Schizodon encompasses approximately 15 species of Neotropical headstanding fishes. Integrative taxonomy, combining molecular and morphometric analyses with traditional taxonomic methods, was used to investigate Schizodon vittatus and its potential new sister species. Molecular differences between the two species in the barcode are greater than intra-specific variation recovered in species of Schizodon, and the two species represent distinct lineages for approximately one million years. The two species are morphologically very similar, and the meristic data showed great overlap. Morphometric analyses also showed overlap among the putative species but indicated differences in caudal-peduncle depth, orbital diameter, and length of anal-fin rays. Color pattern seems to provide a clear diagnostic feature for the two species. Schizodon vittatus usually has four dark brown transversal bars on body, and its sister species has three conspicuous bars, with the fourth, if present, inconspicuous and dorsal to the lateral line. Schizodon vittatus is redescribed based on the type and recently collected specimens, its type locality is revisited, and its known distribution restricted to the Araguaia and Tocantins drainages. The new species, sister to S. vittatus, distributed in the Xingu and Tapajós drainages, is described. A key for the identification of the Amazon clade species of Schizodon is provided.
Diagnosis
Schizodon trivittatus is distinguished from S. isognathus, S. jacuiensis, S. knerii, S. nasutus, S. platae, and S. scotorhabdotus, by having conspicuous dark transversal bars on the trunk formed by the epidermal and dermal pigment (vs. vertical bars absent or inconspicuous and formed exclusively by dermal pigment); from S. australis, S. borellii, S. corti, S. dissimilis, S. fasciatus, S. intermedius, by having a dark midlateral stripe on caudal peduncle (vs. caudal peduncle and base of median caudal-fin rays pale in S. borellii, S. dissimilis, S. intermedius, or a single rounded spot in S. australis, S. corti, S. fasciatus); and from S. vittatus by lacking a dark transversal bar ventral to the adipose fin or having an inconspicuous bar restricted to the region dorsal to the lateral line (vs. possessing a conspicuous dark transversal bar ventral to the adipose fin that extends ventral to the lateral line).
Geographical distribution
Schizodon trivittatus occurs widely in the Xingu and Tapajós drainages, including their tributaries, in Mato Grosso and Pará states, Brazil (Fig. 7).
Etymology
The name trivittatus is an adjective in allusion to the presence of three dark vertical bars on the trunk exhibited by the new species, its main diagnostic feature.