[1] Eocarcinosoma can be distinguished from other carcinosomatids, such as Carcinosoma and Eusarcana, by its marginally placed and kidney-shaped compound eyes and its head shape being more triangular than those of its relatives.

[1] Eocarcinosoma batrachophthalmus was described in 1964 by Kenneth E. Caster and Erik N. Kjellesvig-Waering, based on a well-preserved prosoma (head)[1] from Ashgillian-age[2][4] (Late Ordovician) deposits alongside the Ohio River road (U.S. Route 52), approximately 14.5 kilometres (9 miles) north of Manchester, Ohio.

The specimen was referred to the Carcinosomatidae by Caster and Kjellesvig-Waering without explanation, and named as a distinct genus and species on account of the features separating it from other carcinosomatids.

[1] The name Eocarcinosoma is derived from the Greek word eós (ἠώς) meaning 'dawn',[5] and the related genus Carcinosoma.

The type specimen, consisting of a part and counterpart (the two matching halves of a compression fossil) and given the designation 24147 A and B, was deposited to the Geological Museum of the University of Cincinnati.

[11] Carcinosoma Paracarcinosoma[a] Eocarcinosoma Rhinocarcinosoma Lanarkopterus Mixopterus Echinognathus Megalograptus Holmipterus Salteropterus[b] Carcinosomatid eurypterids such as Eocarcinosoma were among the most marine eurypterids, with the fossil deposits that yielded Eocarcinsoma at one point having been a marginal marine (influenced by both salt and fresh water, such as a lagoon or delta) environment.