Gelyellidae

Gelyella is a genus of freshwater copepods. They live in groundwater in karstic areas of southern France and western Switzerland. The two species are the only members of the family Gelyellidae and, although previously placed in the order Harpacticoida, a new order, Gelyelloida, was erected for this family alone.

Gelyella shows some paedomorphosis, in which animals reach sexual maturity while still partly resembling juveniles. The adults are 300–400 micrometres (0.012–0.016 in) long with a nearly cylindrical body that tapers towards the rear. There are eleven body segments, the last of which is the length of the previous two segments combined.