Cephalocarida is a class inside the subphylum Crustacea that comprises only about 9 shrimp-like benthic species. They were discovered in 1955, and are commonly referred to as horseshoe shrimps. Although a second family, Lightiellidae, is sometimes used, all cephalocarids are generally considered to belong in just one family: Hutchinsoniellidae. Even though there is no fossil record of cephalocarids, most specialists believe them to be primitive among crustaceans. See genus (mathematics) for the use of the term in mathematics. ... The term class, when used by itself, has several meanings in English. ... In biology, a subphylum is a taxonomic grade intermediate between phylum and superclass. ... Classes Remipedia Cephalocarida Branchiopoda Ostracoda Maxillopoda Malacostraca The crustaceans (Crustacea) are a large group of arthropods (55,000 species), usually treated as a subphylum. ... Superfamilies Alpheoidea Atyoidea Bresilioidea Campylonotoidea Crangonoidea Galatheacaridoidea Nematocarcinoidea Oplophoroidea Palaemonoidea Pandaloidea Pasiphaeoidea Physetocaridoidea Procaridoidea Processoidea Psalidopodoidea Stylodactyloidea True shrimp are small, swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. ... In biology, a species is a kind of organism. ... 1955 is a common year starting on Saturday of the Gregorian calendar. ... A fossil Ammonite Fossils are the mineralized remains of animals or plants or other traces such as footprints. ...

Description and anatomy

The anatomy of cephalocarids is relatively simple, compared to that of other crustaceans. Their body is small (2 to 3.7 mm long) and elongate, comprising a head, an 8-segmented thorax with biramous appendages, and an 11-segmented abdomen which bears a telson but no other appendages. The second pair of maxillae closely resemble the appendages of the thorax. The eyes are very tiny and buried in the exoskeleton, which makes them appear eyeless. Anatomical drawing of the human muscles from the Encyclopédie. ... A millimetre (American spelling: millimeter, symbol mm) is an SI unit of length that is equal to one thousandth of a metre. ... Diagram of a tsetse fly, showing the head, thorax and abdomen The thorax is a division of an animals body that lies between the head and the abdomen. ... An appendage is, in general, an external body part that projects from the body, or a natural prolongation or projection from a part of any organism. ... The human abdomen (from the Latin word meaning belly) is the part of the body between the pelvis and the thorax. ... The telson is the last division of the body of a crustacean. ... The maxillae are the largest bones of the face, except for the mandible, and form, by their union, the whole of the upper jaw. ... An exoskeleton, in contrast to an endoskeleton, is an external anatomical feature that supports and protects an animals body. ...

Habitat

Cephalocarids are found from the intertidal zone down to a depth of 1500 m, in all kinds of sediments. The foreshore, also called the intertidal or littoral zone, is that part of a beach that lies between average high tide and average low tide. ... Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. ...

Feeding mode

Cephalocarids feed on marine detritus. To bring in food particles, they generate currents with the thoracic appendages like the branchiopods and the malacostracans. Food particles are then passed anteriorly along a ventral groove, leading to the mouthparts. Detritus may refer to: In geology, detritus is the name for loose fragments of rock that have been worn away by erosion. ... Orders not necessarily a complete list: Anostraca Notostraca Cladocera Conchostraca Branchiopoda is a group of primarily fresh water crustaceans, mostly resembling shrimp. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ...