An order of nematodes comprising the single superfamily Isolaimoidea. The order consists of one family and one genus. They are rather large for free-living soil nematodes (0.1–0.2 in. or 3–6 mm) and are found in seldom-cultivated sandy soils. Some forms have anterior annulations, while others have posterior transverse rows of punctations. The diagnostic characteristics of this superfamily are the presence of six hollow tubes around the oral opening and two whorls of six circumoral sensilla. Amphids are apparently absent, though some authors speculate that their function is taken over by the dorsolateral papillae of the second whorl. The triradiate stoma is elongate and has thickened walls anteriorly. The esophagus is clavate. The female ovaries are opposed and outstretched, and may have flexures. The gubernaculum, supporting the thickened male spicules, has two dorsal apophyses, and male preanal supplementary organs are papilloid. Paired caudal papillae are large in males, small in females.