Data from: Evaluation of the ontogeny and sexual dimorphism in a new species of Middle Triassic Darwinulocopina (Crustacea, Ostracoda) from Argentina

The Darwinulocopina comprise an interest group of ostracods which where among the first invaders of freshwater waters during the late Palaeozoic. The Permian–Triassic extinction greatly reduced their diversity, reaching present times represented by one family. The darwinulids are regarded as "ancient asexuals" since a parthenogenetic mode of reproduction is assumed for all the post-Triassic members of the group. However, the high diversity achieved during the late Palaeozoic is often associated with sexual reproduction. Here we studied a monospecific association of ostracods from the Middle Triassic of the Cuyana Basin, Province of Mendoza, Argentina, and recognized a new species of Darwinulocopina, <i>Prasuchonella</i>? <i>huarpe </i>nov. sp. We discuss the traditional length/height and length/width graphical method to recognized ontogeny and/or sexual dimorphism in fossil ostracod assemblages, and performed a geometric morphometric analysis performed on both lateral and dorsal views of near one hundred seventy carapaces. The best results were obtained from the analysis in dorsal view, and four ontogenetic stages were discriminated (A-3, A-2, A-1 juveniles, adult). This allowed recognizing a main ontogenetic trend related to the development of the brooding chamber. Although subtle in differences, female carapaces are wider not only at the brooding chamber, but also along the whole length, compared to the carapaces of the presumptive males. Finally, full systematic descriptions and discussions, attempting to unify descriptive criteria for recent and fossil darwinulocopin carapaces, are provided. As a result, the need for a review of those Mesozoic records of Darwinulocopina, particularly those from the Triassic, is noted.