Two new species of Xyalidae Chitwood, 1951 (Nematoda, Monhysterida) from Chinese Sea Area Author Li, Ting 0009-0003-5630-314X College of Life Sciences, Liaocheng University, Liaocheng 252059, P. R. China & 15854632111 @ 163. com; https: // orcid. org / 0009 - 0003 - 5630 - 314 X Author Ban, Shuyan 0009-0006-2973-2354 College of Life Sciences, Liaocheng University, Liaocheng 252059, P. R. China & 15098432691 @ 163. com; https: // orcid. org / 0009 - 0006 - 2973 - 2354 Author Huang, Yong 0000-0002-1846-8088 College of Life Sciences, Liaocheng University, Liaocheng 252059, P. R. China & huangy @ lcu. edu. cn; https: // orcid. org / 0000 - 0002 - 1846 - 8088 huangy@lcu.edu.cn text Zootaxa 2023 2023-11-09 5369 2 255 268 https://www.mapress.com/zt/article/download/zootaxa.5369.2.5/52241 journal article 10.11646/zootaxa.5369.2.5 1175-5326 10151718 24A3BCAD-C76F-4704-96E8-9507A2D55AAD Dichotomous key to the species of Metadesmolaimus (modified from Guo et al. 2016) 1. Spicules slender and elongated, longer than two cloacal body diameters.......................................... 2 - Spicules not elongated, shorter than 1.6 cloacal body diameters................................................. 3 2. Body 1.6 mm long, amphids 0.6 head diameter from anterior end............................................................................................... M. caniculus ( Wieser & Hopper, 1967 ) Gerlach & Riemann, 1973 - Body 0.8–1.1 mm , amphids 1 head diameter from anterior end............................ M. varians Lorenzen, 1971 3. Tail conical.......................................................................................... 4 - Tail conico-cylindrical................................................................................. 7 4. Somatic setae long and dense, spicules slightly bent with tooth-shaped distal end.................................................................................................... M. hamatus ( Gerlach, 1956 ) Lorenzen, 1971 - Somatic setae shorter than 0.6 corresponding body diameter, spicules arcuated, distal end not tooth-shaped.............. 5 5. Both spicules distinctly unequal in length.......................................... M. heteroclitus Lorenzen, 1971 - Both spicules equal in length............................................................................ 6 6. Amphids small, 32%–36% corresponding body diameter in diameter, spicules relatively slender, 1.5–1.6 cloacal body diameters long............................................................................... M. gaelicus Platt, 1983 - Amphids large, 50% corresponding body diameter in diameter, spicules broad, 1.3 cloacal body diameters long............................................................................. M. tersus ( Gerlach, 1956 ) Lorenzen, 1971 7. Tail elongated, nine cloacal body diameters long........................... M. coronatus Schuurmans Stekhoven, 1950 - Tail not elongated, shorter than seven cloacal body diameters.................................................. 8 8. Pharynx with 18 bulb-like muscular swellings.............................................. M. bulbosus sp. nov. - Pharynx even without bulb-like muscular swelling........................................................... 9 9. Somatic setae dense and long........................................................................... 10 - Somatic setae sparse and short.......................................................................... 13 10. Outer labial setae jointed, distal end of spicules not hooked......................... M. zhanggi Guo, Chen & Liu, 2016 - Outer labial setae unjointed, distal end of spicules hooked.................................................... 11 11. Gubernaculum absent....................................................... M. psammophilus Tchesunov, 1990 - Gubernaculum present................................................................................ 12 12. Body slightly slender (a=32–37), spicules 32 µm (shorter than 1.4 cloacal body diameters)...... M. aduncus Lorenzen, 1971 - Body slightly stout (a=25–29), spicules 44–46 µm (1.5 cloacal body diameters)................................................................................................ M. gelana ( Warwick & Platt, 1973 ) Lorenzen, 1977 13. Amphids larger than 60% corresponding body diameter in diameter......................... M. pandus Lorenzen, 1971 - Amphids smaller than 50% corresponding body diameter in diameter........................................... 14 14. Cephalic setae shorter than 0.5 head diameter, amphids close to anterior end (less than 1 head diameter from anterior end)................................................................................ M. communis Gagarin, 2013 - Cephalic setae longer than 0.6 head diameter, amphids further from anterior end (longer than 1.5 head diameters from anterior end)............................................................................................... 15 15. Cervical setae longer than 1 corresponding body diameter, gubernaculum broad................ M. elegans Gagarin, 2013 - Cervical setae shorter than 0.5 corresponding body diameter, gubernaculum strip-like or sleeve shaped................ 16 16. Spicules arcuated with terminal teeth, gubernaculum strip-like............................ M. similis Tchesunov, 1990 - Spicules L-shaped, gubernaculum sleeve-shaped surrounding distal half of spicules.......... M. aversivulva Gerlach, 1953