The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures, South Wales, UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Abstract

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5 m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.

Biomechanical properties of the jaws of two species of Clevosaurus and a reanalysis of rhynchocephalian dentary morphospace

“…Clevosaurus cambrica is diagnosed by the fact that its penultimate dentary tooth is the largest, not the ultimate (Keeble et al . 2018), unlike most Clevosaurus (but cf. C. convallis ; Säilä 2005).…”

“…Teeth in Clevosaurus are fused to the mandible, and therefore their limits within the mandible are hard to distinguish in the CT scans, so tooth sizes and limits had to be estimated using microphotographs in the literature for both taxa (Keeble et al . 2018, fig. 5; Chambi‐Trowell et al .…”

“…3F; UMZC T1276, Fraser & Walkden 1983; AUP 11085, Fraser 1988), an additional specimen of C. cambrica (Keeble et al . 2018, fig. 5C) one juvenile of Clevosaurus brasiliensis (UFRGS‐PV‐0613‐T; Romo de Vivar Martinez & Bento Soares 2015), and five additional adult Clevosaurus brasiliensis (MCN‐PV‐2852, UFRGS‐PV‐0738‐T, UFRGS‐PV‐0606‐T, UFRGS‐PV‐0758‐T, UFRGS‐PV‐0750‐T; Romo de Vivar Martinez & Bento Soares 2015); all images were taken from the literature.…”

Osteological redescription of the Late Triassic sauropodomorph dinosaur Thecodontosaurus antiquus based on new material from Tytherington, southwestern England

“…Thecodontosaurus was a key component of the Rhaetian fissure faunas of southwestern Britain. As a medium-sized, predominantly herbivorous biped, it was the main primary consumer of small island ecosystems (Whiteside et al, 2016) that were also inhabited by carnivorous coelophysoid dinosaurs (Whiteside and Marshall, 2008;Foffa et al, 2014;Keeble et al, 2018) that could have preyed on the former, as well as 'sphenosuchian' crocodylomorphs, diverse rhynchocephalians, and other lepidosaurs. These Late Triassic islands housed faunas that might have been similar to those of some modern reptile-dominated subtropical islands (Whiteside and Marshall, 2008).…”

“…Benton et al (2000) formally described the remaining specimens and assigned them to Thecodontosaurus antiquus. A new specimen found in the south Wales locality of Pant-y-Ffynnon (Whiteside et al, 2016;Keeble et al, 2018) that was first interpreted as a juvenile T. antiquus (Kermack, 1984;Benton et al, 2000) was later assigned to a new species, T. caducus (Yates, 2003a), and finally to a different genus, Pantydraco caducus (Galton et al, 2007), based on morphological differences in the cervical vertebrae and humerus from the Durdham Down material. Additionally, an articulated pectoral girdle and forelimb (YPM 2195) from Bristol (Benton et al, 2000) was later named Asylosaurus yalensis, on the basis that it exhibited distinctive humeral traits (Galton, 2007).…”