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Argaliatherium and Carinalestes, new tribosphenic mammals from Lower Cretaceous Cloverly Formation

Ben Creisler

A new online paper:

Richard L. Cifelli & Brian M. Davis (2015)
Tribosphenic mammals from the Lower Cretaceous Cloverly Formation of
Montana and Wyoming.
Journal of Vertebrate Paleontology (advance online publication)

We report a diverse assemblage of tribosphenidan mammals from several
localities in the Cloverly Formation (Lower Cretaceous, Albian) of
Montana and Wyoming. This unit is of historical significance for
yielding well-known dinosaurs (e.g., Deinonychus antirrhopus,
Tenontosaurus tilletti) and early mammals (e.g., Gobiconodon ostromi,
Montanalestes keeblerorum). We provisionally identify 13 taxa (five of
which are formally recognized), including Pappotherium pattersoni, a
new species of the deltatheroidan Oklatheridium (O. wiblei, sp. nov.),
a eutherian (Montanalestes, previously named), and two new basal
tribosphenidans (Argaliatherium robustum, gen. et sp. nov., and
Carinalestes murensis, gen. et sp. nov.). An unnamed taxon,
represented by associated but almost edentulous dentaries, is
interpreted to have had four incisors, a single-rooted canine, three
premolars, and four molars, indicating that the metatherian tooth
formula was established by the Albian. In addition, an indeterminate
lower molar fragment preserving twinned talonid cusps and a buccal
postcingulid provides the earliest evidence for Marsupialiformes. We
also provide a more detailed description of the associated dentaries
(holotype) of Montanalestes keeblerorum. The mammalian fauna from the
Cloverly Formation shares several taxa with the roughly
contemporaneous Trinity Group of Oklahoma and Texas, an observation
that also applies to the dinosaur fauna, suggesting some degree of
latitudinal homogeneity among described terrestrial vertebrates in
this part of the North American Early Cretaceous.