The osteology and affinities of Eotyrannus lengi, a tyrannosauroid theropod from the Wealden Supergroup of southern England

PeerJ. 2022 Jul 7:10:e12727. doi: 10.7717/peerj.12727. eCollection 2022.

Abstract

Eotyrannus lengi Hutt et al., 2001 from the Lower Cretaceous Wessex Formation (part of the Wealden Supergroup) of the Isle of Wight, southern England, is described in detail, compared with other theropods, and evaluated in a new phylogenetic analysis. Eotyrannus is represented by a single individual that would have been c. 4.5 m long; it preserves the anterior part of the skull, a partial forelimb and pectoral girdle, various cervical, dorsal and caudal vertebrae, rib fragments, part of the ilium, and hindlimb elements excluding the femur. Lack of fusion with regard to both neurocentral and sacral sutures indicates subadult status. Eotyrannus possesses thickened, fused, pneumatic nasals with deep lateral recesses, elongate, tridactyl forelimbs and a tyrannosaurid-like scapulocoracoid. The short preantorbital ramus of the maxilla and nasals that are approximately seven times longer than they are wide show that Eotyrannus was not longirostrine. A posterodorsally inclined ridge on the ilium's lateral surface fails to reach the dorsal margin: a configuration seen elsewhere in Juratyrant. Eotyrannus is not arctometatarsalian. Autapomorphies include the presence of curving furrows on the dentary, a block-like humeral entepicondyle, and a distoproximally aligned channel close to the distolateral border of the tibia. Within Tyrannosauroidea, E. lengi is phylogenetically intermediate between Proceratosauridae and Yutyrannus and the clade that includes Xiongguanlong, Megaraptora, Dryptosaurus and Tyrannosauridae. We do not find support for a close affinity between Eotyrannus and Juratyrant. Our analysis supports the inclusion of Megaraptora within Tyrannosauroidea and thus increases Cretaceous tyrannosauroid diversity and disparity. A proposal that Eotyrannus might belong within Megaraptora, however, is based on character states not present in the taxon. Several theropods from the Wessex Formation are based on material that overlaps with the E. lengi holotype but none can be shown to be synonymous with it.

Keywords: Coelurosaurs; Cretaceous; Dinosaurs; Phylogeny; Theropods; Tyrannosauroids; Wealden.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Dinosaurs* / anatomy & histology
  • Fossils*
  • Osteology
  • Phylogeny
  • Skull / anatomy & histology
  • Tibia

Grants and funding

The publication costs of this manuscript were supported by a successful gofundme campaign of July 2018 (https://www.gofundme.com/the-eotyrannus-monograph) which raised the required amount in less than 24 h: (in alphabetical order) Devin Adler, Marko Bosscher, Neil Edmond, Dan Folkes, Everything Dinosaur, Timon Salar Gutleb, Lindsey Ireland, Ivan Kay, Daniel Laird, Alexander Lovegrove, Zach Miller, Dylan Thomas Murphree, Francesco Naldi, David Orr, Tom Parker, James Pascoe, Check Pell, Elizabeth Pendleton, Dick Poelen, Nathan Redland, Mark Scherz, Christina Shears-Ozeki, Rob Vickery, Mark Wildman, Grace Yon, Juan Yu See and five anonymous benefactors. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.