Thanatotheristes

Credit: Teratophoneus on DeviantArt.

*Thanatotheristes* is an extinct genus of tyrannosaurid dinosaur that lived in Alberta, Canada in Late Cretaceous.

## History

*Thanatotheristes* means 'reaper of death' or 'death harvester' in Greek. The name consists of Thánatos (Θάνατος), "Death" and the romanticized theristḗs (θεριστής), "harvester". The specific name *degrootorum* honours John and Sandra De Groot, the discoverers of the type specimen. *Thanatotheristes* is known from Twelve Mile Coulee, Upper Herronton Sandstone, Foremost Formation.

## Description

Thanatotheristes is characterized by several anatomical differences, such as course substance reaching the maxilla anteroventral to the antorbital fossa; a single row containing evenly spaced dorsoventrally-facing ridges on the maxilla ventral and anteroventral of the antorbital fossa; the orbital margin on the jugal is rounded and inflated; the sagittal crest is defined and larger; being broad and rounded; the lacrimal contact surface extends 60° referenced to the interfrontal suture; and the prefrontal has several articulated prongs that project posteriorly and the frontal on the ventral of the skull roof. The primary is long and medial, and the secondary is shorter and lateral. The type of *Thanatotheristes* is estimated at 8 meters long, 5 feet tall and weighing about 2 tons. The holotype specimen was not mature. The holotype of *Thanatotheristes* is TMP 2010.5.7; the right maxilla, jugal, right postorbital, right surangular, right quadrate, right laterosphenoid, left frontal and both dentaries. The skull is ~800 millimeters (31 inches) long, smaller than the close and similar *Daspletosaurus*. The holotype is not osteologically mature. The referred is TMP 2018.016.0001, a partial right maxilla from a subadult.

## Classification

*Thanatotheristes* erected its own tribe: named Daspletosaurini, includes *Daspletosaurus*, *Thanatotheristes*, and FMNH PR308 (Dinosaur Park Formation tyrannosaurid). This group is sister to Tyrannosaurini. Thanatotheristes represents its own branch of this tribe, branching off before FMNH PR308 and *Daspletosaurus*. This erection of this tribe shows how the clades were geographically segregated. The clade with *Bistahieversor* and the clade with *Lythronax* and *Teratophoneus* lived in southern Laramidia. The following split Daspletosaurini: the maxilla tapers at a shallow angle, around <65°, this angle was measured between the alveolar margin of the first two alveoli as well as the anterior margin of the subcutaneous surface; a constricted jugal ramus of the maxilla; the prefrontal is broad in the dorsal viewpoint, however is strongly dorsomedially arced in the anterior viewpoint; the dentary chin is located ventral to the third alveolus or the third interdental plate; and the specimen possesses no less than 14 maxillary teeth. Phylogenetic analysis by Voris et al. (2020):

Analysis from subadult *Daspletosaurus torosus* by Yun (2020) proposes that autapomorphies in some tyrannosaurs are inadequate, since some clades have prominent individual variation in the frontals. This suggests the autapomorphies and synapomorphies in *Thanatotheristes* would cause for it to be reclassified as *"Daspletosaurus degrootorum"*. However, this has been discredited due to many apomorphies in the maxilla alone and Yun's fraudulent career.

## Paleoecology

*Thanatotheristes* lived in Foremost Formation, Late Cretaceous Canada, with animals like *Xenoceratops* and *Colepiocephale*. Due to the fact that *Thanatotheristes* was the only tyrannosaur in its ecosystem; it was likely an apex predator.

## Notable Specimens

* TMP 2010.5.7: The holotype skull of *Thanatotheristes*, preserving elements from the rear of the skull, eye orbits, the maxilla, teeth and parts of the jaws. The skull is roughly 800 millimeters long. The holotype was not fully mature when discovered, however.
* TMP 2018.016.0001: Another skull of *Thanatotheristes*, which consists of maxilla elements, and, like the holotype, was not mature either.

## References

https://en.wikipedia.org/wiki/Thanatotheristes