Eocarcinosoma

Eocarcinosoma is a genus of eurypterid, an extinct group of aquatic arthropods. The type and only species of Eocarcinosoma, E. batrachophthalmus, is known from deposits of Late Ordovician age in the United States. The generic name is derived from the related genus Carcinosoma, and the Greek () meaning 'dawn', referring to the earlier age of the genus compared to other carcinosomatid eurypterids.

Eocarcinosoma is known only from a single specimen, a well-preserved small prosoma (head). In life it would have been a very small eurypterid, given that the head measures just 2.05 centimetres (0.8 in) in length. The main distinguishing features from other carcinosomatids were the eyes being placed on the margins of the carapace (head plate) and the head being more triangular in shape than in its later relatives. Although initially believed to be an adult given the relatively small size of the eyes, some researchers believe Eocarcinosoma to represent a juvenile specimen of the eurypterid Megalograptus.