First and foremost, here is a link to the episode of Dinosaur Train that introduced "Petey the Peteinosaurus" (there are a number of versions of this but this is the only full episode that is not flipped horizontally). The first episode of the original "Walking with..." series was about dinosaurs specifically and mentioned supporting characters like Peteinosaurus (and mammals and amphibians) in passing. Peteinosaurus, however, benefited, in terms of the show, by existing during the Triassic dawn of the dinosaurs. The first episode of Walking with Dinosaurs focuses extensively on the environment that fostered the rise of the dinosaurs. This environment was populated by various protomammals and archosaurs, one of which was the "exotic hunter... Peteinosaurus" as Kenneth Branagh describes it. The short blurb about the flying reptile is not an enormous portion of the episode, but we know that Peteinosaurus is an important member of its environment. Its hypothesized role can be seen clearly in the show, as can its acrobatic capabilities.