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Tooth marks gouged in the rib bone of a large dinosaur by a mammal that lived 75 million years ago. (Nicholas Longrich/Yale University)
Paleontologists have recently discovered the oldest known mammalian tooth marks on the bones of ancient animals, including a few large dinosaurs.
While studying the paleontological collections, Nicholas Longrich of Yale University and Michael Ryan of the Cleveland Museum of Natural History came across several bones displaying tooth marks. The bones all come from the Late Cretaceous epoch, dating back to about 75 million years ago.
“The marks stood out for me because I remember seeing the gnaw marks on the antlers of a deer my father brought home when I was young, so when I saw it in the fossils, it was something I paid attention to,” said Longrich in a press release.
Among the collections of the University of Alberta Laboratory for Vertebrate Paleontology and the Royal Tyrrell Museum of Paleontology were tooth marks on a femur bone from a champsosaurus, an aquatic reptile that grew up to five feet long; the rib of a dinosaur, most likely a hadrosaurid or ceratopsid; the femur of another large dinosaur that was likely an ornithischian; and a lower jaw bone from a small marsupial.
“Of the animals known from the Late Cretaceous of North America, only mammals are capable of making such tooth marks,” the researchers wrote in their research paper published online in the journal Paleontology.
“In particular, multituberculates, which have paired upper and lower incisors, are the most likely candidates for the makers of these traces.”
Multituberculates, an extinct order of archaic mammals that are similar to rodents, were probably gnawing on the bare bones for minerals as opposed to for meat, said Longrich.
“The traces described here represent the oldest known mammalian tooth marks,” the research paper read.
“Although it is possible that some of these tooth marks represent feeding traces, the tooth marks often penetrate deep into the dense cortices of the bone. This raises the possibility that, much as extant mammals gnaw bone and antler, some Cretaceous mammals may have consumed the bones of dinosaurs and other vertebrates as a source of minerals.”
