• Free-living marine nematodes
• Lips usually fused..
• Large cylindrical buccal cavity, usually with 3 immovable teeth of unequal size  surounded in the posterior region by esophageal tissue
• Esophageal glamds open through the teeth.
• Amphidial fovea pocket-shaped, posterior to buccal cavity.
• Esophagus muscular throughout length, esophageal gland openings just posterior to buccal cavity.
• Males mainly diorchic, spicules varied in shape and size; gubernavulum present or absent.
• Females didelphic amphidelphiuc or monodelphic prodelphic; ovaries reflexed.

Specific characteristsics of the subfamily Adoncholaiminae:

• Adoncholaiminae consists of four genera, which usually have the right ventrosublateral onchium largest or both ventrosublateral onchia of equal size;
•  a Demanian system is always present in the greatest degree of development (Shimada and Kajihara, 2014; Smol et al., 2014).
• The presence or absence of terminal canals and pores, and their position (if present),
• the size of spicules, presence or absence of gubernaculum are important characteristics for identification of genera in the Adoncholaiminae genera.

The Demanian system is a set of canals, junctions and pores unique for some genera of Oncholaimidae. The system differs from simple (primitive) to more complex (advanced) in different genera and species.  The Demanian system  features in "traumatic insemination" in which the male uses spicules and secretions to puncture the cuticle of the posterior of the female to form a copulatory pore. Sperm are released into the pore. The sperm injected into the female move through terminal ducts and reach the main duct of the Demanian system. The sperm move forward in the main duct to the uterus through the uvette and ductus uterinus. Eggs are fetrilized in the uterus ( Coomans et al., 1988; Tchesunov, 2015).