A large carnivorous mammal from the Late Cretaceous and the North American origin of marsupials

Abstract

Marsupial mammal relatives (stem metatherians) from the Mesozoic Era (252–66 million years ago) are mostly known from isolated teeth and fragmentary jaws. Here we report on the first near-complete skull remains of a North American Late Cretaceous metatherian, the stagodontid Didelphodon vorax. Our phylogenetic analysis indicates that marsupials or their closest relatives evolved in North America, as part of a Late Cretaceous diversification of metatherians, and later dispersed to South America. In addition to being the largest known Mesozoic therian mammal (node-based clade of eutherians and metatherians), Didelphodon vorax has a high estimated bite force and other craniomandibular and dental features that suggest it is the earliest known therian to invade a durophagous predator–scavenger niche. Our results broaden the scope of the ecomorphological diversification of Mesozoic mammals to include therian lineages that, in this case, were linked to the origin and evolution of marsupials.

Systematic affinities of the extinct metatherian Eobrasilia coutoi Simpson, 1947, a South American Early Eocene Stagodontidae: implications for "Eobrasiliinae"

“…Pariadens was recovered as closely related to stagodontid, following Cifelli & Eaton (1987), Cifelli (2004), Eaton (1993a), Williamson et al (2012), and Wilson et al (2016), who supported the affinities of this taxon with Stagodontidae. The results refute Fox & Naylor (2006) and Williamson et al (2014), who considered this taxon as not closely related to Stagodontidae.…”

“…The results of Wilson et al (2016) suggest an omnivore diet for Didelphodon vorax; following the authors, this taxon probably consumed a range of vertebrate, plant and hard-shelled invertebrate resources but few insects, spiders and annelids . The idea that this animal consumed plants is weakly supported, as the enlarged paraconid more typically occurs in carnivorous species (Zimicz, 2012).…”

“…The matrix is based mainly on dental characters from the upper and lower dentition of fossil and living metatherians presented in Carneiro (2017 and references therein), but it also includes cranial, dentary and postcranial characters from Ladevèze & Muizon (2010), Forasiepi et al (2014), Wilson et al (2016) and Beck (2017). The codification of the morphological matrix followed Carneiro (2017).…”

“…The skull of Didelphodon vorax (see Wilson et al, 2016) presents semi-procumbent first incisors (I1), which are evidently better developed than the remaining ones ( Figure 5). This morphology could not be recovered for Eobrasilia, as the type and only known skull does not preserve the upper incisors.…”

“…Currently represented by Eodelphis Matthew, 1916, Didelphodon, Hoodootherium Cohen, 2017, and Fumodelphodon Cohen, 2017, this lineage is characterized by the presence of inflated premolars, stout dentary, large size and lower molars with an enlarged paraconid (Clemens, 1966;Fox, 1981;Cohen, 2017). Pariadens is an enigmatic taxon with possible stagodontid affinities, following previous studies (Cifelli & Eaton, 1987;Cifelli, 2004;Eaton, 1993a;Williamson et al, 2012Williamson et al, , 2014Wilson et al, 2016). Pariadens is known from the Cenomanian, representing one of the oldest metatherians of North America (Cifelli & Eaton, 1987;Cifelli, 2004;Eaton, 1993a;Williamson et al, 2012Williamson et al, , 2014.…”