| Thanatotheristes | |
|---|---|
 | |
| Life restoration | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Tyrannosauridae |
| Subfamily: | †Tyrannosaurinae |
| Tribe: | †Daspletosaurini |
| Genus: | †Thanatotheristes Voriset al., 2020[1] |
| Type species | |
| †Thanatotheristes degrootorum Voriset al., 2020[1] | |
| Synonyms[2] | |
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Thanatotheristes (meaning "reaper of death" according to the original authors;[1] literally, "death harvester" inGreek:Θάνατος,romanized:Thánatos, "Death"[3] andθεριστής,romanized:theristḗs, "harvester"[4]) is agenus oftyrannosauriddinosaur from theLate Cretaceous ofLaramidia, approximately 80.1-79.5 Ma.Thanatotheristes contains only onespecies,T. degrootorum.Fossils of this taxon are found in theForemost Formation ofAlberta, Canada, coexisting with medium-sizedceratopsids likeXenoceratops foremostensis and smallpachycephalosaurids likeColepiocephale lambei.
Theholotype specimen ofThanatotheristes 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 relatedDaspletosaurus, 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 another subadult individual. It was found at the Twelve Mile Coulee in the upper Herronton Sandstone of the Foremost Formation. Thespecific name honours John and Sandra De Groot, who discovered the type specimen.[1]
T. degrootorum is characterised by:[1]
The type specimen ofThanatotheristes has been estimated at 8 m (26 ft), based on the skull material and comparisons with related genera.[5]
The formal description ofT. degrootorum erected a new clade within Tyrannosauridae, Daspletosaurini, a sister taxon to a clade comprisingZhuchengtyrannus,Tarbosaurus, andTyrannosaurus. It includesT. degrootorum,Daspletosaurus torosus,D. horneri, and a tyrannosaurid from theDinosaur Park Formation (FMNH PR308). The existence of Daspletosaurini shows that there is geographic segregation of clades within Tyrannosauridae, with the clade ofBistahieversor and the clade formed byLythronax andTeratophoneus living in the south of Laramidia, andAlbertosaurinae and Daspletosaurini occupying Canada and northern USA.[1]
The cladogram below is the result of thephylogenetic analysis performed by Voriset al. (2020):[1]
An analysis of a subadultDaspletosaurus 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 ofT. degrootorum are inadequate, and may therefore render it a species ofDaspletosaurus.[2] This identification was based on the 2003 study byPhilip J. Currie.[6] A subsequent analysis ofGorgosaurus ontogeny by Voris et al, 2021 found that Philip Currie's initial identification of this frontal asDaspletosaurus was in error and that the frontal actually belonging to aGorgosaurus. This study further reinforced the frontal autapomorphies ofThanatotheristes initially proposed by Voris et al (2020) as valid noting that Yun (2020)'s consideration of the characters as invalid was due to his misidentification of the specimen asDaspletosaurus and a misinterpretation of the frontal morphology of tyrannosaurids overall.[7]
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