Limulus polyphemus (Atlantic horseshoe crab) (Sanibel Island, Florida, USA) 1
Limulus polyphemus (Linnaeus, 1758) - Atlantic horseshoe crab in Florida, USA. (December 2013)
This is the only living species of Limulus. Several fossil species have been reported from the Mesozoic and Cenozoic. Limulus horseshoe crabs are not true crabs, which are decapod crustaceans. Horseshoe crabs are xiphosuran chelicerates. The exoskeleton is tripartite, consisting of a semicircular cephalon (head), also called the prosoma, a subtriangular opisthosoma that is bordered by a series of spines, and a large posterior spine called a telson.
The dead specimen shown above has a fractured cephalon.
Classification: Animalia, Arthropoda, Chelicerata, Merostomata, Xiphosura, Limulidae
Locality: Lighthouse Beach, near Sanibel Lighthouse, eastern end of Sanibel Island, southwestern Florida, USA