Pseudexostoma is a genus of fish in the familySisoridaeendemic to China. These species are restricted to the upper Salween (Nujiang River) and one upper branch of the Irrawaddy (Dayinjiang River) in China.[1]P. brachysoma is known only from the middle and lower Nujiang River. P. yunnanensis is only known from the upper Dayinjiang.[2] These rivers were once connected, but are now separated. Also, the environment and temperature of the Nujiang River became greatly different between the northern and southern areas, leading to speciation.[2]
Glyptosternum yunnanesis was first described in 1935. However, due to its unique teeth, a separate genus Pseudexostoma was erected in 1979 for this species. The same year, a subspecies of P. yunnanensis was described, P. y. brachysoma. However, it has become apparent that these two groups represent different species. Also, a third species, P. longipterus, was described in 2007.[2] Results obtained by Yang et al., 2016 showed that P. longipterus cannot be distinguished from P. brachysoma from either morphological or molecular analyses and that the former name should thus be considered a junior synonym of the latter.[1]
Speciesedit
There are currently two recognized species in this genus:
Pseudexostoma brachysoma X. L. Chu, 1979
Pseudexostoma yunnanensis (T. L. Tchang, 1935)
Descriptionedit
These species have a continuous groove behind the lip, gill openings not extending onto the underside, heterodont dentition in both jaws with outer teeth shovel-shaped and sparsely arranged in one or two rows and inner teeth conical and numerous, the tooth patches separated in upper jaw, and 16–18 branched pectoral rays.[3] The lips are thick, fleshy and papillated. The paired fin are plaited to form an adhesive apparatus.[3] Species of this genus have a moderately compressed body. The head is depressed and broad; it appears triangular from the side and with a rounded snout from above. The eyes are small and ovoid, located at the middle of the dorsal surface of the head. The mouth is transverse and inferior, with the teeth exposed when the mouth is closed. The teeth are embedded in the skin, shovel-shaped, with the tips exposed and arranged in irregular rows. The gill openings are narrow. The dorsal surface is smooth without tubercles. There are four pairs of barbels. The adipose fin base is not connected to the caudal fin. The caudal fin is emarginate with the upper lobe smaller than the lower lobe. The lateral line is midlateral and complete.[2]
Species of this genus are grey black on the dorsal surface and grey yellow on the ventral region; the caudal fin is grey black with an irregular, small, yellow patch in the middle and the other fins are grey yellow along the distal edge.[2]Pseudexostoma grow to about 9.9–15.3 centimetres (3.9–6.0 inches) SL.[4][5] These species have three notches on the posterior margin of the lower lip. However, in P. yunnanensis, the notches are all the same depth, while in the other two species the middle notch is shallower in depth than the lateral notches. The two median lobes formed by these notches are the same length of the lateral lobes of the lips in P. yunnanensis, but they are longer in the other two species. P. yunnanensis also has more pelvic fin rays (5 vs. 3–4), a shorter adipose fin base, a deeper and longer caudal peduncle, more teeth in the premaxillary tooth band (18–22 vs. 16–18) that are divided into two partially connected patches instead of two isolated patches.[2]
Referencesedit
^ abYang, K., Jiang, W., Chen, X., Zhou, W. & Yang, J. (2016): An integrative approach to reappraising species validity in Pseudexostoma (Teleostei: Sisoridae). Zootaxa, 4158 (3): 352–366.
^ abcdefZhou, W., Yang, Y., Li, X. & Li, M.-H. (2007): A review of the catfish genus Pseudexostoma (Siluriformes: Sisoridae) with description of a new species from the upper Salween (Nujiang) basin of China. Raffles Bulletin of Zoology, 55 (1): 147-155.
^ abThomson, A.W. & Page, L.M. (2006): Genera of the Asian Catfish Families Sisoridae and Erethistidae (Teleostei: Siluriformes). Zootaxa, 1345: 1–96.
^Froese, Rainer; Pauly, Daniel (eds.) (2016). "Pseudexostoma brachysoma" in FishBase. June 2016 version.
^Froese, Rainer; Pauly, Daniel (eds.) (2016). "Pseudexostoma yunnanensis" in FishBase. June 2016 version.
March 03, 2024
pseudexostoma, genus, fish, family, sisoridae, endemic, china, these, species, restricted, upper, salween, nujiang, river, upper, branch, irrawaddy, dayinjiang, river, china, brachysoma, known, only, from, middle, lower, nujiang, river, yunnanensis, only, know. Pseudexostoma is a genus of fish in the family Sisoridae endemic to China These species are restricted to the upper Salween Nujiang River and one upper branch of the Irrawaddy Dayinjiang River in China 1 P brachysoma is known only from the middle and lower Nujiang River P yunnanensis is only known from the upper Dayinjiang 2 These rivers were once connected but are now separated Also the environment and temperature of the Nujiang River became greatly different between the northern and southern areas leading to speciation 2 PseudexostomaScientific classificationDomain EukaryotaKingdom AnimaliaPhylum ChordataClass ActinopterygiiOrder SiluriformesFamily SisoridaeTribe GlyptosterninaGenus PseudexostomaX L Chu 1979Type speciesGlyptosternum yunnanensisTchang 1935 Contents 1 Taxonomy 2 Species 3 Description 4 ReferencesTaxonomy editGlyptosternum yunnanesis was first described in 1935 However due to its unique teeth a separate genus Pseudexostoma was erected in 1979 for this species The same year a subspecies of P yunnanensis was described P y brachysoma However it has become apparent that these two groups represent different species Also a third species P longipterus was described in 2007 2 Results obtained by Yang et al 2016 showed that P longipterus cannot be distinguished from P brachysoma from either morphological or molecular analyses and that the former name should thus be considered a junior synonym of the latter 1 Species editThere are currently two recognized species in this genus Pseudexostoma brachysoma X L Chu 1979 Pseudexostoma yunnanensis T L Tchang 1935 Description editThese species have a continuous groove behind the lip gill openings not extending onto the underside heterodont dentition in both jaws with outer teeth shovel shaped and sparsely arranged in one or two rows and inner teeth conical and numerous the tooth patches separated in upper jaw and 16 18 branched pectoral rays 3 The lips are thick fleshy and papillated The paired fin are plaited to form an adhesive apparatus 3 Species of this genus have a moderately compressed body The head is depressed and broad it appears triangular from the side and with a rounded snout from above The eyes are small and ovoid located at the middle of the dorsal surface of the head The mouth is transverse and inferior with the teeth exposed when the mouth is closed The teeth are embedded in the skin shovel shaped with the tips exposed and arranged in irregular rows The gill openings are narrow The dorsal surface is smooth without tubercles There are four pairs of barbels The adipose fin base is not connected to the caudal fin The caudal fin is emarginate with the upper lobe smaller than the lower lobe The lateral line is midlateral and complete 2 Species of this genus are grey black on the dorsal surface and grey yellow on the ventral region the caudal fin is grey black with an irregular small yellow patch in the middle and the other fins are grey yellow along the distal edge 2 Pseudexostoma grow to about 9 9 15 3 centimetres 3 9 6 0 inches SL 4 5 These species have three notches on the posterior margin of the lower lip However in P yunnanensis the notches are all the same depth while in the other two species the middle notch is shallower in depth than the lateral notches The two median lobes formed by these notches are the same length of the lateral lobes of the lips in P yunnanensis but they are longer in the other two species P yunnanensis also has more pelvic fin rays 5 vs 3 4 a shorter adipose fin base a deeper and longer caudal peduncle more teeth in the premaxillary tooth band 18 22 vs 16 18 that are divided into two partially connected patches instead of two isolated patches 2 References edit a b Yang K Jiang W Chen X Zhou W amp Yang J 2016 An integrative approach to reappraising species validity in Pseudexostoma Teleostei Sisoridae Zootaxa 4158 3 352 366 a b c d e f Zhou W Yang Y Li X amp Li M H 2007 A review of the catfish genus Pseudexostoma Siluriformes Sisoridae with description of a new species from the upper Salween Nujiang basin of China Raffles Bulletin of Zoology 55 1 147 155 a b Thomson A W amp Page L M 2006 Genera of the Asian Catfish Families Sisoridae and Erethistidae Teleostei Siluriformes Zootaxa 1345 1 96 Froese Rainer Pauly Daniel eds 2016 Pseudexostoma brachysoma in FishBase June 2016 version Froese Rainer Pauly Daniel eds 2016 Pseudexostoma yunnanensis in FishBase June 2016 version Retrieved from https en wikipedia org w index php title Pseudexostoma amp oldid 1031643173, wikipedia, wiki, book, books, library,
