Dental ecomorphology and macroevolutionary patterns of North American Late Cretaceous metatherians

Abstract

Metatherian mammals were taxonomically rich and abundant in Late Cretaceous faunas of North America. Although much attention has been paid to metatherian taxonomy, a comprehensive, quantitative study on the ecomorphology of this clade is lacking. Here, we predict the diets of a large sample of metatherians using threedimensional dental topographic analysis, with the aim to better understand macroevolutionary patterns in dental morphology and dietary diversity. Contrary to their taxonomic diversity patterns, our results show that dental disparity and dietary diversity did not significantly change throughout the Late Cretaceous and that most metatherians were invertivorous (diets of insects and soft-bodied invertebrates). Nevertheless, we also found that metatherians occupied a wide range of dietary niches and were arguably the most dietarily diverse of any mammalian clade of the Late Cretaceous. Regarding the timing of metatherian ecomorphological diversification, our results indicate that it began by the mid-Cretaceous in-step with the Cretaceous Terrestrial Revolution and the taxonomic diversification of angiosperms, prior to the ecological diversifications of multituberculates and eutherians that began in the latest Cretaceous and Paleocene.