Exostoma Blyth, 1860 ZBK
Diagnosis: Continuous post-labial groove; gill openings not extending onto venter; homodont dentition; oar-shaped, distally flattened teeth in both jaws; tooth patches separated in upper jaw; 10-11 branched pectoral rays.
Exostoma ZBK is distinguished from Glyptosternon ZBK , Glaridoglanis ZBK , Pareuchiloglanis ZBK , Euchiloglanis ZBK and Parachiloglanis ZBK by having a continuous post-labial groove (Table 5). Exostoma ZBK is distinguished from Pseudexostoma ZBK and Oreoglanis ZBK by having homodont (vs. heterodont) dentition in the lower jaw. It is further distinguished from Oreoglanis ZBK by having oar-shaped, distally flattened (vs. pointed) teeth in the upper jaw, and from Pseudexostoma ZBK by having homodont (vs. heterodont) teeth in the upper jaw. Exostoma ZBK is distinguished from Myersglanis ZBK by having tooth patches separated in the upper jaw and oar-shaped, distally flattened teeth in both jaws (vs. tooth patches juxtaposed and pointed teeth in both jaws). Exostoma ZBK is further distinguished from Pseudexostoma ZBK and Oreoglanis ZBK by having 10-11 branched pectoral rays (vs. 16-18).
Description: 6-7 dorsal rays; 10-11 branched pectoral-fin rays; 6 pelvic-fin rays; 5-8 anal-fin rays. Head depressed; snout broadly rounded; body elongate, flattened ventrally to pelvic fins. Eyes minute, dorsal, subcutaneous. Lips thick, fleshy, papillated. Teeth small to large, moveable, oar-shaped, flattened distally and directed posteriorly in distinct patches. Maxillary barbel with well-developed membrane, soft base, and striated pad of adhesive skin. Gill openings narrow, not extending below pectoral-fin base. Branchiostegal membranes confluent with isthmus. Coracoid process not externally visible. No thoracic adhesive apparatus. Paired fins plaited to form an adhesive apparatus.
Distribution: Brahmaputra drainage, northeast India, east and south to the Salween drainages, Myanmar (Kottelat, 1989; Chu et al., 1999; Jayaram, 1999).
- Alfred W. Thomson, Lawrence M. Page (2006): Genera of the Asian Catfish Families Sisoridae and Erethistidae (Teleostei: Siluriformes). Zootaxa 1345, 1-96: 65-66, URL:http://www.zoobank.org/urn:lsid:zoobank.org:pub:25EFA792-7DA4-4E0D-A69A-12591B8422DE
Molecular Biology and Genetics
Statistics of barcoding coverage
Specimens with Sequences:12
Specimens with Barcodes:12
Species With Barcodes:2
In a 2007 checklist of sisorid and erethistid catfishes, Thomson lists E. stuarti and E. vinciguerrae as valid species. In a 2007 checklist of catfishes, Ferraris lists these two species as species inquerendae, noting that these species are either treated as valid or as synonyms of E. labiatum.
There are currently 7 recognized species in this genus:
- Exostoma barakensis Vishwanath & Joyshree, 2007
- Exostoma berdmorei Blyth, 1860
- Exostoma effrenum H. H. Ng & Vidthayanon, 2014 
- Exostoma labiatum McClelland, 1842 (Burmese bat catfish)
- Exostoma peregrinator H. H. Ng & Vidthayanon, 2014 
- Exostoma stuarti Hora, 1923
- Exostoma vinciguerrae Regan, 1905
Distribution and habitat
Exostoma species are distributed in the Brahmaputra drainage of northeast India, and east and south to the Salween drainages in Burma. E. berdmorei is found in the Sittang and Salween drainages in Burma. E. labiatum is known from the Brahmaputra drainage in northeast India, but has also been recorded in the Salween drainage in Burma, the Ayeyarwady drainage in China, and the Brahmaputra drainage in Tibet and Burma. E. stuarti is from the Ayeyarwady River of Burma and India; however, it has not been collected since its original discovery.
E. labiatum is found in mountain rapids.
Exostoma is distinguished by having a continuous groove behind the lips (post-labial groove), the gill openings not extending onto the underside (venter), homodont dentition of oar-shaped, distally flattened teeth in both jaws, the tooth patches separated in upper jaw, and 10–11 branched pectoral rays. The head is depressed with a broadly rounded snout. The body is elongate and flattened ventrally to the pelvic fins. The eyes are minute, dorsally located, and under the skin (subcutaenous). The lips are thick, fleshy, and papillated. The teeth are small to large, moveable, oar-shaped, flattened distally and directed posteriorly in distinct patches.
- Thomson, Alfred W.; Page, Lawrence M. (2006). "Genera of the Asian Catfish Families Sisoridae and Erethistidae (Teleostei: Siluriformes)" (PDF). Zootaxa 1345: 1–96.
- Ferraris, Carl J., Jr. (2007). "Checklist of catfishes, recent and fossil (Osteichthyes: Siluriformes), and catalogue of siluriform primary types" (PDF). Zootaxa 1418: 1–628.
- Ng, H. H. & Vidthayanon, C. (2014): A review of the glyptosternine catfish genus Exostoma Blyth 1860 from Thailand, with descriptions of two new species (Teleostei: Siluriformes). Zootaxa, 3869 (4): 420–434.
- Froese, Rainer and Pauly, Daniel, eds. (2007). "Exostoma labiatum" in FishBase. July 2007 version.
- Froese, Rainer and Pauly, Daniel, eds. (2007). "Exostoma stuarti" in FishBase. July 2007 version.
- Froese, Rainer and Pauly, Daniel, eds. (2007). "Exostoma berdmorei" in FishBase. July 2007 version.
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