Malacostraca is the second largest of the six classes of pancrustaceans just behind hexapods, containing about 40,000 living species, divided among 16 orders. Its members, the malacostracans, display a great diversity of body forms and include crabs, lobsters, crayfish, shrimp, krill, prawns, woodlice, amphipods, mantis shrimp, tongue-eating lice and many other less familiar animals. They are abundant in all marine environments and have colonised freshwater and terrestrial habitats. They are segmented animals, united by a common body plan comprising 20 body segments, and divided into a head, thorax, and abdomen.
Sea spiders are marine arthropods of the order Pantopoda, belonging to the class Pycnogonida, hence they are also called pycnogonids. They are cosmopolitan, found in oceans around the world. The over 1,300 known species have leg spans ranging from 1 mm (0.04 in) to over 70 cm (2.3 ft). Most are toward the smaller end of this range in relatively shallow depths; however, they can grow to be quite large in Antarctic and deep waters.
Colossendeidae is a family of sea spiders. This family includes more than 100 species distributed among six genera. These sea spiders inhabit the deep sea mostly but are also found in shallower waters, especially in Antarctic and Arctic waters.
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa, trochanter, femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus, patella.
Nymphonidae is a family of sea spiders which has representatives in all the oceans. This family contains some 250 species, most of which are found in the genus Nymphon. Nymphonid bodies are between 1 and 15 mm long, the extent between the points of the legs reaching 150 mm. Most species are predators of hydroids. Like most sea spiders, species in this family have four pairs of legs, except for Pentanymphon antarcticum, which has five pairs, and Sexanymphon mirabilis, which has six pairs.
Nymphon is a genus of sea spiders in the family Nymphonidae. The species of sea spiders within the genus Nymphon are all benthic organisms and are found in abyssal and bathyal areas of the ocean. This is a fully marine group and can be found at various depths ranging from the littoral zones to the deep sea. They are found in most major oceans across the globe with a strong distribution around polar regions: Arctic and Antarctic waters. Out of the sea spider genus, Nymphon is the most rich, with a majority of the species within the genis being found in the Southern Ocean region. This genus may also contain bioluminescent species.
Pycnogonidae is a family of sea spiders.
Pycnogonum is a genus of sea spiders in the family Pycnogonidae. It is the type genus of the family.
Nymphon gracile is a species of sea spider first described by William Elford Leach in 1863. The species highly resembles other members of the genus Nymphon, and species identification from morphological traits alone is, therefore, a complex task.
Colossendeis is a genus of sea spider belonging to the family Colossendeidae. Phylogenetic analysis based on molecular data indicates that this genus is paraphyletic with respect to the genera Decolopoda and Dodecolopoda, which are found to be nested within the genus Colossendeis in a phylogenetic tree.
Thiratoscirtus alveolus is a species of jumping spider in the genus Thiratoscirtus that lives in Nigeria. The species was first described in 2011 by Wanda Wesołowska and Russell-Smith. The holotype was found on Obudu Plateau, Cross River State at an altitude of 1,900 m (6,200 ft) above sea level. The spider is medium-sized, with a cephalothorax that is typically 2.8 mm long and an abdomen that is 2.8 mm in length. The body of the female is generally brown with a covering of delicate hairs. The mouthparts include powerful chelicerae with teeth that have multiple points and a short fang. It can be distinguished from other spiders in the genus by its copulatory organs, particularly the presence of two long and deep parallel troughs in the epigyne that lead to the gonopores. These are recalled in the name for the species, which can be translated "trough".
Callipallene is a genus of sea spiders in the family Callipallenidae. There are more than 30 described species in Callipallene.
Halonoproctidae is a family of mygalomorph spiders, split off from the family Ctenizidae in 2018. Species in the family are widely distributed in North and Central America, Australasia, Asia, southern Europe and North Africa. One species is recorded from Venezuela in South America. They are relatively large, sombrely coloured spiders, that live in burrows with some kind of trapdoor.
Palaeoisopus is a monotypic genus of fossil pycnogonid, known only by one species, Palaeoisopus problematicus, discovered from the Lower Devonian Hunsrück Slate of Germany. It have several characters unusual for a pycnogonid, such as swimming legs with alternating size, medially-arranged eyes, and most significantly, a long, segmented abdomen, which were highly reduced in modern counterparts.
Colossendeis colossea is a species of sea spider in the family Colossendeidae. The species was first described by Edmund B. Wilson in 1881. It is the largest pycnogonid species known to science, reaching a leg span of 70 cm (28 in). Body length, including proboscis and abdomen, can reach 7 cm (2.8 in).
Propallene longiceps is a species of sea spider in the family Callipallenidae. It is found in shallow water in the western Pacific Ocean.
Colossendeis proboscidea is a species of sea spider in the family Colossendeidae. It is native to the Arctic and northeast Atlantic.
Decolopoda is a genus of sea spider belonging to the family Colossendeidae. This genus includes two valid species, D. australis and D. qasimi. As the name of this genus implies, these two species are among the seven species of sea spider with five pairs of legs instead of the usual four leg pairs. The species D. australis is notable as the first polymerous sea spider to be discovered.
