A new species of Ammoglanis (Siluriformes: Trichomycteridae) from Venezuela

A new miniaturized species of the trichomycterid genus Ammoglanis is described from the Rio Orinoco basin in Venezuela. It is distinguished from its only congener, A. diaphanus, by: a banded color pattern formed by internal chromatophores; 5 or 6 pectoral-fin rays (7 in A. diaphanus), 5/5 principal caudal-fin rays (6/6 in A. diaphanus), ii+6 dorsal-fin rays (iii+6+i in A. diaphanus), 30 or 31 vertebrae (33 in A. diaphanus), six or seven branchiostegal rays (five in A. diaphanus), subterminal mouth (inferior in A. diaphanus) and by the lack of premaxillary and dentary teeth. The two species also differ markedly in a number of internal anatomical traits. Synapomorphies are offered to support the monophyly of the two species now included in Ammoglanis, as well as autapomorphies for each of them. Ammoglanis pulex is among the smallest known vertebrates, the largest known specimen being 14.9 mm SL. It is a fossorial inhabitant of shallow sandy sections of clearand light blackwater streams, and probably feeds on interstitial microinvertebrates.