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Ichthyosaurs suffered severe turnover across Triassic–Jurassic boundary in France



Ben Creisler
bcreisler@gmail.com

A new online paper:

Valentin Fischer, Henri Cappetta, Peggy Vincent, Géraldine Garcia,
Stijn Goolaerts, Jeremy E. Martin, Daniel Roggero & Xavier Valentin
(2014)
Ichthyosaurs from the French Rhaetian indicate a severe turnover
across the Triassic–Jurassic boundary.
Naturwissenschaften (advance online publication)
DOI: 10.1007/s00114-014-1242-7
http://link.springer.com/article/10.1007/s00114-014-1242-7


Mesozoic marine reptiles went through a severe turnover near the end
of the Triassic. Notably, an important extinction event affected
ichthyosaurs, sweeping a large part of the group. This crisis is,
however, obscured by an extremely poor fossil record and is regarded
as protracted over the entire Norian–earliest Jurassic interval, for
the lack of a more precise scenario. The iconic whale-sized
shastasaurid ichthyosaurs are regarded as early victims of this
turnover, disappearing by the middle Norian. Here we evaluate the
pattern of this turnover among ichthyosaurs by analysing the faunal
record of two Rhaetian localities. One locality is Autun, eastern
France; we rediscovered in this material the holotypes or partial
'type' series of Rachitrema pellati, Actiosaurus gaudryi,
Ichthyosaurus rheticus, Ichthyosaurus carinatus and Plesiosaurus
bibractensis; a revised taxonomic scheme is proposed. The second
assemblage comes from a new locality: Cuers, southeastern France. Both
these assemblages provide several lines of evidence for the presence
of shastasaurid-like ichthyosaurs in the Rhaetian of Europe. These
occurrences suggest that both the demise of shastasaurids and the
sudden radiation of neoichthyosaurians occurred within a short time
window; this turnover appears not only more abrupt but also more
complex than previously postulated and adds a new facet of the
end-Triassic mass extinction.