Palaeos:		Rhynchonelliformea
Brachiopoda		Rhynchonellata

Class Rhynchonellata

This very diverse group includes the majority of articulate brachiopods, that is, brachiopods with a hinge between the two halves of the shell.  The rhynchonellates range in age from Early Cambrian to Recent.  Rhynchonellate shells are biconvex and articulated by teeth and sockets buttressed with brachiophores, as shown in the image of Alocorthis from Paterson & Brock (2003).  

Most rhynchonellates have a calcified brachidium of the spiriferid type.  The brachidium is a structure which supports the lophophore, the feeding organ of brachiopods.  A spiriferid brachidium is a sort of dual-spring shock absorber.  It consists of  two coiled structures, like bedsprings, which extend off to either side and are braced against the shell.  These brachidia give the lophophore of the rhynchonellates unmatched support and stability.  The diagram of this arrangement is from the University of Kansas Ancient Life site.

The following table lists the taxa which are usually included among the Rhynchonellata, with links to some of the excellent web materials on this taxon:

no image available yet
	Resserella from Nashville Fossils	Cyrtospirifer from Virtual Fossils (Univ. di Padua)	Pentamerus (source unknown)	Beecheria from Catnapin Fossil Gallery
Protorthida	Orthida	Spiriferida	Pentamerida	Terebratulida
Unidentified rhynchonellid in situ from Southern Arizona Fossils	Unidentified atrypid from the Ammonites Page (Wroclaw Univ.)	Composita from Paleobytes	Costispiriferina from Palfy (2003)	Thecidellina from Voskuil (1998)
Rhynchonellida	Atrypida	Athyridida	Spiriferidida	Thecideida

Links:

SYSTEMATICS- Invertebrate Paleontology Selected Classification of ...

Katedra biologie FPE ZCU v Plzni (Czech)

Ancient Life--13--Rhynchonellid Brachiopod: one of several pages on brachiopods, using a more traditional classification scheme

Early Ordovician orthide brachiopods: Full text of Paterson & Brock (2003).  

References:

Pálfy, J (2003), The Pelsonian brachiopod fauna of the Balaton Highland in A Vörös [ed.]. The Pelsonian Substage on the Balaton Highland (Middle Triassic, Hungary). Geol. Hung., Ser. Palaeontol. 55: 139-158.

Paterson, JR & GA Brock (2003), Early Ordovician orthide brachiopods from Mount Arrowsmith, northwestern New South Wales, Australia.  Rec. Aus. Mus. 55: 221-230.  

Voskuil, R (1998), On a small collection of Hawaiian Brachiopoda (Lophophorata).  Internet Haw. Shell News Nov, 1998: 2-13.  Republication.

 

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