Sunday, July 12, 2020

[Ichthyology • 2020] Hypomasticus santanai • A New Species of Hypomasticus (Characiformes, Anostomidae) from Eastern Brazil Based on Morphological and Molecular Data

Hypomasticus santanai Birindelli & Melo

in Birindelli, Melo, Ribeiro-Silva, et al, 2020. 

A new species of Hypomasticus is described from the Rio de Contas, a coastal drainage of eastern Brazil, and its phylogenetic position is proposed based on molecular data. The new species is diagnosed among Anostomidae by possessing a downturned mouth with compressed teeth arranged side by side, 37 or 38 lateral-line scales, three scale series between the dorsal-fin origin and the lateral line and between the lateral line and the pelvic-fin origin, and 12 scale rows around the caudal peduncle. Mitochondrial DNA sequences provide evidence that the new species is closely related to H. mormyrops, H. thayeri, H. copelandii, and H. steindachneri, a clade of species endemic to coastal drainages of eastern Brazil. These results combined with a previous phylogeny support the reallocation of the latter two species from Leporinus to Hypomasticus. The new species is herein considered to be Endangered under the IUCN criteria, due to a small Extent of Occurrence, severely fragmented population, and continued decline of area, extent, and quality of habitat.

Hypomasticus santanai, holotype, MZUEL 18604, 208.2 mm SL,
Brazil, Bahia, Rio Gongogi, tributary of Rio de Contas.

Hypomasticus santanai Birindelli and Melo, new species

Distribution.— Hypomasticus santanai is only known from the Rio Gongogi and so far endemic to the Rio de Contas basin, a coastal drainage in the eastern portion of the state of Bahia, Brazil (Fig. 3).

Etymology.— The new species is named in honor to Edson Santana, a technician at the MZUEL since 1993, for his help in collecting fishes, preparing vertebrate specimens, and maintaining the collections of the MZUEL. His enthusiasm captivated generations of staff and students of the MZUEL. In addition, Edson Santana was in the expedition that resulted in the discovery of H. santanai.

Fig. 4. Sample sites of Hypomasticus santanai.
(A) Rio Gongogi, tributary of Rio de Contas, approximately 2 km above city of Dario Meira, ...; (B) Rio Gongogi, tributary of Rio de Contas, at Zebrinha, ... All in Brazil, Bahia state.

Fig. 5. Maximum likelihood tree of Anostomidae showing the phylogenetic placement of Hypomasticus santanai. Bootstrap support is indicated by black (75-100%) and gray dots (50-75%); nodes with support lower than 50% have no dots. See Data Accessibility for tree file.

José L. O. Birindelli, Bruno F. Melo, Luís R. Ribeiro-Silva, Debora Diniz and Claudio Oliveira. 2020. A New Species of Hypomasticus from Eastern Brazil Based on Morphological and Molecular Data (Characiformes, Anostomidae). Copeia. 108(2); 416-425. DOI: 10.1643/CI-19-335