Phylogeny of the Ichthyopterygia

A phylogenetic hypothesis for ichthyopterygians is proposed, based on a cladistic analysis of 105 discrete osteological characters coded for 27 ingroup and five outgroup taxa. The monophyly of Ichthyopterygia is established; at least nine characters support its basal node. The group contains two basal species and a clade formed by the Ichthyosauria and Grippidia. All ichthyosaurs from post-Triassic strata form an unnamed clade, which in turn forms the group Euichthyosauria (new taxon) with four Late Triassic genera. The traditional Shastasauridae is polyphyletic, with Cymbospondylus forming the sistergroup of a clade containing mixosaurs, shastasaurs, and euichthyosaurs. In addition, Californosaurus and Toretocnemus are not shastasaurs but euichthyosaurs. Two new generic names, Macgowania and Isfjordosaurus, are proposed.