Descriptions and Phylogenetic Relationships of the Guiana Shield Pencil Catfishes

Abstract

The systematics of the catfish genus Trichomycterus Valenciennes 1832 are complicated and unresolved. This genus is paraphyletic, containing all members of the Trichomycterinae that cannot be adequately placed into an established genus due to the paucity of clearly defining characters that separated the lineages within this subfamily. The complete revision of Trichomycterus is a daunting task, and one that cannot be undertaken until most of the diversity within geographically relevant clades are described. This study describes six new species of Trichomycterus of the Pakaraima Mountains and nearby Kusad Mountain of the Guiana Shield region of South America. Additionally, I explore the phylogenetic relationships of these species and construct a time-calibrated phylogeny of the Eremophilus lineage within the Trichomycterinae. The results presented here suggest that there are two clades of Trichomycterus in the Guiana Shield, one species described in this study may constitute a species complex, that the diversification within the Eremophilus lineage occurred concurrently with the rise of the Andes Mountains, and that upper portion of the Ireng River may have flown north into the Grand Pakaraima River before being captured by the modern-day Rio Branco.