Comparative anatomy of the clasper of the subfamily Potamotrygoninae (Chondrichthyes: Myliobatiformes).

Claspers of stingrays (Myliobatiformes) are poorly documented in comparison to claspers of skates, with our knowledge restricted mainly to external morphological characters and skeletal components included in descriptions of new species; more encompassing morphological comparative analyses are lacking. Concerning potamotrygonins, clasper morphology has been described for a handful of species, but without elucidating their variation and systematic potential. The present article analyzed clasper structures in all genera of the subfamily Potamotrygoninae (Potamotrygon, Paratrygon, Plesiotrygon, and Heliotrygon), which were compared to the clasper of Styracura and some dasyatid genera. Potamotrygon shows some morphometric variation among the species analyzed. Anatomically, we found variation mainly in the dorsal terminal 1 and accessory terminal 1 cartilages, which are considered diagnostic among potamotrygonin genera; external morphological structures did not present significant differences among potamotrygonins.