Carcinosoma  Carcinosoma (meaning "crab body") is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of "Carcinosoma" are restricted to deposits of late Silurian (Late Llandovery to Early Pridoli) age. Classified as part of the family Carcinosomatidae, which the genus lends its name to, "Carcinosoma" contains seven species from North America and Great Britain. Carcinosomatid eurypterids had unusual proportions and features compared to other eurypterids, with a broad abdomen, thin and long tail and spined and forward-facing walking appendages. They were not as streamlined as other groups but had considerably more robust and well developed walking appendages. In "Carcinosoma", these spined walking appendages are thought to have been used to create a trap to capture prey in. The telson (final segment of the body) of "Carcinosoma" appears to have possessed distinct segmentation, "Carcinosoma" is the only known eurypterid to possess this feature. At in length, the species "C. punctatum" is the largest carcinosomatoid eurypterid by far and is among the largest eurypterids overall, rivalling the large pterygotid eurypterids (such as "Jaekelopterus") in size. Other species of the genus were considerably smaller, with most ranging from to in length. "Carcinosoma" was among the largest eurypterids, with isolated fossil remains consisting of a long metastoma (a plate overlaying the coxae of the first six appendages) of the species "C. punctatum" indicating a full length of . Fossil prosomal appendages (appendages attached to the head) referred to the species could possibly increase this estimate to an overall length of around . This massive size makes "C. punctatum" the largest of all known carcinosomatoid eurypterids and it rivals the largest pterygotid eurypterids, such as the long "Jaekelopterus", in size. Other species of "Carcinosoma" were smaller, most being in the range of to in length. Perhaps the most recognizable features of "Carcinosoma" are its spined appendages and its broad and flattened mesosoma (the first six segments of its abdomen).