Voris et al., 2020
Voris et al., 2020
Thanatotheristes (meaning "reaper of death" according to the original authors; literally, "death harvester" in Greek: Θάνατος, romanized: Thánatos, "Death" and θεριστής, romanized: theristḗs, "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.
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 800 millimetres (31 in). 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.
T. degrootorum is characterised by:
The type specimen of Thanatotheristes has been estimated at about 8 m (26 ft), based on the skull material and comparisons with related genera.
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:
It has recently suggested that degrootorum should be considered as a species of Daspletosaurus.