Ventral (left) and dorsal (right) views of Sphenorthis niagarensis, from Grubbs (1939).

Belongs within: Rhynchonelliformea.
Contains: Thecideida, Pentamerida, Rhynchonellida, Atrypida, Spiriferida, Terebratulida, Athyridida, Enteletacea, Orthacea.

The Rhynchonellata is the clade of brachiopods that includes all surviving articulate species. They are distinguished from other articulate brachiopods by the presence of a pedicle rudiment and projecting brachiophores (Williams et al. 1996). The pedicle opening is generally unrestricted in the Orthida and Pentamerida, but is restricted by deltidial plates in the more derived orders. These latter groups also developed a persistent non-fibrous primary layer in the shell. Members of the extinct orders Atrypida, Spiriferida and Athyridida are further characterised by the presence of spiral brachidia that would have supported the lophophore in life.

Characters (from Williams et al. 1996): Shells fibrous, endopunctate or impunctate, biconvex, strophic or astrophic, articulated by deltidiodont or cyrtomatodont teeth and sockets buttressed by brachiophores or supported by parallel socket or hinge plates that may converge to form septalium or cruralium; pedicle opening as delthyrium or rounded foramen; cardinal areas and notothyrium commonly vestigial or absent, wide in some later groups; dental plates less commonly converge to form spondylium; posteriomedial ventral adductor scars flanked or enclosed by ventral diductor and laterally placed adjustor scars; dorsal adductor scars petaloid or grouped and quadripartite; crura present in later groups and commonly extended as spiralia or loops; mantle canal systems variable as saccate, digitate, pinnate, or lemniscate impressions.

    |  i. s.: Thecideida F05
    |         Wangyuia EL11
    |         Sphenorthis Grubbs 1939 M65
    |           `--*S. niagarensis Grubbs 1939 M65
    |--+--Pentamerida P98
    |  `--+--Rhynchonellida P98
    |     `--+--Atrypida P98
    |        `--+--Spiriferida P98
    |           `--+--Terebratulida P98
    |              `--Athyridida P98
    `--Orthida [Orthidina, Orthoidea] P98
         |  i. s.: Glyptoria HP95
         |         Israeleria HP95
         |         Leioria HP95
         |         Minororthis Ivanov 1950 M65
         |           `--*M. malivkini Ivanov 1950 M65
         |         Wynnia Walcott 1908 M65
         |           `--*W. warthi (Walcott 1908) [=Orthis warthi] M65
         |         Yeosinella Reed 1932 M65
         |           `--*Y. consignata Reed 1932 M65
         |--Enteletacea WW65
         `--Orthacea WW65

*Type species of generic name indicated


[EL11] Erwin, D. H., M. Laflamme, S. M. Tweedt, E. A. Sperling, D. Pisani & K. J. Peterson. 2011. The Cambrian conundrum: early divergence and later ecological success in the early history of animals. Science 334: 1091–1097.

[F05] Fernández, J. 2005. Noticia de nuevos táxones para la ciencia en el ámbito Íbero-Balear y Macaronésico. Nuevos táxones animales descritos en la península Ibérica y Macaronesia desde 1994 (IX). Graellsia 61 (2): 261–282.

Grubbs, D. M. 1939. Fauna of the Niagaran nodules of the Chicago area. Journal of Paleontology 13 (6): 543–560.

[HP95] Holmer, L. E., L. E. Popov, M. G. Bassett & J. Laurie. 1995. Phylogenetic analysis and ordinal classification of the Brachiopoda. Palaeontology 38: 713–741.

[M65] Moore, R. C. (ed.) 1965. Treatise on Invertebrate Paleontology pt H. Brachiopoda vol. 2. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas Press: Lawrence (Kansas).

[P98] Prothero, D. R. 1998. Bringing Fossils to Life: An introduction to paleobiology. WCB McGraw-Hill: Boston.

Williams, A., S. J. Carlson, C. H. C. Brunton, L. E. Holmer & L. Popov. 1996. A supra-ordinal classification of the Brachiopoda. Philosophical Transactions: Biological Sciences 351 (1344): 1171-1193.

[WW65] Williams, A., & A. D. Wright. 1965. Orthida. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt H. Brachiopoda vol. 1 pp. H299–H359. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas Press: Lawrence (Kansas).

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