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Biol Lett. 2013 May 15;9(4):20130021. doi: 10.1098/rsbl.2013.0021. Print 2013 Aug 23.

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

Author information

1
Paleontology Department, Royal Belgian Institute of Natural Sciences, Brussels, Belgium. v.fischer@ulg.ac.be

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.

KEYWORDS:

Baracromia; Early Cretaceous; Malawania anachronus; Parvipelvia

PMID:
23676653
PMCID:
PMC3730615
DOI:
10.1098/rsbl.2013.0021
[Indexed for MEDLINE]
Free PMC Article

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