A Smithsonian-led team of researchers have discovered North America’s oldest known pterosaur, the winged reptiles that lived alongside dinosaurs and were the first vertebrates to evolve powered flight. In a paper published today, July 7, in Proceedings of the National Academy of Sciences, researchers led by paleontologist Ben Kligman, a Peter Buck Postdoctoral Fellow at the Smithsonian’s National Museum of Natural History, present the fossilized jawbone of the new species and describe the sea gull-sized pterosaur alongside hundreds of other fossils—including one of the world’s oldest turtle fossils—unearthed at a remote bonebed in Petrified Forest National Park in Arizona.
These fossils, which date back to the late Triassic period around 209 million years ago, preserve a snapshot of a dynamic ecosystem where older groups of animals, including giant amphibians and armored crocodile relatives, lived alongside evolutionary upstarts like frogs, turtles and pterosaurs.
“The site captures the transition to more modern terrestrial vertebrate communities where we start seeing groups that thrive later in the Mesozoic living alongside these older animals that don’t make it past the Triassic,” Kligman said. “Fossil beds like these enable us to establish that all of these animals actually lived together.”
The new site helps fill in a gap in the fossil record that predates the end-Triassic extinction (ETE). Around 201.5 million years ago, volcanic eruptions associated with the break-up of the supercontinent Pangaea dramatically altered global climates and wiped out roughly 75% of the species on Earth. This cleared the way for newer groups, like dinosaurs, to diversify and dominate ecosystems worldwide.
Direct evidence of this transition on land is difficult to find due to a lack of terrestrial fossil outcrops from right before the ETE. However, there are few better places to look than Petrified Forest National Park, which is famed for its Triassic fossil beds and colorful deposits of petrified wood.
One of the park’s geologic outcrops, the Owl Rock Member, is rich in volcanic ash. Minerals within the ash have allowed researchers to date the Owl Rock layer to around 209 million years old, making them among the park’s youngest rocks.
These rocks are also among the park’s least studied according to William Parker, a paleontologist at Petrified Forest National Park and co-author of the new study. The exposures of the Owl Rock Member at the park are found in very remote areas and therefore have not received the same attention as other geological members in the park.
In 2011, a team co-led by research geologist Kay Behrensmeyer, the National Museum of Natural History’s curator of vertebrate paleontology, braved the area’s rugged badlands, which are home to rattlesnakes and wild horses. They were searching for fossils of prehistoric precursors to mammals and ended up discovering a bonebed containing an entire Triassic ecosystem.
“That’s the fun thing about paleontology: you go looking for one thing, and then you find something else that’s incredible that you weren’t expecting,” said Kligman, who began working on this site as part of his doctorate in 2018.
This part of northeastern Arizona was positioned in the middle of Pangaea and sat just above the equator 209 million years ago. The area’s semi-arid environment was crisscrossed by small river channels and likely prone to seasonal floods. These floods washed sediment and volcanic ash into the channels.
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