Since Jack Horner and James Gorman’s book How to Build a Dinosaur debuted almost three years ago, periodic lectures, interviews and articles have piqued the public’s curiosity about reverse-engineering a non-avian dinosaur from an avian one. Perhaps a “chickenosaurus” isn’t as outlandish as it sounds.

The possibility of creating a long-tailed chicken with teeth and claws is based on the fact that birds are living dinosaurs. A relatively minimal amount of tinkering could turn a bird into something like its non-avian ancestors. But, during the dinomania of the late 1980s and early 1990s, the idea that birds were derived from dinosaurs was still something that made people tilt their heads and say “What?” Rather than focus on efforts to turn birds into something akin to a dromaeosaur, dinosaur documentaries envisioned the real evolutionary changes by which one lineage of non-avian dinosaurs were adapted into early birds. Even better, two shows animated this change.

Within the array of Mesozoic programming from the early 1990s, one of my favorite shows was The Dinosaurs! This four-part PBS miniseries featured scientists investigating the details of dinosaur lives, and different prehistoric vignettes were presented in colorful animated sequences. The one that stuck with me most powerfully was a short scene about the origin of birds. A small, green dinosaur akin to Compsognathus runs through a forest, but when the theropod pauses on a branch it rapidly grows feathers. In an instant the small coelurosaur changed into Archaeopteryx. The 19th century naturalist Thomas Henry Huxley was absolutely right when he imagined that, when clothed in feathers, a dinosaur like Compsognathus would look little different from archaic birds.

But a similar clip from an earlier, 1989 episode of the series The Infinite Voyage is even better. The episode, “The Great Dinosaur Hunt,” is an excellent snapshot of how perspectives on dinosaurs were changing in the wake of the “Dinosaur Renaissance,” and the program included a similar coelurosaur-to-bird transformation. This time, though, the change starts with a fuzzy, feather-covered dromaeosaurid similar to the sickle-clawed Deinonychus. Rather than focus on the outside of the dinosaur, though, the show gives viewers an animated X-ray view as the skull, arms, shoulders, legs and hips are gradually modified in a transition through Archaeopteryx and modern birds. The change didn’t happen exactly like this—Deinonychus was a larger dinosaur that lived millions of years after Archaeopteryx—but different anatomies represent the general pattern of the evolutionary change.

I still have a fondness for those animations. Part of that affinity is probably due to nostalgia, but I also think that they beautifully illustrate a point that is often taken for granted now. The fact that birds are modern dinosaurs is reiterated in books, museum displays, CGI-ridden documentaries and blogs, but rarely do we see the transitional changes actually laid out in front of us. Both animations could use some updates, but they still vibrantly encapsulate one of the most fantastic transitions in the history of life on earth.