Notoraja hesperindica sp. Nov., a new colorful deep-sea softnose skate (Elasmobranchii, Rajiformes, Arhynchobatidae) and first generic record from the western Indian Ocean

摘要

A new deep-sea softnose skate, Notoraja hesperindica, is described based on six specimens caught in 1230-1600 m depths off southern Mozambique and northwestern Madagascar in the western Indian Ocean. The new species is a medium-sized species of Notoraja Ishiyama, 1958 reaching a total length of at least 539 mm. It is the only Notoraja species known from the western Indian Ocean and differs from most congeners in the intense dark blue-grayish coloration. The only congeners with similarly vibrant coloration are Notoraja azurea McEachran & Last, 2008 from off southern Australia and Notoraja sapphira Seret & Last, 2009 from the Norfolk Ridge (Coral Sea and Tasman Sea), which differ from the new species in a shorter and more obtusely angled snout, a shorter head, a shorter disc, and smaller dorsolateral tail thorns, as well as more predorsal tail and total predorsal vertebrae and more pectoral-fin radials. The large dorsolateral tail thorns also distinguish the new species from most congeners except for the eastern Pacific Notoraja martinezi Concha, Ebert & Long, 2016, which has even larger, randomly patterned dorsolateral tail thorns that give the tail a barbedwire-like appearance. This congener further differs from N. hesperindica sp. nov. in the absence (vs. presence) of malar thornlets, fewer median tail thorns, a shorter snout, more tooth rows in upper and lower jaws, and more pectoral radials. A key to the species of Notoraja in the Indian Ocean is provided.