Benthobatis yangi

Abstract: A new species of electric ray of the genus Benthobatis Alcock, 1898 is described on the basis of five specimens from the continental slope off Tungkang, southwestern Taiwan. Benthobatis yangi, n. sp., is distinguished from all other species of the genus by a unique combination of characters, including a dark brown to purplish–black dorsal and ventral coloration with irregular creamy blotches ventrally, a narrow nasoral region, a small mouth with slender jaws and shallow circumoral groove, a second dorsal fin with a more broadly rounded apex and more convex posterior margin compared to the first dorsal fin, an interdorsal distance greater than the distance between second dorsal and caudal fins, a narrow and not posteriorly arched suprascapula, size at sexual maturity, and a relatively high number of caudal vertebral centra, and consequently, total vertebral centra. Benthobatis yangi is known from adults and juveniles of both sexes. It is only the fourth valid species of Benthobatis, and only the second species from the vast IndoPacific region. Benthobatis is a continental slope, blind electric ray genus that remains poorly understood. The deep-water, blind electric ray genus Benthobatis Alcock, 1898 was recently reviewed by Carvalho (1999b), who recognized four distinct species of which two were undescribed. One of these, referred to as “Benthobatis sp. 2,” was first recorded and illustrated (as B. moresbyi) by Chen and Chung (1971) on the basis of 15 specimens from off Tungkang, southwestern Taiwan. The condition and whereabouts of these specimens is presently unknown, but at least one (THUP 02220, possibly a 316 mm total length, TL, female), illustrated in Chen and Chung (1971), may remain in the ichthyological collection of the Department of Biology, Tunghai University (Taiwan). In addition to the four specimens reported in Carvalho (1999b), a juvenile specimen of this new form was obtained by the third author in the Tungkang fish market in 1988. These five specimens, all from the continental slope of southwestern Taiwan in the South China Sea, form the basis of the present paper, in which they are described as a new species. The taxonomic history of Benthobatis in the Indo-Pacific region is somewhat sporadic. Benthobatis was established by Alcock (1898) for a new species of deep-water electric ray from the Indian Ocean, B. moresbyi, with a uniform dark coloration both dorsally and ventrally, two dorsal fins and greatly reduced eyes. Three syntypes of B. moresbyi, including two males of about 350 mm total length and a smaller individual of unstated size and sex, were originally reported by Alcock (1898) from the Travancore coast of southern India at 787 m in depth. Alcock (1899) gave a verbatim repetition of his original (1898) description, but also attributed to his specimens catalog numbers (232/1–234/1) of the Indian Museum, Calcutta (now Zoological Survey of India, ZSI), without mentioning which of his original specimens was assigned to these numbers. Alcock and McGilchrist (1899) illustrated an adult male B. moresbyi in dorsal view (probably one of the two larger syntypes), but without a catalog number, size, or indication of its type status. Lloyd (1907) recorded a small specimen of B. moresbyi from the Arabian Sea, off southern Yemen (1071 m), which he later (Lloyd, 1909) assigned to “Indian Museum” (ZSI) no.