Paleontologists in the United States have described a new genus and species of extinct crocodile relative based on a partially articulated skeleton found in the Middle Triassic Fossil Hill Member of the Favret Formation in Nevada, a pelagic setting in the eastern Panthalassan Ocean characterized by the presence of abundant ammonites and giant ichthyosaurs.
Benggwigwishingasuchus eremicarminis on the Panthalassan Ocean coast. Image credit: Jorge Gonzalez.
The newly-identified species of pseudosuchian reptile lived during the Middle Triassic epoch between 247.2 and 237 million years ago.
Named Benggwigwishingasuchus eremicarminis, the animal probably reached around 1.5-1.8 m (5-6 feet) in length.
It likely stuck pretty close to the shore; its well-preserved limbs are well-developed without any of the signs of aquatic living like flippers or altered bone density.
“This exciting new species demonstrates that pseudosuchians were occupying coastal habitats on a global basis during the Middle Triassic,” said Dr. Nate Smith, Gretchen Augustyn director and curator of the Dinosaur Institute at the Natural History Museum of Los Angeles County.
“Capturing fossil life from the eastern Panthalassan Ocean of the Triassic, the locality that includes the Favret Formation is known for fossils of sea-going creatures like ammonites along with marine reptiles like the giant ichthyosaur species Cymbospondylus youngorum — finding the newly described Benggwigwishingasuchus eremicarminis came as a bit of a shock.”
“Our first reaction was: What the hell is this?” said Dr. Nicole Klein, a paleontologist at the University of Bonn.
“We were expecting to find things like marine reptiles. We couldn’t understand how a terrestrial animal could end up so far out in the sea among the ichthyosaurs and ammonites.”
“It wasn’t until seeing the nearly completely prepared specimen in person that I was convinced it really was a terrestrial animal.”
Pseudosuchian archosaurs have been unearthed in fossil beds from the shores of the Tethys Ocean, but this is the first coastal representative from the Panthalassan Ocean and western hemisphere, revealing that these crocodile relatives were present in coastal environments worldwide during the Middle Triassic.
Interestingly, these coastal species aren’t all from the same evolutionary group, suggesting that pseudosuchians (and archosauriforms more broadly) were independently adapting to life along the shores.
“Essentially, it looks like you had a bunch of very different archosauriform groups deciding to dip their toes in the water during the Middle Triassic,” Dr. Smith said.
“What’s interesting, is that it doesn’t look like many of these ‘independent experiments’ led to broader radiations of semi-aquatic groups.”
During the Triassic, archosaurs arose and split into two groups with two surviving representatives: birds, the descendants of dinosaurs, and crocodilians (alligators, crocodiles, and gharials), the descendants of pseudosuchian archosaurs like Benggwigwishingasuchus eremicarminis.
While today’s crocodilians are similar enough to be mistaken for one another by most people, their ancient relatives varied wildly in size and lifestyle.
The evolutionary relationships of Benggwigwishingasuchus eremicarminis and its relatives suggest that pseudosuchians achieved great diversity very quickly following the end-Permian mass extinction — the extent of which is waiting to be discovered in the fossil record.
“A growing number of recent discoveries of Middle Triassic pseudosuchians are hinting that an underappreciated amount of morphological and ecological diversity and experimentation was happening early in the group’s history,” Dr. Smith said.
“While a lot of the public’s fascination with the Triassic focuses on the origin of dinosaurs, it’s really the pseudosuchians that were doing interesting things at the beginning of the Mesozoic.”
The discovery of Benggwigwishingasuchus eremicarminis is reported in a paper in the journal Biology Letters.
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Nathan D. Smith et al. 2024. A new pseudosuchian from the Favret Formation of Nevada reveals that archosauriforms occupied coastal regions globally during the Middle Triassic. Biol. Lett 20 (7); doi: 2020240136; doi: 10.1098/rsbl.2024.0136
This article is based on a press-release from the Natural History Museum of Los Angeles County.
Source : Breaking Science News