The rhynchosaur Bentonyx, which lived about 245 million years ago.Credit...Mark Witton
The New York Times "Trilobite" column has a story about animals that dominated the world before dinosaurs. A new study in the journal Palaeontology by Michael Benton, a paleontologist at the University of Bristol in England, looked at how rhynchosaurs ate. He found they chewed by grinding tough plant matter between a row of teeth and bare bone. This strange way of feeding would have ground their teeth down to nothing as they aged, which would have caused old rhynchosaurs to starve as they would have been unable to eat in old age. All of which may have led to their extinction and eventual replacement by dinosaurs.
Dr. Benton started working on rhynchosaur teeth while earning his Ph.D. in the 1980s. While examining their fossils, Dr. Benton noticed that the reptiles appeared to be grinding food by pushing teeth up against their jaws — a surprising technique because grinding food up against jawbones opens up animals to the risk of infection. The development of their jaws also gave adult rhynchosaurs a slope to their mouths — fixing them in a permanent “grin.”
While a few animals chew this way today — including some chameleons — scientists “don’t really understand how the heck they do it,” said Yara Haridy, an evolutionary biologist at the University of Chicago, who was not involved in the paper but reviewed it for the journal. The use of this technique is especially strange for an animal like a rhynchosaur that fed nearly exclusively on tough plants, which would have damaged their teeth over time.
“That wear and tear is not good for you, especially if you want to keep eating,” Dr. Haridy said.
