Very similar to Maretiidae but with a bilobed rather than shield-shaped subanal fasciole and wider, less strongly tapered episternal plates. Although an inner fasciole is present in many not all genera that are included have this. Echinocardiidae differ in having a much shorter labral plate and larger, more ovate sternum, in having episternal plates forming the lower part of the posterior face, not the rear part of the oral face and in having a shield-shape subanal fasciole. Spatangidae have a short labral plate and parallel-sided sternal zone.
The following taxon may belong here but is too poorly known to include in the key below:
Laevipatagus Noetling, 1885
Verbeekia Fritsch, 1877 (probably a Lovenia)