Metadesmolaimus Schuurmans Stekhoven, 1935

Li, Ting, Ban, Shuyan & Huang, Yong, 2023, Two new species of Xyalidae Chitwood, 1951 (Nematoda, Monhysterida) from Chinese Sea Area, Zootaxa 5369 (2), pp. 255-268 : 261

Genus Metadesmolaimus Schuurmans Stekhoven, 1935

Diagnosis: (emended from Fonseca & Bezerra, 2014) Cuticle finely striated with brownish appearance. Somatic setae scattered along the body. Inner labial sensilla setiform. Outer labial setae and cephalic setae at the same level. Ventrolateral setae between the labial and cephalic setae usually present. Amphids circular. Buccal cavity extended, divided into two parts by an annule; anterior part cylindrical, posterior part conical. Two gonads; anterior to the left of intestine, posterior to the right. Spicules curved and proximally cephalated. Gubernaculum without apophyses. Three caudal glands opening at separate pores. Tail conical or conico-cylindrical with or without terminal setae.

The genus is very similar to Daptonema . Some Metadesmolaimus species have only a slightly extended buccal cavity while several Daptonema species also seem to have a slightly extended buccal cavity. However, Metadesmolaimus species possess relative wide oral annule in the middle of buccal cavity, while Daptonema species lack distinct intermediate oral annule. Moreover, Metadesmolaimus species have brownish appearance and setiform inner labial sensilla, while Daptonema species lack brownish appearance and inner labial setae, and their inner labial sensilla are papilliform. When assigning a species to the genus Metadesmolaimus , we should base that on a combination of main characters as brownish appearance, setiform inner labial sensilla, buccal cavity extended and divided into two parts by a relatively wide oral annule and gubernaculum without apophysis.