A new paper:
Highlights
A new genus of tyrannosaurid from the mid Campanian Foremost Formation of southern Alberta is described.
The new genus is found to be the sister taxon to Daspletosaurus spp., and together form the new clade Daspletosaurini.
Tyrannosauridae is revealed to be comprised of multiple, multigeneric clades rather than a series of monogeneric branches.
Geographic segregation of clades provides evidence for provinciality of Tyrannosauridae within North America during the Campanian.
Abstract
Late Cretaceous tyrannosauroid material from North America was primarily known from upper Campanian through Maastrichtian formations until the recent discovery of derived tyrannosaurid taxa from lower-to-mid Campanian deposits in the southwestern United States. However, diagnostic material from contemporaneous deposits further north in Alberta (Canada) and Montana (USA) has yet to be documented. Here we report the discovery of a new tyrannosaurid from the mid-Campanian Foremost Formation of Alberta, Thanatotheristes degrootorum gen. et. sp. nov, which helps fill this gap. Thanatotheristes is found to be the sister taxon to the late Campanian tyrannosaurine genus Daspletosaurus based on several synapomorphies, such as an extremely coarse subcutaneous surface of the maxilla, a constricted jugal ramus of the maxilla, a shallow angle of the anteroventral corner of the maxilla, a high tooth count, a wide prefrontal, and a dentary chin located ventral to either the third alveolus or third interdental plate. Together, these taxa provide evidence for the existence of a clade of long-, deep-snouted tyrannosaurines endemic to northern Laramidia during the Campanian. Our study demonstrates that Tyrannosauridae consists of several geographically segregated clades rather than a series of monogeneric successive sister taxa as recovered by previous studies. The geographic segregation of tyrannosaurid clades within North America provides renewed evidence for provinciality among large theropods during the Late Cretaceous.
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