Lingulata is a class of brachiopods, among the oldest of all brachiopods having existed since the Cambrian period. They are also among the most morphologically conservative of the brachiopods, having lasted from their earliest appearance to the present with very little change in shape. Shells of living specimens found today in the waters around Japan are almost identical to ancient Cambrian fossils.
Craniata is a class of brachiopods originating in the Cambrian period and still extant today. It is the only class within the subphylum Craniiformea, one of three major subphyla of brachiopods alongside linguliforms and rhynchonelliforms. Craniata is divided into three orders: the extinct Craniopsida and Trimerellida, and the living Craniida, which provides most information on their biology. Living members of the class have shells which are composed of calcite, though some extinct forms my have aragonite shells. The shells are inarticulate and are usually rounded in outline. There is no pedicle; the rear edge of the body cavity is a smooth and flat wall perforated by the anus. This class of brachiopods has an unsupported lophophore with only a single row of tentacles. In the absence of a pedicle, the shell is usually attached directly to a hard substrate. Many craniiforms are encrusting animals which attach directly to the shell of another animal, usually another brachiopod. The plicae from the host brachiopod will then appear within the shell of the craniiform.
Terebratulids are one of only three living orders of articulate brachiopods, the others being the Rhynchonellida and the Thecideida. Craniida and Lingulida include living brachiopods, but are inarticulates. The name, Terebratula, may be derived from the Latin "terebra", meaning "hole-borer". The perceived resemblance of terebratulid shells to ancient Roman oil lamps gave the brachiopods their common name "lamp shell".
Orthida is an extinct order of brachiopods which appeared during the Early Cambrian period and became very diverse by the Ordovician, living in shallow-shelf seas. Orthids are the oldest member of the subphylum Rhynchonelliformea, and is the order from which all other brachiopods of this group stem. Physically they are usually strophic, with well-developed interareas. They also commonly have radiating ribs, sulcus, and fold structures. Typically one valve, often the brachial valve, is flatter than the other. The interior structure of the brachial valves are usually simple. In shape they are sub-circular to elliptical, with typically biconvex valves.
A valve is each articulating part of the shell of a mollusc or another multi-shelled animal such as brachiopods and some crustaceans. Each part is known as a valve or in the case of chitons, a "plate". Members of two classes of molluscs, the Bivalvia (clams) and the Polyplacophora (chitons), have valves.
Strophomenida is an extinct order of articulate brachiopods which lived from the lower Ordovician period to the mid Carboniferous period. Strophomenida is part of the extinct class Strophomenata, and was the largest known order of brachiopods, encompassing over 400 genera. Some of the largest and heaviest known brachiopod species belong to this class. Strophomenids were among the most diverse and abundant brachiopods during the Ordovician, but their diversity was strongly impacted at the Late Ordovician mass extinction. Survivors rediversified into new morphologies in the Silurian, only to be impacted once again at the Late Devonian mass extinction. However, they still survived till the mid Carboniferous.
Brachiopods, phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection. Two major categories are traditionally recognized, articulate and inarticulate brachiopods. The word "articulate" is used to describe the tooth-and-groove structures of the valve-hinge which is present in the articulate group, and absent from the inarticulate group. This is the leading diagnostic skeletal feature, by which the two main groups can be readily distinguished as fossils. Articulate brachiopods have toothed hinges and simple, vertically oriented opening and closing muscles. Conversely, inarticulate brachiopods have weak, untoothed hinges and a more complex system of vertical and oblique (diagonal) muscles used to keep the two valves aligned. In many brachiopods, a stalk-like pedicle projects from an opening near the hinge of one of the valves, known as the pedicle or ventral valve. The pedicle, when present, keeps the animal anchored to the seabed but clear of sediment which would obstruct the opening.
The origin of the brachiopods is uncertain; they either arose from reduction of a multi-plated tubular organism, or from the folding of a slug-like organism with a protective shell on either end. Since their Cambrian origin, the phylum rose to a Palaeozoic dominance, but dwindled during the Mesozoic.
Rhynchonelliformea is a major subphylum and clade of brachiopods. It is roughly equivalent to the former class Articulata, which was used previously in brachiopod taxonomy up until the 1990s. These so-called articulated brachiopods have many anatomical differences relative to "inarticulate" brachiopods of the subphyla Linguliformea and Craniformea. Articulates have hard calcium carbonate shells with tongue-and-groove hinge articulations and separate sets of simple opening and closing muscles.
The Rhynchonellata is a class of Lower Cambrian to Recent articulate brachiopods that combines orders from within the Rhynchonelliformea with well developed pedicle attachment. Shell forms vary from those with wide hinge lines to beaked forms with virtually no hinge line and from generally smooth to strongly plicate. Most all are biconvex. Lophophores vary and include both looped and spiraled forms. Although morphologically distinct, included orders follow a consistent phylogenetic sequence.
Pentamerida is an order of biconvex, impunctate shelled, articulate brachiopods that are found in marine sedimentary rocks that range from the Middle Cambrian through the Devonian.
Sharpirhynchia sharpi is a species of extinct, small-sized lampshell, named after Samuel Sharp (1814–1882), an early fossil collector, who discovered the limited time span of some fossils, now known as index fossils. S. sharpi is a marine rhynchonellate brachiopod in the family Rhynchonellidae. It is roughly ½ inch (1.25 cm) measured along the axis, with a slender beak, the brachial valve more convex than the pedunculate valve, and it has 21–31 ribs fanning out from the hinge.
Rhynchonelloidella alemanica is a species of extinct, small-sized brachiopod, a marine rhynchonellate lampshell in the family Rhynchonellidae. It is roughly 1.4 cm (0.55 in), and has about 15 ribs fanning out from the hinge.
Paterinata is an extinct class of linguliform brachiopods which lived from the lower Cambrian ("Tommotian") to the Upper Ordovician (Hirnantian). It contains the single order Paterinida and the subfamily Paterinoidea. Despite being some of the earliest brachiopods to appear in the fossil record, paterinides stayed as a relatively subdued and low-diversity group even as other brachiopods diversified later in the Cambrian and Ordovician. Paterinides are notable for their high degree of convergent evolution with rhynchonelliform (articulate) brachiopods, which have a similar set of muscles and hinge-adjacent structures.
Cyrtospirifer is an extinct genus of brachiopods. The fossils are present in the Middle and Upper Devonian.
Argyrotheca is a genus of very small to minute lampshells. All species share a large pedicel opening, one ridge on the inside of the pedunculate valve, pits in a diamond pattern on the inside of both valves, and without radial ridges that end in tubercles. It occurs in depths between 6 and 1300 m. It is known since the latest Cretaceous.
Kutorginates (Kutorginata) are an extinct class of early rhynchonelliform ("articulate") brachiopods. The class contains only a single order, Kutorginida (kutorginides). Kutorginides were among the earliest rhynchonelliforms, restricted to the lower-middle part of the Cambrian Period.
The orthotetides (Orthotetida) are an extinct order of brachiopods in the class Strophomenata. Though not particularly diverse or abundant relative to strophomenides (Strophomenida) or productides (Productida), orthotetides were nevertheless the longest-lasting order of strophomenates, surviving from the Middle Ordovician (“Llanvirn”) up until the Late Permian. Externally, many orthotetides are difficult to distinguish from strophomenides. Most fundamental differences between the two orders are internal: orthotetides have more elaborate cardinal processes and a greater diversity of shell microstructure.
Askerina is an extinct genus of atrypid brachiopods from subfamily Atrypinae that lived in end-Ordovician (Hirnantian) and Silurian (Aeronian). The type and only known species is Askerina cymbula. Its fossils are known only from the lower parts of the Solvik Formation in central Oslo region, Norway.
Jaffaia is a monotypic genus of brachiopods belonging to the family Dallinidae. The only species is Jaffaia jaffaensis from southern Australia. The species was described by Blochmann in 1910 and recently re-described in the Australian Journal of Taxonomy.
