Glenn W. Storrs

Academic paper

Palaeontologische Zeitschrift

Schweizerbart'sche Verlagsbuchhandlung

67

1-2

177--191

The Triassic marine reptiles at the base of the extinct Order Sauropterygia, traditionally known as nothosaurs, represent and assemblage of superficially similar forms. The traditional grouping of these animals has generally relied on the flawed basis of 'primitive' characteristics whereas two distinct nothosaurian lineages can be identified through the use of cladistic methodology. The Pachypleurosaurs are the most plesiomoprhic, but not the earliest sauropterygians known. The Nothosauriformes include not only 'nothosaurs' but also the monopyletic group Plesiosauria and seemingly also the Placodontia. Rigorous coding of characters for the recently described nothosaurian genus Silvestrosaurus allows expansion of the phylogenetic database for the Sauropterygia. The revised analysis reaffirms recent studies of relationships for the sauropterygians and demonstrates the affinity of Silvestrosaurus with the Nothosauriformes. The explicit hierarchical classification scheme presented incorporates the hypothesised phylogenetic relationships of these long-misunderstood taxa. The traditional Suborder Nothosauruia, now seen to be paraphyletic, must be abandoned.

English