Biology:Daspletosaurini

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Short description: Extinct clade of tyrannosaurid dinosaurs

Daspletosaurins
Temporal range: Late Cretaceous, middle Campanian 80.1–75 Ma
Daspletosaurus-Triebold-800px.png
Skeletal mount of Daspletosaurus torosus
Scientific classification e
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: Tyrannosauridae
Subfamily: Tyrannosaurinae
Clade: Daspletosaurini
Voris et al., 2020
Type species
Daspletosaurus torosus
Russell, 1970
Genera

Daspletosaurini is an extinct clade of tyrannosaurine dinosaurs that lived in Laramidia during the Late Cretaceous (Middle Campanian) period. It consists of two genera: Daspletosaurus and Thanatotheristes. Four species have been described in the two genera, namely Daspletosaurus torosus, Daspletosaurus horneri, Daspletosaurus wilsoni, and Thanatotheristes degrootorum. At one point all of them were assigned as specimens of D. torosus, but several papers since 2017 have found them to represent distinct species. Some researchers found anagenesis in the group, whether contained in a daspletosaurin clade or paraphyletic in respect to the lineage of tyrannosaurines leading up to Tyrannosaurus,[1][2][3] but a 2023 study refuted this theory on the basis of morphological and stratigraphical data.[4]

Description

Size of four daspletosaurin species compared to a human

Daspletosaurins were large predators, reaching around 9 metres (30 ft) in length.[1] However, they were not the largest tyrannosaurids, as more derived taxa, such as Tyrannosaurus, could reach lengths of more than 12 metres (39 ft).[5]

Daspletosaurini is diagnosed by characteristics such as the presence of an extremely coarse subcutaneous surface of the maxilla anteroventral to the antorbital fossa; a constricted jugal ramus of maxilla; the anteroventral corner of the maxilla tapers into a shallow angle (<65°) as measured between the alveolar margin of the first two alveoli and the anterior margin of the subcutaneous surface; a prefrontal that is broad in dorsal view and strongly dorsomedially arced in anterior view; a dentary chin located ventral to either the third alveolus or third interdental plate and possessing no fewer than 14 maxillary teeth.[2]

Classification

In the 2020 description of Thanatotheristes, Voris et al. erected Daspletosaurini as a new clade within Tyrannosauridae, as a sister taxon to a clade comprising Zhuchengtyrannus, Tarbosaurus, and Tyrannosaurus. The cladogram below shows the results of the phylogenetic analyses performed by Voris et al. (2020):[2]

Tyrannosauridae
Albertosaurinae

Gorgosaurus Gorgosaurus.png

Albertosaurus Albertosaurus NT small.jpg

Tyrannosaurinae
Alioramini

Qianzhousaurus Qianzhousaurus sinensis by PaleoGeek.png

Alioramus remotus Alioramus Life Restoration.jpg

Alioramus altai Alioramus altai.jpg

Teratophoneus Teratophoneus2 NT.jpg

Dynamoterror

Lythronax Lythronax by Tomopteryx.png

Nanuqsaurus Nanuqsaurus reconstruction.jpg

Daspletosaurini

Thanatotheristes Thanatotheristes.jpg

Daspletosaurus torosus
Daspletosaurus torosus steveoc flipped.jpg

Daspletosaurus horneri

Zhuchengtyrannus

Tarbosaurus Tarbosaurus Restoration.png

Tyrannosaurus
Tyrannosaurus-rex-Profile-steveoc86 (coloured).png

In 2022, Warshaw & Fowler proposed that the three Daspletosaurus species evolved through anagenesis in the Tyrannosaurinae in a line leading to Zhuchengtyrannus, Tarbosaurus, and Tyrannosaurus. Due to their more fragmentary nature, Thanatotheristes and Nanuqsaurus were excluded from this analysis. The cladogram below shows the results of the phylogenetic analysis performed by Warshaw & Fowler (2022).[3]

Tyrannosaurinae

Alioramus remotus Alioramus Life Restoration.jpg

Alioramus altai Alioramus altai.jpg

Qianzhousaurus Qianzhousaurus sinensis by PaleoGeek.png

Dynamoterror

Teratophoneus Teratophoneus curriei by PaleoGeek.png

Lythronax Lythronax by Tomopteryx.png

Daspletosaurus torosus
Daspletosaurus torosus steveoc flipped.jpg

Daspletosaurus wilsoni

Daspletosaurus horneri

Zhuchengtyrannus

Tarbosaurus Tarbosaurus Restoration.png

Tyrannosaurus
Tyrannosaurus-rex-Profile-steveoc86 (coloured).png

In 2023, Scherer and Voiculescu-Holvad argued that the stratigraphic ranges of D. torosus, D. wilsoni and an unnamed species from the Dinosaur Park Formation and Oldman Formation show a clear overlap, indicating that anagenesis may not be the predominant factor of speciation within the genus, since all species of Daspletosaurus were contemporaneous with each other at some point during its evolution. Phylogenetic analyses resolved D. horneri as the most basal species, in spite of the fact that it's stratigraphically the youngest. While the authors did not completely refute the possibility that anagenesis was the main driver of Daspletosaurus evolution based on the intermediate morphological features, they also suggested that D. wilsoni may be a junior synonym of D. torosus, since there is a near lack of autapomorphic characters that can differentiate this species. They also claimed that Daspletosaurus did not evolve from Thanatotheristes, since they found no support on the basis of morphological and stratigraphical data, and that anagenesis will not be supported unequivocally due to the limited sample and nature of the fossil record which doesn't show a great degree of variation in morphology. The cladogram presented for their phylogenetic analysis is shown below.[4]

Tyrannosaurinae
Alioramini

Alioramus remotus Alioramus Life Restoration.jpg

Alioramus altai

Qianzhousaurus Qianzhousaurus sinensis by PaleoGeek.png

Teratophoneini

Lythronax Lythronax by Tomopteryx.png

Teratophoneus

Dynamoterror

Daspletosaurini

Thanatotheristes

Daspletosaurus horneri

Daspletosaurus wilsoni

Daspletosaurus torosus
Daspletosaurus torosus steveoc flipped.jpg

Dinosaur Park and Oldman formations taxon (TMP 2001.36.1)

Tyrannosaurini

Zhuchengtyrannus

Tarbosaurus Tarbosaurus Restoration.png

Tyrannosaurus
Tyrannosaurus-rex-Profile-steveoc86 (coloured).png

References

  1. 1.0 1.1 Carr, Thomas D.; Varricchio, David J.; Sedlmayr, Jayc C.; Roberts, Eric M.; Moore, Jason R. (2017). "A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system". Scientific Reports 7: 44942. doi:10.1038/srep44942. PMID 28358353. Bibcode2017NatSR...744942C. 
  2. 2.0 2.1 2.2 Voris, Jared T.; Therrien, Francois; Zelenitzky, Darla K.; Brown, Caleb M. (2020). "A new tyrannosaurine (Theropoda: Tyrannosauridae) from the Campanian Foremost Formation of Alberta, Canada, provides insight into the evolution and biogeography of tyrannosaurids". Cretaceous Research 110: 104388. doi:10.1016/j.cretres.2020.104388. 
  3. 3.0 3.1 Warshaw, Elías A.; Fowler, Denver W. (2022). "A transitional species of Daspletosaurus Russell, 1970 from the Judith River Formation of eastern Montana". PeerJ 10: e14461. doi:10.7717/peerj.14461. PMC 9703990. https://peerj.com/articles/14461. 
  4. 4.0 4.1 Scherer, Charlie Roger; Voiculescu-Holvad, Christian (2023-11-28). "Re-analysis of a dataset refutes claims of anagenesis within Tyrannosaurus-line tyrannosaurines (Theropoda, Tyrannosauridae)". Cretaceous Research (In press): 105780. doi:10.1016/j.cretres.2023.105780. ISSN 0195-6671. https://www.sciencedirect.com/science/article/pii/S0195667123003087. 
  5. Holtz, T. R. (2011). "Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2011 Appendix". http://www.geol.umd.edu/~tholtz/dinoappendix/HoltzappendixWinter2011.pdf. 

Wikidata ☰ Q84050109 entry