Ageneiosus, LA CEPEDE, 1803

Calegari, Bárbara B., Vari, Richard P. & Reis, Roberto E., 2019, Phylogenetic systematics of the driftwood catfishes (Siluriformes: Auchenipteridae): a combined morphological and molecular analysis, Zoological Journal of the Linnean Society 187, pp. 661-773 : 758-759

GENUS AGENEIOSUS LA CEPÈDE, 1803 (CLADE 115)

Ageneiosus La Cepède, 1803: 132 (type species: Ageneiosus armatus La Cepède, 1803 ; type by subsequent designation by Eigenmann & Eigenmann, 1890: 299. Gender masculine).

I n c l u d e d s p e c i e s: A g e n e i o s u s a k a m a i R i b e i r o, Py-Daniel & Walsh, 2017, * Ageneiosus apiaka Ribeiro, Py-Daniel & Walsh, 2017 , Ageneiosus dentatus Kner, 1857 , Ageneiosus inermis ( Linnaeus, 1766) , Ageneiosus intrusus Ribeiro, Py-Daniel & Walsh, 2017 , Ageneiosus lineatus Ribeiro, Py-Daniel & Walsh, 2017 , * Ageneiosus magoi Castillo & Brull, 1989 , Ageneiosus militaris Valenciennes, 1836 , Ageneiosus pardalis Lütken, 1874 , Ageneiosus polystictus Steindachner, 1915 , Ageneiosus ucayalensis Castelnau, 1855 , Ageneiosus uranophthalmus Ribeiro & Py-Daniel, 2010 and Ageneiosus vittatus Steindachner, 1908 .

Diagnosis: Ageneiosus is diagnosed by six morphological synapomorphies. Non-exclusive: (1) bones of cephalic shield trabeculated (char. 3531: 0 → 1), convergent in Tympanopleura atronasus and Tympanopleura rondoni ; (2) epioccipital not exposed, not participating of cephalic shield (char. 3555: 1 → 2), convergent in Pseudepapterus ; (3) bony expansion present on posteromedial portion of premaxilla (char. 3585: 0 → 1), reversed in Ageneiosus uranophthalmus and Ageneiosus intrusus , convergent in Auchenipterus fordicei and Trachycorystes ; (4) coronoid process of anguloarticular developed as a large and laminar process (char. 3602: 0 → 1), convergent in Tympanopleura rondoni , Tympanopleura atronasus , Auchenipterichthys , Pseudauchenipterus , Trachelyichthys , Gephyromochlus , Pseudotatia , Duringlanis , Balroglanis and most species of Tatia ; (5) Müllerian ramus reduced, not surpassing half the length of the transcapular process (char. 3661: 0 → 1), convergent in Asterophysus , Gelanoglanis and Pseudepapterus ; and (6) serrations absent on posterior margin of dorsal-fin spine (char. 3693: 0 → 1), reversed in Ageneiosus dentatus and Ageneiosus vittatus , convergent in Asterophysus , Duringlanis perugiae , Epapterus , Gelanoglanis travieso , Pseudepapterus , Tatia (except Tatia intermedia and Tatia simplex ), Tocantinsia , Trachelyopterichthys , Spinipterus , Trachycorystes trachycorystes , Trachelyopterus insignis and Trachelyopterus amblops .

Additional diagnosis: Posterior diverticula on gas bladder absent; epaxial muscles almost completely covering tympanic region in adults, except Ageneiosus pardalis .

Comparisons: Ageneiosus is a large body-sized Ageneiosini that is distinguished from other auchenipterids, except Tympanopleura , by having the snout strongly depressed, resembling a duck’s beak (vs. snout only slightly depressed, or laterally compressed in Gelanoglanis ), with the eye ventrolaterally positioned, in such a way that it is as visible in ventral and dorsal views (vs. eye not visible in ventral view), mouth subterminal, upper jaw extended well anteriorly to the lower jaw (vs. mouth terminal, both upper and lower jaws extended anteriorly to the same vertical line), and absence of mental barbels (vs. two pairs of mental barbels present, but one pair in Tetranematichthys and Gelanoglanis ). It is further distinguished from all auchenipterines, except Tympanopleura and Tetranematichthys , by the short maxillary barbel, not surpassing the anterior margin of the orbit (vs. long maxillary barbel, extending beyond the anterior margin of the orbit) and, except for Pseudepapterus , the epioccipital not exposed, not participating in the cephalic shield (vs. epioccipital exposed on the dorsal surface of head). It is distinguished from Tympanopleura by a longitudinal sulcus on the posterior margin of the anterior cranial fontanel (vs. longitudinal sulcus absent, except in Tympanopleura rondoni ); pseudotympanum not visible externally, or very little visible externally (vs. prominent pseudotympanum, conspicuously visible externally); posterior margin of the dorsal-fin spine smooth, not serrated, except for Ageneiosus vittatus and Ageneiosus dentatus (vs. posterior margin of dorsal-fin spine serrated); and Müllerian ramus reduced, not surpassing half the length of the transcapular process (vs. Müllerian ramus large, surpassing the suture in the posterolateral margin of the transcapular process).

Remarks: The condition of an ossified gas bladder was suggested by Ribeiro et al. (2017) as diagnostic for Ageneiosus . The present hypothesis, however, has not recovered this feature as synapomorphic for the genus, because the gas bladder of Tympanopleura cryptica and Tympanopleura piperata are ossified but that of Ageneiosus lineatus is unossified, a condition also shared with Ageneiosus pardalis , not observed in this study but reported by Ribeiro et al. (2017).