Abstract Few records of Late Jurassic fishes have been reported previously from Antarctica. They include an indeterminate teleost from the Ameghino (Nordenskjold) Formation at Longing Gap and two incomplete aspidorhynchiforms from James Ross Island, all of presumed Late Jurassic age. New fish material recently recovered in the Upper Jurassic of Longing Gap is described. The new material consists of one piece of body squamation, which, based on the structure of the scales, corresponds to a new genus and species (Ameghinichthys antarcticus gen. et sp. nov.) of an indeterminate actinopterygian family; one aspidorhynchiform identified as Vinctifer sp. due to the structure and distribution of the scales; and numerous specimens of a new ichthyodectiform, Antarctithrissops seymouri gen. et sp. nov. This new genus differs from European ichthyodectiforms in the shape of the preopercle, the presence of long sensory preopercular branches almost reaching the posterior margin of the bone, and the uncommon structure of...