The Rhynchonellata is a class of

Lower Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago ...

Recent The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

articulate Articulate may refer to: * ''Articulate!'', a board game in which players describe words from different categories * Articulate brachiopods, brachiopods with toothed hinges and simple opening and closing muscles * Articulate sound, to move the ton ...

brachiopod 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, ...

s that combines orders from within the

Rhynchonelliformea Rhynchonelliformea is a major subphylum and clade of brachiopods. It is equivalent to the former class Articulata, which was used previously in brachiopod taxonomy. Articulate brachiopods have many anatomical differences relative to "inarticulat ...

(Articulata revised) 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.

Orders

Orders assigned to the Rhynchonellata, in temporal sequence, include: * Protorthida ''L Camb - U Dev'' *

Orthida 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 ord ...

''L Camb - U Perm'' *

Pentamerida 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.Moore, Lalcker and Fischer, 1952, Invertebrate Fossils, McGraw-Hil ...

''M Camb - U Dev'' * Atrypida ''L Ord - U Dev'' *

Rhynchonellida The taxonomic order Rhynchonellida is one of the two main groups of living articulate brachiopods, the other being the order Terebratulida. They are recognized by their strongly ribbed wedge-shaped or nut-like shells, and the very short hing ...

''L Ord -Rec'' *

Spiriferida Spiriferida is an order of extinct articulate brachiopod fossils which are known for their long hinge-line, which is often the widest part of the shell. In some genera (e.g. '' Mucrospirifer'') it is greatly elongated, giving them a wing-like ap ...

''U Ord - U Perm'' *

Athyridida Athyridida is an order of Paleozoic brachiopods included in the Rhynchonellata, which makes up part of the articulate brachiopods. The Athyridida are the Rostrospracea of R.C Moore, 1952,Moore, Lalcker and Fischer, 1952, Invertebrate Fossils, Mc ...

''U Ord - L Jura'' * Spiriferinida ''L Dev - L Jura'' *

Terebratulida 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 deriv ...

''L Dev - Rec'' * Thecideida ''U Trias - Rec'' The Atrypida, Athyridida, Spiriferida, and Spiriferinida were previously considered as suborders in the Spiriferida and in the

Treatise A treatise is a formal and systematic written discourse on some subject, generally longer and treating it in greater depth than an essay, and more concerned with investigating or exposing the principles of the subject and its conclusions." Treat ...

part H, all having coiled spiralia for lophophore support. In the other orders the supporting brachidia are commonly looped. The Orthida and Spiriferida have wide hinge lines where the two valves (or shells) articulate. The Pentamerida, Terebratulida, Atrypida and Athyridida have narrow hinge lines. Some, like the Rhynchonellida and Spiriferida, may be strongly plicate, with a median fold and sulcus. Others, like the Spiriferinida and Terebratulida are basically smooth. Most have shells without perforations known as punctae and are impunctate but some e.g. Orthida and Rhynchonellida have punctate offshoots.

References

External links

Rhynchonellata

Paleobiology Database
{{Taxonbar, from=Q276055 Protostome classes