Belongs within: Dielasmatidae.
Dielasma is a genus of brachiopods known from the Upper Mississippian to the Permian (Muir-Wood et al. 1965).
Characters (Muir-Wood et al. 1965): Small to large; normally with dorsal fold, ventral sulcus and uniplicate anterior commissure but occasionally with folds anteriorly resulting in sulciplicate commissure; halves of cardinal plate separate or jointed near union with floor of valve; dental plates present.
<==Dielasma King 1859 [incl. Dielasmoides Weller 1914, Epithyris King 1850 non Phillips 1841]M-WS65
|--*D. elongatum (von Schlotheim 1816)M-WS65 (see below for synonymy)
|--D. acutangulum Waagen 1882 [incl. D. acutangulum var. minor Grabau 1931]G31
|--D. angustaG31
|--D. arcuatum [=Terebratula (Dielasma) arcuata]W77
|--D. bovidens (Morton 1836) [=Terebratula (Dielasma) bovidens; incl. T. geniculosa McChesney 1860]W77
|--D. breviplicatum Waagen 1882HB93
|--D. burlingtonensis (White 1860) [=Terebratula (Dielasma) burlingtonensis]W77
|--D. carinthiacumG31
|--D. curvatumG31
|--D. dieneriG31
|--D. ellipticaG31
|--D. giganteum Tschernyschew 1902 [incl. D. giganteum var. anteplicatum Grabau 1931]G31
|--D. hastata [=D. sacculum var. hastata; incl. D. hastata var. globosa Laseron 1910]F71
|--D. itaitubensis (Derby 1874) [=Terebratula itaitubense, D. itaitubense]DX84
|--D. jakowlewiG31
|--D. jisuense Grabau 1931G31
|--D. juresanenseG31
|--D. latouchiiG31
|--D. mapingensisG31
|--D. millepunctatum (Hall 1856) (see below for synonymy)G31
|--D. moelleriG31
|--D. mongolicum Grabau 1931 [=D. truncatum var. mongolicum]DX84
|--D. nikitiniG31
|--D. plicaG31
|--D. raraG31
|--D. rudisG31
|--D. sacculusG31
|--D. timanicum Tschernyschew 1902G31
|--D. toulaiG31
|--D. truncatum Waagen 1882 [incl. D. truncatum var. antecedens Grabau 1931]G31
`--D. zelandicaRW49
*Dielasma elongatum (von Schlotheim 1816)M-WS65 [=Terebratulites elongatusM-WS65, Epithyris elongatumG31, Terebratula elongataF71; incl. Terebratula complanatus Schlotheim 1816G31, Terebratula latus Schlotheim 1816G31, Dielasma elongatum var. orientalis Grabau 1931G31]
Dielasma millepunctatum (Hall 1856) [=Terebratula millepunctata; incl. D. darvasicum Tschernyschew 1914, D. millepunctatum var. mongolicum Grabau 1931 non D. truncatum var. mongolicum Grabau 1931]G31
*Type species of generic name indicated
References
[DX84] Ding Y., Xia G., Duan C., Li W., Liu X. & Liang Z. 1984. Study on the early Permian stratigraphy and fauna in Zhesi district, Nei Mongol Zizhiqu (Inner Mongolia). Bulletin of the Tianjin Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences 10: 1–244, 258 pls.
[F71] Fletcher, H. O. 1971. Catalogue of type specimens of fossils in the Australian Museum, Sydney. Australian Museum Memoir 13: 1–167.
[G31] Grabau, A. W. 1931. The Permian of Mongolia: A report on the Permian fauna of the Jisu Honguer limestone of Mongolia and its relations to the Permian of other parts of the world. American Museum of Natural History: New York.
[HB93] Harper, D. A. T., C. H. C. Brunton, L. R. M. Cocks, P. Copper, E. N. Doyle, A. L. Jeffrey, E. F. Owen, M. A. Parkes, L. E. Popov & C. D. Prosser. 1993. Brachiopoda. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 427–462. Chapman & Hall: London.
[M-WS65] Muir-Wood, H. M., F. G. Stehli, G. F. Elliott & K. Hatai. 1965. Terebratulida. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt H. Brachiopoda vol. 2 pp. H728–H857. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas Press: Lawrence (Kansas).
[RW49] Rout, M. V., & R. W. Willett. 1949. The geology of the Wairaki survey district, Southland. Transactions and Proceedings of the Royal Society of New Zealand 77 (2): 291–305.
[W77] White, C. A. 1877. Report upon the invertebrate fossils collected in portions of Nevada, Utah, Colorado, New Mexico, and Arizona, by parties of the expeditions of 1871, 1872, 1873, and 1874. U.S. Geographical Surveys West of the One Hundredth Meridian 4 (1): 1–219, pls 1–21.