Short cylindrical stoma with short stegostom (pharyngeal collar).  Long tapering corpus with no offset metacorpus.  Valve in postcorpus.  Female monovarial, prodelphic, ovary reflexed, offset spermatheca.  Rapidly moving, very active nematodes.

Per the emended diagnosis of the family provided by Bert et al. (2003):

• Lip region without probolae or fi?mbriate processes.
• Labial sensilla papilliform, cephalic sensilla papilliform or rarely setiform.
• Cuticul ?finely striated.
•  Stoma fairly wide anteriorly, stegostom usually tapering, comprising between 50 and 66% of stoma length, without subdivisions of its lining.
• Pharynx with cylindrical procorpus, metacorpus cylindrical or with valveless median bulb, terminal bulb valvate.
• Female reproductive system monodelphic, prodelphic.
• Spermatheca usually absent or axial, rarely offset as in Cephalobidae. Uterus-oviduct junction sometimes with two offset spermatheca-like pouches.
• Postvulval sac present or absent.
• Female tail conical with pointed tip.
• Males without bursa, with one unpaired papilla and fi?ve to seven pairs of genital papillae, arrangement variable.
• Spicules  often with wide velum,
• Gubernaculum often with posterior expansion

In general, the Panagrolaimidae differ from the Cephalobidae in that :

• the anterior sections of the stoma is more spacious with the cheilostom and gymnostom wider than the stegostom
• the postvulval section of the reflexed ovary is either straight of has a single flexure.
• spermatheca absent or usually not offset.

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