Edwards, Ben Thomas; (2001) The Upper Triassic microvertebrate assemblage of Ruthin Quarry, South Wales. Doctoral thesis (Ph.D), UCL (University College London).

Preview

Text The_Upper_Triassic_microverteb.pdf Download (29MB) | Preview

Abstract

Bone-rich sediments recovered from the Upper Triassic cave systems of Ruthin Quarry, South Wales, preserve a diverse assemblage of small vertebrates. These include procolophonids (2 taxa), archosauriforms (4 taxa), lepidosaurs (2 taxa) and a Trilophosaurus-like animal, Tricuspisaurus thomasi. The most common Ruthin procolophonid had an extensive covering of dermal armour. Skull bones and osteoderms share a pronounced dermal ornament (deeply pitted surface with one or more distinct bosses) characteristic of certain parareptiles (pareiasaurs, lanthanosuchids, Sclerosaurus). The second procolophonid, recognised largely by characters of the tooth-bearing elements, is a rare component of the assemblage and closely resembles Haligonia bolodon from the Wolfville Formation of Nova Scotia. The two forms are considered congeneric. The most common archosauriform is a suchian closely related to the Crocodylomorpha. The suchian shares two derived characters with sphenosuchian crocodylomorphs, osteoderm morphology (paired, elongate, ornamented osteoderms with an anterior articulatory process) and prefrontal-frontal articulation (in which the prefrontal underlaps the frontal); but retains a postfrontal. The second notable archosauriform is a prosauropod dinosaur, known principally from a tiny ilium (4mm long) of a hatchling, or very juvenile animal. The two lepidosaurs found at Ruthin are the sphenodontian Planocephalosaurus and a basal lepidosaur, possibly, but not necessarily, a rhynchocephalian. Contrary to previous reports, Clevosaurus is not present at Ruthin. The previously described, and enigmatic, Tricuspisaurus is a trilophosaurid archosauromorph. Attribution of this form, and others like it (Variodens, Xenodiphyodon, Trilophosaurus jacobsi [=Chinleogomphius]), to the Procolophonidae are not supported. Although wholly terrestrial, the Ruthin assemblage shares many groups (procolophonids, archosaurs, lepidosaurs, trilophosaurids) in common with the more typical aquatic/terrestrial mix from other Upper Triassic localities. The Ruthin fossil assemblage may be correlated with that of the Wolfville Formation of Nova Scotia, dating the fauna as late Carnian.

Download activity - last month

Export as JSONXMLCSV

Download activity - last 12 months

Export as JSONXMLCSV

Downloads by country - last 12 months

Export as CSVXMLJSON

Archive Staff Only

View Item