Three genera seem to be ancestral to later Proetidae. Griffithidella n. gen. and Thigriffides n. gen. have the same type of cephalon as Griffithides and other late trilobites. Griffithidella is more primitive, with 10 thoracic segments. Richterella n. gen. is similar to Pennsylvanian Ameura. Three distinct faunas occur in the Easley Group: the Chouteau Limestone has Breviphillipsia, with the aberrant Snake Den fauna characterized by Proetides and Richterella. The Darty, Chappel, Welden, and Rockford Limestones contain Proetus (Pseudoproetus), Griffithidella, and Thigriffides. New species are Griffithidella newarkensis, G. waverlyensis, Thigriffides? ameuroides, Richterella snakesdenensis, R. mauvaisensis and R. hindsvillensis.

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