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.
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.
Reptantia is a clade of decapod crustaceans named in 1880 which includes lobsters, crabs and many other well-known crustaceans.
Pleocyemata is a suborder of decapod crustaceans, erected by Martin Burkenroad in 1963. Burkenroad's classification replaced the earlier sub-orders of Natantia and Reptantia with the monophyletic groups Dendrobranchiata (prawns) and Pleocyemata. Pleocyemata contains all the members of the Reptantia, as well as the Stenopodidea, and Caridea, which contains the true shrimp.
The Achelata is an infra-order of the decapod crustaceans, holding the spiny lobsters, slipper lobsters and their fossil relatives.
Anomura is a group of decapod crustaceans, including hermit crabs and others. Although the names of many anomurans include the word crab, all true crabs are in the sister group to the Anomura, the Brachyura.
Astacidea is an infraorder of decapod crustaceans including lobsters, crayfish, and their close relatives.
Thalassinidea is a former infraorder of decapod crustaceans that live in burrows in muddy bottoms of the world's oceans. In Australian English, the littoral thalassinidean Trypaea australiensis is referred to as the yabby, frequently used as bait for estuarine fishing; elsewhere, however, they are poorly known, and as such have few vernacular names, "mud lobster" and "ghost shrimp" counting among them. The burrows made by thalassinideans are frequently preserved, and the fossil record of thalassinideans reaches back to the late Jurassic.
Glypheidea is an infraorder of lobster-like decapod crustaceans, comprising a number of fossil forms and the two extant (living) genera Neoglyphea and Laurentaeglyphea: The infraorder was thought to be extinct until a living species, Neoglyphea inopinata, was discovered in 1975. They are now considered "living fossils", with over 256 fossil species discovered, and just two extant species.
Axiidea is an infraorder of decapod crustaceans. They are colloquially known as mud shrimp, ghost shrimp, or burrowing shrimp; however, these decapods are only distantly related to true shrimp. Axiidea and Gebiidea 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.
Cyclodorippoida is a group of crabs, ranked as a section. It contains the single superfamily Cyclodorippoidea, which holds three families, Cyclodorippidae, Cymonomidae and Phyllotymolinidae.
Upogebiidae is a family of mud shrimp crustaceans belonging to the infraorder Gebiidea, within the order Decapoda. They are infauna, living their entire adult lives in seafloor burrows. Over 100 species have been identified, with different species often highly specialized for different types of substrate, even including sea sponges or coral. They are filter feeders, although some species also deposit feed.
Dromioidea is a superfamily of crabs mostly found in Madagascar. Dromioidea belongs the group Dromiacea, taxonomically ranked as a section, which is the most basal grouping of Brachyura crabs. Dromiacea likely diverged from the rest of Brachyura around the Late Triassic or Early Jurassic, and the earliest fossils attributable to the Dromioidea date from the Late Jurassic.
Polychelida is an infraorder of decapod crustaceans. Fossil representatives are known dating from as far back as the Upper Triassic. A total of 38 extant species, all in the family Polychelidae, and 55 fossil species have been described.
Eubrachyura is a group of decapod 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 eubrachyura is well known for actively and constantly building its own burrows. The fossil record of the Eubrachyura extends back to the Cretaceous; the supposed Bathonian representative of the group, Hebertides jurassica, ultimately turned out to be Cenozoic in age.
Palaemonoidea is a large superfamily of shrimp, containing nearly 1,000 species. The position of the family Typhlocarididae is unclear, although the monophyly of a group containing the remaining seven families is well supported.
Gourretiidae is a family of crustaceans belonging to the infraorder Axiidea, within the order Decapoda.
Laomediidae is a family of mud shrimp crustaceans belonging to the infraorder Gebiidea, within the order Decapoda.
Axianassidae is a family of mud shrimp crustaceans belonging to the infraorder Gebiidea, within the order Decapoda.
Callianideidae is a family of crustaceans belonging to the infraorder Axiidea, within the order Decapoda.
