/proh'toh ay"vis/ , n.
a fossil bird of the genus Protoavis, from the Triassic Period, having a birdlike, partly toothless jaw structure, a tail and hind legs resembling those of the dinosaur, and the hollow bones and keellike breast that are characteristic of modern birds: the oldest known avian type, preceding the archaeopteryx by an estimated 75 million years.
[ proto- PROTO- + L avis bird ]