New Trichomycterus (Siluriformes: Trichomycteridae) from an Offshore Island of Colombia

Abstract

Abstract Trichomycterus gorgona, the first insular trichomycterid species, is described from a small stream on Gorgona Island, located approximately 56 km west of the Pacific coast of Colombia. The new species differs from all congeners in the possession of a thick transverse skin flap between the pelvic fins. It is further distinguished by the following combination of characteristics: presence of eight or nine paired ribs (vs 12 or more), reduced pigmentation, and eyes reduced to small ovoid dots. Although epigean, the new species shares features commonly observed among troglomorphs, yet is distinguished from troglobitic Trichomycterinae in having the maxillary barbel extending to the anterior pectoral-fin margin, nasal barbels reaching the opercular odontodes, three supraorbital pores on the head (vs four pores), eight pectoral-fin rays (vs nine or 10) and the first ray prolonged as a filament, tip of adpressed pelvic-fin not reaching anal-fin origin (vs reaching origin of anal-fin), 39 or 40 vertebrae ...