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.