The group is closely related to the Clypeasteroida, and may be representative of its ancestral clypeasteroid.

However unlike them, oligopygoids have a well-developed lantern uncommon amongst urchins and holectypoids, but similar to that of clypeasteroids.

Phylogenetic analysis has shown the clypeasteroids to be a sister group to oligopygoids.

[1] However they are differentiated by the lack of accessory ambulacral pores, which are characteristic of that group.

[2] Early research into this order recognized one family (Oligopygidae; Duncan 1889), and two genera, (Haimea; Michelin, 1851; Oligopygus; de Loriol, 1888).