Tribosphenic mammal from the North American Early Cretaceous

0Citations
Citations of this article
51Readers
Mendeley users who have this article in their library.
Get full text

Abstract

The main groups of living mammals, marsupials and eutherians, are presumed to have diverged in the Early Cretaceous1, but their early history and biogeography are poorly understood. Dental remains have suggested that the eutherians may have originated in Asia2, spreading to North America in the Late Cretaceous, where an endemic radiation of marsupials was already well underway3. Here I describe a new tribosphenic mammal (a mammal with lower molar heels that are three-cusped and basined) from the Early Cretaceous of North America, based on an unusually complete specimen. The new taxon bears characteristics (molarized last premolar, reduction to three molars) otherwise known only for Eutheria among the tribosphenic mammals. Morphometric analysis and character comparisons show, however, that its molar structure is primitive (and thus phylogenetically uninformative), emphasizing the need for caution in interpretation of isolated teeth. The new mammal is approximately contemporaneous with the oldest known Eutheria from Asia. If it is a eutherian, as is indicated by the available evidence, then this group was far more widely distributed in the Early Cretaceous than previously appreciated. An early presence of Eutheria in North America offers a potential source for the continent's Late Cretaceous radiations, which have, in part, proven difficult to relate to contemporary taxa in Asia.

Cite

CITATION STYLE

APA

Cifelli, R. L. (1999). Tribosphenic mammal from the North American Early Cretaceous. Nature, 401(6751), 363–366. https://doi.org/10.1038/43860

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Save time finding and organizing research with Mendeley

Sign up for free