The short-tail stingray or smooth stingray (Bathytoshia brevicaudata) is a common species of stingray in the family Dasyatidae. It occurs off southern Africa, typically offshore at a depth of , and off southern Australia and New Zealand, from the intertidal zone to a depth of . It is mostly bottom-dwelling in nature and can be found across a range of habitats from estuaries to reefs, but also frequently will swim into open water. One of the largest stingrays in the world, this heavy-bodied species can grow upwards of across and in weight. Its plain-colored, diamond-shaped pectoral fin disc is characterized by a lack of dermal denticles even in adults, and white pores beside the head on either side. The body can have colors as well as dark grey or black with rows of white spots along each wing. Its tail is usually shorter than the disc and thick at the base. It is armed with large tubercles and a midline row of large thorns in front of the stinging spine which has the dorsal and ventral fin folds behind.
The diet of the short-tail stingray consists of invertebrates and bony fishes, including burrowing and midwater species. It tends to remain within a relatively limited area throughout the year, preferring deeper waters during the winter, and is not known to perform long migrations. Large aggregations of rays form seasonally at certain locations, such as in the summer at the Poor Knight Islands off New Zealand. Both birthing and mating have been documented within the aggregations at Poor Knights. This species is aplacental viviparous, with the developing embryos sustained by histotroph ("uterine milk") produced by the mother. The litter size is typically but litter sizes of up to fifteen are not unheard of.
The short-tail stingray is not aggressive, but is capable of inflicting a lethal wound with its long, venomous sting. It is often caught incidentally by commercial and recreational fisheries throughout its range, usually surviving to be released. Because its population does not appear threatened by human activity, the International Union for Conservation of Nature (IUCN) lists it under least concern.
Taxonomy
The original description of the short-tail stingray was made by Frederick Hutton, curator of the Otago Museum, from a female specimen across caught off Dunedin in New Zealand. He published his account in an 1875 issue of the scientific journal Annals and Magazine of Natural History, in which he named the new species Trygon brevicaudata, derived from the Latin brevis ("short") and cauda ("tail"). Although long assigned to Dasyatis, recent work by Last et al. (2016) resurrected Bathytoshia for it and the broad stingray, as well as the roughtail stingray. The short-tail stingray may also be referred to as giant black ray, giant stingray, New Zealand short-tail stingaree, Schreiners ray, short-tailed stingaree, shorttail black stingray, and smooth short-tailed stingray. It is closely related to the similar-looking but smaller pitted stingray (Dasyatis matsubarai) of the northwestern Pacific. A review based on Molecular phylogenetic data in 2016 added Dasyatis matsubarai and Dasyatis multispinosa as populations of this species.
Description
Heavily built and characteristically smooth, the pectoral fin disc of the short-tail stingray had a rather angular, rhomboid shape and is slightly wider than long. The leading margins of the disc are very gently convex, and converge on a blunt, broadly triangular snout. The eyes are small and immediately followed by much larger spiracles. The widely spaced nostrils are long and narrow; between them was a short, skirt-shaped curtain of skin with a fringed posterior margin. The modestly sized mouth has an evenly arched lower jaw, prominent grooves at the corners, and five to seven papillae (nipple-like structures) on the floor. Additional, tiny papillae are scattered on the nasal curtain and outside the lower jaw. Short Tailed Stingrays have between 45-55 densely arranged teeth, which are small, blunt, and conical. The teeth are arranged in a gridded, quincunx pattern, and have a flat, planar appearance. The pelvic fins are somewhat large and rounded at the tips.