Sharpsnout stingray
The sharpsnout stingray or wingfin stingray is a species of stingray in the family Dasyatidae, found from off Venezuela to northern Brazil. It inhabits shallow, brackish water, shifting towards the coast in the dry season and away from it in the rainy season. Typically measuring across, this dark brown ray is easily identifiable by its long, projecting snout and elongated, acutely pointed pelvic fins. Its diet consists of bottom-dwelling invertebrates. Reproduction is aplacental viviparous, with females bearing one to three pups annually. Naturally uncommon and slow-reproducing, the sharpnose stingray is under pressure by both artisanal and commercial fisheries, leading the International Union for Conservation of Nature to assess it as critically endangered.
Taxonomy and phylogeny
Dutch ichthyologist Marinus Boeseman described the sharpsnout stingray in a 1948 issue of the scientific journal Zoologische Mededelingen, based on a juvenile male caught off Suriname with a disc length of. The whereabouts of this type specimen is unknown. In a 2001 phylogenetic analysis based on morphological characters, Lisa Rosenberger found that the longnose stingray is the sister species of the sharpsnout stingray, and that the two form a clade with the pale-edged stingray, the pearl stingray, the sharpnose stingray, and the smooth butterfly ray. These results support the growing consensus that neither Dasyatis nor Himantura are monophyletic.Distribution and habitat
One of the less common stingrays within its range, the sharpsnout stingray is found in nearshore, brackish waters along the northeastern coast of South America, from Venezuela and Trinidad and Tobago to northern Brazil; many occur in the estuarine area affected by the freshwater discharge of the Amazon River. It favors muddy habitats deep, with low visibility. However, Uyeno et al. gave a depth of for this species. The sharpsnout stingray conducts annual movements that are affected by salinity, entering coastal bays such as Marajó Bay during the rainy season and shifting to offshore waters during the rainy season.Description
The pectoral fin disc of the sharpsnout stingray is about as wide as long, with strongly concave leading margins and rounded corners. The snout is long and projecting, measuring 39-54% as long as the disc is wide. The eyes are minute and followed by much larger spiracles. There is a flap of skin between the nares, with a finely fringed posterior margin. The line of the mouth is slightly indented at the center. The upper and lower jaws both contain 56-68 tooth rows; the teeth are blunt and arranged with a quincunx pattern. A transverse row of 5 papillae are present on the floor of the mouth.The pelvic fins are distinctive, being over twice as long as wide with a gently sinuous trailing margin, and tapering to an acute tip that sometimes extends past the disc. The whip-like tail measures over twice the length of the disc and bears 1-2 serrated spines on top. Posterior to the spines are a subtle dorsal keel and a ventral fin fold about half as long as the disc. A band of small tubercles runs along the dorsal midline from behind the eyes to the base of the tail, with larger tubercles in a central row and on each "shoulder". More conical tubercles are scattered over the upper surface of the tail past the spines. The coloration is a uniform brown above, and white below darkening towards the disc margin. This species typically attains a disc width of, but individuals up to across have been recorded.