A new species of extinct crocodile relative is changing life on the Triassic coast

The surprising discovery of a new species of extinct crocodile from the Triassic Favret Formation in Nevada, USA, changes the story of coastal life during the first act of the age of the dinosaurs.

Described in a study published in Biology LettersThe new species Benggwigwishingasuchus eremicarminis shows that the giant ichthyosaurs ruled the oceans, while the ancient crocodile family known as pseudosuchian archosaurs ruled the coasts throughout the Middle Triassic between 247.2 and 237 million years ago.

“This exciting new species demonstrates that pseudosuchians occupied coastal areas worldwide during the Middle Triassic,” said Dr. Nate Smith, lead author of the paper, and Gretchen Augustyn, director and curator of the Dinosaur Institute at the Natural History Museum of Los Angeles County.

The site where the Favret Formation is located is an area where fossils of marine animals such as ammonites and marine reptiles such as the gigantic ichthyosaur C. youngorum have been found. The discovery of the recently described B. eremicarminis therefore came as a shock.

“Our first reaction was: what on earth is this?” said co-author Dr. Nicole Klein of the University of Bonn. “We expected to find things like marine reptiles. We couldn’t understand how a land animal could end up so far out at sea among the ichthyosaurs and ammonites. It wasn’t until I saw the almost completely prepared specimen in real life that I was convinced that this really was a land animal.”

Pseudosuchian archosaurs have been unearthed in fossil layers from the shorelines of the ancient Tethys Ocean, but this is the first coastal representative from the Panthalassan Ocean and the Western Hemisphere, revealing that these crocodilian relatives were present in coastal areas worldwide during the Middle Triassic. Interestingly, these coastal species do not all belong to the same evolutionary group, suggesting that pseudosuchians (and archosauriforms more broadly) adapted to shoreline life independently.

“Essentially, it looks like you had a bunch of very different archosauriform groups that decided to dip their toes in the water during the Middle Triassic. What’s interesting is that it doesn’t look like many of these ‘independent experiments’ led to broader radiations of semi-aquatic groups,” Smith said.

During the Triassic, the archosaurs, ‘the ruling reptiles’, emerged and split into two groups with two surviving representatives: birds, the descendants of the dinosaurs, and crocodilians (alligators, crocodiles and gharials), the descendants of pseudosuchian archosaurs such as B. eremicarminis.

Although modern crocodiles look similar enough to be confused with one another by most people, their ancient relatives varied greatly in size and lifestyle. The evolutionary relationships of B. eremicarminis and its relatives suggest that pseudosuchians reached a great diversity very soon after the End-Permian mass extinction, the extent of which has yet to be discovered in the fossil record.

“A growing number of recent discoveries of pseudosuchians from the Middle Triassic suggest that there was an underestimated amount of morphological and ecological diversity and experimentation going on in the early history of the group. While much of the public’s fascination with the Triassic focuses on the origin of dinosaurs, it was actually the pseudosuchians that were doing interesting things at the beginning of the Mesozoic,” Smith said.

The new species underscores the diversity of these ancient reptiles during the Triassic, from giants like Mambawakale ruhuhu to smaller animals like the recently described B. eremicarminis , which likely grew to about 5-6 feet in length. Exactly how long B. eremicarminis was and how it survived along the coasts remains shrouded in history.

Only a few elements of the individual’s skull were found, and clues about how the animal fed and hunted are also lacking. What is clear is that B. eremicarminis probably stayed relatively close to the coast. Its well-preserved limbs are well developed with no signs of aquatic life, such as fins or altered bone density.

The research team wanted a name that would honor the original human inhabitants of the Augusta Mountains, where the specimen was found, so they consulted a member of the Fallon Paiute Shoshone tribe to come up with a suitable name.

“Benggwi-Gwishinga,” a word that means “fish” in Shoshone, was combined with the Greek word for Sobek, the crocodile-headed Egyptian god, to create the new genus Benggwigwishingasuchus. The specific epithet eremicarminis translates to “song of the desert,” in honor of two NHMLAC supporters who are passionate about Southwestern paleontology and opera. The full name thus roughly translates as “The Desert Song of the Fishing Crocodile.”