Hypoptopoma sp., photo by K.S. Cummings
Nannoptopoma spectabilis, photo by J.W. Armbruster
Hypoptopomatines can be separated from all other loricariids based on the presence of an exposed pectoral girdle lateral to the coracoid strut. The entire pectoral girdle may be expsoed as in the Hypoptopoma below, or just a portion as in the Parotocinclus.
Schaefer, S. A. 1998. Conflict and resolution:
impact of new taxa on phylogenetic studies of the Neotropical cascudinhos
(Siluroidei: Loricariidae). Pp. 375-400 In Malabarba, L.R.
R.E. Reis, R.P. Vari, Z.M.S. Lucena, and C.A.S. Lucena (editors), Phylogeny
and Classification of Neotropical Fishes,