Systematic revision of the South American armored catfish genus Loricaria (Siluriformes: Loricariidae)

The genus Loricaria Linnaeus of the family Loricariidae is diagnosed as a monophyletic group based on two uniquely derived synapomorphies: lower lip surfaces covered with filiform papillae and absence of buccal papillae surrounding the dentary teeth. Loricaria are small to moderate-sized catfishes widely distributed throughout most of the major river drainages of cis-Andean South America, including the Amazon, Orinoco, Paraguay, Paraná, and smaller coastal rivers draining the Guyana and Brazilian Shields. Based on multivariate analyses of morphometric and meristic data in combination with qualitative assessment of external morphological characters, 15 nominal species are accepted as valid, with an additional nine described as new. Among the nominal species, L. lentiginosa is synonymized with L. prolixa. Loricaria carinata is resurrected from synonymy with L. cataphracta and L. simillima is treated as a junior synonym of L. carinata. Formal diagnoses, descriptions, and a key to all 24 species are provided. Phylogenetic analyses of Loricaria and related taxa (Spatuloricaria, Crossoloricaria, Planiloricaria, Brochiloricaria, Paraloricaria, and Ricola) based on a combined data set of 32 gap-coded quantitative (morphometric and meristic) characters and 24 qualitative characters derived from external morphology resulted in fully resolved, but poorly supported phylogenies under equal weights and implied weighting criteria. Implied weights analyses using a concavity constant (K) of 24-49 recovered Loricaria as a monophyletic group with L. piracicabae as basal and sister to six terminal clades containing all other species. Species originally described as Loricaria, but subsequently transferred to Brochiloricaria, Paraloricaria, and Ricola, were recovered as paraphyletic in each analysis and should be treated as congeneric with Loricaria. Distributions of Loricaria exhibit patterns of endemism similar to those documented for other groups of Neotropical fishes. Species diversity is highest in the Amazon basin (13 species, including 10 endemics), followed by the Paraguay region (5 species, including 4 endemics), Guianas region (5 species, including 2 endemics), Orinoco basin (3 species, including 2 endemics), and a single species occurring in both the São Francisco basin and drainages of Northeastern Brazil. Loricaria is apparently absent from coastal Atlantic drainages south of the São Francisco basin. Such shared patterns of endemism provide some insight into past geomorphological processes that have influenced diversification in Loricaria and serves as a foundation for further tests of biogeographic hypotheses based on phylogenetic and geological evidence