The subphylum Chelicerata constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, horseshoe crabs, and arachnids, as well as a number of extinct lineages, such as the eurypterids and chasmataspidids.
Amplexus is a type of mating behavior exhibited by some externally fertilizing species in which a male grasps a female with his front legs as part of the mating process, and at the same time or with some time delay, he fertilizes the eggs, as they are released from the female's body. In amphibians, females may be grasped by the head, waist, or armpits, and the type of amplexus is characteristic of some taxonomic groups.
The Atlantic horseshoe crab, also known as the American horseshoe crab, is a species of marine and brackish chelicerate arthropod. Despite their name, horseshoe crabs are more closely related to spiders, ticks, and scorpions than to crabs. It is found in the Gulf of Mexico and along the Atlantic coast of North America. The main area of annual migration is Delaware Bay along the South Jersey Delaware Bayshore.
Horseshoe crabs are marine and brackish water arthropods of the family Limulidae and the only living members of the order Xiphosura. Despite their name, they are not true crabs or crustaceans: they are chelicerates, most closely related to arachnids, such as spiders and scorpions.
Xiphosura is an order of arthropods related to arachnids. They are more commonly known as horseshoe crabs. They first appeared in the Hirnantian. Currently, there are only four living species. Xiphosura contains one suborder, Xiphosurida, and several stem-genera.
Limulus amebocyte lysate (LAL) is an aqueous extract of blood cells (amoebocytes) from the Atlantic horseshoe crab Limulus polyphemus. LAL reacts with bacterial endotoxin lipopolysaccharide (LPS), which is a membrane component of gram-negative bacteria. This reaction is the basis of the LAL test, which is widely used for the detection and quantification of bacterial endotoxins.
Mesolimulus is an extinct genus of horseshoe crab. The best known examples are found in Solnhofen limestone near Solnhofen, Bavaria, Germany. Originally assigned to the living genus Limulus, they are related to and look virtually identical to modern horseshoe crabs. Other species assigned to Mesolimulus have been recorded spanning over 140 million years from the Middle Triassic to Late Cretaceous from England, Spain, Siberia and Morocco.
The mangrove horseshoe crab, also known as the round-tailed horseshoe crab, is a chelicerate arthropod found in tropical marine and brackish waters in India, Bangladesh, Indonesia, Malaysia, Brunei, Singapore, Thailand, Cambodia, Vietnam, China and Hong Kong. It may also occur in Sri Lanka, Myanmar and the Philippines, but confirmed records are lacking.
Tachypleus is a genus of south, southeast and east Asian horseshoe crabs in the family Limulidae.
Mixopterus is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Mixopterus have been discovered in deposits from Late Silurian age, and have been referred to several different species. Fossils have been recovered from two continents; Europe and North America.
Campylocephalus is a genus of eurypterid, a group of extinct aquatic arthropods. Fossils of Campylocephalus have been discovered in deposits ranging from the Carboniferous period in the Czech Republic to the Permian period of Russia. The generic name is composed of the Greek words καμπύλος (kampýlos), meaning "curved", and κεφαλή (kephalē), meaning "head".
Salteropterus is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Salteropterus have been discovered in deposits of Late Silurian age in Britain. Classified as part of the family Slimonidae, the genus contains one known valid species, S. abbreviatus, which is known from fossils discovered in Herefordshire, England, and a dubious species, S. longilabium, with fossils discovered in Leintwardine, also in Herefordshire. The generic name honours John William Salter, who originally described S. abbreviatus as a species of Eurypterus in 1859.
Bembicosoma is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Bembicosoma was regarded as part of the clade Planaterga. Fossils of the single and type species, B. pomphicus, have been discovered in deposits of the Silurian period in the Pentland Hills, Scotland. Bembicosoma had been tentatively assigned as an eurypterid before its synziphosurine affinities revealed.
Bunaia is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Bunaia was tentatively placed as part of the clade Planaterga. The genus contains at least one species: Bunaia woodwardi from the Silurian period in Svalbard, Norway. Only a few morphological information of B. woodwardi had been confirmed, as the species known only from poorly preserved specimens compose of semicircular carapace, fragments of opisthosoma and disarticulated telson. The placement of "Bunaia" heintzi within this genus had been questioned and required further investigation.
Bunodes is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Bunodes was regarded as part of the clade Planaterga. Fossils of the single and type species, B. lunula, have been discovered in deposits of the Silurian period in Ludlow, England. Bunodes is the type genus of the family Bunodidae, the other genera of the same family being Limuloides.
Cyamocephalus is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Cyamocephalus was regarded as part of the clade Planaterga. Fossils of the single and type species, C. loganensis, have been discovered in deposits of the Silurian period in Lesmahagow, Scotland. Cyamocephalus is one of the two members of the family Pseudoniscidae, the other being Pseudoniscus. Cyamocephalus differ from Pseudoniscus by the fused tergites of 6th and 7th opisthosomal segments.
Pseudoniscus is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Pseudoniscus was regarded as part of the clade Planaterga. Fossils of the genus have been discovered in deposits of the Silurian period in the United Kingdom, the United States and Estonia. Pseudoniscus is one of the two members of the family Pseudoniscidae, the other being Cyamocephalus.
Tachypleus gigas, commonly known as the Indo-Pacific horseshoe crab, Indonesian horseshoe crab, Indian horseshoe crab, or southern horseshoe crab, is one of the four extant (living) species of horseshoe crab. It is found in coastal water in South and Southeast Asia at depths to 40 m (130 ft). It grows up to about 50 cm (20 in) long, including the tail, and is covered by a sturdy carapace that is up to about 26.5 cm (10.4 in) wide.
Venustulus is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Venustulus was regarded as part of the clade Prosomapoda. Fossils of the single and type species, V. waukeshaensis, have been discovered in deposits of the Silurian period in Wisconsin, in the United States. Venustulus is one of the few synziphosurine genera with fossil showing evidence of appendages, the other ones being Weinbergina, Anderella and Camanchia. Despite often being aligned close to Horseshoe crabs, it has been found that Venustulus and its relatives form a group made up of various basal euchelicerate arthropods more distant to the xiphosurans.
H. Jane Brockmann is an emeritus professor at the University of Florida known for her research on animal behavior, especially in the mating and nesting behavior of horseshoe crabs. In 2008, she was elected a fellow of the American Association for the Advancement of Science.
