocodilian-dinosaur split. Probably the most likely ancestor of the dinosaurs at the time would be a basal dinosauromorph, likely quadrupedal.
The therocephalians featured in the program, Euchambersia, would already be extinct 248 million years ago. They lived from 256-252 million years ago A possible replacement would be Moschorhinus, which survived into the Early Triassic.
Euparkeria, Euchambersia and Proterosuchus never lived in Antarctica, but instead lived in South Africa, which was, nevertheless, geographically close to Antarctica.
Proterosuchus was not the ancestor of crocodilians due to it being more basal than the crocodilian-dinosaur split.

Chased by Dinosaurs[]

The Giant Claw[]

The program is set 75 MYA in the Nemegt Formation, but more recent studies favor an age of 70 MYA for the formation.
Velociraptor may not have lived in heavily forested areas. All of the sites where Velociraptor fossils were found suggest that the animal lived in arid environments with many sand dunes (with one specimen apparently being smothered to death by a sand dune). However, knowing that there were two distinct species of Velociraptor, and that they were formidable and adaptable predators, it's still possible that some populations hunted in forested areas, although this can't be currently confirmed.
Velociraptor in the show lacks feathers. All Dromaeosaurids/Raptors had pennaceous feathers running from head to tail. It even had them on its arms making them resemble wings.
Velociraptor's claw could not disembowel prey because the underside was round therefore the claw was used for stabbing and for immobilizing prey.
Despite living in Mongolia, Velociraptor did not live in the Nemegt Formation. A replacement would be another dromaeosaurid called Adasaurus which lived there and was a velociraptorine just like Velociraptor itself. There are also other indeterminate dromaeosaurid fossils found in the formation.
Velociraptor was actually a nocturnal animal, so it would have likely hunted at night, not at daytime as shown in the program.
The arms of the Tarbosaurus should be facing inwards not downwards. Its head is also slightly off.
Tarbosaurus was depicted as being smaller than Therizinosaurus, when in reality it was larger than it.
Saurolophus and hadrosaurs, in general, didn't have thumb spikes like their ancient Iguanodon relatives.
Therizinosaurus was depicted featherless. Therizinosaurs are known to have had feathers, though.
It is now known that the frill bones of Protoceratops increased in length and width during the ontogeny of the animal and that the growth of the frill was greater than than the overall growth of the animal.
It is believed that Protoceratops most likely used its frill for sexual and dominance signaling.
Mononykus should have had more feathers, when taking into account its phylogenetic position. However, the shape of the feathers depicted in the program seems unlikely, as they would likely be more hair or string-like in appearance.
Mononykus was too large compared to the real animal. Few alvarezsaurs reached or surpassed that size, with one example being Bonapartenykus.
Azhdarcho is portrayed living during the Campanian 75 million years ago in the Nemegt Formation of Mongolia, when in reality it lived in the Turonian Bissekty Formation of Uzbekistan 92 million years ago. However, the pterosaur in the program could have actually been a yet-to-be-named azhdarchid found in the Nemegt Formation often dubbed the Mongol Giant.

Land of Giants[]

Giganotosaurus was depicted on the show as the largest carnivorous dinosaur, though current size estimates favor Spinosaurus as the largest carnivorous dinosaur. However, it is true that Giganotosaurus was one of the largest land-dwelling carnivorous dinosaurs that ever existed, as Spinosaurus was semi-aquatic. Tyrannosaurus might have been heavier than Giganotosaurus however, despite the latter winning in length.
When the documentary was being made, the fossils of Mapusaurus had been dug and were kept in storage. It was thought that those fossils belonged to Giganotosaurus carolinii, however, after they were studied, they were classified as Mapusaurus which could, in the future turn out to be synonymous with Giganotosaurus, though that is disputed.
Giganotosaurus never coexisted with Argentinosaurus. Mapusaurus coexisted with Argentinosaurus however, as Argentinosaurus was found in the Huincul Formation, while Giganotosaurus was found in the Candeleros Formation. There was a titanosaur in the Candeleros Formation called Andesaurus that would have coexisted with Giganotosaurus.
Nigel claims that Giganotosaurus weighed " 2 tons more than T.rex". In real life that is hard to ascertain. Giganotosaurus's weight has been estimated to have been around 8 tonnes, more or less around the same as Tyrannosaurus. The fact that the two carnivorous dinosaurs were at around the same length and that precise mass estimates are complicated to obtain in these extinct taxa, it is hard to ascertain which of the two would exactly be the biggest.
Argentinosaurus is said to have been the biggest dinosaur. Though that title is contested, due to the fragmentary nature of several sauropods. Maraapunisaurus might have been the biggest one.
Argentinosaurus's neck was probably held more vertical than horizontal.
Argentinosaurus's body shape is largely based on Saltasaurus, like most titanosaurs were in the past. However, newer studies show that Saltasaurus had very different proportions from most titanosaurs.
Pteranodon didn't live in South America. It was endemic only to North America, and it lived 86,000,000-84,500,000 BCE, not 100,000,000 BCE (anhanguerids would have been possible replacements). Ornithocheiromorphs and azhdarchoids were pretty common at the time, however.
Tropeognathus (called Ornithocheirus in this program) was found in Brazil, not Argentina. However, the likelihood that pterosaurs were migrating creatures would make sense for these animals to, hypothetically, find their way into other regions of the globe, and given the geographical distance between Brazil and Argentina, it is not too far fetched.
Same issues with Tropeognathus as in Giant of the Skies.
Pteranodon should have had pycnofibers (fuzz) on its body.
Male Pteranodon may have had a more vividly colored crest to attract females. The beak of Pteranodon is also known to have curved slightly upwards.
Sarcosuchus would never have encountered many of the animals in the program, as it lived 133 to 112 million years ago, in comparison to the program's setting of 100 million years ago, and lived in a different region of South America, Brazil. However, it is still possible that other crocodylomorphs existed at the time and place of the show.

Sea Monsters[]

Intro[]

Same issues with Velociraptor as seen above.
Velociraptor and Tarbosaurus were unlikely to live so close to the sea, but it is possible that the featured animals were just close relatives of these animals or a determined population of the said species that lived close to the sea.
Same issues with the Tarbosaurus as seen above.

Ordovician[]

Some "Sea scorpions" could go on land only for short intervals, and eat washed-up carcasses.
Orthocones most likely swam with the shell upright. Although The Complete Guide to Prehistoric Life classifies this animal as Cameroceras, the largest known orthocone is actually Endoceras giganteum which had around 5.7 m long shell.
Mild time map issues, see below.

Devonian[]

Dunkleosteus is stated to have reached lengths of 10 meters. However, the largest species, D. terrelli, is estimated at slightly lower lengths of between 4 and 8.79 meters.

Triassic[]

Tanystropheus was an archosauromorph, and there is no phylogenetic evidence to support it would shed their tails like lizards. However, taking into account several species of sauropsids practiced tail autotomy, and that the extant archosauromorph diversity is very limiting, in comparison to the wide variety of extinct ones, back in the Triassic, for example, it is not completely unreasonable to speculate that some primitive archosauromorphs could have practiced tail autotomy.
Cymbospondylus is depicted as a predator of marine reptiles. However, its teeth were small and conical, likely meaning that it ate small fish and cephalopods. A possible replacement would be Thalattoarchon, an ichthyosaur that looked very similar to Cymbospondylus, but was known to have eaten other marine reptiles. However, it was only discovered after the show had aired. Moreover, Thalattoarchon didn't live in the late Triassic, while Cymbospondylus did, and with the latter's huge size, it is still possible that it hunted small prey (including very small marine reptiles like pachypleurosaurs).
Coelurosaurs didn’t even exist until the Mid-Jurassic and possibly as far back as the Early-Jurassic, not the Mid-Triassic.

Jurassic[]

Leedsichthys size is grossly exaggerated. In reality, it was 8–17 m rather than the 27 m in the show.
Leedsichthys had a smoother, more elongated head than in the show.
Same issues with Liopleurodon as in Cruel Sea. (see above)

Cretaceous[]

Pteranodon were diving creatures that hunted fish similar to gannets, unlike the skim feeders they were portrayed as in the program.
Same other errors with Pteranodon as in Chased by Dinosaurs
Tyrannosaurus did not live 75,000,000 BCE. Probably the dinosaur featured in the show was actually Daspletosaurus.
Mosasaurs, like Tylosaurus and Halisaurus, and plesiosaurs, like Elasmosaurus, are believed to have had more pronounced tail flukes instead of lizard-like tails.
Tylosaurus was 14 m long, not 17 m long.
A recent study on mosasaurs has concluded that they were likely mainly black or dark in color, with a more whitish underbelly, not brown like the series' depiction of the animal.
There is no certain evidence that mosasaurs like Tylosaurus lived in large family groups. Although, it is still possible that they gathered in large groups (not necessarily family groups), like many snakes, their closest living relatives (i.e. garter snakes).

Eocene[]

Arsinoitherium probably did not have a trunk.
Basilosaurus ability to "sing" is quite inaccurate. It and other early whales lacked the melon organ that modern whales have that is used for this action. However, Basilosaurus possibly could still produce vocalizations, however not through the melon organ.
Same issues with Dorudon as in Whale Killer. (see above)
Basilosaurus and other early whales had slightly twisted snouts.

Pliocene[]

Megalodon was depicted a little bit too similar to modern-day great whites. Though scientists suggest that Megalodon did look like a stockier version of the great white. The true shape of Megalodon has been under constant debate even to this day.

Time map[]

Creatures have the same issues as described in their respective sections. (See above)
Time periods of planet earth go much farther back than the Ordovician, but this was probably a design choice, as Nigel didn't go any farther back than this, and the time map would be significantly longer, if so.
Basilosaurus should be a bit further back in the timeline.
The Cenozoic section should be a bit bigger.

Walking With Dinosaurs: The Arena Spectacular[]

All the theropods are incorrectly shown with pronated (downward-facing) wrists, even in the show's later reruns.
The adult Plateosaurus is depicted as fully quadrupedal and its young are shown as obligate bipeds, when, in reality, it was actually the other way around.
In later reruns, Liliensternus has been given a layer of speculative feathers on its head and neck, although no evidence suggests this. However, this is not implausible speculation.
The guide states that Liliensternus had five fingers. The model used for Liliensternus actually has only four fingers, just like its real counterpart.
Also in the guide, Allosaurus is once referred to as Albosaurus.
In the show, Allosaurus is claimed to be directly descended from Liliensternus, when, in reality, both theropods were not closely related, asAllosaurus was a carnosaur while Liliensternus was a coelophysoid.
The show's Brachiosaurus are actually based on the African Giraffatitan and should have a less pronounced nasal crest.
The nostrils on the Brachiosaurus should be placed on the snout rather than the forehead.
Ornithocheirus likely did not migrate to North America.
In earlier reruns of the show, Utahraptor was depicted without any feathers. This was fixed in later runs with the addition of feathers on its head, tail, and parts of the arms. However, the real animal was actually fully feathered.
Like the Utahraptor mentioned above, Tyrannosaurus was depicted without any speculative feathers in the earlier runs of the show, but this was fixed in the later shows, with a thicker layer of feathers for the young individual and a light amount of feathering on the adult's head and neck areas.
The Ankylosaurus featured in the show shares the same inaccuracies as the one from the original documentary, such as being taller and bulkier than the real animal.

Walking with Dinosaurs: Inside Their World[]

The theropods featured in the app have pronated hands, which isn't scientifically plausible
Gallimimus is shown with only a few quills when it would have been covered in feathers in reality.
Psittacosaurus is depicted as a quadrupedal animal, unlike the real animal, which was bipedal.
Psittacosaurus, according to a study in 2016, had a series of brown colors to camouflage and had a membrane on its hind legs. However, the specimen containing the fossilized melanosomes is only assigned to an unknown species of the genus (P. sp.), meaning that it is possible that the coloration seen in the app was present in life. In addition, these discoveries were made after the app's release.
Some specimens of Microraptor and Archaeopteryx possess fossilized melanosomes that show that they were black or iridescent black in color. However, the specimens containing these melanosomes are only assigned to unknown species of both genera (A. sp. and M. sp.), meaning that it is possible that the coloration seen in the app was present in life.
Spinosaurus didn't have the jaw strength or neck muscles to lift up and throw an adult Suchomimus.
Spinosaurus and Suchomimus never coexisted, as they lived in different regions and at different times.
Spinosaurus had shorter hind legs, unlike the long-limbed one seen in the app. Its hallux should also be touching the ground, and its toes might have been webbed. However, these conclusions were made with subsequent discoveries made after the app's release.

Walking with Dinosaurs: The Movie[]

The Gorgosaurus shown in the movie should now be known as Nanuqsaurus, as analysis of the Alaskan Gorgosaurus remains suggest they belong to this new tyrannosaurid genus.
The design of the horns of Pachyrhinosaurus are based on Pachyrhinosaurus lakustai, but the actual Alaskan species is Pachyrhinosaurus perotorum, while Pachyrhinosaurus lakustai was native to Canada.
The Edmontosaurus shown in the movie has since been often classified as Ugrunaaluk, as analysis of the Alaskan Edmontosaurus remains supported their referral to a separate genus. However, this classification is still debated, now with a considerable amount of paleontologists believing that Ugrunaaluk is indeed a synonym of Edmontosaurus, which seems to be a proper conclusion.
Edmontosaurus regalis had a fleshy crest, however, it may have only been present in this species as opposed to all Edmontosaurus species. For example, Edmontosaurus annectens specimens have been found with extensive skin impressions, with none seeming to support the presence of such a crest.
Quetzalcoatlus had a bigger head and longer neck.
Quetzalcoatlus was not native to Alaska, with it only being known from the western United States. A possible replacement would be Cryodrakon, even though fossils of this genus have only been found in Alberta, Canada.
Alexornis was native to Baja California, Mexico, not Alaska. However, considering that he is meant to be some spiritual narrator that also takes the form of a rook (which is also not native to Alaska), this is somewhat excusable.
Alexornis should have feathery owl-like feet with (possibly) Microraptor-like hind-wings, fused wing fingers (as opposed to three separated clawed fingers), and more of an actual snout with teeth that are not exposed.
Chirostenotes fossils have only been found in Canada, not Alaska. However, it isn't too unlikely that some populations made their way to Alaska.
When Scowler defeats Patchi and abandons him, the sun sets and rises like a normal day further south. This contradicts the previously shown polar summer and winter cycle, unless Patchi was somehow trapped all winter, though he probably should've starved to death if that was the case.
It is very possible that Gorgosaurus possessed feathers.
The movie continuously mocks the tiny arms of the Gorgosaurus. However, despite their small size, tyrannosaur arms were indeed quite powerful.
Gorgosaurus lived in Canada, rather than the film's location.

Walking with Dinosaurs: Prehistoric Planet 3D[]

Same issues with Pachyrhinosaurus, Edmontosaurus, Chirostenotes, Alexornis, and Quetzalcoatlus as seen above. However, since Alexornis is never referred to by name, it is possible that it could be a different species of avialan.
Minus the location issue, Nanuqsaurus has the same errors as Gorgosaurus, with an additional one; it is slightly oversized. However, the holotype specimen might represent a subadult.
The same polar winter error from above.

Wonderbook: Walking with Dinosaurs[]

The Great Exodus[]

Same issues with Pachyrhinosaurus, Edmontosaurus, Nanuqsaurus, and Alexornis, as seen above.
The head of Edmontosaurus would not have resembled that of Maiasaura.
Pentaceratops lived in New Mexico, not Alaska.
Deinosuchus lived in Texas, not Alaska.
Adult Patchi and Juniper look the same as when they were juveniles, when they would have bigger more pronounced frills and horns.

March of the Titans[]

Pterodaustro lived before Argentinosaurus and Mapusaurus.
Pterodaustro did not prey on hatching Argentinosaurus and would have been a filter feeder instead.
Only the female Pterodaustro is shown as being pink when both genders would have been pink in reality.

Terror in the Swamp[]

A Pachyrhinosaurus skeleton is briefly seen, though this genus didn't live in the Jurassic.

Impenetrable Fortress[]

Tarchia would not have resembled Euoplocephalus.
Rose is briefly seen running when Ankylosaurs were too heavy to run.

King of Dragons[]

Alexornis did not live in Hell Creek.
Pachycephalosaurus could not headbutt a Tyrannosaurus and make it fall over.

List of scientific errors

Walking with Dinosaurs Pilot[]

Walking with Dinosaurs[]

New Blood[]

Time of the Titans[]

Cruel Sea[]

Giant of the Skies[]

Spirits of the Ice Forest[]

Death of a Dynasty[]

The Ballad of Big Al[]

Walking with Beasts[]

New Dawn[]

Whale Killer[]

Land of Giants[]

Next of Kin[]

Sabre-Tooth[]

Mammoth Journey[]

Walking with Cavemen[]

Walking with Monsters[]

Water Dwellers[]

Reptile's Beginnings[]

Clash of Titans[]

Chased by Dinosaurs[]

The Giant Claw[]

Land of Giants[]

Sea Monsters[]

Intro[]

Ordovician[]

Devonian[]

Triassic[]

Jurassic[]

Cretaceous[]

Eocene[]

Pliocene[]

Time map[]

Walking With Dinosaurs: The Arena Spectacular[]

Walking with Dinosaurs: Inside Their World[]

Walking with Dinosaurs: The Movie[]

Walking with Dinosaurs: Prehistoric Planet 3D[]

Wonderbook: Walking with Dinosaurs[]

The Great Exodus[]

March of the Titans[]

Terror in the Swamp[]

Impenetrable Fortress[]

King of Dragons[]

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