Like a bat out of the Jurassic, a 163-million-year-old aerial dinosaur has been discovered whose wings had more in common with modern bats than any bird. It proves the one previous identification of a bat-like dinosaur was not an error as some have argued.
The dominant flying creatures of the Jurrasic and Cretaceous were the pterosaurs, such as pterodactyls. Contrary to common perception, these were not dinosaurs. Nevertheless, some dinosaurs certainly did take to the skies, most famously Archeopteryx, and we now know modern birds are members of the Dinosauria clade, some better disguised than others.
A lesser-known example of flying dinosaurs were the scansoriopterygids, that weighed just 200 grams (7 ounces) and probably lived in trees. Four years ago a new fossil that had a skull resembling the other scansoriopterygids enough to be placed among them, but had a long, pointed wrist bone that supported a membrane wing, was announced. That creature was named Yi qi, and it now has company.
Dr Min Wang of the Chinese Academy of Sciences has found a new scansoriopterygid, which he has named Ambopteryx longibrachium, and it helps us understand the origins of flight.
Ambopteryx was found near Lingyuan City, China. It had forelimb bones that were wider than Yi's and a short tail that lacked a clear transition point and ended with fused vertebrate. The ratios between the lengths of several of its bones were unlike other known dinosaurs.
Like modern birds, Ambopteryx ingested stones to break up its food, and some of these, along with possible stomach contents, can still be seen in the fossil, leading Wang to conclude it was omnivorous.
The reason these discoveries are so exciting, Wang explains in Nature, is it seems Ambopteryx was a pioneer of the air. “The early fossil records of pterosaurs and bats are sparse,” Wang and co-authors write. However, Ambopteryx and Yi were apparently new to this whole airborne thing. We don't yet know if they were capable of true flight, or if they just glided from tree to tree like sugar gliders or flying squirrels.
The scansoriopterygids and birds were fairly close relatives, having evolved prerequisites for flight before diverging, and then finding different paths into the air. The close alignment in time and space between these scansoriopterygids, their feathered relatives with more birdlike wings, and the first true birds shows that “Close to the origin of flight, dinosaurs closely related to birds were experimenting with a diversity of wing structures,” the authors note.
In the end feathers and the bird wings proved the more successful way to dominate available niches, and Ambopteryx and its relatives vanished from the fossil record. However, the fact the unrelated bats and pterosaurs used similar means to reach for the skies prove their approach also had merit.