Gymnocranius obesus, a new large-eye seabream from the Coral Triangle

Abstract

Two previously recorded new species of the large-eye seabream genus Gymnocranius (Gymnocranius sp. D and Gymnocranius sp. E) remain undescribed. Here we describe Gymnocranius sp. E as Gymnocranius obesus sp. nov. This new species is morphologically distinct from all other known species under Gymnocranius by the following combination of characters: relatively deep body, with ratio of standard length to body depth 2.2–2.4; protruding large eye, with eye diameter about equal to or slightly larger than inter-orbital width; caudal fin moderately forked; no blue spots or wavy blue lines on cheek and snout in adults; fourth transversal dark bar on flank running from the sixth spine of the dorsal fin to the origin of the anal fin; anal, caudal and dorsal fins drab with yellowish to yellow margins. Gymnocranius obesus sp. nov. is distinct from G. griseus, with which it has been previously confused by a relatively larger head, scales above lateral line without dark basal patch, and a smaller number of front scales on the dorsal side of the head. Gymnocranius obesus sp. nov. is genetically distinct from its closest known relative, Gymnocranius sp. D by 104 diagnostic nucleotide characters, which translates into a 9.6% sequence divergence at the mitochondrial cytochrome b gene. Gymnocranius obesus sp. nov. reaches a length of at least 295mm. Its distribution, from the Ryukyu Islands to Bali, including Taiwan and the Flores Sea, mostly coincides with the western half of the Coral Triangle.