Before Dinosaurs, These Guys Had a Serious Eating Flaw

In the age before the towering dinosaurs we know so well from textbooks and Jurassic Park movies, an ugly-cute creature about the size of a pig called the rhynchosaur roamed the Earth, chomping on tough plants with a single row of teeth. As the New York Times reports, they were relatively successful for the time (around 245 million years ago in the Triassic Era), but scientists have determined they had a critical, physical design flaw that we now know made their fossil-based reputation as "grinning" reptiles a lie. In research done by scientists at the University of Bristol in the UK, CT scans found that due to physiological limitations in their jaws, rhynchosaurs likely starved to death once they hit old age.

New Atlas notes in its coverage that rhynchosaurs favored a diet consisting of tough vegetation that likely "ground their teeth down to such a point that they would no longer be able to get adequate nutrition." The problem was an inefficient, scissor-like chewing action. A rhynchosaur might tear at some tasty, leathery plant leaves, then spend time mashing them to a digestible state with just one set of teeth grinding matter against a bony ridge. Those teeth deteriorated over time, and unlike some modern animals with similar ways of eating, rhynchosaurs couldn't grow replacements. In the end, they would be left with a nub or two, unable to chew properly anymore. The changes to their jaw and mouth also left them with what appeared to be a permanent grin, notes the Times.

"That wear and tear is not good for you, especially if you want to keep eating," University of Chicago evolutionary biologist Yara Haridy, who was not involved with the research, tells the Times. Study co-author Thitiwoot Sethapanichsakul said in a press release that rhynchosaurs "were clearly eating really tough food such as ferns, that wore the teeth down to the bone of the jaw, meaning that they were basically chopping their meals by a mix of teeth and bone." Still, a changing climate that affected the availability of plants is probably more to blame for their ultimate demise than the physical glitch, per the news release. There are still mysteries to unravel about these ancient herbivores, however, and as Phys.org reported in April, the discovery of new rhynchosaur fossils in Wyoming might bring them into sharper focus. (More dinosaurs stories.)