Francis Hamilton and the freshwater stingrays described in his Gangetic fishes (1822)

Abstract

Direct evidence bearing on identification of the two new species of Gangetic stingrays named Raia fluviatilis and R. sancur by Hamilton, 1822 comprises 1) the first written account by Hamilton (then Buchanan) of his encounters with Gangetic stingrays in 1807–1813, written at the time in manuscript, but not published until 1877; 2) Hamilton's accounts of Raia fluviatilis and Raia sancur published in 1822; 3) Hamilton drawing IV 7 in the archives of the Asiatic Society of Bengal (never published, original now lost); and 4) Hamilton drawing IV 65 in the same archives (published by Hora, 1929, original now lost; this drawing is not a copy or a version of drawing IV 7). The description of R. sancur clearly is based on a species of the genus Pastinachus. Drawing IV 7 presumably is the unfinished drawing of R. sancur mentioned by Hamilton, 1822, and is therefore also of a Pastinachus. Drawing IV 65, not mentioned by Hamilton, a complete drawing with dorsal and ventral views of a newborn male Pastinachus with an intact sting, is identified as based on Raia fluviatilis. Pending revision of the genus Pastinachus, the Gangetic species is tentatively identified as P. sephen (Forsskål, 1775). Identification of Raia fluviatilis with a large freshwater species of Gangetic Himantura advocated by Annandale, 1910; Chaudhuri, 1912; Compagno and Cook, 1996; and Zorzi, 1996 is based on unwarranted assumptions. There is no definite evidence that Hamilton ever saw a Gangetic Himantura. Himantura chaophraya Monkolprasit and Roberts, 1990 is the only available name applicable to huge large tropical Asian freshwater stingrays of the dasyatid genus Himantura. No specimens of Gangetic Himantura exist in present museum collections.