Birds use their beaks to do a lot, such as build nests, gather food, or defend themselves; scientists use birds’ beaks to put them in one of two categories. For over a century, extant birds have been classified based on the type of beak they have. The first group are called palaeognaths, and have palate bones that are fused together. The second group, neognaths, have palate bones that are connected by a mobile joint. 99% of all living birds today are neognaths; only emus, ostriches, and their relatives fall into the palaeognath category.
As you may have guessed by their names—“neo” means new and “palaeo” means ancient—scientists assumed that the fused-together style of beak evolved first, and the mobile beak of most modern birds evolved later. A new look at an ancient fossil, however, upends that century-old assumption.
The fossil at the center of the story is Janavis finalidens, a fossil found near the Belgian-Dutch border of a bird that lived about 66.7 million years ago, at the tail-end of the Age of Dinosaurs. Researchers recently took another look at this fossil using CT scanning technology, and realized that a bone previously thought to be a shoulder bone was actually a palate bone. Surprisingly, it was almost identical to that of a modern turkey, which led the researchers to conclude that the ancient bird had a mobile beak.
That means that what we’ve called the “modern” jaw of neognaths actually evolved before modern birds did—making the phrase “modern jaw” a bit of a misnomer.