Hypoptopoma Günther, 1868

Delapieve, Maria Laura S., A., Pablo Lehmann & Reis, Roberto E., 2017, An appraisal of the phylogenetic relationships of Hypoptopomatini cascudinhos with description of two new genera and three new species (Siluriformes: Loricariidae), Neotropical Ichthyology 15 (4), No. e 170079, pp. 1-38 : 22

Genus Hypoptopoma Günther, 1868

Hypoptopoma Günther, 1868: 477 . Type-species: Hypoptopoma thoracatum Günther, 1868 . Type by monotypy. Gender neuter.

Aristommata Holmberg, 1893: 96 . Type-species: Aristommata inexspectata Holmberg, 1893 . Type by monotypy. Gender feminine.

Diapeltoplites Fowler, 1915: 237 . Type-species: Hypoptopoma gulare Cope, 1878 . Type by original designation. Gender masculine.

Included species. Hypoptopoma baileyi Aquino, Schaefer, 2010 ; Hypoptopoma bianale Aquino, Schaefer, 2010 ; Hypoptopoma brevirostratum Aquino, Schaefer, 2010 ; Hypoptopoma elongatum Aquino, Schaefer, 2010 ; Hypoptopoma guianense Boeseman, 1974 ; Hypoptopoma gulare Cope, 1878 ; Hypoptopoma incognitum Aquino, Schaefer, 2010 ; Hypoptopoma inexspectatum (Holmberg, 1893) ; Hypoptopoma machadoi Aquino, Schaefer, 2010 ; Hypoptopoma muzuspi Aquino, Schaefer, 2010 ; Hypoptopoma psilogaster Fowler, 1915 ; Hypoptopoma steindachneri Boulenger, 1895 ; and Hypoptopoma thoracatum Günther, 1868 .

Diagnosis. Hypoptopoma is diagnosed as monophyletic based on a single non-exclusive synapomorphy: odontodes enlarged on posterior margin of trunk plates (char. 96.1). This character is uniquely shared with Nannoptopoma sternoptychum .

Comparisons. The species of Hypoptopoma are further distinguished from other hypoptopomatins by having a pointed, triangular snout (vs. snout rounded) and a very robust trunk, such that some of its species hold the largest body size within the Hypoptopomatinae , with standard length surpassing 100 mm (vs. smaller size). The dorsal profile of the head and body is straight from the snout tip to the dorsalfin origin (vs. dorsal profile convex). The greatest body width is at the eye, due to its large size and ventrolateral position (vs. greatest body width at cleithrum). The dermal plates of Hypoptopoma are very thick and strongly articulated to each other (vs. dermal plates normally developed and more loosely articulated). Unlike other hypoptopomatins, in most species of Hypoptopoma , the adipose fin may be present and there are enlarged and flattened odontodes positioned along the posterior margin of the trunk plates. Hypoptopoma is also differentiated from other hypoptopomatines, except Nannoptopoma , by having the trunk straight from the posteriormost dorsal and anal fin rays to the caudal fin (vs. trunk slightly concave). Contrary to all other genera, except Oxyropsis , Hypoptopoma have a ventrolateral displacement of the eyes, which are also visible in ventral view. Additionally, Hypoptopoma can be distinguished from Nannoptopoma , Otocinclus , Leptotocinclus , and from most species of Acestridium by the possession of serrations along the inner margin of the pectoral-fin spine (vs. serrations absent).