The skeletal anatomy of most if not all freshwater stingrays still is insufficiently known due to the lack of detailed morphological studies. Here we describe the morphology of an adult male specimen of Potamotrygon motoro to form the basis for further studies into the morphology of freshwater stingrays and to identify potential skeletal features for analyzing their evolutionary history. Potamotrygon is a member of Myliobatiformes and forms together with Heliotrygon, Paratrygon and Plesiotrygon the Potamotrygonidae. Potamotrygonids are exceptional because they are the only South American batoids, which are obligate freshwater rays. The knowledge about their skeletal anatomy still is very insufficient despite numerous studies of freshwater stingrays. These studies, however, mostly consider only external features (e.g., colouration patterns) or selected skeletal structures. To gain a better understanding of evolutionary traits within sting-rays, detailed anatomical analyses are urgently needed. Here, we present the first detailed anatomical account of a male Potamotrygon motoro specimen, which forms the basis of prospective anatomical studies of potamotrygonids.