Tylencholaimus de Man, 1876 = Xenonchium Siddiqi & Khan, 1964 Diagnosis (Dorylaimida: Tylencholaimidae): Small sized nematodes, between 0.3 and 1.2 mm in length. Cuticle tylencholaimoid, with irregular radial refractive elements; outer layer generally with fine transverse striations. Lip region always cap-like, offset by constriction or sometimes by depression; lips more or less amalgamated, with the perioral area either transformed into a disc-like structure or not. Cheilostom a truncate cone, often with perioral thickenings. Amphid aperture slit-like, about half as wide as corresponding lip region diameter. Odontostyle somewhat shorter than lip region diameter, its aperture about one-fourth to one-third of total length. odontophore rod-like, with more or less distinct basal knobs. Pharynx consisting of anterior slender part extending gradually or abruptly into the basal expansion with thickened inner lining, which occupies one-third to two-fifths of the total neck length. Cardia usually hemispheroid to rounded-conoid. Female genital system amphidelphic, monoprodelphic or mono-opisthodelphic. Vulva transverse. Males with dorylaimoid spicules, lateral guiding pieces and a few spaced (very rarely numerous and contiguous) ventromedian supplements. Tail similar in sexes, elongateconoid to hemispherical. Type species: Tylencholaimus mirabilis (Bütschli, 1873) de Man, 1876 = Tylenchus mirabilis Bütschli, 1873 = Dorylaimellus mirabilis (Bütschli, 1873) Thorne, 1939 = Dorylaimellus (Tylencholaimus) mirabilis (Bütschli, 1873) Meyl, 1953 = Discomyctus brevicaudatus Tarjan, 1953 = Tylencholaimus brevicaudatus (Tarjan, 1953) Tarjan, 1956 Other species: T. airolensis Loof & Jairajpuri, 1968 T. americanus Peña-Santiago & Coomans, 1996 T. arakii sp. n. T. asymmetricus Khan & Ahmad, 1994 T. australis Yeates, 1979 T. cedari (Siddiqi & Khan, 1964) Jairajpuri & Ahmad, 1992 = Xenonchium cedari Siddiqi & Khan, 1964 T. chathami Yeates, 1979 T. confusus Ahmad & Araki, 2003 T. congestus Loof & Jairajpuri, 1968 T. conicuadatus Peña-Santiago & Coomans, 1994 T. constrictus Vinciguerra, 1986 T. cosmos (Dhanam & Jairajpuri, 1999) Peña-Santiago, 2008 = Amphitylencholaimus cosmos Dhanam & Jairajpuri, 1999 T. crassus Loof & Jairajpuri, 1968 T. cynodonti Nasira, Erum & Shahina, 2005 T. decens Andrássy, 1991 T. formosus Loof & Jairajpuri, 1968 T. gallaicus Seijas, Hernandez, Abolafia & Peña-Santiago, 2007 T. gertii Kruger, 1965 T. ibericus Peña-Santiago & Coomans, 1994 = T. japonicus Ahmad & Araki, 2003 T. imperanus Mohilal & Dhanachand, 2003 = Tylencholaimus (Discotylencholaimus) imperanus Mohilal & Dhanachand, 2003 = Tylencholaimus (Discotylencholaimus) lokus Mohilal & Dhanachand, 2003 T. innebus Ahmad & Jairajpuri, 1979 T. koreanus Ahmad, Park, Lee & Choi, 2009 T. ladakhiensis sp. n. T. leptodorus Monteiro, 1970 T. leptonchoides Loof, 1964 = T. macrurus Siddiqi, 1964 = T. similis Jairajpuri, 1965 T. longicaudatus Peña-Santiago & Coomans, 1994 T. loofi Dhanachand, 1994 = T. minutus apud Dhanachand, Mohilal & Joymati, 1992 T. maritus Loof & Jairajpuri, 1968 = Tylencholaimus sp. Loof, 1964 T. micronanus Yeates, 1979 = T. vanguimus Mohilal & Dhanachand, 2000 T. minimus de Man, 1876 T. minutus Vinciguerra, 1986 T. mongolicus Andrássy, 1967 T. nagauriensis Baqri & Bohra, 2001 T. nanus Thorne, 1939 T. notrus Khan, Jairajpuri & Ahmad, 1990 T. obscurus Jairajpuri, 1965 = T. dorae Kruger, 1965 T. orientalis Li, Baniyamuddin, Ahmad & Wu, 2008 T. paracrassus Monteiro, 1970 T. parvus Ahmad & Araki, 2003 T. pini Mushtaq, Naz & Ahmad, 2007 T. porosus Vinciguerra & Zullini, 1980 T. proximus Thorne, 1939 T. pusillus Loof & Jairajpuri, 1968 T. rumjhumi Khan & Laha, 1982 T. savaryi Loof & Jairajpuri, 1968 T. sinensis Li, Baniyamuddin, Ahmad & Wu, 2008 T. singaporensis Ahmad & Baniyamuddin, 2010 T. stecki Steiner, 1914 = T. alpinus Vinciguerra, 1982 T. suryawanshii Ali & Chisty, 1972 T. tahatikus (Yeates, 1967) Siddiqi, 1968 = Dorylaimellus tahatikus Yeates, 1967 T. teres Thorne, 1939 T. terrestris Peña-Santiago & Coomans, 1996 T. vigil Andrássy, 1959 T. vulvulatus Rahman, Jairajpuri, Ahmad & Ahmad, 1987 = Protylencholaimus longisaccus Dhanam & Jairajpuri, 1999 Ahad & Ahmad (2016) recently transferred T. pakistanicum to the genus Tantunema Siddiqi, 1982, and hence it is not included in this list.

Published as part of Ahad, Sumaya & Ahmad, Wasim, 2016, Description of two new and six known species of the genus Tylencholaimus de Man, 1876 (Nematoda: Dorylaimida) with a diagnostic compendium and key to species, pp. 451-490 in Zootaxa 4107 (4) on pages 452-454, DOI: 10.11646/zootaxa.4107.4.1, http://zenodo.org/record/267748