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Rodents, multis, and dino bones



I'm kind of late on this thread, but I wanted to offer a few thoughts.
David Brez Carlisle is correct in saying that rodents (sensu stricto)
we're not contemporaneous with dinosaurs, although the group first appears
in the late Paleocene, not the late Eocene as stated by him.
If we want to evaluate the possibility that dinosaurs bones were gnawed
by certain species of mammals, we must first understand why certain
mammals gnaw hard objects such as bone. The rodents, for example, have
evergrowing incisors, which makes it necessary for them to gnaw such
hard objects in order to "sharpen" their teeth. The need for calcium is,
in my opinion, a secondary factor. Many other groups of mammals have
developed evergrowing teeth, and it is reasonable to assume that they
need to chew or gnaw tough objects if they don't want their teeth to 
grow too much or incorrectly. Certain groups of mammals, such as multis
and plesiadapiforms, had a superficially rodent-like dentition, but
there is no evidence that they gnawed hard objects; there was no need
to, since their incisors had determinate growth. There is, however,
one group of multis, the taenolabidoids, that possessed evergrowing
incisors. This is a primarily late Cretaceous- early Paleogene group,
so the possibility remains that the late Cretaceous species of
taenolabidoids did in fact gnaw dinosaur bones. One way to test this
idea would be, of course, to find dinosaur bones with gnaw marks that
correspond in size and shape to the incisors of taenolabidoids multis.
Maybe such bones can be found in museums, and maybe some researchers
have already observed such gnaw marks on their subjects of study.

Michel Chartier