Abstract Endolimnadiopsis rusconii sp. nov. is the first record of paleolimnadiopseid conchostracan from the lower Upper Triassic Cacheuta Formation, Mendoza Province, Argentina. An extended diagnosis of the genus Endolimnadiopsis Shen is presented, and some comments about its taxonomic position in Family Palaeolimnadiopseidae and Subfamily Asiolimnadiopseinae are also given. The paleobiological, paleobiogeographical, and evolutionary implications of this finding are briefly discussed. The find supports a close relationship between southamerican and asiatic conchostracan faunas. From an evolutionary point of view, the new species shows a combination of both characters, primitive and more advanced, that corresponds with a transitional form between primitive paleozoic to advanced mesozoic species. E . rusconii sp. nov. is compared with other paleolimnadiopseids such as Endolimnadiopsis eichwaldi Netshajev from the Upper Permian of Russia.