Loricaria thomasi, new species, is described from large and predominantly whitewater river channels draining into the middle río Orinoco. The new species is distinguished from all nominal congeners by its uniquely developed buccal tuft, a medial cluster of 25–29 simple, elongate papillae supported by a fleshy protuberance from the anterior roof of the buccal cavity, internal to premaxillae. Adult specimens of L. thomasi are distinguished from nominal congeners by having dorsal surfaces of head and anterior body relatively smooth, lacking distinct ridges or crests (vs. paired, longitudinal, odontode ridges conspicuous on supraoccipital and predorsal plates). Loricaria thomasi apparently feeds on nonbiting midge larvae (Chironomidae) in the subfamilies Chironominae (Cryptochironomus, Pelomus) and Tanypodinae (Coelotanypus) in the río Guariquito near its confluence with the Orinoco.