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Cretaceous Wars - The Revenge of the Rat...uh...I mean Mammal



As time goes by, the role of mammals in Cretaceous ecosystems becomes more complex than previously thought. The "small nocturnal insectivorous mammal" dogma has been indeed questioned in the last decade following the discovery of new well preserved forms, such as the dog-sized triconodont *Repenomamus* of which the diet included juvenile dinosaurs or the very small (~6 gs !) fossorial *Fruitafossor*.

The taphonomic studies of Nicholas Longrich and Michael Ryan on on dinosaur, *Champsosaurus*, and *Eodelphis* bones from the Late Cretaceous of Alberta brings new evidence for complex - here gnawing - behaviour in Cretaceous mammals - including probably multituberculates. There are so many papers on Neogene taphonomy and comparatively too few on older material, although taphonomy deals with behaviour, ecology, diet preferences, and so many things of which we know little for extinct taxa - even non-avian dinosaurs which are not the least studied of Mesozoic taxa.

Anyway, here is the paper (in press): http://www3.interscience.wiley.com/journal/123529400/abstract/

Longrich N.R. & Ryan M.J. In press. Mammalian tooth marks on the bones of dinosaurs and other Late Cretaceous vertebrates. Palaeontology.

We describe bones from the Late Cretaceous of Alberta – including bones of large dinosaurs, a femur from the aquatic reptile Champsosaurus, and a dentary from the marsupial Eodelphis– that bear tooth marks made by animals with opposing pairs of teeth. Of the animals known from the Late Cretaceous of North America, only mammals are capable of making such tooth marks. In particular, multituberculates, which have paired upper and lower incisors, are the most likely candidates for the makers of these traces. The traces described here represent the oldest known mammalian tooth marks. 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. However, none of the tooth marks described here resemble the extensive gnaw traces produced by Cenozoic multituberculates or rodents. This suggests that specialized gnawing forms may have been rare or absent in the Late Cretaceous of North America.

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Jocelyn FALCONNET
PhD student -> The early radiation of amniotes
Supervisors -> J-C Rage and J-S Steyer (MNHN)

CR2P, UMR 7207, CNRS
Département Histoire de la Terre
Muséum national d'Histoire naturelle
Case Postale 38
57 rue Cuvier
75231 Paris cedex 05, France