Neusticosaurus was a relative of Nothosaurus, but it was much smaller in size. This enabled it to coexist with its bigger relative probably by living closer to the shore and by feeding on much smaller animals. (Neusticosaurus was less than a meter in length.) It died out during the Triassic, just as the rest of the nothosaur family did.
In Walking with... series[]
Sea Monsters: Prehistoric Predators of the Deep featured Neusticosaurus as a background creature that coexisted with Nothosaurus in the Triassic seas.