The winged reptiles that once roamed the skies over North America 209 million years ago could have easily made it to Europe–and not because of their wings. All of Earth’s continents were still connected in the supercontinent Pangaea. Now, a team led by researchers and volunteers from the Smithsonian’s National Museum of Natural History have uncovered the oldest known pterosaur in North America. The new sea-gull size pterosaur Eotephradactylus mcintireae is detailed in a study published July 7 in the journal Proceedings of the National Academy of Sciences, and also includes one of the world’s oldest turtle fossils.
“Our discoveries from this study show how paleontologists have only just started scratching the surface of the fossil record,” study co-author and paleontologist Ben T. Kligman tells Popular Science.
In the run up to mass extinction
The fossils were uncovered at a remote bonebed in present-day Arizona’s Petrified Forest National Park. They date back to the late Triassic period and offer paleontologists a snapshot of an ecosystem full of older species like giant amphibians and armored crocodilians and some new-for-the-time animals like turtles, frogs, and pterosaurs.
“The climate was arid and monsoonal, where most of the year was hot and dry, and for a short period there were monsoonal rains,” Kligman says. “The setting in which Eotephradactylus and the other animals discovered in this study were living was in and around river channels. The banks of these rivers would have been vegetated by coniferous trees and horsetail plants.”
This important site within the popular national park captures a period in Earth’s history when the more modern terrestrial vertebrates that thrived later on during the Mesozoic living alongside older animals that went extinct by the time the Triassic era came to its fiery end.
Roughly 201.5 million years ago, volcanic eruptions associated with the break-up of the
Pangaea drastically changed global climates. About 75 percent of all species on Earth were wiped out, clearing the way for newer groups–like dinosaurs. These new species diversified and dominated ecosystems worldwide. Direct fossil evidence of this transition period on land is difficult to find, largely due to a lack of terrestrial fossil outcrops from right before the end-Triassic extinction. However, Petrified Forest National Park is famed for its Triassic fossil beds alongside its signature colorful deposits of petrified wood.
Additionally, one of the park’s geologic outcrops–the Owl Rock Member–is full of volcanic ash. The minerals within the ash allowed the researchers to date the Owl Rock layer to around 209 million years old. They are among the park’s youngest rocks, but are also among the park’s least studied, according to study co-author William Parker, a paleontologist at Petrified Forest National Park. The Owl Rock Member exposures are found in very remote areas, making their study a bit more difficult.
[ Related: ‘Remarkable’ fossils offer clues to perplexing pterosaur question. ]
Pterosaurs on the river
This part of northeastern Arizona was positioned in the middle of Pangea 209 million years ago, sitting just above the equator. Small river channels crisscrossed the area and were likely prone to seasonal floods. It’s this flooding that washed sediment and volcanic ash into the channels. One flood likely buried these animal carcasses, preserving them in the bonebed.
In total, the team has uncovered over 1,200 individual fossils, including bones, teeth, fish
scales, coprolites (aka fossilized poop), and the oldest known North American pterosaur. At the size of a small seagull, “it could have perched on your shoulder,” according to Kligman.
“We think it was eating fish. Fish fossils are abundant in the bonebed that yielded Eotephradactylus mcintireae, and these would have been primitive fish related to living gar. These fish were covered in bony mineralized scales that would have acted like a touch [of] armor,” he says.
Eotephradactylus also shows an unusual degree of wear on the tips of its teeth. This indicates that it was eating animals with hard mineralized parts, likely the fish living in the area’s crisscrossing rivers. This wear-and-tear on its teeth is unique among early pterosaurs, indicating that specialized feeding on fish was an important aspect of early pterosaur evolution.
It is also the oldest pterosaur from North America, and one of the oldest pterosaur fossils on Earth.
“The oldest ones are only 5 million years older, and from Europe,” says Kligman. “Unlike later pterosaurs from after the Triassic, this one has many types of tooth shapes in its jaw, including large fang-like teeth (presumably for grabbing prey) at the front of its jaw, and blade-like teeth with up to 7 sharp cusps at the back of the jaw (presumably for slicing up prey). Later pterosaurs either have no teeth, or lack the differentiation of teeth in the jaw.”
In total, this rock assemblage has 16 different groups of vertebrate animals: armored herbivores and toothy predators that looked like giant crocodiles, early frog species, and an ancient turtle with spike-like armor and a small shell that could fit inside a shoebox. This tortoise-like animal lived at roughly the same time as the oldest known turtle–Solnhofia parsonsi–whose fossils were uncovered in Germany. This suggested that the shelled reptiles rapidly dispersed across the Pangea.
“Our study helped partially close a 13 million year gap in the fossil record preceding the end Triassic extinction, however there is still a 7 million year gap remaining which obscures when many groups of animals actually go extinct,” says Kligman. “The only way to fully understand what happened during transformative events in Earth history like the end Triassic extinction is to go out and find new fossil sites that fill critical gaps in the fossil record.
[ Related: Dinosaur Cove reveals a petite pterosaur species. ]
Volunteer power
The remarkable pterosaur fossil was found by preparator Suzanne McIntire, who volunteered in the National Museum of Natural History’s FossiLab for 18 years.
“What was exciting about uncovering this specimen was that the teeth were still in the bone, so
I knew the animal would be much easier to identify,” McIntire said in a statement.
The new species is named Eotephradactylus mcintireae. Eotephradactylus means “ash-winged dawn goddess,” and references the site’s volcanic ash and the animals’ position towards the base of the pterosaur evolutionary tree. The species name also references McIntire, who retired last year.
“Because of the painstaking and time consuming nature of preparing these fossils, the entire study would not have been possible without the thousands of hours of time FossilLab volunteers put into this study,” Kligman adds.
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