Abstract
Modern marine turtles (chelonioids) are the remnants of an ancient radiation that roots in the Cretaceous. The oldest members of that radiation are first recorded from the Early Cretaceous and a series of species are known from the Albian-Cenomanian interval, many of which have been allocated to the widespread but poorly defined genus Rhinochelys, possibly concealing the diversity and the evolution of early marine turtles. In order to better understand the radiation of chelonioids, we redescribe the holotype and assess the taxonomy of Rhinochelys amaberti Moret (1935) (UJF-ID.11167) from the Late Albian (Stoliczkaia dispar Zone) of the Vallon de la Fauge (Isère, France). We also make preliminary assessments of the phylogenetic relationships of Chelonioidea using two updated datasets that widely sample Cretaceous taxa, especially Rhinochelys. Rhinochelys amaberti is a valid taxon that is supported by eight autapomorphies; an emended diagnosisis proposed. Our phylogenetic analyses suggest that Rhinochelys could be polyphyletic, but constraining it as a monophyletic entity does not produce trees that are significantly less parsimonious. Moreover, support values and stratigraphic congruence indexes are fairly low for the recovered typologies, suggesting that missing data still strongly affect our understanding of the Cretaceous diversification of sea turtles.
Highlights
IntroductionModern marine turtles (chelonioids) are the remnants of an ancient radiation that roots in the Cretaceous
Modern marine turtles are the remnants of an ancient radiation that roots in the Cretaceous
We describe a series of previously unreported chelonioid skulls originating from the lower part of the Cambridge Greensand (Upper Albian) of the United Kingdom (Collins, 1970; Hirayama, 1997; Hooks, 1998)
Summary
Modern marine turtles (chelonioids) are the remnants of an ancient radiation that roots in the Cretaceous. The oldest members of that radiation are first recorded from the Early Cretaceous and a series of species are known from the AlbianCenomanian interval, many of which have been allocated to the widespread but poorly defined genus Rhinochelys, possibly concealing the diversity and the evolution of early marine turtles. The diversity of Early Cretaceous chelonioid and the nature and tempo of their radiation are poorly understood To contribute to this wide issue, we redescribe the holotype of Rhinochelys amaberti Moret (1935) from the Upper Albian of France, which has never been re-assessed since 1935. We evaluate the relationships of chelonoids and the monophyly of Rhinochelys using two updated matrices Bardet et al (2013) and Cadena & Parham (2015)
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