|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Rhynchonellata - Orthida - Phragmorthidae
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.
|A. Williams 1962||Subrectangular, turgid Phragmorthis, with a pedicle valve, commonly slightly emarginate antero-medianly, attaining a maximum average depth of one-half the length just anterior to the long, curved, apsacline interarea; brachial valve strongly and uniformly convex laterally but deeply cleft by a narrow sulcus medianly, about two-thirds as long as wide; ornamentation finely multicostellate, varying from 5 to 9 costellae per millimetre antero-medianly with a mode of 7; median costa of pedicle valve commonly accentuated; cardinalia about one-third the length of the brachial valve; ventral muscle-scar deeply impressed, subtriangular in ventral outline, averaging less than one-third of the length of the pedicle valve.|
|C. M. O. Rasmussen et al. 2012||Shell strongly ventri-biconvex in profile and transverse to subcircular or subquadrate in outline. Maximum width at hinge line; anterior commissure weakly sulcate. Ventral valve unevenly convex, almost triangular to subpyramidal with marked umbo posterior to hinge line. Interarea high, catacline to weakly apsacline; delthyrium high and narrow. Dorsal valve moderately convex, sulcate; dorsal interarea high, wide and strongly anacline; notothyrium narrow. Ornamentation multicostellate with costellae sporadically swollen; concentric growth lines variably developed, increasing in number towards the anterior commissure.
Ventral interior with large deltidiodont teeth supported by dental plates that converge to form spondylium simplex. Dorsal interior lacking cardinal process, or with one very small ridge developed anteriorly on notothyrial platform. Brachiophores long with supporting plates converging to dorsal median septum, more elevated towards the anterior margin. Thin, deep grooves on valve floor.