Hypoptopomatini Eigenmann,, 1890

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 : 21

Tribe Hypoptopomatini Eigenmann, Eigenmann, 1890

Hypoptopomatini Eigenmann, Eigenmann, 1890: 8 , 12, 353, 388.

Type genus: Hypoptopoma Günther, 1868 .

Included genera. Acestridium Haseman, 1911 ; Hypoptopoma Günther, 1868 ; Nannoptopoma Schaefer, 1996 ; Niobichthys Schaefer, Provenzano, 1998 ; Otocinclus Cope, 1871 ; Oxyropsis Eigenmann, Eigenmann, 1889 ; Leptotocinclus n. gen.; and Nannoxyropsis n. gen.

Diagnosis. Hypoptopomatini is diagnosed as a monophyletic group based on ten exclusive synapomorphies: posterolateral portion of ventral surface of lateral ethmoid with ventral strut (char. 9.1); posterolateral portion of lateral ethmoid wider than anterior margin (char. 10.1); condyle of hyomandibula articulated to neurocranium at compound pterotic only (char. 15.1); crest for insertion of levator arcus palatini muscle reduced or absent (char. 18.1); ventral margin of preopercle not flat and not exposed (char. 24.1); posterior extension of preopercle reduced (char. 25.1); posterior ramus of preopercle oriented horizontally (char. 27.1); preopercle latero-sensory canal absent (char. 28.1); ventral surface of pectoral girdle completely exposed (char. 55.2); and arrector fossa of pectoral girdle completely closed (char. 56.2). In addition, there are four non-exclusive synapomorphies: dorsal canal of metapterygoid present and shallow (char. 17.2); metapterigoyd-hyomandibula suture reduced (char. 21.1); interhyal present (char. 33.0); and infraorbital 4 shallow, its depth equal to depth of infraorbital canal (char. 72.0).

Comparisons. The species of Hypoptopomatini are small in size, usually 30–60 mm SL, but some Hypoptopoma species can reach 100 mm SL, and are distinguished from most other loricariids (except the remaining Hypoptopomatinae ) by the ventral surface of the pectoral girdle, which is partially or completely exposed ventrally and bears odontodes (vs. the ventral surface of the pectoral girdle being covered by skin or plates). The Hypoptopomatini are further distinguished from the other hypoptopomatines by the preopercle, which is completely enclosed by the lateral plates of the cheek in a way such that the 4 th and the 5 th infraorbitals make ventral contact with the canal plate and the opercle (vs. the posterior ramus of the preopercle exposed on the lateral surface of the head and located between those same elements).