New fossil species rewrites coastal life in the age of the dinosaur

11 Jul. () –

The surprising discovery of a new fossil species of a crocodile relative in a rock formation in Nevada rewrites the history of coastal life at the beginning of the Age of Dinosaurs.

Described in a study published in Biology Lettersthe new species Benggwigwishingasuchus eremicarminis reveals that while giant ichthyosaurs ruled the oceans, ancient crocodile relatives known as pseudosuchian archosaurs dominated coastlines around the globe in the Middle Triassic between 247.2 and 237 million years ago.

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

The area that includes the Favret Formation, the location of the study’s find in Nevada, which is characterized by the capture of fossils of Triassic eastern Panthalassan ocean life, is known for its fossils of marine creatures such as ammonites and marine reptiles such as the giant ichthyosaur C. youngorum. The discovery of the newly described B. eremicarminis was a surprise.

“Our first reaction was: what the hell is this?” said co-author Dr Nicole Klein from the University of Bonn. “We were expecting to find things like marine reptiles. We couldn’t understand how a land animal could end up so far out at sea between the ichthyosaurs and ammonites. It wasn’t until I saw the almost fully prepared specimen in person that I was convinced it was indeed a terrestrial animal.”

Pseudosuchian archosaurs have been unearthed in fossil beds on the shores of the ancient Tethys Ocean, but this is the first coastal representative of the Panthalassan Ocean and the Western Hemisphere, revealing that These relatives of crocodiles were present in coastal environments around the world during the Middle TriassicInterestingly, these coastal species do not all belong to the same evolutionary group, suggesting that pseudosuchians (and archosauriforms in general) independently adapted to life on the coasts.

“Basically, it looks like there were a bunch of very different groups of archosauriforms that decided to go underwater during the middle Triassic. What’s interesting is that it doesn’t look like many of these ‘independent experiments’ lead to broader radiations of semiaquatic groups,” Smith said.

During the Triassic, archosaurs emerged, “the dominant reptiles”, which were divided into two groups with two surviving representatives: birds, descendants of dinosaurs, and crocodilians (alligators, crocodiles and gharials), descendants of pseudosuchian archosaurs such as B. eremicarminis.

Although modern crocodilians are similar enough that most people confuse them with each other, their ancient relatives varied greatly in size and lifestyle. The evolutionary relationships of B. eremicarminis and its relatives suggest that pseudosuchians achieved great diversity very quickly after the end-Permian mass extinction, whose scope 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 occurring early in the group’s history. While much of the public’s fascination with the Triassic centers on the origin of the dinosaurs, “It was really the pseudosuchians that were doing interesting things at the beginning of the Mesozoic”Smith said.

The new species underlines the multiplicity of these ancient reptiles during the Triassic, from giants like Mambawakale ruhuhu to smaller animals like the newly described B. eremicarminis, which probably reached around 1.5-2 metres in length. The exact length of B. eremicarminis and how it survived along the coasts remains a mystery.

Only a few elements of the individual’s skull were found, and any clues about how it fed and hunted are equally absent. What is clearer is that B. eremicarminis probably stayed fairly close to the coast. Its limbs, well preserved, are well developed and show no signs of aquatic life, such as fins or altered bone density.

The research team wanted a name that honored the original human inhabitants of the Augusta Mountains, where the specimen was found, so they consulted with a member of the Fallon Paiute Shoshone tribe to decide on an appropriate name.

“Benggwi-Gwishinga,” a word meaning “to fish” in Shoshone, was combined with the Greek word for Sobek, the Egyptian crocodile-headed god, to coin the new genus, Benggwigwishingasuchus. The specific epithet eremicarminis translates to “desert song,” after two NHMLAC supporters with a passion for paleontology and Southwestern opera. Thus, the full name roughly translates to “Desert Song of the Fishing Crocodile”.