Cells are diverse in morphology; they may be coccoid to spindle-shaped in shape, with rounded or pointed ends.

Except in the genus Chlorolobion, the pyrenoid lacks a starch covering, making it difficult to observe using light microscopy.

A distinguishing characteristic of this family is the method of autospore formation: the protoplast divides serially, with divisions being perpendicular to the longer axis of the cell.

[6] The genus Closteriopsis consists of narrow, sickle-shaped cells with one chloroplast and multiple pyrenoids.

It has been placed in the Selenastraceae due to its morphological similarity to genera such as Monoraphidium, but genetic analyses have shown that it is unrelated.