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Superregnum: Eukaryota
Regnum: Animalia
Phylum: Brachiopoda
Subphylum: Rhynchonelliformea
Classis:Rhynchonellata
Ordo: †Orthida
Familiae: Dalmanellidae - Orthidae

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.[1] 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.

There is some debate over the forms that first appeared of this order as to how they should be classified. However, they began to differentiate themselves by the late Early Cambrian period, and by the late Cambrian period had diversified into numerous varieties and reach 2 to 5 cm in width. Specimens from the late Cambrian to the earliest Ordovician exhibit shells with rounded and pointed pedicle valves, with sharp to obtuse extremities and ridges that are fine to course. Punctate shells appear during the mid-Ordovician, which establish the suborder Dalmanellidina. The Ordovician is a productive period which gives rise to numerous genera in this order. However, they started to become greatly reduced by the end of the Ordovician extinction event. Both the impunctate and punctate survived through to the early Devonian Eventually, though, only the punctate lived on, and would play a minor role in benthic ecosystems until the late Permian, when they became extinct.[2]
Tropidoleptus carinatus, an orthid brachiopod from the Middle Devonian of New York.

Taxonomy

The taxonomy taken from the 2000 treatise[3] is as follows:
Suborder Orthidina

Superfamily Orthoidea
Family Orthidae
Family Anomalorthidae
Family Bohemiellidae
Family Glyptorthidae
Family Hesperonomiidae
Family Hesperorthidae
Family Lycophoriidae
Family Nanorthidae
Family Orthidiellidae
Family Plaesiomyidae
Family Poramborthidae
Family Productorthidae
Family Whittardiidae
Superfamily Plectorthoidea
Family Plectorthidae
Family Cremnorthidae
Family Cyclocoeliidae
Family Eoorthidae
Family Euorthisinidae
Family Finkelnburgiidae
Family Giraldiellidae
Family Phragmorthidae
Family Platystrophiidae
Family Ranorthidae
Family Rhactorthidae
Family Tasmanorthidae
Family Wangyuiidae

Suborder Dalmanellidina

Superfamily Dalmanelloidea
Family Dalmanellidae
Family Angusticardiniidae
Family Dicoelosiidae
Family Harknessellidae
Family Heterorthidae
Family Hypsomyoniidae
Family Kayserellidae
Family Mystrophoridae
Family Paurorthidae
Family Platyorthidae
Family Portranellidae
Family Proschizophoriidae
Family Rhipidomellidae
Family Tyronellidae
Superfamily Enteletoidea
Family Enteletidae
Family Draboviidae
Family Chrustenoporidae
Family Linoporellidae
Family Saukrodictyidae
Family Schizophoriidae

Notes

Patzkowsky, Mark E (2003). Orthida Archived 2007-03-12 at the Wayback Machine. McGraw-Hill Encyclopedia of Science & Technology Online. Retrieved on July 24, 2006.
Kazlev, M. Alan (1999). Order Orthida. Paleos, Invertebrates. Retrieved on July 24, 2006.
Williams, Alwyn; Carlson, S.J.; Brunton, C.H.C.; Holmer, L.E.; Popov, L.E.; Mergl, M.; Laurie, J.R.; Bassett, M.G.; Cocks, L.R.M.; Rong, J.-Y.; et al. (2000). Paul Selden (ed.). "Part H, Brachiopoda. Linguliformea, Craniiformea, and Rhynchonelliformea". Treatise on Invertebrate Paleontology. Geological Society of America.

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