A new species of Ptychochromis from northeastern Madagascar (Teleostei: Cichlidae), with an updated phylogeny and revised diagnosis for the genus

摘要

A new species belonging to the endemic Malagasy cichlid genus Ptychochromis is described. Ptychochromis ernestmagnusi is known only from the middle to lower reaches of the Mananara River in northeastern Madagascar. Based on a unique configuration of the palatine, the new species is placed among the species of Ptychochromis considered to have an eastern-type palatine morphology by Stiassny and Sparks (2006). The new species is further distinguished from members of the "western clade" of Ptychochromisby anterior displacement of the first supraneural such that it overlies the dorsoposterior margin of the supraoccipital. Among species of Ptychochromis with eastern-type palatine morphology, P. ernestmagnusi shares with P. makira the possession of supraneurals with a characteristically flattened dorsal profile. Although P. makira and P. ernestmagnusi both possess paired lateral barring pigmentation patterns, the lateral flank bars in P. makira are distinctively V-shaped, whereas in P. ernestmagnusi theyare oriented vertically. Ptychochromis ernestmagnusi is further distinguished from P. makira by prominent iridescent spangling on the flank and dorsal fin near its base, dusky grayish-green base coloration (vs. whitish), four laterosensory foramina on the lachrymal (vs. three), and a series of seven (vs. six) infraorbital bones. In addition, an updated phylogeny and diagnosis for Ptychochromis is presented, including anatomical data for the new species and novel anatomical data for the genus.