Xiphosura
Guides
Limulidae
Horseshoe Crabs
Limulidae is a family of marine arthropods comprising four extant species: Limulus polyphemus in North America and three Indo-Pacific species (Tachypleus tridentatus, T. gigas, and Carcinoscorpius rotundicauda). These organisms possess a distinctive horseshoe-shaped prosoma, long telson, and compound eyes. Populations are declining globally, with T. tridentatus classified as Endangered by the IUCN. The family is notable for its ancient evolutionary lineage and biomedical importance due to hemolymph containing endotoxin-sensitive coagulation factors.