An extinct weasel parent with a confusing skull probably ate meat with a side of vegetables

A new research on an extinct weasel parent reveals what he could have eaten when he lived in North America and Asia about 20 million years ago. The oddly shaped skull of Leptarctus primus has long led to conflicting theories about his diet. But the new work, based on biomechanical modeling and published this week in the Journal of Vertebrate Paleontology, shows that Leptarctus was probably a carnivorous predator, able to have an omnivory and a larger diet when its prey was scarce, and whose skull functioned similarly to that of the living American badger.

Leptarctus primus, who lived in the Miocene and was just a little taller than a domestic cat, intrigued the researchers because of its unusual and extremely robust skull.

"For a mammal, his skull is really strange," said co-author Z. Jack Tseng, associate researcher at the American Museum of Natural History and assistant professor of pathology and anatomical sciences at the Jacobs School of Medicine and Biomedical Science of the University of Buffalo. "He is heavily built – like a tank – with very thick zygomatic cheekbones, the top of his head looks like a helmet."

Leptarctus primus has two parallel ridges that line the top of the head (other carnivores usually have a single central ridge or smooth skull). For many years, paleontologists have debated the ecological niche of Leptarctus based on contradictory interpretations of the strong parallel ridges of the skull, the distinct shape of the skull and the shape of its teeth and wear. Previous interpretations of their dietary lifestyle varied widely, for virtually all types of feeding behavior known to carnivores (dogs, cats, hyenas, bears, seals and weasels, and their parents), including herbivores, carnivores, insectivores, and omnivores. . But lack of quantitative research on the functioning of the skulls of Leptarctus, the question of their diet remained unanswered.

In this study, led by Alixandra Prybyla, a student in the Summer Research Experience program for undergraduate students at the Museum's National Science Foundation, the researchers adopted an engineering approach. The team compared an almost complete fossil skull of Leptarctus primus to 18 modern carnivore species with known diets, as well as other fossil species, using simulations of bites based on skull tomodensitograms and virtual modeling of the skulls. feeding mechanisms.

According to John Flynn, co-author of the study, head of the Frick Research and Conservation Team of Fossil Mammals at the Museum's Division of Paleontology, "the traditional methods of studying the history of the museum," Anatomy of the skull, tooth and skeleton remains essential for understanding the lifestyle of fossil species High resolution CT scans and sophisticated computer modeling tools have completely transformed our ability to accurately reconstruct dietary habits. missing animals. "

They found that among the other species analyzed, the Leptarctus skull is mechanically very similar to the skull of the American badger. Despite some differences in the appearance of the skull, computer simulations indicate that the badger is the best living biomechanical analogue for understanding the dietary lifestyle of Leptarctus. Based on these comparisons, the team determined that it was primarily a carnivore and an active predator, but that it was also an omnivore feeding on a wider variety of food for humans. plants and insects if necessary.

"He was probably hunting for prey and taking what he had access to most of the time," Tseng said.

Prybyla added, "This complete Leptarctus skull represents an untapped source of information on the story of the ancient parents of weasels, otters, badgers and skunks. that a specimen can enlighten for researchers. "To lead a project of this magnitude undergraduate student was extremely empowering."

Researchers will conduct future studies using similar engineering modeling tools to examine variations in skull feeding mechanics in other species of the leptarctin group, in order to determine the number of of different types of dietary adaptations that may exist in these unusual extinct predators.

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More information:
Alixandra N. Prybyla et al., Biomechanical simulations of Leptarctus primus (Leptarctinae, Carnivora) and new evidence of a feeding capacity similar to that of the badger. Journal of Vertebrate Paleontology (2019). DOI: 10.1080 / 02724634.2018.1531290