The University of Southampton
University of Southampton Institutional Repository

The cranial osteology of Tyrannoneustes lythrodectikos (Crocodylomorpha: Metriorhynchidae) from the Middle Jurassic of Europe

The cranial osteology of Tyrannoneustes lythrodectikos (Crocodylomorpha: Metriorhynchidae) from the Middle Jurassic of Europe
The cranial osteology of Tyrannoneustes lythrodectikos (Crocodylomorpha: Metriorhynchidae) from the Middle Jurassic of Europe
Tyrannoneustes lythrodectikos is one of numerous metriorhynchid crocodylomorph species known from the Oxford Clay Formation of England (Callovian-Oxfordian; Middle-Late Jurassic). This taxon is of evolutionary importance, as it is the oldest and most basal known macrophagous metriorhynchid. It has a mosaic of plesiomorphic and derived feeding related characteristics, including: teeth with microscopic, poorly formed and non-contiguous denticles; increased tooth apicobasal length; ventrally displaced dentary tooth row (increased gape); reduced dentary tooth count; and a proportionally long mandibular symphysis. However the type specimen, and current referred specimens, all lack a preserved cranium. As such, the craniofacial morphology of this taxon, and its potential feeding ecology, remains poorly understood. Here we describe two skulls and two lower jaws which we refer to T. lythrodectikos. Previously these specimens were referred to ‘Metriorhynchus’ brachyrhynchus. They share with the T. lythrodectikos holotype: the in-line reception pits on the dentary, dorsal margin of the surangular is strongly concave in lateral view, and the most of the angular ventral margin is strongly convex. Based on our description of these specimens, the skull of T. lythrodectikos has three autapomorphies: very long posterior processes of the premaxilla terminating in line with the 4th or 5th maxillary alveoli, deep lateral notches on the lateral surface of the maxillary with reception pits for dentary teeth, and the premaxilla forms the anterior margin of the first maxillary alveoli. Our description of the cranial anatomy of Tyrannoneustes lythrodectikos confirms that some macrophagous characteristics evolved during the Middle Jurassic, and were not exclusive to the clade Geosaurini. Moreover, the skulls further highlight the mosaic nature of Tyrannoneustes lythrodectikos and wide-gape macrophagous evolution in Geosaurinae.
2167-8359
e608
Foffa, Davide
a0a5e738-a340-4b36-b4c7-39e44994f22e
Young, Mark T.
d9880973-1dd1-4b1c-81a8-7494170dbac2
Foffa, Davide
a0a5e738-a340-4b36-b4c7-39e44994f22e
Young, Mark T.
d9880973-1dd1-4b1c-81a8-7494170dbac2

Foffa, Davide and Young, Mark T. (2014) The cranial osteology of Tyrannoneustes lythrodectikos (Crocodylomorpha: Metriorhynchidae) from the Middle Jurassic of Europe. PeerJ, 2, e608. (doi:10.7717/peerj.608).

Record type: Article

Abstract

Tyrannoneustes lythrodectikos is one of numerous metriorhynchid crocodylomorph species known from the Oxford Clay Formation of England (Callovian-Oxfordian; Middle-Late Jurassic). This taxon is of evolutionary importance, as it is the oldest and most basal known macrophagous metriorhynchid. It has a mosaic of plesiomorphic and derived feeding related characteristics, including: teeth with microscopic, poorly formed and non-contiguous denticles; increased tooth apicobasal length; ventrally displaced dentary tooth row (increased gape); reduced dentary tooth count; and a proportionally long mandibular symphysis. However the type specimen, and current referred specimens, all lack a preserved cranium. As such, the craniofacial morphology of this taxon, and its potential feeding ecology, remains poorly understood. Here we describe two skulls and two lower jaws which we refer to T. lythrodectikos. Previously these specimens were referred to ‘Metriorhynchus’ brachyrhynchus. They share with the T. lythrodectikos holotype: the in-line reception pits on the dentary, dorsal margin of the surangular is strongly concave in lateral view, and the most of the angular ventral margin is strongly convex. Based on our description of these specimens, the skull of T. lythrodectikos has three autapomorphies: very long posterior processes of the premaxilla terminating in line with the 4th or 5th maxillary alveoli, deep lateral notches on the lateral surface of the maxillary with reception pits for dentary teeth, and the premaxilla forms the anterior margin of the first maxillary alveoli. Our description of the cranial anatomy of Tyrannoneustes lythrodectikos confirms that some macrophagous characteristics evolved during the Middle Jurassic, and were not exclusive to the clade Geosaurini. Moreover, the skulls further highlight the mosaic nature of Tyrannoneustes lythrodectikos and wide-gape macrophagous evolution in Geosaurinae.

Full text not available from this repository.

More information

Published date: 2 October 2014
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 374171
URI: http://eprints.soton.ac.uk/id/eprint/374171
ISSN: 2167-8359
PURE UUID: 5e59395e-6bb1-4c88-8412-61d94bb3d012

Catalogue record

Date deposited: 06 Feb 2015 13:46
Last modified: 15 Jul 2019 21:30

Export record

Altmetrics

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×