In the Smithsonian’s FossiLab, volunteer preparator Suzanne McIntire sat hunched over a microscope, chiseling rock away from a tiny jawbone that had traveled a long way to reach her — hauled out of Arizona’s remote badlands inside a plaster-encased block of ancient sediment.
She had already logged thousands of hours like this, carefully freeing bones from the Triassic mud that had buried them. But something was different about this one.
The teeth were still in the bone — small, worn at the tips, and 209 million years old. They had a story to tell.
A bonebed hiding in plain sight
The Owl Rock Member of Petrified Forest National Park sits among the park’s youngest rock layers — dated to roughly 209 million years ago using minerals extracted from volcanic ash. Despite the park’s global reputation for Triassic fossils, these particular outcrops had gone largely unexplored. The reason is simple: they’re hard to reach. Rugged badlands, rattlesnakes, and roaming wild horses had kept serious excavation teams away for decades.
That changed in 2011, when a team co-led by Kay Behrensmeyer, curator of vertebrate paleontology at the Smithsonian’s National Museum of Natural History, pushed into the remote terrain looking for fossils of mammal precursors. They found something far bigger.
“That’s the fun thing about paleontology,” said Ben Kligman, who later joined the project for his doctorate. “You go looking for one thing, and then you find something else that’s incredible that you weren’t expecting.”
What they uncovered was an entire Triassic ecosystem compressed into a single bonebed. Too fossil-rich to excavate in the field, the team encased large sediment blocks in plaster and transported them back to Washington. Volunteers at the FossiLab — often working in full view of museum visitors — then spent thousands of hours chiseling rock from bone under microscopes, one careful scrape at a time.
More than 1,200 fossils and 16 vertebrate groups
The excavation has produced over 1,200 individual specimens: bones, teeth, fish scales, and coprolites representing 16 distinct vertebrate groups. Together, they paint a clear picture of a semi-arid landscape crisscrossed by river channels, prone to seasonal floods, sitting just above the equator on the supercontinent Pangaea.
The rivers were alive. Freshwater sharks and coelacanths shared the water with giant amphibians stretching up to six feet long, while armored herbivores grazed on land alongside toothy predators that resembled enormous crocodiles — creatures that had dominated Triassic ecosystems for millions of years.
Living beside them, though, were animals that pointed toward the future. Early frogs, relatives of the modern tuatara, and a small spike-shelled turtle — with a shell that could fit inside a shoebox — all appear in the fossil record here. That turtle is roughly contemporary with the oldest known turtle fossil, previously found in Germany, suggesting turtles spread across Pangaea faster than expected.
“This suggests that turtles rapidly dispersed across Pangaea, which is surprising for an animal that is not very large and is likely walking at a slow pace,” Kligman noted.
That’s what makes the bonebed so scientifically valuable. It doesn’t show one era or another — it shows both at once, ancient Triassic lineages and evolutionary newcomers sharing the same rivers, the same floodplains, the same seasonal floods that ultimately buried them all.
Meet Eotephradactylus mcintireae — the ‘ash-winged dawn goddess’
Among those newcomers, one fossil stands apart. The jawbone McIntire uncovered belongs to Eotephradactylus mcintireae — North America’s oldest known pterosaur and one of the oldest found anywhere outside Europe. Small enough to perch comfortably on a person’s shoulder, this gull-sized flying reptile soared above the same rivers the freshwater sharks patrolled below.
The teeth embedded in that jaw told researchers something specific: their tips were worn down in a pattern consistent with feeding on heavily scaled fish, the kind that filled the site’s ancient waterways. It’s a rare case where a fossil offers direct behavioral evidence rather than just anatomical data.
The species name honors McIntire directly. She had volunteered in the FossiLab for 18 years before retiring, and it was her trained eye and patient hands that freed the specimen from the rock. The generic name translates to “ash-winged dawn goddess” — a nod both to the volcanic ash that preserved the site and to the pterosaur’s position near the base of the entire pterosaur evolutionary tree.
A world on the brink of catastrophe
This thriving ecosystem existed roughly 7.5 million years before everything changed. Around 201.5 million years ago, massive volcanic eruptions tied to the breakup of Pangaea reshaped global climates and triggered the end-Triassic extinction — an event that erased approximately 75% of species on Earth. The armored herbivores, the giant amphibians, the crocodile-like predators: most didn’t survive. Pterosaurs and early turtles did, eventually flourishing in the world that followed.
Terrestrial fossil records from just before that extinction are extraordinarily rare. The Arizona bonebed is one of the few places on Earth where scientists can see, in concrete detail, what life looked like in those final millions of years. Kligman describes it as capturing “the transition to more modern terrestrial vertebrate communities” — a window that almost no other site can offer.
That framing deserves a moment’s reflection. Every fossil in that bonebed was alive, unaware of what was coming. The pterosaur hunting fish above a Triassic river had no way of knowing it belonged to a lineage that would outlast the catastrophe — neither did the turtle, or the frog. The extinction that cleared the stage for dinosaurs was still millions of years away, and in the meantime, life was simply living. The fact that we can now read that story, from a jawbone prepared under a microscope in a Washington museum, is its own kind of remarkable.
You can learn more about this exciting discovery here: Ben T. Kligman, Robin L. Whatley, Jahandar Ramezani, Adam D. Marsh, Tyler R. Lyson, Adam J. Fitch, William G. Parker, Anna K. Behrensmeyer. Unusual bone bed reveals a vertebrate community with pterosaurs and turtles in equatorial Pangaea before the end-Triassic extinction. Proceedings of the National Academy of Sciences, 2025; 122 (29) DOI: 10.1073/pnas.2505513122
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