Nicholl, Cecily Sarah Clementina; (2025) The Evolutionary History of Notosuchian Crocodylomorphs. Doctoral thesis (Ph.D), UCL (University College London).

Preview

Text Cecily Nicholl PhD Thesis.pdf - Accepted Version Download (295MB) | Preview

Abstract

Notosuchia encompasses a taxonomically and morphologically diverse clade of largely terrestrial crocodyliforms known predominantly from the Cretaceous of Gondwana. The internal systematics of this group are in continuous debate, most notably concerning the phylogenetic placement of the group Sebecidae, which is found to have affinities with both baurusuchians and peirosaurians. Much of the uncertainty surrounding the interrelationships of these crocodyliforms stems from the fact that many specimens assigned to these groups are highly fragmentary, particularly those from the Paleogene of Africa and Europe. Several of these specimens are re-described, and a novel species is erected following the description of new remains from the Cretaceous of Morocco. Few analyses have critically examined the underlying characters utilised in Notosuchian systematics, particularly in terms of their construction. In order to re-evaluate the systematics of the group, I compiled the largest and most comprehensive notosuchian dataset to date, comprising 540 morphological characters scored for 115 species. All existing characters were reviewed, and many were extensively modified. 113 novel characters were constructed, many of which focus on previously undersampled regions of the skeleton (postcrania and the endocranium). Continuous characters were utilised for the first time in the context of Notosuchia, and taxon sampling was increased, in part via inclusion of seven notosuchians that have not previously been assessed in a phylogenetic context. All well-resolved analyses conducted under maximum parsimony revealed support for a monophyletic Sebecosuchia, regardless of character treatment and weighting scheme. Both Peirosauria and Uruguaysuchidae are uniquely positioned as successive sister taxa to Ziphosuchia. The confirmed sebecid affinities of the newly assessed Eremosuchus elkoholicus from the Eocene of Algeria, imply the presence of a diverse, deeply nested clade of sebecids and closely affiliated taxa outside of South America, providing insights into the evolutionary and biogeographic history of this group.

Download activity - last month

Export as JSONCSVXML

Download activity - last 12 months

Export as CSVJSONXML

Downloads by country - last 12 months

Export as XMLJSONCSV

Archive Staff Only

View Item