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| Malawania anachronus, the Jurassic-style Cretaceous ichthyosaur from Iraq. Illustrations by Robert Nicholls, paleocreations.com; coloring by C. M. Kosemen, cmkosemen.com |
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: Parvipelvia, Baracromia, Malawania anachronus, Early Cretaceous
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| Figure 1. Holotype specimen of Malawania anachronus gen. et sp. nov., NHMUK PV R6682. |
Fossil saved from mule track revolutionizes understanding of ancient dolphin-like marine reptile
| An international team of scientists have revealed a new species of ichthyosaur (a dolphin-like marine reptile from the age of dinosaurs) from Iraq, which revolutionises our understanding of the evolution and extinction of these ancient marine reptiles.
Fischer V, Appleby RM, Naish D, Liston J, Riding JB, Brindley S and Godefroit P. 2013. A basal thunnosaurian from Iraq reveals disparate phylogenetic origins for Cretaceous ichthyosaurs. Biology Letters, 9: 20130021. DOI: 10.1098/rsbl.2013.0021
