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Cretaceous Ichthyosaurs: Dwindling Diversity, or the Empire Strikes Back?
South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
Received: 5 March 2012; in revised form: 19 March 2012 / Accepted: 30 March 2012 / Published: 12 April 2012
Abstract: Recent descriptions of new taxa and recognition of survivorship of Jurassic genera across the Jurassic–Cretaceous boundary bring the total number of Cretaceous ichthyosaur genera to eight. Taxa currently known from the Cretaceous include Ophthalmosaurus, Caypullisaurus, Aegirosaurus, Platypterygius, Maiaspondylus, Athabascasaurus, Sveltonectes, and Acamptonectes. This review summarizes the occurrence of all Cretaceous genera. A discussion of morphological diversity demonstrates the different, though overlapping, ecological niches occupied by the different taxa, while the comparison of phylogenetic hypotheses shows the problems inherent in understanding the evolutionary relationships between Cretaceous genera. The Late Jurassic radiation indicated in the competing phylogenetic hypotheses may correlate with the opening of the Atlantic Ocean or additional dispersal routes established by the breakup of Gondwana. Inclusion of the stratigraphically oldest Platypterygius species may aid in resolving these evolutionary relationships.
Keywords: Jurassic; Cretaceous; Ichthyosauria; ecological niche; phylogeny
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Zammit, M. Cretaceous Ichthyosaurs: Dwindling Diversity, or the Empire Strikes Back? Geosciences 2012, 2, 11-24.
Zammit M. Cretaceous Ichthyosaurs: Dwindling Diversity, or the Empire Strikes Back? Geosciences. 2012; 2(2):11-24.
Zammit, Maria. 2012. "Cretaceous Ichthyosaurs: Dwindling Diversity, or the Empire Strikes Back?" Geosciences 2, no. 2: 11-24.