PROC. BIOL. SOC. WASH. 104(4), 1991, pp. 840-869 EXALLODONTUS AGUANAI, A NEW GENUS AND SPECIES OF PIMELODIDAE (PISCES: SILURIFORMES) FROM DEEP RIVER CHANNELS OF SOUTH AMERICA, AND DELIMITATION OF THE SUBFAMILY PIMELODINAE John G. Lundberg, Francisco Mago-Leccia, and Pedro Nass Abstract. —A new genus and species of pimelodid catfish, Exallodontus agua-nai, is described from the deep channels of the Orinoco and Amazon rivers. This taxon is diagnosed by autapomorphically robust jaw teeth reduced to 2-3 rows, and an obtusely triangular "lacrimal" (=infraorbital 1+2). Also, this taxon has a unique combination of phylogenetically advanced characters— long adipose fin, short dorsal-fin spine, short head, very small eye, vertical neural spines on middle vertebrae, sharply ridged supraoccipital process, paddle-like anterior anal-fin rays, and transversely oriented posterior nares. The subfamily Pimelodinae is circumscribed to include 32 nominal genera: Aguarunichthys, Bagropsis, Bergiaria, Brachyplatystoma, Calophysus, Chei-rocerus, Conorhynchos, Duopalatinus, Exallodontus, Goslinia, Hemisorubim, Hypophthalmus, Iheringichthys, Leiarius, Luciopimelodus, Megalonema, Merodontodus, Perrunichthys, Parapimelodus, Paulicea, Phractocephalus, Pi-melodina, Pimelodus, Pinirampus, Piramutana, Platynematichthys, Platysilu-rus, Platystomatichthys, Pseudoplatystoma, Sorubim, Sorubimichthys, and Steindachneridion. This subfamily is supported by three synapomorphic char-acters—the dendritic arrangement of lateral line system on the head and nape, an elongated lateral ethmoid-palatine condyle, and a sutural joint between the fifth and sixth centra. Within the Pimelodinae three nested subgroups are delineated and diagnosed but not named formally: (1) "Group A," comprising all pimelodines except Phractocephalus, Leiarius and Perrunichthys; (2) ^^Cal-ophysus-Pimelodus clade" that includes Stewart's (1986a) '^Calophysus group" {Calophysus, Pinirampus, Pimelodina, Luciopimelodus and Aguarunichthys) plus Megalonema plus our third group; (3) ""Pimelodus group" composed of the nominal genera Bagropsis, Bergiaria, Cheirocerus, Conorhynchos, Duopa-latinus, Exallodontus, Iheringichthys, Parapimelodus, Pimelodus, Platysilurus, and Platystomatichthys. Variations of the trigeminofacial nerve foramina are described in relation to a possible phylogenetic diagnosis of Pimelodus. Resumen.— En este trabajo se describe a Exallodontus aguanai, un nuevo genero y nueva especie de bagre pimelodido proveniente de los canales pro-fundos de los rios Orinoco y Amazon. Exallodontus se reconoce por dos caracteres autapomorficos: (1) dientes mandibulares robustos y reducidos a 2 6 3 filas, y (2) presencia de un lacrimal (infraorbitario 1+2) triangular con angulos obtusos. Este taxon tiene, ademas, una combinacion unica de caracteres filogeneticamente avanzados— aleta adiposa larga, espina de la aleta dorsal corta, cabeza relativamente pequefia, ojo muy pequeno, espinas neurales ver-ticales en las vertebras localizadas hacia la mitad de la columna, processo
Exallodontus aguanai, a new genus and species of Pimelodidae (Pisces: Siluriformes) from deep river channels of South America, and delimitation of the subfamily Pimelodinae
BioStor
