Reg. Charity No. 1168330
The 'perleidiform' Mendocinichthys and Pseudobeaconia from the Potrerillos and Santa Clara Abajo formations (Upper Triassic; Argentina) are reviewed. Mendocinichthys has been known from a review of this species that is not based on the type material, but on referred specimens in the American Museum of Natural History. However, those specimens are found here to represent a new species of Pseudobeaconia, P. celestae sp. nov. Consequently, Mendocinichthys is restricted here to the type material and, within it, to the only specimen that clearly represents a distinct taxon and is thus designated lectotype. We further performed a cladistic analysis and propose a new family, Pseudobeaconiidae for these two South American Triassic genera, which is mainly characterized by the presence of an incomplete dorsal ridge of spine-like scales between the skull and the dorsal fin, and scales with straight posterior border, an elevated central region and marginal concentric ridges of ganoine. The cladistic analysis further indicates the existence of some lineages endemic to certain areas of Gondwana and Europe. Pseudobeaconia celestae sp. nov. represents the first record of Pseudobeaconia in the Cacheuta sub-basin of the Cuyana Basin. The genus was previously known from the Santa Clara sub-basin of the Cuyana Basin only, and the new record confirms the previous hypothesis of correlation between the sedimentary infilling of these sub-basins. KEYWORDS Pseudobeaconia • Mendocinichthys • Pseudobeaconiidae • Perleidiformes • Actinopterygii • Triassic • Gondwana