Friday, September 8, 2023

[Ichthyology • 2023] Schistura palma • A New Species of Loach (Cypriniformes: Nemacheilidae) from the Nam Ngiep Drainage, central Laos


 Schistura palma
 Kottelat, 2023

 RAFFLES BULLETIN OF ZOOLOGY. 71

Abstract
 Schistura palma, new species, is described from the middle Nam Ngiep drainage, central Laos. It is distinguished from all other species of Schistura in Southeast Asia by the combination of having a dorsal keel on the entire length of the caudal peduncle in small individuals that develops into a conspicuous crest in large ones; cheeks conspicuously swollen in large individuals; lips smooth or with short, shallow wrinkles, their free edge entire; 8½ branched dorsal-fin rays; 7–10 [commonly 8–9] uniformly dark brown bars on body; plain brown cheeks. It occurs in fast-flowing stretches of the main river and lower course of main tributaries.

 Key words. Cobitoidei, Schistura, Mekong basin, stone loach

 Schistura palma, new species, MHNG 2790.080, holotype, 63.5 mm SL;
 Laos: Saysomboune Province: Nam Ngiep watershed.

Schistura palma, new species

Diagnosis. Schistura palma is characterised among other named species of Schistura sensu lato in Indochina by the presence of a dorsal keel along the entire length of the caudal peduncle in small individuals, that develops into a conspicuous crest in large ones. A low keel or crest exists in some other species of the genus, but in these it is restricted to the posterior part of the caudal peduncle. Among Southeast Asian species, such a crest extending along the entire length of the caudal peduncle is known in S. porthos (Figs. 6, 7) from the Mekong drainage in northern Laos and Xishuangbanna in China, and in S. alticrista (Fig. 8) from the Salween drainage in Thailand.
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Etymology. From the Latin palma, the blade of an oar, an allusion to the shape of the caudal peduncle and caudal fin in large adults. A noun in apposition.

 
Maurice Kottelat. 2023. Schistura palma, A New Species of Loach from the Nam Ngiep Drainage, central Laos (Teleostei: Nemacheilidae). RAFFLES BULLETIN OF ZOOLOGY. 71; 520–530.