After Eight Decades: a New Species of Pterobunocephalus (siluriformes: Aspredinidae) from the Upper Putumayo, Napo and Pastaza Rivers, Ecuador

Abstract Pterobunocephalus currently comprises two valid species: P. depressus described from the Guaporé River basin and P. dolichurus from the Trombetas River at its confluence with the Amazon River. A third nominal species, Bunocephalus albofasciatus, described from the upper Mamoré River basin, is presently considered a junior synonym of P. depressus. Based on a morphological approach, we describe here a new species of Pterobunocephalus from the upper Amazon basin (Napo, Pastaza, and Putumayo rivers) in Ecuador. The new species is distinguished from its congeners by the following combination of characters: (1) large eyes; (2) anterior margin of the mesethmoid relatively wide, shallowly concave, and sunken between anterior margins of premaxillae; (3) total number of anal-fin rays 10–11; and (4) in dorsal view, parapophysis of the fifth vertebra shaped like the blade of a shepherd’s axe with distal portion conspicuously and abruptly expanded.