A new crurotarsan archosaur from the Late Triassic of South Wales

ABSTRACT

We report a third archosaur from the Late Triassic cavity-fill sediments of Pant-y-ffynnon Quarry in South Wales, in addition to the basal crocodylomorph Terrestrisuchus and the basal sauropodomorph dinosaur Pantydraco. The new taxon, Aenigmaspina pantyffynnonensis, previously referred to informally as ‘Edgar,’ was recovered in 1952 and is preserved as a tight cluster of vertebrae, ribs, and a scapula in a single block, as well as numerous associated, but now isolated, elements, including skull bones, vertebrae, further putative elements of the forelimb, and a partial pelvis. We present a digital model based on computed tomography (CT) scans of the main associated blocks, which shows exquisite detail of an associated series of 12 cervical and anterior dorsal vertebrae, with ribs and a scapula. The well-developed spine tables and eight matching osteoderms confirm that this is a crurotarsan archosaur, but it lacks apomorphies of all major crurotarsan clades. Phylogenetic analysis gives equivocal results, showing weak relationships with Proterochampsidae and Ornithosuchidae; the new taxon might lie close to Erpetosuchidae, based on the ‘Y’-shaped spine tables.

ACKNOWLEDGMENTS

This paper stems from a thesis by E.P. submitted as part of the requirements of the M.Sc. degree in paleobiology at the University of Bristol. We thank T. G. Davies for his assistance with CT scanning and the Avizo software. We thank the Natural History Museum in London, and especially L. Steele, S. D. Chapman, M. O. Day, and S. C. R. Maidment, for specimen loans and for allowing us to visit and inspect their collections. We also acknowledge funding from the University of Bristol for museum visits by E.P. and for CT scanning costs. We thank M. Stocker and J. Desojo for their thorough and very helpful reviews of the original manuscript.

DATA ARCHIVING STATEMENT

The CT scan is the property of the NHMUK and may be accessed with a reasonable request by contacting the Palaeontology Section, Earth Science Department, The Natural History Museum, Cromwell Road, London SW7 5BD, U.K.

ORCID

Erin L. Patrick http://orcid.org/0000-0001-6601-6732

David I. Whiteside http://orcid.org/0000-0003-1619-747X

Michael J. Benton http://orcid.org/0000-0002-4323-1824