The Oldest Jurassic Dinosaur: A Basal Neotheropod from the Hettangian of Great Britain

Abstract

Approximately 40% of a skeleton including cranial and postcranial remains representing a new genus and species of basal neotheropod dinosaur is described. It was collected from fallen blocks from a sea cliff that exposes Late Triassic and Early Jurassic marine and quasi marine strata on the south Wales coast near the city of Cardiff. Matrix comparisons indicate that the specimen is from the lithological Jurassic part of the sequence, below the first occurrence of the index ammonite Psiloceras planorbis and above the last occurrence of the Rhaetian conodont Chirodella verecunda. Associated fauna of echinoderms and bivalves indicate that the specimen had drifted out to sea, presumably from the nearby Welsh Massif and associated islands (St David’s Archipelago). Its occurrence close to the base of the Blue Lias Formation (Lower Jurassic, Hettangian) makes it the oldest known Jurassic dinosaur and it represents the first dinosaur skeleton from the Jurassic of Wales. A cladistic analysis indicates basal neotheropodan affinities, but the specimen retains plesiomorphic characters which it shares with Tawa and Daemonosaurus.

Developmental patterns and variation among early theropods

“…; Martill et al. ), making the genus Coelophysis paraphyletic and therefore taxonomically undesirable. Because synonymizing Camposaurus with Coelophysis to resolve this problem could simply result in a similar taxonomic problem arising in the future with other analyses and more taxa, I here follow Ivie et al.…”

“…; Martill et al. ), I refer to this taxon with the generic name in quotes. I follow the definition of Coelophysoidea Sereno et al.…”

“…Bristowe & Raath (2004) synonymized Megapnosaurus with Coelophysis, making the formal name of the Zimbabwean coelophysoid Coelophysis rhodesiensis, because Coelophysis had taxonomic priority. However, recent phylogenetic analyses have placed Coelophysis rhodesiensis as more closely related to Camposaurus arizonensis than to Coelophysis bauri (Ezcurra & Brusatte, 2011;You et al 2014;Martill et al 2016), making the genus Coelophysis paraphyletic and therefore taxonomically undesirable. Because synonymizing Camposaurus with Coelophysis to resolve this problem could simply result in a similar taxonomic problem arising in the future with other analyses and more taxa, I here follow Ivie et al (2001) in referring to the Zimbabwean coelophysoid theropod as Megapnosaurus rhodesiensis.…”

“…Because synonymizing Camposaurus with Coelophysis to resolve this problem could simply result in a similar taxonomic problem arising in the future with other analyses and more taxa, I here follow Ivie et al (2001) in referring to the Zimbabwean coelophysoid theropod as Megapnosaurus rhodesiensis. Because the generic name of the Early Jurassic coelophysoid 'Syntarsus' kayentakatae (Rowe, 1989) has not been formally changed to either Coelophysis or Megapnosaurus (nor should it be, because this would render either generic name used non-monophyletic; Ezcurra & Brusatte, 2011;You et al 2014;Martill et al 2016), I refer to this taxon with the generic name in quotes. I follow the definition of Coelophysoidea Sereno et al (2005) as the clade that includes all taxa that share a more recent common ancestor with Coelophysis bauri than with Allosaurus fragilis.…”

A re-evaluation of the historical ‘dinosaur’ remains from the Middle-Upper Triassic of Poland

“…15-17% of total length of fibula) in Dilophosaurus. Fibulae of Liliensternus, Dracoraptor and Velocipes are virtually indistinguishable in shape at first glance (MB.R.2175.7.9, MB.R.2175.7.10.1, MB.R.2175.7.12 andMB.R.2175.7.11;Martill et al 2016). However, Liliensternus lacks well visible M. iliofibularis attachment.…”