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Rare Desert Pterosaur Fossil Discovered in Utah

The rare Triassic fossil is the most complete early pterosaur ever found, and gives new insight into the evolution of the first flying vertebrates

Caelestiventus hanseni. (Michael Skrepnic/BYU)
smithsonian.com

Researchers in Utah have unearthed one of the most detailed pterosaur—aka pterodactyl—fossils found to date, a discovery that tells us the first known vertebrates to take to the skies were more diverse and widespread than previously thought.

While dinosaurs ruled the land, pterosaurs ruled the heavens during the late Triassic and Jurassic periods. Unlike the dinosaurs, whose heavy bones make pretty good fossils, we don’t know much about the early evolution of the pterosaurs. Their fine bones were easily pulverized, meaning we have bits and pieces of just 30 pterosaurs dating from the Triassic, roughly 220 million years ago.

The new find comes from a rock formation on public land in northeastern Utah known as the Saints and Sinners Quarry. Hundreds of millions of years ago, it’s believed the area was an oasis in a massive dune-covered desert, drawing animals from all over the place during droughts. Some such visitors were preserved as fossils after dying at the hands of predators or getting stuck in the mud as the water dried up.

According to a press release, the area is so jam packed with thousands of Triassic bones researchers don’t pluck them out of the rock one at a time. Instead, they remove large chunks of rock and bring them back to their lab at Brigham Young University in Provo, Utah, where they painstakingly remove the fossils from the stone.

That’s what paleontologists were doing when they discovered the new pterosaur species, Caelestiventus (heavenly wind) hanseni. After chiseling out five crocodile fossils from one slab, they realized they had found something rare in the 200 to 210 million-year-old rock. They found part of the little pterosaur’s face, the complete roof of the skull, the complete lower jaw and part of a wing, which they detail in the journal Nature Ecology & Evolution.

“This one site we've pulled out 18,000 bones from an area the size of a good sized living room,” BYU’s Brooks Britt, the study’s lead author, tells Mary Halton at the BBC. “And there’s only one pterosaur.”

The amount of material is unprecedented. In most cases, researchers only find tiny or fragmentary fossils of pterosaurs, like a finger bone or vertebrae. But the new specimen likely died in soft sand or sediment that hardened into rock, keeping the specimen intact. “Most [pterosaur fossils] are heavily distorted; literally like roadkill,” Britt tells Halton. “The bones are so delicate, you can't take them all the way out of the rock because they would just fall apart.”

The researchers didn’t completely dig out the pterosaur bits, instead leaving them encased in sandstone, getting 3-D images of the bones with a CAT-scan, which they used to make models of the fossils. The scans reveal some interesting info about the flying beast. The BBC reports that the fossil comes from a juvenile with a wingspan about five feet wide, likely the largest pterosaur of the era (in later times, pterosaurs would evolve to reach the size of small airplanes). The animal had 112 teeth and the size and shape of its brain indicates it could see well though its sense of smell was poor.

Gemma Tarlach at Discover also reports that a bony crest on its lower jaw suggests that the animal also had a pouch similar to a pelicans, used either to make vocalizations or to carry prey. It’s believed the animal probably hung around the watering hole, snapping up any smaller critters stopping by to quench their thirst.

But it’s the habitat the animal lived in that’s most exciting for paleontologists. Marlowe Hood at Agence France Press reports the other pterosaur specimens dating back to the Triassic all come from what used to be coastal areas in Greenland and Europe. The fact that the new specimen was found in what used to be a vast desert suggests that the pterosaurs were evolving earlier than previously thought and moved into specialized ecological niches. The next oldest desert pterosaur doesn’t appear in the fossil record for 65 million years.

According to the press release, the fossil also seems to be related to another species found in Britain called Dimorphodon macronyx. Those fragmentary bones are from the Jurassic period, meaning Caelestiventus hanseni’s line was able to weather the Triassic-Jurassic mass extinction event when huge numbers of species went extinct. It turns out the pelican-like pterosaur was a rare genetic survivor, just likes its delicate bones.

About Jason Daley

Jason Daley is a Madison, Wisconsin-based writer specializing in natural history, science, travel, and the environment. His work has appeared in Discover, Popular Science, Outside, Men’s Journal, and other magazines.

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