The Caridea, commonly known as caridean shrimp or true shrimp, from the Greek word καρίς, καρίδος, are an infraorder of shrimp within the order Decapoda. This infraorder contains all species of true shrimp. They are found widely around the world in both fresh and salt water. Many other animals with similar names – such as the mud shrimp of Axiidea and the boxer shrimp of Stenopodidea – are not true shrimp, but many have evolved features similar to true shrimp.
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting tail-like abdomen, usually hidden entirely under the thorax. They live in all the world's oceans, in freshwater, and on land. They are generally covered with a thick exoskeleton. They generally have five pairs of legs, and they have pincer claws on the ends of the frontmost pair. They first appeared during the Jurassic period, around 200 million years ago.
The Decapoda or decapods are an order of crustaceans within the class Malacostraca, and includes crabs, lobsters, crayfish, shrimp, and prawns. Most decapods are scavengers. The order is estimated to contain nearly 15,000 extant species in around 2,700 genera, with around 3,300 fossil species. Nearly half of these species are crabs, with the shrimp and Anomura including hermit crabs, porcelain crabs, squat lobsters making up the bulk of the remainder. The earliest fossils of the group date to the Devonian.
Porcelain crabs are decapod crustaceans in the widespread family Porcellanidae, which superficially resemble true crabs. They have flattened bodies as an adaptation for living in rock crevices. They are delicate, readily losing limbs when attacked, and use their large claws for maintaining territories. They first appeared in the Tithonian age of the Late Jurassic epoch, 145–152 million years ago.
Astacidea is an infraorder of decapod crustaceans including lobsters, crayfish, and their close relatives.
The hairy stone crab is a crab-like anomuran crustacean that lives in the littoral zone of southern Australia from Bunbury, Western Australia, to the Bass Strait. It is the only species in the family Lomisidae. It is 1.5–2.5 cm (0.6–1.0 in) wide, slow-moving, and covered in brown hair which camouflages it against the rocks upon which it lives.
Maja is a genus of majid crabs erected by Jean-Baptiste Lamarck in 1801. It includes the following extant species:
Petrolisthes is a genus of marine porcelain crabs, containing these extant species:
The Paguridae are a family of hermit crabs of the order Decapoda. The king crabs, Lithodidae, are now widely understood to be derived from deep within the Paguridae, with some authors placing their ancestors within the genus Pagurus.
Neopetrolisthes maculatus is a species of porcelain crab from the Indo-Pacific region. It is a small, colourful crustacean with a porcelain-like shell. This porcelain crab is usually found within the stinging tentacles of a number of sea anemone species.
Galathea is a genus of squat lobsters in the family Galatheidae. It is one of the largest genera of squat lobsters that in 2008 contained 73 species. Most species of Galathea live in shallow waters.
Munidopsis is a genus of squat lobster. It is the second largest of all the genera of squat lobsters, after Munida, with over 200 species. Its members are mainly found on continental slopes and on abyssal plains. A few fossil species are also known, including specimens from the Campanian (Cretaceous).
Actumnus is a genus of crabs in the family Pilumnidae. Alongside the 28 extant species, it has a fossil record extending back into the Miocene.
Gebiidea is an infraorder of decapod crustaceans. Gebiidea and Axiidea are divergent infraoders of the former infraorder Thalassinidea. These infraorders have converged ecologically and morphologically as burrowing forms. Based on molecular evidence as of 2009, it is now widely believed that these two infraorders represent two distinct lineages separate from one another. Since this is a recent change, much of the literature and research surrounding these infraorders still refers to the Axiidea and Gebiidea in combination as "thalassinidean" for the sake of clarity and reference. This division based on molecular evidence is consistent with the groupings proposed by Robert Gurney in 1938 based on larval developmental stages.
Echinoecus pentagonus, the sea urchin crab, is a species of crab in the family Pilumnidae found from the Red Sea and East Africa to French Polynesia and the Hawaiian Islands. This crab is a parasite that lives in the rectum of a sea urchin. In Hawaii, it chooses only Echinothrix calamaris, leaving few of these urchins unpopulated. Its curved and pointed carapace reaches only 0.5 inches (1.3 cm) in width.
The Galatheoidea are a superfamily of decapod crustaceans comprising the porcelain crabs and some squat lobsters. Squat lobsters within the three families of the superfamily Chirostyloidea are not closely related to the squat lobsters within the Galatheoidea. The fossil record of the superfamily extends back to the Middle Jurassic genus Palaeomunidopsis.
Echinoecus is a genus of crabs that live in association with sea urchins. Formerly considered monotypic, the genus is now thought to contain three species:
Porcellana is a genus of decapod crustaceans in the widespread family Porcellanidae, the porcelain crabs, which superficially resemble true crabs. The genus Porcellana includes the following species:
Porcellana sayana is a species of porcelain crab that lives in the western Atlantic Ocean, often as a commensal of hermit crabs. It is red with white spots, and has a characteristic bulge behind each claw.
Polyonyx is a genus of porcelain crabs in the family Porcellanidae. There are at least 42 described species in Polyonyx.
