O. F. Müller, 1785
Species: L. polyphemus
The Atlantic horseshoe crab (Limulus polyphemus) is a marine chelicerate arthropod. Despite its name, it is more closely related to spiders, ticks, and scorpions than to crabs. Horseshoe crabs are most commonly found in the Gulf of Mexico and along the northern Atlantic coast of North America. A main area of annual migration is Delaware Bay, although stray individuals are occasionally found in Europe.
The other three extant species in the family Limulidae are also called horseshoe crabs. These are Tachypleus tridentatus, Tachypleus gigas and Carcinoscorpius rotundicauda, which all are restricted to Asia. All four are quite similar in form and behavior.
This group of animals is also known as horsefoot, or saucepan. Some people call the horseshoe crab a “helmet crab”, but this common name is more frequently applied to a true crab, a malacostracan, of the species Telmessus cheiragonus. The term “king crab” is sometimes used for horseshoe crabs, but it is more usually applied to a group of decapod crustaceans.
Limulus means “askew” and polyphemus refers to the giant in Greek mythology. It is based on the misconception that the animal had a single eye.
Former scientific names include Limulus cyclops, Xiphosura americana, and Polyphemus occidentalis.
It is the tail that earns this order its name Xiphosura, which derives from the Greek for ‘sword tail’.