This article is currently under construction by a user. To avoid edit clashes, please do not edit until this template has been removed.
This article is not part of the Walking with... universe.
This article covers a subject that is part of the real world, and thus should not be taken as a part of the Walking with... universe.
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.
The theropods featured in the app have pronated hands, which isn't scientifically possible
The ceratopsians featured in the app lacked quills protruding from their backs, despite evidence for these structures being found on the basal ceratopsid Psittacosaurus and the more advanced ceratopsid Triceratops.
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 probably didn't have the jaw strength or neck muscles to lift up and throw an adult Suchomimus.
Spinosaurus and Suchomimus likely never coexisted, as they lived in different parts of Africa (Egypt and Niger respectively), although they did live at the same time.
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 were most likely webbed. However, these discoveries were made after the app's release.
There is no conclusive evidence that Coelophysis was cannibalistic. This was based on a fossil of Coelophysis with jumbled up bones in its stomach cavity, but these turned out to be species of small crocodylomorphs, rather than the juveniles they were long mistaken to be. However, this was discovered after the release of this episode, and it is not implausible, given that cannibalism is not rare in theropods.
Coelophysis may have had feathers, but this is still highly debated.
The hands of the Coelophysis should not be pronated.
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 episode are depicted with identical body proportions.
Coelophysis lived from 216,000,000 BCE to 196,000,000 BCE, not 220,000,000 BCE.
Placerias were probably not hippo-like in behavior.
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.
Placerias may have had some hair coverage on their bodies, though this is still debated.
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.
Placerias is called a reptile in the program, when it is 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.
Postosuchus is now known not to 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 lived 251,000,000 BCE to 247,000,000 BCE, not 220,000,000 BCE and 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, Boreogomphodon and Oligokyphus, lived 220,000,000 BCE in what is now North America, but these species were most likely all herbivores, and don't match the morphology of the cynodont seen in the episode.
Plateosaurus couldn't move in a quadrupedal stance, and was an obligate biped. However, this discovery was made after the release of this episode.
Plateosaurus lived in Europe, not North America, and despite the continents all being connected, it most likely wouldn't have traveled such long distances.
Plateosaurus lived 214,000,000 BCE to 204,000,000 BCE, not 220,000,000 BCE.
Peteinosaurus lived in Europe, not North America, and despite the continents all being connected and the episode stating that it is "an exotic hunter from far and wide," it most likely wouldn't have 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, and lived around 210-201 million years ago, after the setting of the episode.
The head of the Peteinosaurus is a little bit smaller than it would have been in life. In addition, its wingtips are pointed instead of rounded like they would be in real life.
Although pycnofibers are present on the Peteinosaurus animatronic, they would 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 backwards.
Diplodocus held its neck in a slightly higher position than shown in the series, though this discovery came after the episode was made.
There is no evidence for an ovipositor in Diplodocus. It was pure speculation by the creators of the series, who based it off 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 of the nest.
Diplodocus could not reach adulthood in only a decade. The average amount of time it would take for Diplodocus to reach full size was forty years.
Sauropods like Diplodocus had more soft tissue around their necks, but this was discovered after the episode was released.
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 semi-circle, 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. It was thought to have during the production of the show, however, due to the holotype specimen having a broken nose.
Ornitholestes almost certainly was covered in feathers, which did appear in the companion book.
Ornitholestes lived 154,000,000 BCE, not 152,000,000 BCE.
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 model.
Ornitholestes and Allosaurus could not pronate their hands.
Anurognathus were micro nightjar-like insectivores, and probably did not behave like modern oxpeckers. Its anatomy is also very inconsistent with the real animal, with a typically elongated neck, deep skull, small wings with pointed tips that fold in from the sides, and a too thin coat of pycnofibers with no "whiskers" around the mouth.
Anurognathus lived 150,000,000 BCE, not 152,000,000 BCE, and wasn't found in North America, only in Germany, although there are other types of pterosaurs 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 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. These errors were mostly corrected in The Ballad of Big Al.
Allosaurus may have been a solitary hunter as opposed to the hunting pairs seen in the episode, but this is still debated.
The Brachiosaurus model is based on Giraffititan, which at the time was 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, which may have also sprawled slightly to the sides.
Brachiosaurus lived from 154,000,000 BCE to 153,000,000 BCE, not 152,000,000 BCE.
Brachiosaurus weighed between 28 and 60 tons, not 70 tons as mentioned in the program.
The raised bump on the head of the Brachiosaurus model is somewhat thin. In reality, the bump would have had more soft tissue around it.
Brachiosaurus is stated to be "the largest land animals that have ever existed," and it is later suggested that "life would never again be this large." However, several titanosaur species in the Cretaceous reached even larger dimensions than those of Brachiosaurus.
Stegosaurus could not change the colors of its plates by flushing blood into them, as preserved integument impressions of Hesperosaurus have shown stegosaur plates were covered in a horny sheath, not skin.
The scales of Stegosaurus were polygonal in shape with large oval tubicles interrupting them. These tubicles 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 episode 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.
While dung beetles did evolve to feed off of the dung of dinosaurs, they didn't evolve until the Early Cretaceous.
The environment of the episode is depicted as forested with some plains, while the actual environment of the Morrison Formation was far more arid. However, this does not mean that the type of environment depicted in the episode did not exist in the formation.
Ophthalmosaurus is not known to have migrated towards coasts to give birth, although this is still disputed, as large groups of female ichthyosaurs with their young still inside of them or in the process of being born have been found in multiple localities in Germany, suggesting that they may have gathered in one location to breed.
Ophthalmosaurus lived from 165,000,000 BCE to 160,000,000 BCE, and was already extinct by 149,000,000 BCE.
A study of a few ichthyosaurs, Tylosaurus, and an extinct sea turtle indicates that ichthyosaurs were mostly black or dark in color, although a more recent study of the ichthyosaur Stenopterygius does suggest that at least some ichthyosaurs may have possessed countershading colors. This doesn't mean that they were completely black, or that other non-detected colors weren't there. It also doesn't directly involve Ophthalmosaurus, which is already depicted with a somewhat dark color in the episode. In addition, this discovery came long after the series was made.
The narration in the episode states that Ophthalmosaurus possessed "long, toothless snouts." However, analysis of fully grown Ophthalmosaurus specimens shows that they did possess some small teeth. Interestingly, these teeth are present in the Ophthalmosaurus model used in the episode, meaning that this error was likely the result of a narration mistake.
Liopleurodon wasn't even half as big as it was in the show. It wasn't 25 meters long and 150 tonnes, but around 6–10 meters long and 2-3 tons, about the size of an orca. This gargantuan size comes from very fragmentary remains of which the 20-meter measurement given has been considered dubious, and it is unlikely that these remains belonged to Liopleurodon.
This may have been lamp-shaded in-universe, as according to the narrator, the size of the male was "...big even for his kind. His size means he is probably over 100 years old."
Liopleurodon lived from 160,000,000 BCE to 155,000,000 BCE, and was extinct by 149,000,000 BCE. A possible replacement would be the larger Pliosaurus, which lived at the time.
There is slight shrinkwrapping on the heads of the Liopleurodon and the Eustreptospondylus. In reality, the skull openings would not be externally visible.
Long-necked plesiosaurs and short-necked pliosaurs such as Cryptoclidus and Liopluerodon respectively are now thought to have flukes on their tails, not smooth lizard-like tails like in the series. However, the specimens that possess the flukes on their tails 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 it would be more of the equivalent of a whale or shark going on land: it would be beached and dead.
Cryptoclidus did not get as big as 8 tons. It probably only weighed around 1 ton.
Cryptoclidus lived from 166,000,000 BCE to 164,000,000 BCE, not 149,000,000 BCE. A possible replacement would be Colymbosaurus or Kimmerosaurus, which lived at the time.
The head of the Cryptoclidus seen in the episode is slightly too large compared to the rest of its body.
Rhamphorhynchus lacks many skeletal features required for a skim-feeder, therefore it probably didn't fish that way; it most likely dove underwater.
Rhamphorhynchus had a shorter, thicker neck and longer wings that folded in from behind when walking and had more rounded wingtips.
Rhamphorhynchus, like all pterosaurs, is believed to have possessed skin covered in a coat of pycnofibers through most of its body, a feature not present in the reconstruction of the species seen in the episode.
The tail vanes of the Rhamphorhynchus seen in the episode should be slightly more asymmetrical.
The tips of the jaws of the Rhamphorhynchus seen in the episode seem to be hard, keratinized structures, when in reality the tips were soft tissue structures.
Eustreptospondylus lived 162,000,000 BCE, not 149,000,000 BCE. A possible replacement would be the recently discovered Juratyrant, which was a five-meter-long relative of the Cretaceous Tyrannosaurus.
The head design of the Eustreptospondylus is inaccurate; the head is far too short and wide, there are crests present above the eyes, which the real animal lacked, and the snout is straight at the end, whereas the snout had a slight downturning in the real animal.
Eustreptospondylus could not pronate its hands.
The Eustreptospondylus seen in the episode 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 episode.
Modern sea turtles hadn't evolved yet. They evolved in the Early Cretaceous. However, the species shown in the show could be an unrelated species of sea turtle, like Plesiochelys. This one wasn't related to the modern sea turtle lineage, belonging to a completely different extinct lineage of saltwater turtles, that lived in the late Jurassic.
The episode is set in the Oxford Clay, a formation which dates from 166,000,000 BCE to 157,000,000 BCE, not 149,000,000 BCE.
The species of Ornithocheirus featured in the program (O. mesembrinus) has recently been reclassified as its own genus, Tropeognathus, rather than being a species of Ornithocheirus. However, it was classified as a species of Ornithocheirus when the program was made.
Tropeognathus had a wingspan of only 7-8.2 m (23–27 ft), so it was not as large as depicted in the show.
There is no evidence that Tropeognathus traveled the globe, as fossils have only been discovered in Brazil.
Giant pterosaurs are now known to not have been consummate gliders.
Tapejara might have been herbivores/frugivores in a similar fashion to toucans, instead of piscivores as the series interpretation implies (though like toucans, it may still have had a taste for some meat).
Tapejara are 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 azhdarcid relatives, had longer hind limbs and shorter wings (albeit still obviously much larger than the hind-limbs), allowing them to be effective terrestrial foragers.
The Tapejara shown (according to morphological issues) would more accurately be identified as a species of Tupandactylus.
Sexual dimorphism isn't documented in tapejarids, although some species could have had it.
Tapejarids lived inland, not on the coast. However, it is possible that at least one species specialized in coastal life.
The walking pose of all the pterosaurs are far off from our current knowledge.
Tropeognathus and Tupandactylus, like all pterosaurs, are both believed to have possessed skin covered in a coat of pycnofibers through most of its body, a feature not present in the reconstructions of the two species seen in the episode.
The N. American "Iguanodon" are now classified as their own genus, Dakotadon.
Iberomesornis has modern bird traits not found in Enantiornithes, like scaly feet (instead of owl-like feathered feet or even Microraptor-like hindwings) and rectrices.
Iberomesornis lacks the two long tail feathers that the real animal had.
Utahraptor wasn't found in Europe. Other dromaeosaurs lived in Early Cretaceous Europe, like Nuthetes and Dromaeosauroides, but these lived in the Berriasian stage, not the Barremian stage. Another dromaeosaur, Ornithodesmus, did exist in the European Barremian, however, it was too small to replace the Utahraptor on the show; the Utahraptor hunting segment should have happened in North America in real life.
Utahraptor measured 20-23 feet (6-7 meters) in length at its full size, not 16 feet (5 meters) as said in the program.
Utahraptor had feathers running head, to toe, to tail; only the tip of the snout was visible. It even had feathers on its arms that made them look like wings. Additionally, it was impossible for the hands to be pronated without being broken. They held them at the side. These errors are prominent in all dromaeosaurs in the Walking with... Series.
Polacanthus isn't known from North America, only Europe. A possible replacement for this animal during the North America segment would be Gastonia or Hoplitosaurus, since they lived in the Barremian in North America.
There is no evidence that Leaellynasaura could go into a form of hibernation, but it is still possible.
Leaellynasaura lived from 118,000,000 BCE to 110,000,000 BCE, and would've been extinct by 106,000,000 BCE.
Muttaburrasaurus was less hadrosaur-like then shown in the show, as it was an iguanodont. It should be wholly bipedal rather than partially.
There is no evidence Muttaburrasaurus were migratory, but this is not implausible.
It's now known that Australovenator is not an allosaurid, but instead belongs to a group of dinosaurs know as megaraptorids, a group whose classification is disputed. However, the show does identifies them as allosaurs, a name that could represent Allosauroids in general (which therefore may include the Megaraptorids).
Australovenator didn't live 106,000,000 BCE. It lived as early as 95,000,000 BCE. However, it is known that other allosauroids lived around that time and place, as a foot bone of an allosauroid has been found in Australia that is dated very close to 106,000,000 BCE.
Muttaburrasaurus could not make noises with its nasal arch, as it was actually bony.
Muttaburrasaurus did not have thumb spikes.
Steropodon is depicted as looking similar to a modern coatimundi, having been live-acted by one, when in reality, it was a monotreme and looked more like the modern platypus.
Steropodon lived from 99,700,000 BCE to 94,300,000 BCE, and hadn't evolved by the time the episode takes place, 106,000,000 BCE.
Koolasuchus lived 120,000,000 BCE and was extinct by 106,000,000 BCE due to the fact that the temperature had warmed enough for crocodylomorphs to colonize the area. Due to inhabiting a similar niche, crocodylomorphs most likely replaced them, as said in the program for all continents outside Australia.
Many aspects of Tyrannosaurus mating behavior in the show was speculation, and may not be reflected by the real nature of the animal.
Tyrannosaurus likely would have some form of feathers, even as an adult
The Tyrannosaurus is depicted as a solitary creature. However, Phil Currie has found some evidence supporting that tyrannosaurids hunted in groups, but this isn't conclusive.
Mother Tyrannosaurus most likely took care of their young for more than the short three months the program states (the chicks are a month old when they are introduced, and it states that the mother will only take care of them for an additional two months).
Tyrannosaurus hands should be facing inwards, not downwards. The rear teeth, legs, and tail also seem a little shorter. The head is just very slightly too blocky. Tyrannosaurus is depicted as being 5 tonnes, but specimens 8-10 tonnes are not uncommon. However, The Complete Guide To Prehistoric Life seems to have corrected these mistakes.
Concrete evidence that female Tyrannosaurus were bigger than males isn't solid anymore.
It is now believed that young Tyrannosaurus had feathers and a more gracile build than adults. However, this discovery was made after the episode's release.
Dromaeosaurus has the same mistakes as Utahraptor as well as two additional ones. The head is too blocky and stout and they died out 72,000,000 BCE, not 65,500,000 BCE. (although there were two different dromeosaurids, Acheroraptor and Dakotaraptor, which lived in Hell Creek, but they weren't discovered at the time).
Dinilysia was already extinct by 65,500,000 BCE, living 85,000,000 BCE. It also only lived in South America, while the episode takes place in North America. A good replacement would possibly be Coniophis, which lived in North America.
Triceratops and Torosaurus probably had quills on their tails, unlike the ones in the program, but this is still debated.
E. annectens and hadrosaurs in general didn't have thumb spikes like their iguanodontid cousins.
Deinosuchus was extinct by this time, living from 80,000,000 BCE to 73,000,000 BCE. There were crocodilians during this time and period, Borealosuchus and Brachychampsa, but both were too small to fill the role of the crocodilian shown in the episode.
Deinosuchus is described as being a "1-ton crocodile". In reality, Deinosuchus weighed 9 tons and was an alligatoroid, not a crocodile.
We now know that the eyes of smaller ornithopods are more pronounced than depicted in the episode. This feature is also seen in eagles.
Due to being a re-skin of the Ornithocheirus model with only the beak crests removed, there are multiple inaccuracies for Quetzalcoatlus: the head is bigger and has a large flat crest instead of a tiny notch at the back of the head. The neck is much, much, longer than the program's design. The final result ends up looking more like another pterosaur, Ludodactylus. The design of the animal would be more accurate if it was a nyctosaurid or a pteranodontid (despite the size not really matching).
Didelphodon was not badger-like. In reality, it had a head like a Tasmanian Devil and a body like an otter.
Ankylosaurus was not as tall and bulky in reality as it appeared in the series.
The notion that mammals from the Paleocene and the early Eocene were all tiny creature living under the oppressive thumb of giant birds and other surviving archosaurs, such as the land dwelling crocodile 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, the mammals took up the role of dominant land vertebrates much faster than them, and by the time of the show (49my) mammals were already dominating the landscape.
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 afrothere affinities.
Ambulocetus was depicted as living in Germany, when in reality it was only found in Pakistan. However, the episode 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.
The primate Godinotia was a strepsirrhin, like a lemur, and would probably have resembled a modern lemur in life (as they are one of the most basal of primates) in contrast to the monkey-like reconstruction seen in the show.
Basilosaurus could not live as deep in the ocean as portrayed in the episode. A study of its vertebrae reveals that it was too weak to specialize in deep diving. It instead would stay close to the surface.
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. 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.
Moeritherium and Apidium did not live near the ocean, and neither did the swamps they lived in.
Dorudon was most likely not a social animal. But because they were mammals, socialization is far from unlikely.
It is unlikely Australopithecus afarensis could scare off large chalicotheres, unless these were quite skittish in nature (something that hardly can be determined with mere fossils).
Deinotherium most likely had a longer trunk in real life. If its trunk was as short as in the series, it would have trouble drinking as its legs were long and poorly built for kneeling, like an elephant's.
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 are active hunters and also pair for life in mating. It is possible that their social structure was more like that of modern day wolves, with males and females providing a simillar role in the pack order, if they were indeed social.
Macraucheniaprobably 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 prehinsile lip, though this is unlikely.
Smilodon was a bulky, short legged predator that was built to ambush and wrestle its prey to the ground like a bear, and was ill-equipped for high speed chases and quick, sharp turns like modern big cats, so the Macrauchenia chase scene is entirely 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, though still most likely 10 feet (3 meters) tall.
Phorusrhacos lived in the Miocene, from 20,000,000 BCE to 13,000,000 BCE, not the Pleistocene a mere 1,000,000 BCE. With accuracy, the show should not have shown any terror birds in that matter, as the last surviving member of this group was the North American Titanis, which also became extinct 800,000 years earlier. Its role should have been replaced in the show by a mammalian predator such as Arctotherium.
Terror birds such as Phorusrhacos could fight and even kill Smilodon, unlike in the program where they are shown being easily fended off by them.
There is no evidence that Megatherium ate carrion to supplement its diet, but it is far from unlikely as some herbivores today have been recorded eating meat, and some paleontologist do believe Megatherium was partly carnivorous. 
Cave Lions had much longer, tufted, tails, like a modern lion, a primitive mane, and a faint striped pattern, we know this from cave art. The one seen in the episode shared a similar (or identical) model with Smilodon minus the sabres, which is why it exhibits these inaccuracies.
The Neanderthal species had died out 40,000 years ago, 10,000 years before the time that the episode takes place.
Some paleanthropologists believe the African Homo heidelbergensis is merely an archaic form of modern humans. However, this is debated.
Some paleanthropologists 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 H. floresiensis. Anyway, Homo ergaster is still a valid species, as well as Homo erectusand it is required a further research to reach to a conclusion to this systematic problem.
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.
Homo naledi is more likely to be our ancestor than Homo habilis, due to the fact that it had a Nuchel ligament, and H. habilis does not. However H. naledi was discovered in 2015, more than a decade after Walking with Cavemen aired, so they could not have known this. Also, this is more likely not true at all, because Homo naledi lived from 335 to 236 thousand years B.C., which means, they were too young to be considered our ancestors. Homo habilis is more primitive and probably evolved to Homo sapiens and Homo naledi separately.
During a brief moment when going underwater, a Basilosaurus can be seen. However, it says that this is happening during 8,000,000 BCE, and Basilosaurus lived until 36,000,000 BCE. However, very slightly similar cetaceans lived during that time, like the beaked whales.
There is no evidence for Cephalaspis swimming into fresh water to lay eggs, although it is not impossible.
Brontoscorpio lived at a different time then Cephalaspis, one in the Silurian, the other in the Devonian, with only a four million year gap between the extinction of the former and the arrival of the latter.
Brontoscorpio was found in England, not Wales, and was possibly a terrestrial true scorpion. However, given the geographical proximity of the two places (even during the Silurian) it's still considerable that Brontoscorpio inhabited Wales.
Pterygotus was not the largest of the sea scorpions, nor did it reach the sizes mentioned. However, the true holder of the title, Jaekelopterus rhenaniae could attain such proportions.
There is no evidence that Pterygotus took care of its young, although true scorpions do exhibit parental care.
The arthropods' transition onto land was not an abrupt event like shown in the documentary, it was a slow process encompassing multiple generations.
Cephalaspis was not ancestral to tetrapods. At the Late Silurian, the most likely replacement would be the already full jawed Psarolepis.
In the Devonian segment, there is an angelfish. It appears when the segment starts and reappears 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).
Hyneria was smaller than depicted in the episode, attaining lengths of 2-4 metres, as opposed to five metres.
In the program, Petrolacosaurus is incorrectly identified as an ancestral synapsid, when in fact, it was an early diapsid, and could therefore not have been the ancestor of any synapsids. The most basal synapsid, Archaeothyris, would have been a more suitable candidate.
No species of spider is known to have been as large as the Mesothelae seen in this episode, now that Megarachne has been proven to be a species of eurypterid. This doesn't mean that there isn't a Carbonifourus spider of this size, it just means that one has not yet been found.
Proterogyrinus was not an amphibian, though it did live 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, it's reasonable to assume they were soft and weak.
Arthropleura's ability to rear up is purely speculation.
The Dimetrodon hatchlings are shown with their back sails fully erect, when they probably wouldn't have grown yet.
The skin texture of Edaphosaurus and Dimetrodon are slightly off. They had scutes on their skin, similar but different to the ones on crocodilians. They are believed to lack the scales of lepidosaurian reptiles.
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 nureal spines may have been exposed bone rather than covered with a full sail.
Dimetrodon had incisors that were longer than the rest of their teeth.
Gorgonops and the Rhinesuchus are only known from South Africa, yet in Clash of Titans, they are portrayed living with Scutosaurus and a Siberian species of Diictodon, which were 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 and the Siberian species of Diictodon. Yet, in the show, the Rhinesuchus is only identified as a Labyrinthodont, which is a subclass that already encompasses many other amphibians that could have lived in Siberia at the time.
It is possible that Gorgonopsids had fur.
Euparkeria is not an ancestor of the dinosaurs, being basal to crocodile-dinosaur split. Probably the most likely ancestor of the dinosaurs at the time was Tsylmosuchus an animal more closely related to archosaurs.
The Therocephalian's featured in the episode, Euchambersia, would already be extinct 248,000,000 BCE. They lived from 256,000,000 to 255,000,000 BCE.
Velociraptor may not have lived in heavily forested areas. All of the sites where Velociraptor fossils were found suggest that the animal lived in sandy, 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 to make them resemble wings.
Giganotosaurus was depicted on the show as the largest carnivorous dinosaur, though current size estimates favor Spinosaurus. However, it is true that Giganotosaurus was the largest land-dwelling carnivorous dinosaur that ever existed, as Spinosaurus was semi-aquatic.
Argentinosaurus is said to have been the biggest dinosaur. Though that title may also belong to poorly known forms such as Amphicoelias fragilimus, Puertasaurus reuli, Bruhathkayosaurus matleyi, or Futalognkosaurus dukei.
Argentinosaurus's neck was probably held vertical not horizontal.
Argentinosaurus's body shape is largly based off Saltasaurus, like most titanosaurs were in the past. However, newer studies show that Saltasaurus had very different proportions from most titanosaurs.
Velociraptor's claw could not disembowel prey because the underside was round therefore the claw was used for stabbing and for imobilizing prey.
Tarbosaurus's arms 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 Iguanodon cousins.
Therizinosaurus was depicted featherless. It is almost certain that therizinosaurs had feathers.
Pteranodon didn't live in South America. It was endemic only to North America.
Pteranodon lived 86,000,000-84,500,000 BCE (possibly as late as 80,500,000 BCE), not 100,000,000 BCE (Pterodaustro would be a good choice because it also lived in Argentina but it was extinct 5 million years before the show even takes place). Ornithocheiromorphs and azhdarchoids were pretty common at the time, however. Perhaps, Aerotitan would be a good candidate for the role, as it was a toothless azhdarchid with a five-meter long wingspan. However, it was discovered nearly ten years after the show was released.
Tropeognathus (called here Ornithocheirus ) 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 probably had a more vividly colored crest to attract females. The beak of all Pteranodons is also known to have curved slightly upwards.
Sarcosuchus would never have encountered any of the other animals in the episode, as it lived 112 million years ago, in comparison to the episode's setting of 100 million years ago, and lived in a different region of South America, Brazil. However, it is still possible that other pholidosaurs existed at the time and place of the show.
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 known that Protoceratops most likely used it frill for sexual and dominance signaling
Protoceratops probably had quills on their tails, unlike how they are portrayed in the program.
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, or a determined population of the said species that lived close to the sea.
Tanystropheus was an archosauromorph, they can't shed tails in defence.
Tanystropheus is depecited as a primarily aquatic animal, while most paleontologists now believe that it was more terrestrial, sitting on the coast and using its long neck to catch fish from afar.
Cymbospondylus is depicted as a predator of marine reptiles. However, its teeth were small and conical, likely meaning that it ate small fish, squid, and belemites. A better choice 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. In anyway, 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).
Tylosaurus was 15 m and 7 tons, not 17 m and 20 tons.
A recent study on Tylosaurus has concluded that the animal was mainly black or dark in color, 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 of it's close relatives the snakes and monitor lizards (i.e. garter snakes, komodo dragons).
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 could still produce vocalizations, however not through the melon organ.
Same issues with Dorudon as in Whale Killer. (see above)
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. This cannot however be confirmed.
There's no total evidence that juvenile Megalodon would have lived in the shallows but its possible.
Megalodon lived in warm water more or less near from the coast, not in dark open sea like depicted in the series. However, this can be debated.
Creatures have the same issues as described in their respective sections. (See above)
Time periods of planet earth go much farther back then the Ordovician, but this was probably an artistic choice, as Nigel didn't go any farther back than this, and the time map would be significantly longer.
The Ankylosaur in the movie is referred to as an Ankylosaur, rather than an actual name such Edmontonia
The Edmontosaurus shown in the movie may now be known as Ugrunaaluk, as analysis of the Alaskan Edmonstosaurus remains supported their referral to a separate genus. However, this classification is still debated, with some paleontologists believing that Ugrunaaluk is indeed a synonym of Edmontosaurus.
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 have been found with extensive skin impressions, and none seem to heavily support the presence of such crest.
Alexornis was native to Baja California, Mexico, not Alaska.
Alexornis should have feathery owl-like feet with (possibly) Microraptor-like hind-wings, fused fingers with a single claw (as opposed to three separated clawed fingers), and more of a actual snout (rather than a beak-like snout), as evidenced by other enantiornithes.