Abstract
The first report of a western South Atlantic soft skate, genus Malacoraja Stehmann, 1970, is described as Malacoraja obscura, new species, from the southeastern Brazilian continental slope off the states of Espírito Santo and Rio de Janeiro, in depths ranging from 808-1105 m. The new species is known from five specimens and is distinguished from congeners by its unique dorsal coloration with small, faded white spots on disc and pelvic fins, by retaining in larger specimens an irregular row of thorns along dorsal midline of tail (extending from tail base to two-thirds of tail length in 680 mm total length female), and by presenting a ventral tail midline devoid of small denticles only at base (naked region not extending posterior to pelvic fin rear margin). Further diagnostic characters in combination include the lack of scapular thorns in larger specimens, elevated number of tooth rows (64/62 tooth rows in subadult male of 505 mm TL, and 76/74 in large female of 680 mm TL) and vertebrae (27-28 Vtr, 68-75 Vprd), ventral disc and tail with a uniform dark brown coloration, paired postventral fenestrae on scapulocoracoid, enlarged posterior postventral fenestra, circular foramen magnum and paired internal carotid foramina on braincase floor. Adult males were unavailable for study, but an anatomical description of M. obscura, n. sp., is provided. Comparisons are made with all known material of M. kreffti, literature accounts of M. senta, and with abundant material of South African M. spinacidermis; M. obscura, n. sp., most closely resembles M. spinacidermis from the eastern South Atlantic in squamation, coloration and size. Malacoraja is monophyletic due to its unique squamation and rostral appendices, and apparently comprises two species-groups, one for M. obscura and M. spinacidermis, and the other for M. kreffti and M. senta, but clarification of species-level relationships must await more anatomical information, particularly of the latter two species.
Highlights
F of its unusual squamation composed of small, closely-set dermal denticles which are evenly scattered on dorsal disc and dorsal and ventral tail regions, in conjunction with a general lack of thorns posterior to the scapular area
R distribution of all Malacoraja species, being more abundant at depths between 110 and 457 m (McEachran & Musick, 1975), whereas its congeners are more plentiful below 900 m; M. senta
Cape Town that it became apparent that the Brazilian material, even though very similar in overall morphology to M. spinacidermis, represents a new species of Malacoraja, which we describe below
Summary
It was only after comparisons with other Malacoraja species in the collections of Hamburg and Skates of the genus Malacoraja Stehmann, 1970 occur mostly in deep waters of the continental slope and are restricted to the Atlantic Ocean. O colloquially known as “soft skates” (Compagno, 1999), remains taxonomically undiverse including only M. senta (Garman, 1885), M. spinacidermis Cape Town that it became apparent that the Brazilian material, even though very similar in overall morphology to M. spinacidermis, represents a new species of Malacoraja, which we describe below. Species-limits are subtle in Malacoraja, a difficulty compounded by the lack of adult males of the Brazilian form (and of western North Atlantic M. spinacidermis, referred to hereafter as “M. mollis”). Our new species is distinguished on the basis of characters other than those from the clasper
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