Around 95 million years ago, small crocodile-like creatures with strange, sheathed teeth burrowed along the shores of the Western Interior Seaway in what is now southwest Montana, a new study suggests.
The new research describes the first such creature ever discovered — a teenage croc nicknamed Elton that measured about 2 feet (60 centimeters) long from nose to tail tip. Elton's fossilized remains were discovered in 2021 during an organized dig in the Blackleaf geological formation, which dates to the middle of the Cretaceous period (145 million to 66 million years ago).
The first fossil Allen noticed was Elton's skull, which was just 2 inches (5 cm) long and embedded in rock, according to the statement. Allen showed the miniature skull to David Varricchio, a professor of paleobiology, taphonomy and ichnology at Montana State University, who immediately understood the fossil's significance.
"After the dig, Dr. Varricchio told me why he was so excited the day I found the initial specimen," Allen said. "It has so much visible anatomy to explore, and he could see it was a tiny, tiny croc skull, fully articulated and preserved — it was a special thing."
It turns out, Elton belonged to a now-extinct family of crocodile-like creatures, or crocodyliforms, that researchers previously didn't know existed. This family, called Wannchampsidae, sits within the lineage Neosuchia, which includes all modern crocodilians and their closest extinct relatives. Its members lived in North America during the Cretaceous, and they were much smaller than other neosuchian crocs are; had Elton survived until adulthood, he would have grown to just 3 feet (90 cm) long, according to the statement.
Neosuchians are typically semi-aquatic or marine carnivores with simple, conical teeth — but not Elton. He and fellow members of the newfound species, named Thikarisuchus xenodentes, had an assortment of differently shaped teeth, including sheathed and other specialized fangs, which they used to devour plants and insects, according to the statement.
Elton and his kind also lived on land, and they likely made burrows in the ground, based on how densely packed Elton's bones were when Allen and his colleagues analyzed them, the statement said.
Shortly after finding Elton's skull, Allen returned to collect bagfuls of the surrounding sediment to search it for more clues about the animal. He spent hours sifting through the dirt, extracting fragments of bone and reconstructing the Thikarisuchus skeleton bit by bit. He worked with his classmate Dane Johnson, now a paleontology lab and field specialist at the Museum of the Rockies in Montana — often to the tune of Elton John's 1972 song "Crocodile Rock," which inspired the name Elton.
To get a clear picture of the fossils, Allen then made CT scans, which helped him distinguish between the bones and chunks of rock that were still stuck to Elton's remains. "Harrison worked super hard to digitally reconstruct the animal, and it came out beautifully," Varricchio, who is a co-author of the new study, said in the statement.
A detailed description and pictures of T. xenodentes, as well as a discussion of the newfound species' position in the evolutionary tree, are included in the study, published Sept. 22 in the Journal of Vertebrate Paleontology. Notably, the researchers highlight a family of ancient crocodyliforms called Atopasauridae that was previously found in Eurasia and looks like Elton, with a small body size and similar dental features.
"It suggests that during the same time period, we're seeing convergent evolution between two distantly related groups due to similar environmental conditions, prey availability and who-knows-what that prompted crocs on opposite sides of the planet to develop similar features," Allen said.
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