Unexpectedly high diversity in a small basin: A taxonomic revision of Eurycheilichthys (Siluriformes: Loricariidae), with descriptions of seven new species

ABSTRACT

A taxonomic revision of Eurycheilichthys is provided, and seven new species are described in addition to the two previously known species in this genus: E. pantherinus from the upper rio Uruguay, and E. limulus from the upper rio Jacuí. The genus is diagnosed based on the uniquely derived presence of seven branched pectoral-fin rays, and on the possession of reduced filamentous gill rakers in the oral surface of the hyobranchial skeleton, and presence of a distinct fleshy flap along the posterodorsal margin of the pectoral-fin spine in adult males. The seven new species are described from tributaries to the rio Taquari basin, itself a tributary to the rio Jacuí in Rio Grande do Sul State, southern Brazil. The new species are diagnosed based on color variation, abdominal plate morphology, lip size, parieto-supraoccipital shape, the number of dermal plates, the number of teeth, and body proportions. The high diversity and degree of species endemism in a limited area are discussed and compared to other fish groups. Genetic sequences (GenSeq) of mitochondrial and nuclear DNA, distribution maps, an identification key, and illustrations are presented for all species.

Keywords:
Biodiversity; Catfish; Endemism; Identification key; Systematics