Foffa, Davide, Johnson, Michela M, Young, Mark T, Steel, Lorna and Brusatte, Stephen L (Research Associate) (2019) Revision of the Late Jurassic deep-water teleosauroid crocodylomorph Teleosaurus megarhinus Hulke, 1871 and evidence of pelagic adaptations in Teleosauroidea. PeerJ, 7 (e6646). ISSN 2167-8359

[img] Other (Published version of article)
2331 Revision of the Late Jurassic deep-water teleosauroid crocodylomorph Teleosaurus megarhinus Hulke, 1871 and - Published Version
Available under License Creative Commons Attribution.

Download (3MB)

Abstract

Teleosauroids were a successful group of semi-aquatic crocodylomorphs that were an integral part of coastal marine/lagoonal faunas during the Jurassic. Their fossil record suggests that the group declined in diversity and abundance in deep water deposits during the Late Jurassic. One of the few known teleosauroid species from the deeper water horizons of the well-known Kimmeridge Clay Formation is ‘Teleosaurus’ megarhinus Hulke, 1871, a poorly studied, gracile longirostrine form. The holotype is an incomplete snout from the Aulacostephanus autissiodorensis Sub-Boreal ammonite Zone of Kimmeridge, England. The only other referred specimen is an almost complete skull from the slightly older A. eudoxus Sub-Boreal ammonite Zone of Quercy, France. Recently, the validity of this species has been called into question. Here we re-describe the holotype as well as the referred French specimen and another incomplete teleosauroid, DORCM G.05067i-v (an anterior rostrum with three osteoderms and an isolated tooth crown), from the same horizon and locality as the holotype. We demonstrate that all specimens are referable to ‘Teleosaurus’ megarhinus and that the species is indeed a valid taxon, which we assign to a new monotypic genus, Bathysuchus. In our phylogenetic analysis, the latest iteration of the ongoing Crocodylomorph SuperMatrix Project, Bathysuchus megarhinus is found as sister taxon to Aeolodon priscus within a subclade containing Mycterosuchus nasutus and Teleosaurus cadomensis. Notably Bathysuchus has an extreme reduction in dermatocranial ornamentation and osteoderm size, thickness and ornamentation. These features are mirrored in Aeolodon priscus, a species with a well-preserved post-cranial skeleton and a similar shallow and inconspicuous dermal ornamentation. Based on these morphological features, and sedimentological evidence, we hypothesise that the Bathysuchus + Aeolodon clade is the first known teleosauroid lineage that evolved a more pelagic lifestyle.

Item Type: Article
Uncontrolled Keywords: Crocodylomorpha, Teleosauroidea, Kimmeridgian, Aquatic adaptations
Subjects: D History General and Old World > D History (General) > D051 Ancient History
D History General and Old World > DA Great Britain
Q Science > QE Geology
Q Science > QL Zoology
Theme: Understanding the natural world
Department: Natural Sciences
Related URLs:
Depositing User: Ross Anderson
Date Deposited: 30 May 2019 11:18
Last Modified: 03 Jun 2019 08:42
URI: http://repository.nms.ac.uk/id/eprint/2331

Actions (login required)

Modify Record Modify Record