[1] These fish are generally small, usually about 5 to 15 cm (2–6 in) in standard length, although the largest, T. rivulatus, can reach more than twice this size.

[1] Species differ from one another primarily in body proportions, fin ray counts and colouration.

[6] Some authors have tentatively defined putative monophyletic assemblages within the genus Trichomycterus based on the possession of unique morphological features.

[7] However, an assemblage of species from south and southeastern Brazil is also supported that includes T. araxa,[8] T. castroi, T. davisi, T. guaraquessaba, T. immaculatus, T. itatiayae, T. mboycy, T. mirissumba, T. naipi, T. nigricans, T. papilliferus, T. plumbeus, T. stawiarski, T. taroba, T. triguttatus and T. zonatus,[5] T. aguarague, T. alterus, T. belensis, T. boylei and T. ramosus also form a diagnosable species assemblage.

[2] Species of Trichomycterus inhabit a diversity of habitats throughout South and Central America from Costa Rica in the north to Patagonia in the south and from lowland Atlantic rainforest in the east to Andean highland streams in the west.