|Leptograpsus variegatus , Grapsidae|
Thoracotremata is a clade of crabs, comprising those crabs in which the genital openings in both sexes are on the sternum, rather than on the legs. It comprises 17 families in four superfamilies .
A clade, also known as monophyletic group, is a group of organisms that consists of a common ancestor and all its lineal descendants, and represents a single "branch" on the "tree of life".
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen), usually entirely hidden under the thorax. They live in all the world's oceans, in fresh water, and on land, are generally covered with a thick exoskeleton and have a single pair of pincers. Many other animals with similar names – such as hermit crabs, king crabs, porcelain crabs, horseshoe crabs, and crab lice – are not true crabs.
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.
The Ocypodoidea, or ocypoid crabs, are a superfamily of crabs, named after the genus Ocypode. It contains over 300 extant species in these eight families:
The Camptandriidae are a family of crabs, with 38 species in 21 genera:
The Dotillidae are a family of crabs with 59 species, nearly half of which are in the genus Ilyoplax. The two genera Scopimera and Dotilla are collectively the sand bubbler crabs, which leave conspicuous collections of sand pellets on sandy beaches across the tropical and subtropical Indo-Pacific.
Cryptochiridae is a family of crabs known commonly as gall crabs or coral gall crabs. They live inside dwellings in corals and cause the formation of galls in the coral structure. The family is currently placed in its own superfamily, Cryptochiroidea.
The Grapsoidea are a superfamily of crabs; they are well known and contain many taxa which are terrestrial (land-living), semiterrestrial, or limnic. Another well-known member with a more conventional lifestyle is the Chinese mitten crab, Eriocheir sinensis.
The Gecarcinidae, the land crabs, are a family of true crabs that are adapted for terrestrial existence. Similar to all other crabs, land crabs possess a series of gills. In addition, the part of the carapace covering the gills is inflated and equipped with blood vessels. These organs extract oxygen from the air, analogous to the vertebrate lungs. Adult land crabs are terrestrial, but visit the sea periodically, where they breed and their larvae develop. Land crabs are tropical omnivores which sometimes cause considerable damage to crops. Most land crabs have one of their claws larger than the other.
Hermit crabs are decapod crustaceans of the superfamily Paguroidea.
The Selenopidae are a family of araneomorph spiders, sometimes called wall crab spiders, but also wall spiders and flatties. The Selenopidae are one of several families whose English name includes the phrase "crab spider".
Pagurus pollicaris is a hermit crab commonly found along the Atlantic coast of North America from New Brunswick to the Gulf of Mexico. It is known by a number of common names, including gray hermit crab, flat-clawed hermit crab, flatclaw hermit crab, shield hermit crab, thumb-clawed hermit crab, broad-clawed hermit crab, and warty hermit crab.
Horseshoe crabs are marine and brackish water arthropods of the family Limulidae, suborder Xiphosurida, and order Xiphosura. Their popular name is actually a misnomer, for they are not true crabs.
The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. The word cephalothorax is derived from the Greek words for head and thorax. This fusion of the head and thorax is seen in chelicerates and crustaceans; in other groups, such as the Hexapoda, the head remains free of the thorax. In horseshoe crabs and many crustaceans, a hard shell called the carapace covers the cephalothorax.
The decapod crustacean, such as a crab, lobster, shrimp or prawn, is made up of 20 body segments grouped into two main body parts, the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various groups these may be reduced or missing. They are, from head to tail:
The Crab Orchard Mountains are a rugged, detached range of the southern Cumberland Mountains. They are situated in East Tennessee atop the Cumberland Plateau just west of the plateau's eastern escarpment, and comprise parts of Morgan, Anderson, and Cumberland counties. The Crab Orchard Mountains have many peaks over 3,000 ft., with the highest being Big Fodderstack at 3,340 feet (1,020 m) and Frozen Head at 3,324 feet (1,013 m), the latter and part of the former being located in Frozen Head State Park. The mountains are made rugged by the erosion of many streams that have cut deep gorges into the mountains. The Crab Orchard Mountains are still one of the most rural areas in all of Appalachia.
Raninoida is a taxonomic section of the crabs, containing a single superfamily, Raninoidea. This group of crabs is unlike most, with the abdomen not being folded under the thorax. It comprises 46 extant species, and nearly 200 species known only from fossils.
Potamoidea is a superfamily of freshwater crabs, comprising the two families Potamidae and Potamonautidae. Two previously recognised families, Deckeniidae and Platythelphusidae, are now treated as parts of the family Potamonautidae.
She-crab soup is a rich soup, similar to bisque, made of milk or heavy cream, crab or fish stock, Atlantic blue crab meat, and (traditionally) crab roe, and a small amount of dry sherry added as it is plated. It may be thickened either by heat reduction or with a purée of boiled rice; it may also include such seasonings as mace and shallots or onions. The soup is a regional specialty from Tidewater, Virginia, the South Carolina Lowcountry and Georgia coast. It is commonly featured on the menus of many Charleston, South Carolina and Savannah, Georgia restaurants.
Xanthoidea is a superfamily of crabs, comprising the three families Xanthidae, Panopeidae and Pseudorhombilidae. Formerly, a number of other families were included in Xanthoidea, but many of these have since been removed to other superfamilies. These include Carpilioidea, Eriphioidea, Hexapodoidea, Pilumnoidea and Trapezioidea. Even in this reduced state, Xanthoidea remains one of the most species-rich superfamilies of crabs.
The Majoidea are a superfamily of crabs which includes the various spider crabs.
Potamonautidae is a family of freshwater crabs endemic to Africa, including the islands of Madagascar, the Seychelles, Zanzibar, Mafia, Pemba, Bioko, São Tomé, Príncipe and Sherbro Island. It comprises 18 extant genera and 138 extant species. Fossil remains dating from the Late Miocene period have been attributed to the family Potamonautidae.
Homolodromiidae is a family of crabs, the only family in the superfamily Homolodromioidea. In contrast to other crabs, including the closely related Homolidae, there is no strong linea homolica along which the exoskeleton breaks open during ecdysis. The family comprises two genera, Dicranodromia, which has 18 species, and Homolodromia, with five species.
The coconut crab is a species of terrestrial hermit crab, also known as the robber crab or palm thief. It is the largest land-living arthropod in the world, and is probably at the upper size limit for terrestrial animals with exoskeletons in recent times, with a weight up to 4.1 kg (9.0 lb). It can grow to up to 1 m in length from leg to leg. It is found on islands across the Indian Ocean, and parts of the Pacific Ocean as far east as the Gambier Islands and Pitcairn Islands, mirroring the distribution of the coconut palm; it has been extirpated from most areas with a significant human population, including mainland Australia and Madagascar.
Eubrachyura is a group of crustaceans comprising the more derived crabs. It is divided into two subsections, based on the position of the genital openings in the two sexes. In the Heterotremata, the openings are on the legs in the males, but on the sternum in females, while in the Thoracotremata, the openings are on the sternum in both sexes. This contrasts with the situation in other decapods, in which the genital openings are always on the legs. Heterotremata is the larger of the two groups, containing the species rich superfamilies Xanthoidea and Pilumnoidea and all the freshwater crabs. The fossil record of Eubrachyura extends back to the Cretaceous; the supposed Bathonian representative of the group, Hebertides jurassica, ultimately turned out to be Cenozoic in age.
Heterotremata is a clade of crabs, comprising those crabs in which the genital openings are on the sternum in females, but on the legs in males. It comprises 68 families in 28 superfamilies.
Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The larvae of crustaceans often bear little resemblance to the adult, and there are still cases where it is not known what larvae will grow into what adults. This is especially true of crustaceans which live as benthic adults, more so than where the larvae are planktonic and therefore more easily caught.
There are around 1,300 species of freshwater crabs, distributed throughout the tropics and subtropics, divided among eight families. They show direct development and maternal care of a small number of offspring, in contrast to marine crabs which release thousands of planktonic larvae. This limits the dispersal abilities of freshwater crabs, so they tend to be endemic to small areas. As a result, a large proportion are threatened with extinction.
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