Psammon rotifers in Central Vietnam, with the descriptions of three new species (Rotifera: Monogononta) Author Dang, Mau Trinh Author Segers, Hendrik Author Sanoamuang, La-Orsri text Zootaxa 2015 4018 2 249 265 journal article 10.11646/zootaxa.4018.2.5 e16773a1-5a85-4214-aab5-f10e31f3e996 1175-5326 232742 57750359-8B78-4655-AC5E-F3A460ED0848 Trichocerca bauthiemensis new species (Figs 41–45, 46–49) Type specimens. holotype (IG 33091 RIR 243) and two paratypes (IG 33091 RIR 244, 245) in permanent slides deposited in the Royal Belgian Institute of Natural Sciences, Brussels, Belgium ( RBINS ). Four slides containing one paratype each (SK-R0151-01, -04) deposited in the Science Museum, Khon Kaen University, Khon Kaen, Thailand . Type locality. Bau Thiem Lake ( 16°38'6.60"N , 107°21'51.00"E ), Phong Binh community, Phong Dien district, Thua Thien Hue province, Vietnam . Differential diagnosis. Trichocerca bauthiemensis n. sp. can be confused with T. brachyura (Gosse, 1851) , T. obtusidens (Olofsson, 1918) and T. vernalis (Hauer, 1936) . The species is, however, diagnosed by its head aperture having longitudinal folds only, without the characteristic blunt process on the left of the head sheath, and by absence of a dorsal keel. Further, its trophi has relatively slender right alulae that are more sharply bent outwards than in any of the species mentioned, and its right manubrium is single-crutched, not double-crutched. Its toes are equal, which is unlike T. vernalis and T. obtusidens . Description. Small species; body elongate cylindrical, slightly curved. Head sheath without spine or projection, retracting into a series of longitudinal folds around the head aperture. Of these, the three dorsal elements are the larger, and the left anterior elements protrude slightly beyond the right. Head separated from trunk by a weak constriction; no dorsal keel. Foot conical, subterminal. Toes spiniform, curved, inserted sub-distally and ventrally, with some substyli present. Two equal toes present. Trophi asymmetrical. Fulcrum elongate, with well-developed ventral crest and basal plate. Left ramus more developed, with outwardly curved and acutely pointed alula. Left suprauncus consisting of a row of large and elongate, curved teeth, right a row of smaller, spines. Large supraramus present. Left uncus with single basal part, and fan-shaped distal part consisting of 3 teeth. Right uncus with a long and thin tooth. Right manubrium rodshaped, slightly curved. Left manubrium more developed, distally inward curved with a triangular dorsal projection which dissolves quickly if exposed to NaOCl. Measurements (mean (SD), in Μm): body length 71.5 (5.1), body width 23.6 (4), toe length 24 (2.6), total trophi length 27 (fulcrum 21, left manubrium 20, right manubrium 14, rami width 10). Ecology and distribution. This species is only known from the hygropsammon of Bau Thiem Lake, Thua Thien Hue Province, Vietnam . On this account it is here considered a psammobiontic species. Etymology. The name of this species is an adjective, and refers to type locality of the animal, Bau Thiem Lake.