Description of two new and five known species of the genus Axonchium Cobb, 1920 (Nematoda: Dorylamida) from India with diagnostic compendia and keys to species of the genera Axonchium and Syncheilaxonchium Coomans & Nair, 1975 Author Naz, Tabbasam Author Ahmad, Wasim text Zootaxa 2012 3264 1 37 journal article 10.5281/zenodo.215075 26e91ae0-6b90-4095-b674-971182352c80 1175-5326 215075 Genus Syncheilaxonchium Coomans & Nair, 1975 Coomans and Nair (1975) proposed the subgenus Syncheilaxonchium as one of the subgenera of the genus Axonchium Cobb, 1920 and differentiated it from other subgenera of this genus mainly in the presence of a continuous lip region with amalgamated lips. They (l.c.) designated Axonchium ( Syncheilaxonchium ) rotundum Thorne, 1964 as the type species and also included A. ( S .) amalgans Thorne, 1939 ; A. ( S .) asacculum Siddiqi, 1968 ; A. ( S.) baldum Thorne, 1964 ; A . ( S .). coomansi Nair, 1975 ; A. ( S. ). deconincki Nair, 1975 ; A . ( S .) indicum Siddiqi, 1964 and A. ( S .). nairi Altherr, 1974 under this subgenus. Andrássy (2009) , while raising this subgenus to generic rank, transferred Axonchium banaticum Popovici, 1990 (= Syncheilaxonchium banaticum ( Popovici, 1990 ) Andrássy, 2009 ) and Axonchium perplexans Siddiqi, 1995 (= Syncheilaxonchium perplexans ( Siddiqi, 1995 ) Andrássy, 2009 ) to Syncheilaxonchium without giving any reason. Although A . banaticum has a continuous lip region and suitably fits under the generic diagnosis of Syncheilaxonchium ; A. perplexans , because of its offset lip region, does not. Naz et al. (2007) described Axonchium sturhani and Axonchium parassaculum , from New Zealand and Ahmad & Naz (2010b) described Axonchium singaporense from Singapore . These three species have a continuous lip region with amalgamated lips. The main distinguishing character between these two genera is the nature of the lip region:, Axonchium has an offset lip region and partly or distinctly separate lips whereas the lip region is continuous in Syncheilaxonchium and the lips are completely amalgamated. Because of the presence of continuous lip region with amalgamated lips, the above three species completely fit under the generic diagnosis of Syncheilaxonchium and hence are being transferred here to the genus Syncheilaxonchium as Syncheilaxonchium sturhani ( Naz et al., 2007 ) n. comb. ; S. parassaculum ( Naz et al., 2007 ) n. comb. and S. singaporense ( Ahmad & Naz, 2010b ) n. comb. With the transfer of these three species, the total number of valid species under Syncheilaxonchium comes to twelve. Diagnosis. Small to large-sized ( 0.9–2.9 mm ) nematodes; body almost straight to open C-shaped upon fixation. Cuticle usually smooth which appears finely transversely striated at higher magnification; lateral chords with or without distinct glandular bodies. Lip region rounded, continuous with body conour; lips amalgamated. Odontostyle short fusiform; guiding ring usually simples; odontophore rod-like with thickened walls, usually equal to odontostyle length. Anterior part of pharynx more or less muscular, separated from the postertior part by deep constriction or a short isthmus. Female genital system mono-opisthodelphic with or without prevulval sac. Vulva transverse; pars refringens vaginae absent. Males with well-developed massive, straight to ventrally arcuate spicules; sclerotised, rod-like lateral guiding pieces with distal bifid ends and spaced ventromedian supplements. Tail bluntly rounded or slightly clavate, similar in sexes. Type species: Syncheilaxonchium rotundum ( Thorne, 1964 ) Coomans & Nair, 1975 = Axonchium rotundum Thorne, 1964