Dasyatis dipterura

The diamond stingray (Dasyatis dipterura) is a species of stingray in the family Dasyatidae. It is found in the coastal waters of the eastern Pacific Ocean from southern California to northern Chile, and around the Galápagos and Hawaiian Islands. This bottom-dweller generally inhabits sandy or muddy flats near rocky reefs and kelp forests, to a depth of 30 m (98 ft), though off Hawaii it may range considerably deeper. As its common name suggests, this species has an angular, diamond-shaped pectoral fin disc that is plain brown or gray above, with rows of tubercles along the midline and on the 'shoulders'. The long, whip-like tail has both dorsal and ventral fin folds, which distinguish this ray from the closely similar longtail stingray (D. longa). It typically grows to 1 m (3.3 ft) across. When searching for food, diamond stingrays may form groups of up to hundreds of individuals. It is most active at night and preys mainly on burrowing invertebrates and small bony fishes, which are extracted from the bottom via suction or digging. This species is aplacental viviparous: once the embryos exhaust their yolk supply, they are nourished by histotroph ('uterine milk') produced by the mother. Females bear 1–4 pups every summer in estuaries; mating is followed by a ten-month period of either sperm storage or arrested embryonic development, after which the embryos rapidly mature over 2–3 months. The slowest-growing stingray known, this species is not resilient against fishing pressure. It is caught for food by artisanal fishers in Latin America, particularly in Mexico where it is one of the most economically important rays. This has led it to be assessed as Near Threatened in Mexico by the International Union for Conservation of Nature (IUCN), while the species as a whole is listed as Data Deficient. Though innocuous towards humans, the diamond stingray's long, venomous tail spine is potentially dangerous. In 1880, the diamond stingray was described twice by three American ichthyologists: as Dasybatus dipterurus by David Starr Jordan and Charles Henry Gilbert in Proceedings of the United States National Museum, and as Trygon brevis by Samuel Garman in Bulletin of the Museum of Comparative Zoology. Jordan and Gilbert's account was published in May while Garman's was published in October, making dipterurus (feminine dipterura) the correct name as it was published first. However, when Garman synonymized the two in 1913 he inappropriately gave precedence to brevis, leading to long-standing confusion. Both Dasybatus and Trygon were later synonymized with the genus Dasyatis, but many authors still listed D. brevis in place of or in addition to D. dipterura. Garman also synonymized the Hawaiian stingray (D. hawaiensis) with D. dipterura in 1913, which has since been followed by most authors but requires more study for confirmation. The species syntypes were collected from San Diego Bay, California. The specific epithet dipterura is derived from the Latin di ('two'), ptero ('wing'), and ura ('tail'), referring to the fin folds on both sides of its tail. Rat-tailed stingray is a former common name for this species. Lisa Rosenberger's 2001 phylogenetic analysis, based on morphology, determined the diamond stingray and the bluntnose stingray (D. say) of the western Atlantic Ocean to be sister species, that likely diverged before or with the formation of the Isthmus of Panama (c. 3 Ma). In addition, the two were found to be the second-most basal taxa in their genus, after the common stingray (D. pastinaca). The diamond stingray is found in the eastern Pacific Ocean from southern California to northern Chile, as well as around the Galápagos and Hawaiian Islands; it is very abundant around Baja California and in the Gulf of California. At the northern and southern extremes of its range, it is generally only present during periods of suitably warm water brought about by El Niño. There is a record of this ray from off British Columbia, which is unconfirmed and would be highly anomalous as it is known to be a tropical and warm-temperate species. A bottom-dwelling inhabitant of inshore waters, the diamond stingray favors sandy or muddy bottoms, often near rocky reefs or kelp forests. Off southern California, it usually occurs from the intertidal zone to a depth of 7 m (23 ft) during the summer, shifting to depths of 13–18 m (43–59 ft) during late fall and winter. For unknown reasons, it prefers to overwinter in kelp forests rather than sandy flats. Off Chile, the diamond stingray occurs at a similar depth of 3–30 m (10–100 ft). On the other hand, this species has been reported from as far down as 355 m (1,165 ft) off Hawaii, which if accurate would suggest that it utilizes a much greater range of depths than previously realized. The diamond stingray attains a disc width of 1 m (3.3 ft) or possibly 1.2 m (3.9 ft); females grow larger than males. Its pectoral fin disc is rhomboid in shape, slightly wider than long, with angular outer corners and subtly convex margins. The snout is blunt-angled and non-projecting. The eyes are fairly large and immediately followed by the spiracles (paired respiratory openings). The mouth is strongly curved, containing 21–37 upper tooth rows and 23–44 lower tooth rows; the teeth are small and blunt, and arranged into flattened surfaces. Three or five papillae (nipple-like structures) are found in a row across the floor of the mouth. The whip-like tail generally measures up to one and half times the length of the disc, and bears one (more if replacements have grown in) long, slender, serrated spine on the upper surface, closer to the base than the tip. Behind the spine, there are long dorsal and ventral fin folds that rise gradually, reaching a relatively high apex before sloping down abruptly. The presence of the upper fin fold separates this species from the similar longtail stingray (D. longa), which shares most of its range. However, the tail is often damaged, in which case differentiating the two species in the field becomes all but impossible. Young rays have completely smooth skin, while adults develop a row of low tubercles along the midline of the back, flanked by two shorter rows on the 'shoulders'. The tail also becomes covered in prickles. This species is a uniform olive to brown to gray above, darkening to black on the tail, and off-white below.