Trimerodytes praemaxillaris is a species of snake in the subfamily Natricinae of the family Colubridae. It is also known commonly as Angel's mountain keelback, Angel's stream snake, and the brown stream snake. The species is endemic to Southeast Asia.
Geographic range T. praemaxillaris is found in China (Yunnan province), northern Laos, and Thailand.
Habitat The preferred natural habitats of T. praemaxillaris are forest and freshwater wetlands, at altitudes of .
Description Dorsally, T. praemaxillaris is brown. Ventrally, it is dirty yellowish. The dorsal scales are smooth and are in 19 rows at midbody.Smith MA (1943). The Fauna of British India, Ceylon and Burma, Including the Whole of the Indo-Chinese Sub-region. Reptilia and Amphibia. Vol. III.—Serpentes. London: Secretary of State for India. (Taylor and Francis, printers). xii + 583 pp. ("Opisthotropis premaxillaris [sic]", p. 332).
Diet T. praemaxillaris preys upon aquatic annelids.
Reproduction T. praemaxillaris is oviparous. The cotypes are hatchlings, each with an egg-tooth and a fresh umbilical scar.Pope CH (1935). The Reptiles of China: Turtles, Crocodilians, Snakes, Lizards. (Volume X of the Natural History of Central Asia series, edited by Chester A. Reeds). New York: American Museum of Natural History. lii + 604 pp. + Plates I-XXVII. (Opisthotropis praemaxillaris, p. 164). Each of these little snakes has a total length of , which includes a tail long.
References
Further reading Angel F (1929). "Liste de reptiles et batraciens du Haut-Laos recueillis par M. Delcour. Descriptions d'un genre, de 2 espèces et d'une variété d'ophidiens ". Bulletin du Muséum national d'histoire naturelle de Paris, série 2, 1: 75-81. (Paratapinophis, new genus; P. praemaxillaris, new species). (in French). Das I (2012). A Naturalist's Guide to the Snakes of South-East Asia: Malaysia, Singapore, Thailand, Myanmar, Borneo, Sumatra, Java and Bali. Oxford, England: John Beaufoy Publishing. 176 pp. . Murphy JC, Chan-ard T, Mekchai S, Cota M, Voris HK (2008). "The Rediscovery of Angel's Stream Snake, Paratapinophis praemaxillaris Angel, 1929 (Reptilia: Serpentes: Natricidae)". The Natural History Journal of Chulalongkorn University 8 (2): 169-183. Rasmussen JB (1982). "A new record of the rare Opisthotropis praemaxillaris (Serpentes: Colubridae)". Amphibia-Reptilia 3 (2): 279-280.