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, Prasuchonella? huarpe 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 hun...