Thanatotheristes

Thanatotheristes (meaning "reaper of death" according to the original authors; literally, "death harvester" in Greek: , , "Death" and , , "harvester") is a genus of tyrannosaurid dinosaur from the Late Cretaceous of Laramidia, approximately 80.1-79.5 Ma. "Thanatotheristes" contains only one species, T. degrootorum. Fossils of this taxon are found in the Foremost Formation of Alberta, Canada, coexisting with medium-sized ceratopsids like "Xenoceratops foremostensis" and small pachycephalosaurids like "Colepiocephale lambei".
Discovery and naming.
The holotype specimen of "Thanatotheristes degrootorum" (TMP 2010.5.7) is based on a right maxilla, right jugal, right postorbital, right surangular, right quadrate, right laterosphenoid, left frontal, and both dentaries. The length of the skull has been approximated to be . It was smaller than the closely related "Daspletosaurus", but the holotype individual was not osteologically mature at the time of death. A referred specimen, TMP 2018.016.0001, is based solely on a partial right maxilla from a subadult individual. It was found at the Twelve Mile Coulee in the upper Herronton Sandstone of the Foremost Formation. The specific name honours John and Sandra De Groot, who discovered the type specimen.
Description.
"T. degrootorum" is characterised by:
The type specimen of "Thanatotheristes" has been estimated at about , based on the skull material and comparisons with related genera.
Classification.
The formal description of "T. degrootorum" erected a new tribe within Tyrannosauridae, Daspletosaurini, a sister taxon to Tyrannosaurini. It includes "T. degrootorum", "Daspletosaurus torosus", "D. horneri", and a tyrannosaurid from the Dinosaur Park Formation (FMNH PR308). The existence of Daspletosaurini shows that there is geographic segregation of clades within Tyrannosauridae, with the clade of "Bistahieversor" and the clade formed by "Lythronax" and "Teratophoneus" living in the south of Laramidia, and Albertosaurinae and Daspletosaurini occupying Canada and northern USA.
Daspletosaurini is diagnosed by the following characteristics:
The cladogram below is the result of the phylogenetic analysis performed by Voris "et al." (2020):
An analysis of a subadult "Daspletosaurus torosus" frontal by Yun, 2020 suggests that features of the bone would effectively demonstrate that autapomorphies of some tyrannosaurid taxa would be inadequate, due to the broad range in morphology of frontals within particular clades. This may suggest that any autapomorphies or synapomorphies pertaining to the frontal of "T. degrootorum" are inadequate, and may therefore render it a species of "Daspletosaurus".