Sigmolenchus sinuosus n. gen., n. sp. (Tylenchidae, Ecphyadophorinae) a new member for the family.

Sigmolenchus n. gen., is proposed as a new member of the Tylenchidae. The new genus is proposed based upon light and scanning electron microscopic (LM and SEM) observations and phylogenetic analyses based upon small, large and internal transcribed spacer sequences of ribosomal DNA (SSU, LSU D2-D3, ITS rDNA) and mitochondrial cytochrome c oxidase I gene (COI mtDNA) sequences. It is characterised partly by its slender body, but mainly by having a dorso-ventrally ¿attened, smooth and elevated cephalic region, unique elongate sinuous amphidial openings, each appearing as a wavy slit with three peaks, originating from the vicinity of the labial plate, extending posteriorly and reaching and passing the ¿rst body annulus, and a spacious amphidial fovea. It has an anteriorly rounded outline under LM, knobbed stylet, its conus comprising about one-third of the total length, lateral ¿eld with a single band, metacorpus with a distinct valve, vulva with small lateral ¿aps, and males common with tylenchoidiform spicules. The new genus is morphologically compared with seven tylenchid genera, viz., Chilenchus, Ecphyadophoroides, Filenchus, Labrys, Lelenchus, Sakia, and Tenunemellus, mainly by having small slender body and dorso-ventrally ¿at cephalic region, and is placed under the subfamily Ecphyadophorinae because of its slender body, elevated smooth cephalic region, long amphidial openings and spacious amphidial fovea. It was recovered from marine muddy sediments taken 2 m deep in mangrove forests off southern Iran. Currently S. sinuosus n. gen., n. sp. is monotypic. In SSU phylogeny, the new genus formed an unsupported sister relationship with Filenchus discrepans,and in LSU phylogeny it occupied a placement inside a major clade including several Tylenchinae genera