Ciurcopterus is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Ciurcopterus have been discovered in deposits of Late Silurian age in North America. Classified as part of the family Pterygotidae, the genus contains two species, C. sarlei from Pittsford, New York and C. ventricosus from Kokomo, Indiana. The genus is named in honor of Samuel J. Ciurca, Jr., who has contributed significantly to eurypterid research by discovering a large amount of eurypterid specimens, including the four specimens used to describe Ciurcopterus itself.

Slimonidae is a family of eurypterids, an extinct group of aquatic arthropods. Slimonids were members of the superfamily Pterygotioidea and the family most closely related to the derived pterygotid eurypterids, which are famous for their cheliceral claws and great size. Many characteristics of the Slimonidae, such as their flattened and expanded telsons, support a close relationship between the two groups.