Carcinosomatidae

Carcinosomatidae (the name deriving from the type genus Carcinosoma, meaning "crab body") is a family of eurypterids, an extinct group of aquatic arthropods. They were members of the superfamily Carcinosomatoidea, also named after Carcinosoma. Fossils of carcinosomatids have been found in North America, Africa, Europe and Asia, the family possibly having achieved a worldwide distribution, and range in age from the Early Ordovician to the Early Devonian. They were among the most marine eurypterids, known almost entirely from marine environments.

Carcinosomatids varied considerably in size, from species only a few centimetres in length to some of the largest known arthropods. The largest carcinosomatid species, Carcinosoma punctatum, reached lengths of at least and rivalled the largest eurypterid of all, Jaekelopterus, in size. Morphologically, carcinosomatids were highly distinct from other eurypterids, known for their powerful and spiny set of forelimbs, a broad and rounded central body and a slender and tubular tail ending in a telson (the posteriormost division of the body) that was typically curved in some way. With these adaptations, the carcinosomatids were quite similar to scorpions, and the group may have helped contribute to the common name of eurypterids becoming 'sea scorpions'. The family contains five, possibly six, genera: Carcinosoma, Eusarcana, Rhinocarcinosoma, Cruinnopterus, Tigrisopterus, and possibly the problematic genus Holmipterus.