Abstract A new species of Farlowella is described from the upper Paraguai River basin, Mato Grosso State, Brazil. The species was investigated by morphological and molecular datasets. The new species can be distinguished from its congeners by the following character combination: (1) absence of gular plates, (2) absence of breeding odontodes, (3) absence of the mid-dorsal plate series, (4) complete series of central abdominal plates, (5) five total rays in the pelvic fin, (6) modally i,10,i rays in the caudal fin, (7) lateral contour of the snout distinctly concave in dorsal view and (8) dorsal caudal-fin lobe fully covered with melanophores and ventral lobe pigmented only ventrally in adults. The new species has the smallest body size recorded for any species of Farlowella, not exceeding 96 mm in standard length (SL). Genetic divergence between the new species and other Farlowella ranged from 3.1–12.5% and three delimitation analyses recovered it as an independent lineage. A review of the cytochrome c oxidase subunit I (COI) sequences for Farlowella deposited in public repositories, an additional record of sexual dimorphism in the cloaca and a discussion about other species from the Paraguai River basin are provided.
Dopazo et al. (Wed,) studied this question.