Researchers have described a new species of Late Triassic pterosaur. It has been named Eotephradactylus mcintireae and it represents North America’s oldest known flying reptile. A field team led by the Smithsonian National Museum of Natural History and Columbia College Chicago discovered the fossil remains. They were exploring outcrops of the Owl Rock Member of the Chinle Formation in north-eastern Arizona. They come from an unusual bonebed that preserves the remains of a variety of Late Triassic vertebrates. The assemblage provides evidence of animals that persisted into the Jurassic co-existing with archaic lineages such as phytosaurs, armoured aetosauriforms and ancient temnospondyls.
The bonebed provides a snapshot of an ecosystem prior to the End Triassic Mass Extinction event.
North America’s oldest pterosaur described to date Eotephradactylus mcintireae disturbs some frogs whilst catching a ray-finned fish. An early tortoise is seen in the background and the bones of an armoured crocodilian are visible. Picture credit: Brian Engh.
Picture credit: Brian Engh
Eotephradactylus mcintireae – North America’s Oldest Pterosaur
The study has been published in the “Proceedings of the National Academy of Sciences.” The pterosaur fossils identified from the bonebed include a partial left mandible (lower jaw), isolated teeth and a phalanx (digit bone). The fossils are approximately 209 million years old (Norian faunal stage of the Late Triassic).
Corresponding author Ben Kligman (Peter Buck Postdoctoral Fellow at the Smithsonian’s National Museum of Natural History), stated:
“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. Fossil beds like these enable us to establish that all of these animals actually lived together.”
Kay Behrensmeyer (left), the curator of vertebrate palaeontology at the Smithsonian’s National Museum of Natural History. Robin Whatley (right), professor and associate dean at Columbia College Chicago in the Petrified Forest National Park digging for fossils in a quarry in 2023. Picture credit: Ben Kligman, (Smithsonian).
Picture credit: Ben Kligman (Smithsonian)
“Ash-winged Dawn Goddess”
The genus name translates as “ash-winged dawn goddess”, it references the location’s volcanic ash layers and the pterosaur’s position as a basal member of the Pterosauria family tree. The species name honours preparator Suzanne McIntire, who discovered the fossil material in 2013 when preparing a block from the site.
The pterosaur fossil was unearthed by preparator Suzanne McIntire, a volunteer at the museum’s FossiLab for eighteen years. Picture credit: Bill King.
Picture credit: Bill King
The Owl Rock Member
The Owl Rock Member strata are some of the least explored parts of the Petrified Forest National Park. The extensive volcanic ash layers in the quarry, permitted the scientists to calculate the age of the bonebed. It represents the remains of an ecosystem that existed around 209 million years ago (Norian faunal stage of the Late Triassic). These are some of the geologically youngest sediments in the Petrified Forest National Park.
In the Late Triassic, Arizona was positioned in the central part of the supercontinent Pangaea. The area was just north of the equator. It was a low-lying, semi-arid environment criss-crossed with small river channels and prone to seasonal floods. The bonebed likely preserves the remains of a community of animals that were caught up in a flash flood.
The bonebed is rich vertebrate fossils. So many fossils were found that excavating them in the field was impossible. Field team members took large chunks of rock, entombed in plaster jackets back to the preparation laboratory at the Smithsonian National Museum of Natural History. Volunteers spent thousands of hours carefully excavating the fossil material.
Ben Kligman (right), a Peter Buck Postdoctoral Fellow at the Smithsonian’s National Museum of Natural History with several of the museum’s FossiLab volunteers who contributed to the study of the fossils from the bonebed. Richard Cline (far left), Hillary Cochard, James Morrison and far right Lynn Sharp. Picture credit: Abby Telfer, (Smithsonian).
Picture credit: Abby Telfer (Smithsonian)
A Diverse Community of the Familiar and Not So Familiar
The gull-sized pterosaur Eotephradactylus mcintireae shared its home with a huge variety of other vertebrates. Some of these animals would be familiar to us, others represent taxa that did not survive into the Jurassic. For example, coelacanths swam in the rivers along with freshwater sharks. In addition, frogs were present and an ancient tortoise.
The tortoise fossils are of particular interest. They are some of the world’s oldest tortoise remains. The tortoise had a robust shell, with protruding spikes for additional protection. Stem members of the Testudinata clade (reptiles with a true carapace and plastron shell) are known from the Late Triassic. For instance, the genus Proterochersis was present in Germany and Poland and is roughly contemporaneous with the Owl Rock Member biota.
Ben Kligman commented:
“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.”
Animals that are familiar to us today coexisted with animals that were very different to modern faunas. For example, whilst relatives of New Zealand’s tuatara were present (rhynchocephalians), there were also giant, ancient amphibians, aetosaurs and phytosaurs.
Over 1,200 Fossils Including the Pterosaur Eotephradactylus mcintireae
The team has uncovered more than 1,200 individual fossils. They include bones, teeth, fish scales and coprolites. Sixteen different types of vertebrate were identified from this single bonebed indicating a diverse ecosystem. Amongst these fossils were the remains of North America’s oldest known pterosaur Eotephradactylus mcintireae. Its discovery motivates research teams to continue to explore the remote and difficult to access Owl Rock Member exposures.
Suzanne McIntire reflecting on the significance of her discovery said:
“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.”
The teeth provide important clues to the pterosaur’s diet; the worn-down crowns suggest it was durophagous, adapted for consuming hard-shelled prey. The researchers conclude that this flying reptile fed on the site’s fish. Ray-finned fish are known from this locality (actinopterygians). Many had armour-like scales, and a diet of these types of fish would have resulted in extensive tooth wear.
Everything Dinosaur acknowledges the assistance of a media release by the Smithsonian National Museum of Natural History in the compilation of this article.
The scientific paper: “Unusual bone bed reveals a vertebrate community with pterosaurs and turtles in equatorial Pangaea before the end-Triassic extinction” by Ben T. Kligman, Robin L. Whatley, Jahandar Ramezani, Adam D. Marsh, Tyler R. Lyson, Adam J. Fitch, William G. Parker and Anna K. Behrensmeyer published in the Proceedings of the National Academy of Sciences.
The award-winning Everything Dinosaur website: Pterosaur and Prehistoric Animal Models.
