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 redes cribed from its type host, Potamotrygon motoro (Potamotrygonidae), from spe cimens recently collected in Argentina and type material. The armature comb ines features of Eutetrarhynchus, Oncomegas, and Dollfusiella, indicating t hat its current placement in Eutetrarhynchus is incorrect and that the spec ies represents a new genus. Paroncomegas n. gen. is proposed within the Eut etrarhynchidae Guiart, 1927, to accommodate Tentacularia araya as Paroncome gas 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 Oncomeg as, which possesses an asymmetrical basal swelling on the internal face of the tentacle and a single macrohook on the external face of the basal armat ure. Paroncomegas is unique among these genera in possessing a chainette in the basal armature. All other genera currently recognized within the Eutet rarhynchidae can be distinguished from Paroncomegas by a distinct spatial d ivergence of hooks files 1(1'), resulting in a prominent space in views of the internal face. Two different morphotypes of P. araya can be distinguish ed 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 r eproductive anatomy remain comparable.