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Rhynchonellata - Orthida - Draboviidae

Diorthelasma was named by Cooper (1956) [Sepkoski's age data: O Cara-l Sepkoski's reference number: 1].

It was assigned to Schizophoriinae by Cooper (1956); to Draboviinae by Williams et al. (2000); and to Orthida by Sepkoski (2002).

Synonymy list
YearName and author
1956Diorthelasma Cooper pp. 996 - 997
2000Diorthelasma Williams et al. p. 826
2002Diorthelasma Sepkoski, Jr.

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phylumBrachiopodaCuvier 1805
subphylumRhynchonelliformeaWilliams et al. 1996
classRhynchonellataWilliams et al. 1996
orderOrthidaSchuchert and Cooper 1932
suborderDalmanellidinaMoore 1952
superfamilyEnteletoideaWaagen 1884
familyDraboviidaeHavlicek 1950
subfamilyDraboviinaeHavlicek 1950

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

G. A. Cooper 1956Shell minute, subrectangular in outline ; sides rounded; anterior commissure strongly sulcate; unequally biconvex, the pedicle valve much deeper than the brachial valve. Surface somewhat distantly costellate. Punctate?

Pedicle valve with small teeth, curved and apsacline interarea, and· small, incurved beak. Delthyrium partially closed by lateral plates.

Dental plates receding, short, divergent. Delthyrial cavity shallow; muscle field wide and short, with large diductor scars and short, narrow adductors; floor of muscle field thickened. Vascula media strongly divergent when visible.

Brachial valve with shallow and narrow notothyrial cavity bounded by slightly divergent or slightly convergent, erect brachiophore supporting plates ; brachiophores long and slender; fulcral plates rudimentary; cardinal process varying from a slender ridge to a thick triangular boss filling the notothyrial cavity. Adductor scars small, elongate, the posterior pair located outside the anterior pair ; no median ridge.