Dinosaur-Chewing Mammals Leave Behind Oldest Known Tooth Marks

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Paleontologists have discovered the oldest mammalian tooth marks yet discovered dated at around 75 milllion years, on the bones of ancient dinosaurs and reptiles. The find includes a femur bone from a Champsosaurus, an aquatic reptile that grew up to five feet long, the rib of a hadrosaurid or ceratopsid and the femur of another large ornithischian dinosaur.

The marks were created by opposing pairs of teeth, a trait seen only in mammals at that time. From the impressions scientist believe that the most likely candidate is a member of the multituberculates, an extinct order of archaic mammals resembinge rodents who had paired upper and lower incisors. Multituberculates which went extinct about 35 million years ago are outside either of the two main groups of living mammals Theria, including the placentals and marsupials, and the Monotremata.

The culprit probably would have looked something like this handsome multituberculate, Ptilodus.

http://www.sciencedaily.com/releases/2010/06/100616161207.htm

Paleontologists have discovered the oldest mammalian tooth marks yet on the bones of ancient animals, including several large dinosaurs.

They report their findings in a paper published online June 16 in the journal Paleontology.

Nicholas Longrich of Yale University and Michael J. Ryan of the Cleveland Museum of Natural History came across several of the bones while studying the collections of the University of Alberta Laboratory for Vertebrate Palaeontology and the Royal Tyrrell Museum of Palaeontology. They also found additional bones displaying tooth marks during fieldwork in Alberta, Canada. The bones are all from the Late Cretaceous epoch and date back about 75 million years.