Paroncomegas araya (Woodland, 1934) n. gen. et comb. (Cestoda: Trypanorhyncha: Eutetrarhynchidae) from the freshwater stingray Potamotrygon motoro in South America

The trypanorhynch cestode originally designated Tentacularia araya is redescribed from its type host, Potamotrygon motoro (Potamotrygonidae), from specimens recently collected in Argentina and type material. The armature combines features of Eutetrarhynchus, Oncomegas, and Dollfusiella, indicating that its current placement in Eutetrarhynchus is incorrect and that the species represents a new genus. Paroncomegas n. gen. is proposed within the Eutetrarhynchidae Guiart, 1927, to accommodate Tentacularia araya as Paroncomegas araya n. comb. Eutetrarhynchus differs from Paroncomegas in the absence of a basal armature and basal swelling on the tentacles, from Dollfusiella by lacking macrohooks associated with the basal armature, and from Oncomegas, which possesses an asymmetrical basal swelling on the internal face of the tentaclc and a single macrohook on the external face of the basal armature. Paroncomegas is unique among these genera in possessing a chainette in the basal armature. All other genera currently recognized within the Eutetrarhynchidae can be distinguished from Paroncomegas by a distinct spatial divergence of hooks files 1(1'), resulting in a prominent space in views of the internal face. Two different morphotypes of P. araya can be distinguished in the material from Argentina, both infecting the same individual host specimens. They differ in the number and size of mature and gravid segments. Other characters concerning the tentacle armature, scolex features, and reproductive anatomy remain comparable.