Is this fragile jawbone a pterosaur or not? Other researchers also had questions about the fossil, unearthed along with thousands of others during a decades-long archaeological dig at a remote bone bed in the Petrified Forest National Park in Arizona.

The 209-million-year-old fossil offers clues to the evolution of the reptiles, which have more than 150 named species including the well-known pterodactyl.

A single deposit has produced a wealth of fossils revealing the late Triassic ecosystem, where giant amphibians cohabited with newcomers, including turtles and pterosaurs. The 12 million years leading up to the end-Triassic extinction have been relatively poorly represented in the fossil record,