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A basal thunnosaurian from Iraq reveals disparate phylogenetic origins for Cretaceous ichthyosaurs

A basal thunnosaurian from Iraq reveals disparate phylogenetic origins for Cretaceous ichthyosaurs
A basal thunnosaurian from Iraq reveals disparate phylogenetic origins for Cretaceous ichthyosaurs
Cretaceous ichthyosaurs have typically been considered a small, homogeneous assemblage sharing a common Late Jurassic ancestor. Their low diversity and disparity have been interpreted as indicative of a decline leading to their Cenomanian extinction. We describe the first post-Triassic ichthyosaur from the Middle East, Malawania anachronus gen. et sp. nov. from the Early Cretaceous of Iraq, and re-evaluate the evolutionary history of parvipelvian ichthyosaurs via phylogenetic and cladogenesis rate analyses. Malawania represents a basal grade in thunnosaurian evolution that arose during a major Late Triassic radiation event and was previously thought to have gone extinct during the Early Jurassic. Its pectoral morphology appears surprisingly archaic, retaining a forefin architecture similar to that of its Early Jurassic relatives. After the initial latest Triassic radiation of early thunnosaurians, two subsequent large radiations produced lineages with Cretaceous representatives, but the radiation events themselves are pre-Cretaceous. Cretaceous ichthyosaurs therefore include distantly related lineages, with contrasting evolutionary histories, and appear more diverse and disparate than previously supposed.
parvipelvia, baracromia, malawania anachronus, early cretaceous
1744-9561
20130021
Fischer, V.
aca5dbab-dba2-4bdf-9d40-19e1d95a9caa
Appleby, R.M.
4e258c89-3afd-48f5-bce9-62c93bee3e61
Naish, D.
1244eec0-fd34-4995-a78b-f1d16a24c6fd
Liston, J.
ca7f4270-1260-46ad-98ad-7c9296f4cfe4
Riding, J.B.
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Brindley, S.
eb54ed9b-0688-4cf5-8c68-b2ea2cab5abf
Godefroit, P.
ebde9bd3-cf65-4e22-a5cb-b773a47bedae
Fischer, V.
aca5dbab-dba2-4bdf-9d40-19e1d95a9caa
Appleby, R.M.
4e258c89-3afd-48f5-bce9-62c93bee3e61
Naish, D.
1244eec0-fd34-4995-a78b-f1d16a24c6fd
Liston, J.
ca7f4270-1260-46ad-98ad-7c9296f4cfe4
Riding, J.B.
a7ee4075-b243-4da7-9782-5b961980b9d4
Brindley, S.
eb54ed9b-0688-4cf5-8c68-b2ea2cab5abf
Godefroit, P.
ebde9bd3-cf65-4e22-a5cb-b773a47bedae

Fischer, V., Appleby, R.M., Naish, D., Liston, J., Riding, J.B., Brindley, S. and Godefroit, P. (2013) A basal thunnosaurian from Iraq reveals disparate phylogenetic origins for Cretaceous ichthyosaurs. Biology Letters, 9 (4), 20130021. (doi:10.1098/rsbl.2013.0021).

Record type: Article

Abstract

Cretaceous ichthyosaurs have typically been considered a small, homogeneous assemblage sharing a common Late Jurassic ancestor. Their low diversity and disparity have been interpreted as indicative of a decline leading to their Cenomanian extinction. We describe the first post-Triassic ichthyosaur from the Middle East, Malawania anachronus gen. et sp. nov. from the Early Cretaceous of Iraq, and re-evaluate the evolutionary history of parvipelvian ichthyosaurs via phylogenetic and cladogenesis rate analyses. Malawania represents a basal grade in thunnosaurian evolution that arose during a major Late Triassic radiation event and was previously thought to have gone extinct during the Early Jurassic. Its pectoral morphology appears surprisingly archaic, retaining a forefin architecture similar to that of its Early Jurassic relatives. After the initial latest Triassic radiation of early thunnosaurians, two subsequent large radiations produced lineages with Cretaceous representatives, but the radiation events themselves are pre-Cretaceous. Cretaceous ichthyosaurs therefore include distantly related lineages, with contrasting evolutionary histories, and appear more diverse and disparate than previously supposed.

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More information

Published date: 23 August 2013
Keywords: parvipelvia, baracromia, malawania anachronus, early cretaceous
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 353042
URI: http://eprints.soton.ac.uk/id/eprint/353042
ISSN: 1744-9561
PURE UUID: d45e684c-519b-42ba-b7d7-81282acdae89

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Date deposited: 24 May 2013 08:39
Last modified: 09 Jan 2022 05:54

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Contributors

Author: V. Fischer
Author: R.M. Appleby
Author: D. Naish
Author: J. Liston
Author: J.B. Riding
Author: S. Brindley
Author: P. Godefroit

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