Reference : High diversity in late Early Cretaceous ichthyosaurs part II: The Cambridge Greensand...
Scientific congresses and symposiums : Unpublished conference/Abstract
Physical, chemical, mathematical & earth Sciences : Earth sciences & physical geography
High diversity in late Early Cretaceous ichthyosaurs part II: The Cambridge Greensand material
Fischer, Valentin mailto [Université de Liège - ULiège > Département de géologie > Paléontologie animale et humaine >]
59th Symposium of Vertebrate Palaeontology and Comparative Anatomy
12-17 September 2011
Lyme Regis
[en] Ichthyosauria ; Ophthalmosauridae ; Cretaceous ; Diversity
[en] Recent and on-going work on Canadian and French Cretaceous ichthyosaurs has unveiled a high diversity of Albian ophthalmosaurids, suggesting the extinction of ichthyosaurs which occurs during the Cenomanian was a much more severe event than previously supposed. Yet the ichthyosaur assemblages from other areas such as the USA and Australia are monospecific, suggesting that the diversity of ichthyosaurs was not universally high.

The Cambridge Greensand ichthyosaur material, which has not been the subject of any thorough study since 1869, consists of about 900 specimens, the vast majority of which are isolated bones. Nevertheless, this abundant material offers a good opportunity to assess the diversity of the ichthyosaurs that roamed the western England Sea during the late Albian–Early Cenomanian interval. In order to assess this diversity, diagnostic bones such as basioccipitals, stapes, humeri and femora were compared to that of other ophthalmosaurids. Several morphotypes, some represented by 10+ specimens are recognized. Articulated specimens were used to unite cranial and appendicular bone morphotypes to a taxon. An extremely diverse assemblage of at least 5 distinct taxa is recognized in the Cambridge Greensand Formation: Platypterygius sp., two new genera that have representatives in southeastern France and Germany, a Brachypterygius/Aegirosaurus morphotype, and the long-forgotten but diagnostic Cetarthrosaurus walkeri, for which we found a second and better preserved specimen. The diversity of the ‘mid’ Cretaceous ichthyosaurs from Europe now matches that of the Early Jurassic, a period sometimes seen as the ‘Golden Age’ of post-Triassic ichthyosaurs.
Fonds de la Recherche Scientifique (Communauté française de Belgique) - F.R.S.-FNRS
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