Record of the freshwater stingrays Potamotrygon brachyura and P. motoro (Chondrichthyes, Potamotrygonidae) in the lower Uruguay river, South America

freshwater stingrays, or potamotrygonids, are restricted to neotropical river drainages. these elasmobranchs are well adapted to freshwater environments and the number of described species gradually increases as further research is carried out. some of the first studies on their systematics and natural history were carried out in the 1960s and 1970s in southern south america. however, there is no new published data on potamotrygonids from uruguayan waters since then (except for local journal reports from sportive fishermen and specimens deposited in uruguayan collections). the present study aims to record the recent occurrence of two species of potamotrygonids caught by sport fishermen, with comments on other published historical records for the same area. as many other elasmobranchs, these species have an important, but not always well understood, role in the uruguayan rivers ecosystems.