Besanosaurus

Besanosaurus is an extinct genus of ichthyosaur, a group of marine reptiles that dominated Mesozoic oceans. It lived during the Middle Triassic, with fossils found in the Besano Formation at Monte San Giorgio, a site spanning what is now the Italy–Switzerland region. The type species is Besanosaurus leptorhynchus. The taxonomic placement of Besanosaurus has been debated, with some classifications placing it in its own family Besanosauridae and others placing it within broader ichthyosaur groups such as Shastasauridae or as a basal ichthyosaur, reflecting ongoing revisions in early ichthyosaur relationships.

Anatomically, Besanosaurus is known from relatively well-preserved material that indicates a streamlined, aquatic mode of life. It possessed a long, narrow snout and a body adapted to efficient swimming, with limb elements modified into paddle-like flippers suitable for life in marine environments. Its long neck and elongated skull relative to some other ichthyosaurs are distinguishing features in several analyses.

Ecology and paleobiology suggest a piscivorous or small-vertebrate–grazing diet, inferred from its shallow-water habitat and tooth morphology typical of fish-eating ichthyosaurs. The genus contributes to understanding the early diversification of ichthyosaurs in the Middle Triassic, a period marked by rapid evolutionary experimentation that yielded a range of body plans and ecological roles.

Besanosaurus remains a key taxon for studying the early evolution and biogeography of ichthyosaurs, particularly in the well-preserved Triassic records of Monte San Giorgio.