Two new species of S aurichthys ( A ctinopterygii: S aurichthyidae) from the Middle T riassic of M onte S an G iorgio, S witzerland, with implications for character evolution in the genus

S aurichthys , characterized by a long slender body and an elongated rostrum, is one of the most iconic genera of L ate P aleozoic– E arly M esozoic fishes. The genus was particularly speciose in the T riassic, with a global distribution in both marine and freshwater habitats. Here, we describe two new species from the M iddle T riassic B esano F ormation of M onte S an G iorgio, S witzerland, S aurichthys breviabdominalis sp. nov. and S aurichthys rieppeli sp. nov. S.  breviabdominalis is characterized by a proportionately long operculum, short abdominal region and rib‐like mid‐lateral scales, whereas S.  rieppeli is divergent from other M iddle T riassic saurichthyids in the block‐like haemal arches, fringing fulcra on the pelvic and unpaired fins, and reduction of the squamation to a single row in the abdominal region. Phylogenetic analysis places S.  rieppeli in a basal position relative to congeners from the A lpine T riassic, and supports previous hypotheses regarding the convergent evolution of reduced squamation within saurichthyids. S.  breviabdominalis forms a monophyletic group with species from the same locality, suggesting divergence in sympatry. This finding has implications for our understanding of disparity and character evolution in saurichthyid fishes, as well as ecomorphological divergence and resource partitioning between closely related fishes in Triassic marine ecosystems. © 2015 The Linnean Society of London