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Poster (Scientific congresses and symposiums)
High diversity in late Early Cretaceous ichthyosaurs
Fischer, Valentin; Guiomar, Myette; Godefroit, Pascal
200969th Annual Meeting of the Society of Vertebrate Paleontology and 57th Symposium of Vertebrate Palaeontology and Comparative Anatomy
 

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Keywords :
Ichthyosauria; late Early Cretaceous; southeastern France
Abstract :
[en] Considered as the last survivors of a dying group, all Cretaceous ichthyosaurs have traditionally been incorporated within a single genus, Platypterygius. This waste-basket genus includes large ichthyosaurs with numerous, large and conical tooth crowns and bulbous polygonal root well anchored in dental grooves. With such a dentition, Platypterygius can be included within the “Smash guild”. However, the study of new specimens from the Aptian-Albian marls of the Vocontian basin (SE France) reveals an unexpected diversity of late Early Cretaceous ichthyosaurs. Beside “classical” Platypterygius specimens, another type of ichthyosaur with very tiny and pointed teeth has been found in the mid-Albian marls of Sisteron, in High-Provence Alps. This new taxon is based on a partial crushed skull, two basioccipitals, 8 teeth, and 15 centra. The teeth range from 20mm to 2cm and are highly compressed labio-lingualy, with a thickness/wideness ratio of the root sometimes as low as 1/4. Crowns are slightly curved and sharply pointed, indicating a diet of small and soft preys. Interestingly, although the rostral bones are slender and delicate – thus radically different from conventional Late Early Cretaceous ichthyosaurs – the basioccipital of this taxon shares many characters with Platypterygius and is of the same overall size. Together with the recently named genus Maiaspondylus from the Albian of western Canada, these specimens suggest a higher diversity of late Early Cretaceous ichthyosaurs, in contradiction with the current view of ichthyosaur extinction, said to be gradually decreasing in diversity since the Middle Jurassic. In fact, the number of ecological niches occupied by ichthyosaurs apparently even increased from the Late Jurassic until the late Early Cretaceous. Therefore, the ecological impact of the Cenomanian-Turonian boundary on marine reptile faunas was probably more severe than previously thought.
Research center :
Centre de Géosciences
Disciplines :
Earth sciences & physical geography
Author, co-author :
Fischer, Valentin  ;  Université de Liège - ULiège > Département de géologie > Paléontologie animale et humaine
Guiomar, Myette;  Réserve Géologique de Haute-Provence
Godefroit, Pascal;  Institut Royal des Sciences Naturelles de Belgique
Language :
English
Title :
High diversity in late Early Cretaceous ichthyosaurs
Publication date :
October 2009
Event name :
69th Annual Meeting of the Society of Vertebrate Paleontology and 57th Symposium of Vertebrate Palaeontology and Comparative Anatomy
Event organizer :
University of Bristol
Event place :
Bristol, United Kingdom
Event date :
10-13 October 2009
Audience :
International
Commentary :
Journal of Vertebrate Paleontology, 29 (3) suppl, 96A.
Available on ORBi :
since 15 February 2010

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