In Montana’s ancient rocks, scientists uncovered the tiny remains of a land-dwelling crocodyliform that challenges what we thought we knew about crocodile evolution.
Around 95 million years ago, a small crocodyliform affectionately called Elton roamed what is now southwest Montana, near the ancient shoreline of the Western Interior Seaway.
According to Montana State University paleontology professor David Varricchio, the juvenile measured less than 2 feet long from snout to tail—roughly the size of a large lizard. Even as an adult, it would have reached only about 3 feet in length, making it much smaller than most members of the Neosuchia clade, which includes modern crocodiles and their extinct relatives. Most of these species were aquatic or semi-aquatic predators equipped with simple, conical teeth suited for catching prey in the water.
Elton, however, was different. It lived on land and likely fed on plants, insects, or small animals, using its varied and specialized teeth to process a wider range of food. Its distinctive features revealed that it belonged to a newly identified family of crocodyliforms native to Cretaceous-era North America.
This remarkable discovery might never have happened without the keen observation of Harrison Allen, a 2023 graduate of MSU’s Department of Earth Sciences in the College of Letters and Science. During a 2021 field excavation in the Blackleaf Formation near Dillon, Montana, Allen—then a student in Varricchio’s paleontology course—spotted a tiny fossil, no larger than his pinkie tip, with a “weird texture on it.”
“I brought it to Dr. Varricchio and knew it must be something good, because he said, ‘Take me to where you found this,’” said Allen, who is now studying croc paleontology as a doctoral student at Stony Brook University in New York.
It was an exciting moment for Allen, originally from Kentucky, who chose MSU because it offers a paleontology track for undergraduates majoring in earth sciences. Four years and hundreds of hours of study later, he is the lead author of a paper published this week in the Journal of Vertebrate Paleontology that describes the morphology and scientific significance of the creature whose remains he found in the Blackleaf Formation.
Naming a New Species
“After the dig, Dr. Varricchio told me why he was so excited the day I found the initial specimen. It had 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,” Allen said. “We have found dinosaurs (in the Blackleaf) before, but this was the second known vertebrate animal we’d ever found in this formation.”
The extinct animal, which Allen and the paper’s co-authors later named Thikarisuchus xenodentes for its strange, sheathed teeth, has provided new information about the paleoecology of the Blackleaf ecosystem and about patterns of evolution in the croc family tree.
It also provided the ultimate undergraduate research project for Allen, who delved into the painstaking process of excavating, sifting, and reconstructing the Thikarisuchus remains with the help of some fellow students.
“As an undergraduate student new to research, I nervously went up to Dr. Varricchio and asked if I could study this specimen,” Allen said. “It led me down the rabbit hole into this amazing world of prehistoric, extinct crocs and their evolutionary niches.”
The day after Allen recovered the first piece of skeleton, he and his classmates scooped up several bags of sediment from the mound where it was found. Back in Bozeman, Allen and his friend Dane Johnson, who graduated in 2022 and is now a paleontology lab and field specialist at MSU’s Museum of the Rockies, spent between 10 and 20 hours sifting out fine particulate matter and dirt, eventually recovering dozens of tiny pieces of the Thikarisuchus skeleton that collectively fit into the palm of Allen’s hand. As they worked, they listened to music, including Elton John’s 1970s hit “Crocodile Rock.” The nickname “Elton” stuck, long before the specimen was assigned the scientific name that reflects its physical traits.
Digital Reconstruction and Research Breakthroughs
Allen and Johnson recovered bits of bone from almost all areas of the animal’s body, including its limbs, vertebrae, jaw and 50-millimeter-long skull. Because the fragments were tiny and exceptionally fragile, the students didn’t attempt to physically reassemble them. Instead, they took them for a series of CT scans, including some at MSU’s Subzero Research Laboratory. Allen estimates that he spent well over 100 hours coloring the digital, 2D segment slices that the scans produced, a process necessary to visually distinguish the bones from the rocks they were embedded in.
“Harrison worked super hard to digitally reconstruct the animal, and it came out beautifully,” said Varricchio.
During the process, Allen discovered that the bones of Thikarisuchus were densely concentrated and organized in a manner consistent with fossils of organisms found in burrows in the Blackleaf Formation and the nearby Wayan Formation in Idaho. He said this suggests that Thikarisuchus was likewise preserved within a burrow, further supporting the notion that fossils recovered from these formations are biased toward those that were preserved in burrows.
The specimen also presented clues about Thikarisuchus’ newly named family group Wannchampsidae and a similar group found in Eurasia known as Atopasauridae. Both groups were tiny and terrestrially adapted, and they shared certain cranial and dental features found in another more distantly related group from the Cretaceous of Africa and South America.
“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.
As he works toward his Ph.D. and a career as a paleontology professor, Allen said his experiences with Elton cemented his research interest, which has since broadened to include extinct crocs from all over the world.
“The majority of diversity of crocodyliforms is in the past. There were fully marine crocs, fully terrestrial crocs, herbivorous crocs, omnivores, and some that cracked shells,” he said. “That amazed me and made me want to get into this more specific realm of paleontology.”
Varricchio said he feels fortunate that students like Allen choose to study at MSU.
“It was a true pleasure to have Harrison as a student here – so much positive enthusiasm, followed up with great research,” he said.
Reference: “A new, diminutive, heterodont neosuchian from the Vaughn Member of the Blackleaf Formation (Cenomanian), southwest Montana, and implications for the paleoecology of heterodont neosuchians” by Harrison J. Allen, Eric W. Wilberg, Alan H. Turner and David J. Varricchio, 22 September 2025, Journal of Vertebrate Paleontology.
DOI: 10.1080/02724634.2025.2542185
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