Background: Ichthyosaurs are reptiles that inhabited the marine realm during most of the Mesozoic. Their Cretaceous representatives have traditionally been considered as the last survivors of a group declining since the Jurassic. Recently, however, an unexpected diversity has been described in Upper Jurassic–Lower Cretaceous deposits, but is widely spread across time and space, giving small clues on the adaptive potential and ecosystem control of the last ichthyosaurs. The famous but little studied English Gault Formation and ‘greensands’ deposits (the Upper Greensand Formation and the Cambridge Greensand Member of the Lower Chalk Formation) offer an unprecedented opportunity to investigate this topic, containing thousands of ichthyosaur remains spanning the Early–Late Cretaceous boundary. Methodology/Principal Findings: To assess the diversity of the ichthyosaur assemblage from these sedimentary bodies, we recognized morphotypes within each type of bones. We grouped these morphotypes together, when possible, by using articulated specimens from the same formations and from new localities in the Vocontian Basin (France); a revised taxonomic scheme is proposed. We recognize the following taxa in the ‘greensands’: the platypterygiines ‘Platypterygius’ sp. and Sisteronia seeleyi gen. et sp. nov., indeterminate ophthalmosaurines and the rare incertae sedis Cetarthrosaurus walkeri. The taxonomic diversity of late Albian ichthyosaurs now matches that of older, well-known intervals such as the Toarcian or the Tithonian. Contrasting tooth shapes and wear patterns suggest that these ichthyosaurs colonized three distinct feeding guilds, despite the presence of numerous plesiosaur taxa. Conclusion/Significance: Western Europe was a diversity hot-spot for ichthyosaurs a few million years prior to their final extinction. By contrast, the low diversity in Australia and U.S.A. suggests strong geographical disparities in the diversity pattern of Albian–early Cenomanian ichthyosaurs. This provides a whole new context to investigate the extinction of these successful marine reptiles, at the end of the Cenomanian.
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The Ypresian Cambay Formation at Vastan Mine in Gujarat, western India, has yielded a rich herpetological fauna including snakes, lizards and amphibians, but strangely, lizards are only represented by Acrodonta. Here we describe the acrodontan assemblage based on numerous, diverse and well-preserved dentaries, premaxillae, and maxillae. Among the five taxa described one new genus and species characterised by a short splenial represents the youngest occurrence of the extinct family Priscagamidae. The other four taxa belong to the extant family Agamidae. Two of them previously known, Vastanagama susanae and Tinosaurus indicus, are here revised. The two other taxa are new. The first one, Suratagama neeraae gen. and sp. nov., is characterised by the presence of six small pleurodont teeth with a nearly cylindrical shaft and an obtusely pointed apex. The second one, Indiagama gujarata gen. and sp. nov., has rectangular teeth in lateral view, unicuspid crowns forming a nearly horizontal cutting edge, and wear facets on both the lingual and labial sides of the dentary. Our results confirm that Acrodonta is the only lizard group present in Vastan, whereas many other groups are already present from the beginning of the Early Eocene on the other continents. The diversity of the agamids in Vastan and the absence of non-acrodontan lizard in India tentatively support the Out-of-India hypothesis for agamids.
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