Pendraig milnerae , a new small-sized coelophysoid theropod from the Late Triassic of Wales

Abstract

We describe a new small-bodied coelophysoid theropod dinosaur, Pendraig milnerae gen. et sp. nov, from the Late Triassic fissure fill deposits of Pant-y-ffynnon in southern Wales. The species is represented by the holotype, consisting of an articulated pelvic girdle, sacrum and posterior dorsal vertebrae, and an associated left femur, and by two referred specimens, comprising an isolated dorsal vertebra and a partial left ischium. Our phylogenetic analysis recovers P. milnerae as a non-coelophysid coelophysoid theropod, representing the first-named unambiguous theropod from the Triassic of the UK. Recently, it has been suggested that Pant-y-ffynnon and other nearby Late Triassic to Early Jurassic fissure fill faunas might have been subjected to insular dwarfism. To test this hypothesis for P. milnerae , we performed an ancestral state reconstruction analysis of body size in early neotheropods. Although our results indicate that a reduced body size is autapomorphic for P. milnerae , some other coelophysoid taxa show a similar size reduction, and there is, therefore, ambiguous evidence to indicate that this species was subjected to dwarfism. Our analyses further indicate that, in contrast with averostran-line neotheropods, which increased in body size during the Triassic, coelophysoids underwent a small body size decrease early in their evolution.

Scleromochlus and the early evolution of Pterosauromorpha

“…Maximum parsimony. Maximum parsimony analyses were performed in TNT 1.5 [51][52] using equally weighted parsimony. A tree space was generated and searches for the most parsimonious trees (MPTs) were conducted using a similar protocol to that in ref.…”

“…This was followed by a final round of tree bisection reconnection (TBR) branch swapping, with a 50% collapsing rule. Consistency Index (CI) and Retention Index (RI) were calculated using the script statsB.run 51 , which, unlike stats.run [52][53] , does not include deactivated terminals when calculating CI and RI 51 . Branch support was calculated using bootstrap resampling analyses, with 1,000 technical pseudo-replicates for both absolute and group present/contradicted (GC) frequencies, and Bremer support.…”

A taxonomic revision and cranial description of Terrestrisuchus gracilis (Archosauria, Crocodylomorpha) from the Upper Triassic of Pant‐y‐Ffynnon Quarry (southern Wales)

“…Terrestrisuchus gracilis probably shared the predator niche on the islands of the Bristol Channel archipelago with a small coelophysoid theropod, Pendraig milnerae (Spiekman et al . 2021), and it is conceivable that these two taxa were ecologically partitioned. The skull of Pendraig milnerae is not preserved, but a sclerotic ring is found in the closely related coelophysoid Megapnosaurus rhodesiensis .…”

“…However, it is possible that larger bodied animals are absent at Pant‐y‐Ffynnon due to a preservational bias related to the depositional conditions of the fissures (Spiekman et al . 2021). Resolution of this issue is complicated by the generally isolated, fragmentary nature of specimens for most taxa, hampering observations on skeletal maturity.…”

New specimen and redescription of Anisodontosaurus greeri (Moenkopi Formation: Middle Triassic) and the spatiotemporal origins of TrilophosauridaeCitation for this article: Foffa, D., Nesbitt, S. J., Kligman, B. T., Butler, R. J., & Stocker, M. R. (2023) New specimen and redescription of Anisodontosaurus greeri (Moenkopi Formation: Middle Triassic) and the spatiotemporal origins of Trilophosauridae. Journal of Vertebrate Paleo

“…We then performed an additional round of tree bisection reconnection (TBR) branch swapping, which recovers the most parsimonious trees (MPTs) that were then used to calculate a Strict Consensus topology (when more than one MPT was recovered). Consistency index (CI) and Retention index (RI) were calculated using the script “statsb.run” of Spiekman et al (2021). Branch support was calculated using Bremer support values.…”