Loricariidae - Taxonomy and Evolution

Taxonomy and Evolution

Because of their highly specialized morphology, loricariids have been recognized as a monophyletic assemblage in even the earliest classifications of the Siluriformes, meaning it consists of a natural grouping with a common ancestor and all of its descendents. Loricariidae are one of seven families in the superfamily Loricarioidea, along with Amphiliidae, Trichomycteridae, Nematogenyidae, Callichthyidae, Scoloplacidae, and Astroblepidae. Some of these families also exhibit suckermouths or armor, although never together as in loricariids.

This is the largest catfish family, including about 684 species in around 92 genera, with new species being described each year. However, this family is in flux and revisions are likely. For example, the subfamily Ancistrinae is accepted in as late as the 2006 edition of Nelson's Fishes of the World; it later becomes grouped as a tribe because of its recognition as a sister group to the Pterygoplichthyini. Under Ambruster, six subfamilies are recognized: Delturinae, Hypoptopomatinae, Hypostominae, Lithogeneinae, Loricariinae, and Neoplecostominae.

Monophyly for the family is strongly supported, except, possibly, the inclusion of Lithogenes. Lithogenes is the only genus within the subfamily Lithogeneinae. This genus and subfamily, the most basal group in Loricariidae, is the sister group to the rest of the family. Neoplecostominae are the most basal group among the loricariids with the exception of Lithogeneinae. However, the genera of Neoplecostominae do not appear to form a monophyletic assemblage. The two subfamilies Loricariinae and Hypoptopomatinae appear to be generally regarded as monophyletic. However, the monophyly and composition of the other subfamilies are currently being examined and will likely be altered substantially in the future. The Hypostominae are the largest subfamily of Loricariidae. It is made up of five tribes. Four of the five tribes, Corymbophanini, Hypostomini, Pterygoplichthyini, and Rhinelepini, include about 24 genera. The fifth and largest tribe, Ancistrini (formerly recognized as its own subfamily), includes 30 genera.

Loricariid fossils are extremely rare. The fossil record of Loricariidae extends back to the upper Miocene. Within the superfamily Loricarioidea, the Loricariidae are the most derived; in this superfamily, the trend is toward increasingly complex jaw morphology, which may have allowed for the great diversification of the Loricariidae, which have the most advanced jaws.