Reconstructing Daspletosaurus wilsoni.

Skye McDavid

Originally posted November 27, 2022

Updated December 16, 2022 and April 9, 2024

Update 12/16/2022: fixed shape of mandibular fenestra and added comments on anagenesis.Update 4/9/2024: fixed links, added comment on validity of D. wilsoni.

The second species of Daspletosaurus has finally been named. Yes, second. Daspletosaurus "horneri" is a nomen nudum, as it was published in the online-only journal Scientific Reports without registration in ZooBank. (This means that theoretically, it could be validly named with a different specific epithet.) Daspletosaurus wilsoni, from the Judith River formation, is described as transitional between Daspletosaurus torosus from the Oldman Formation and Daspletosaurus "horneri" from the Two Medicine Formation. While I'm reluctant to say the anagenesis hypothesis is wrong, I think three data points is insufficient to establish that it is the case.

Update 4/9/2024: Daspletosaurus wilsoni has been argued to be a junior synonym of D. torosus. So far, this has only come in the form of an SVP presentation and abstract, and based on what is currently published I am neither confident that D. wilsoni is valid nor am I confident that it is a junior synonym of D. torosus. Either way, this is a cranial reconstruction of Daspletosaurus based on BDM 107, the holotype of D. wilsoni.

The holotype includes some postcrania, the most important part is the skull, which is nicely preserved and decently complete.

Anyway, here's my reconstruction. As usual, preserved elements are in white and reconstructed elements are in grey, though in this case it's worth pointing out that some of these elements are mirrored. I reconstructed missing parts, where possible, based on other Daspletosaurus species, including torosus, "horneri," (based on photos of the proposed holotype sent to me by Montana Rosslyn) and other published specimens simply labeled Daspletosaurus sp. I did also reference Tyrannosaurus rex AMNH 5027 a bit since that's my go-to Tyrannosaurine skull. (And yes, I do believe AMNH 5027 is referable to T. rex, and while we're at it, referring it to "Tyrannosaurus incertae sedis" is a misuse of the term incertae sedis.) Thanks to Elías Warshaw for providing useful feedback on my reconstruction of the dinosaur he co-named.

MOR 590, the proposed holotype of Daspletosaurus "horneri"Photo by Montana Aster Rosslyn, used with permission.

References

Warshaw EA & Fowler DW (2022) A transitional species of Daspletosaurus Russell, 1970 from the Judith River Formation of eastern Montana. PeerJ e14461 [OA link]

Carr TD, Varricchio DJ, Sedlmayr JC, Roberts EM, Moore JR (2017) A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system. Scientific Reports 7:e44942 [OA link]

Hone DWE & Tanke DH (2015) Pre- and postmortem tyrannosaurid bite marks on the remains of Daspletosaurus (Tyrannosaurinae: Theropoda) from Dinosaur Provincial Park, Alberta, Canada. PeerJ e885 [OA link]

Osborn HF (1912) Crania of Tyrannosaurus and Allosaurus. Memoirs of the American Museum of Natural History 1:1 [OA link]

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