The Siamese frog, Sylvirana cubitalis, is a “true frog” (family Ranidae) reported from the Karan Hills in Myanmar, Thailand, northern Laos, northeastern Vietnam, and across the northern borders of these countries into isolated parts of southern China.Its multiple country distribution has complicated its taxonomy; recent study recognizes S. cubitalis (described from Laos/Thailand) as synonymous with Rana nigrotympanica (from China) and distinct from Sanguirana varians, a species with which it has been confused (Ohler 2007). Some suggest more investigation is needed to resolve these relationships.Phylogenetic analysis now places this frog in genus Sylvirana, although it was previously classified in the genera Rana and Hylarana. The Siamese frog is known by several common names: the Siam frog, yellow stream frog, the darkeared frog, and the black-eared frog.
Siamese frogs are slender frogs, with a narrow, pointed head, about 75 mm in snout-vent length.They have long limbs and mostly-webbed toes each tipped with a toe disc.Their dorsal surface is red-brown/tan/olive green in coloring with olive-gold flecks.While the skin on the head is smooth, the rest of the dorsal surface has fine granules and their white belly is smooth.Dark lines run from their nose to their eyes, across their tympanum, and continue laterally to their hind legs. Other scattered dark markings occur on their limbs and sides, and their hind limbs have dark brown crossbars.The underside of their foot and hind limb is dark purple.Males have a noticable round gland on the inside of their elbows.
Although wide in its distribution, this species is rarely encountered and poorly known.Siamese frogs inhabit the forest floor of closed-canopy evergreen monsoon and rainforests located at elevations between 500-760 m asl. These frogs occur near fast-flowing streams, which are presumably where they breed.While the IUCN lists these frogs as “of least concern,” it acknowledges that their population is declining, probably threatened by development and logging, and also by environmental destruction by fires.
(Frost 2016; Ohler 2007; Oliver et al. 2015; Stuart et al. 2006; Taylor 1962; van Dijk 2008)
