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Large Triassic eusauropterygians from Lower Muschelkalk in The Netherlands

Ben Creisler

A new online paper:

Dennis F. A. E. Voeten, P. Martin Sander & Nicole Klein (2014)
Skeletal material from larger Eusauropterygia (Reptilia:
Eosauropterygia) with nothosaurian and cymatosaurian affinities from
the Lower Muschelkalk of Winterswijk, The Netherlands.
Paläontologische Zeitschrift (advance online publication)
DOI: 10.1007/s12542-014-0250-4

Eusauropterygian elements from the Lower Muschelkalk (Vossenveld
Formation) of Winterswijk, The Netherlands, comprising three mandibles
and a selection of postcranial material, are described. The new
mandibles correspond to crania larger than eusauropterygian cranial
material previously known from this locality. The postcranial material
represents a selection of isolated and associated material of
comparably large size. Two of the mandibles conform to the morphology
commonly recognized in Nothosaurus from the Lower Muschelkalk, but the
third mandible accommodates five fangs per ramus in the symphyseal
domain and exhibits a symphyseal ratio of 1.04, a condition not yet
described for Eusauropterygia from the Vossenveld Formation. Body
length for the animals represented by the finds was estimated through
dimensional comparison with MB.R.27, a nearly complete skeleton from
the lower Middle Muschelkalk locality of Rüdersdorf (Germany) assigned
to Nothosaurus marchicus. Body length estimates for the individuals
represented by the largest mandible and by a selection of associated
postcranial material exceed 1,500 mm; approximately 50 % larger than
the eusauropterygian taxa from Winterswijk described so far.
Furthermore, certain morphological characters identified in one
mandible and in the postcranial elements suggest a cymatosaurian
affinity over a nothosaurian affinity. The present study indicates
eusauropterygian diversity during the Lower Muschelkalk was greater
than traditionally believed. This challenges the concept of a slow
paced, gradual biotic response to the origination and expansion of the
Muschelkalk Sea, which commenced only 5 million years after the
Permian–Triassic mass extinction event.