Paragnomoxyala, Jiang, Weijun & Huang, Yong, 2015

Jiang, Weijun & Huang, Yong, 2015, Paragnomoxyala gen. nov. (Xyalidae, Monhysterida, Nematoda) from the East China Sea, Zootaxa 4039 (3), pp. 467-474 : 469

Genus Paragnomoxyala gen. nov.

Body slender, gradually tapering towards both terminal ends. Cuticle with transverse striations, beginning at base of buccal cavity and ending at tail tip. Internal labial sensilla not visible; outer labial setae absent. Only four short cephalic setae. Sub-cephalic setae absent. Amphidial fovea circular at the level of buccal cavity. Lips high. Buccal cavity large, funnel-shaped with cuticularized walls and extended anteriorly, 1.6-1.8 hd long, 63–79% cbd wide, lacking teeth, not surrounded by pharyngeal tissue. Tail conico-cylindrical with three terminal setae. Spicules straight. Gubernaculum absent. Female monodelphic; anterior outstretched ovary to the left of the intestine.

Etymology. The genus name refers to the close genus Gnomoxyala .

Diagnosis and discussion. Paragnomoxyala gen. nov. is characterized by large buccal cavity unique in Xyalidae , funnel-shaped with cuticularized walls and extended anteriorly; cuticle transversely striated; only four cephalic setae, without outer labial sensilla setae; subcephalic setae and cervical setae absent; circular amphidial fovea; straight spicules; no gubernaculum; tail conico-cylindrical with three terminal setae; and female monodelphic with an anterior outstretched ovary. It is similar to other genera of the family in possessing large cuticularised buccal cavities or straight spicules without gubernaculum, namely Gnomoxyala Lorenzen, 1977 , Coronema Nicholas & Stewart, 1995, Sphaerotheristus Timm, 1968 , Hofmaenneria Gerlach & Meyl, 1957 and Elzalia Gerlach, 1957 . Paragnomoxyala gen. nov. differs from Gnomoxyala by its large buccal cavity with extended anteriorly, striated cuticle, circular amphidial fovea, and spicules longer than abd. In Gnomoxyala , the buccal cavity is cylindrical, not extended anteriorly, the lips not high, cuticle is only faintly striated, amphidial fovea absent, cervical setae are present, and spicules are shorter than abd. It differs from Coronema by having fine cuticle striations, no buccal ring and tail conico-cylindrical with three terminal setae. In Coronema, the cuticle is strongly annulated with eight ridges, a buccal ring is present and the tail is conical without terminal setae. This new genus differs from Sphaerotheristus which has cuticle with longitudinal ridges, and cephalic sensilla in two crowns with the posterior crown bearing 10 or 12 setae ( Fonseca & Bezerra 2014). The new genus differs from Hofmaenneria by having a wider buccal cavity, the amphidial fovea almost at the level of buccal cavity vs posterior to the cavity, spicules short and straight vs slender and ventrally arcuate, gubernaculum absent vs present, and tail with terminal setae vs elongated without terminal setae. It differs from Elzalia by having a wider buccal cavity, only four cephalic setae, outer labial setae absent, spicules short and no gubernaculum. In Elzalia , the anterior sensilla are in two circles, the posterior circle with ten setae, the spicules are elongate, and the gubernaculum is usually complex. Xyalidae usual has six outer labial setae and four cephalic setae in one circle. However, with a few exceptions, Gnomoxyala and Retrotheristus Lorenzen, 1977 have only four cephalic setae in one circle, and the outer labial setae are absent. Thus, by this character, the new genus is also similar to Gnomoxyala and Retrotheristus . It differs from Retrotheristus which has a conoid buccal cavity, arcuate spicules and a gubernaculum, cuticle with faint striations, no amphidial fovea, and does have cervical setae. Based on these features, which are regarded as characteristic of the above genera, we propose Paragnomoxyala as a new genus. Paragnomoxyala gen. nov. differs from other genera of Xyalidae by the combination of a large funnel-shaped buccal cavity which is extended anteriorly, by lacking subcephalic setae and cervical setae and by having straight spicules without a gubernaculum. The type species of this new genus is Paragnomoxyala breviseta sp. nov.