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Diorthelasma
Taxonomy
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).
It was assigned to Schizophoriinae by Cooper (1956); to Draboviinae by Williams et al. (2000); and to Orthida by Sepkoski (2002).
Species
Synonymy list
| Year | Name and author |
|---|---|
| 1956 | Diorthelasma Cooper pp. 996 - 997 |
| 2000 | Diorthelasma Williams et al. p. 826 |
| 2002 | Diorthelasma Sepkoski |
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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. †Diorthelasma Cooper 1956
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†Diorthelasma parvum Cooper 1956
†Diorthelasma semotum Baarli 1988
†Diorthelasma weissi Rice 1987
Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| G. A. Cooper 1956 | Shell 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. |