A transitional species of Daspletosaurus Russell, 1970 from the Judith River Formation of eastern Montana

Elías A Warshaw; Denver W Fowler

doi:10.7717/peerj.14461

A transitional species of Daspletosaurus Russell, 1970 from the Judith River Formation of eastern Montana

PeerJ. 2022 Nov 25:10:e14461. doi: 10.7717/peerj.14461. eCollection 2022.

Authors

Elías A Warshaw^{1

2}, Denver W Fowler¹

Affiliations

¹ Badlands Dinosaur Museum, Dickinson, North Dakota, United States.
² Department of Earth Sciences, Montana State University, Bozeman, MT, United States.

Abstract

Here we describe a new derived tyrannosaurine, Daspletosaurus wilsoni sp. nov., from Judithian strata (~76.5 Ma) intermediate in age between either of the previously described species of this genus. D. wilsoni displays a unique combination of ancestral and derived characteristics, including a cornual process of the lacrimal reduced in height relative to D. torosus and more basal tyrannosaurines, and a prefrontal with a long axis oriented more rostrally than in D. horneri and more derived tyrannosaurines. The description of this taxon provides insight into evolutionary mode in Tyrannosaurinae, lending strength to previous hypotheses of anagenesis within Daspletosaurus and increasing the resolution with which the evolution of this lineage can be reconstructed. Cladistic phylogenetic methods, stratigraphy, and qualitative analysis of the morphology of relevant taxa supports an anagenetic model for the origin of morphological novelty in this genus, highlighting the predominance of anagenetic evolution among contemporary dinosaur lineages.

Keywords: Anagenesis; Daspletosaurus; Paleontology; Tyrannosaur.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, Non-U.S. Gov't

MeSH terms

Animals
Dinosaurs* / anatomy & histology
Fossils*
Montana
Phylogeny
Rivers

Grants and funding

Funding for this project was provided by the City of Dickinson, ND; the US Bureau of Land Management, TC Energy, Conoco-Phillips, TC Energy employees, Destiny and Craig Wolf, Google employees. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.