The composition of this group is somewhat restricted in comparison to previous usage. The precise course of the peripetalous fasciole is highly conservative in this family and provides the key feature that distinguish this clade. Prenasteridae also have a single anterior fasciole but this crosses the anterior interambulacra on plate 3 and plate 4 in interambulacra 1b and 4a. Furthermore the fasciole passes two or more ambulacral plates below the ends of the petals.
The differentiation of many genera has been based on the presence or absence of the lateroanal fasciole and the number of gonopores developed. Both the loss of the lateroanal fasciole and the reduction of the anterior gonopores seems to have occurred several times independently and the monophyly of several of the genera is suspect.
The following taxon probably belongs to this family but is currently too poorly known to be meaningfully compared and is omitted from the key given below. It represents a nomen dubium
Hemifaorina Jeannet & Martin, 1937