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,
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 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.