pdf: http://www.palaeodiversity.org/pdf/Palaeodiversity_1_14_227-272.pdf

On the basis of an investigation of the type material and more than 100 additional skulls and skeletons, the Lower Jurassic ichthyosaur genus Stenopterygius is revised taxonomically. New diagnoses of all valid species are presented. They are mostly based on body proportions and their changes during ontogeny. This new taxonomic approach allows it to refer all sufficiently preserved adult specimens investigated to one of only four taxa. The typespecies of the genus, Stenopterygius quadriscissus, also includes S. eos, S. incessus, and S. macrophasma, as well as specimens previously referred to S. hauffianus and S. megacephalus. A lectotype is proposed for S. eos and S. incessus. Ichthyosaurus triscissus is a valid taxon, referred to the genus Stenopterygius as Stenopterygius triscissus, following Woodward in von Zittel 1932. The type specimens of S. longifrons, S. megacephalus, and S. megalorhinus are all referable to this species. Part of the material previously referred to S. megalorhinus, as well as the typespecimen of S. cuneiceps, belong to a species of their own for which the binomen Stenopterygius uniter is available. As the holotype of S. uniter was destroyed in World War II, a neotype is proposed. The species S. hauffianus and S. promegacephalus are nomina dubia. The lectotype of S. hauffianus can only be determined as Stenopterygius cf. S. quadriscissus. Most specimens previously referred to S. hauffianus are, in fact, members of S. quadriscissus. The remaining specimens belong to a highly distinctive, easily recognizable, but rare taxon. It was recognized as a distinct subspecies by von Huene (1931) and named Stenopterygius hauffianus forma typica. This subspecies is here elevated to specific rank. The species is so distinct from S. quadriscissus, S. triscissus, and S. uniter that it has to be referred to a genus of its own, for which the name Hauffiopteryx n. gen. is proposed. Hauffiopteryx n. gen. is most probably a basal stenopterygiid. A lectotype is proposed for S. promegacephalus. As it is a juvenile, it is currently not determinable to specific level. Specimens of the type-series of this species, which are largely lost, are figured for the first time. The stratigraphic distribution of the stenopterygiid species is revealing and well in accordance with the taxonomy proposed here. S. quadriscissus is the only species currently known from the Lower Posidonia shale. In the Middle Posidonia shale it is joined by S. triscissus and H. n. gen. typicus. Whereas both S. quadriscissus and S. triscissus are known from the entire Middle Posidonia shale, H. n. gen. typicus is restricted to Lias ε II,2 to Lias ε II,5. S. uniter, however, is only found from Lias ε II,6 to Lias ε II,11, so H. n. gen. typicus and S. uniter exclude each other stratigraphically. Thus, there were never more than three coeval species of the Stenopterygiidae in the Posidonia shale sea of southwestern Germany. Currently, there is no evidence for sexual dimorphism in Stenopterygius.