|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Rhynchonellata - Rhynchonellida - Orthorhynchulidae
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.
|H. J. Howe 1979||Shell subtriangular to occasionally subelliptical in outline; apical angle slightly more than 90°; sides broadly rounded; valves subequal in depth, the brachial valve deeper and showing greatest width at the middle; width somewhat exceeding length; hinge line short, averaging somewhat less than half of the shell width. Surface costate, ornamented with 3 costae in sulcus, 4 on the fold, and 7 to 13 on the flanks.
Pedicle valve gently to moderately convex in in lateral profile, displaying the greatest convexity between the umbo and the middle of the valve. Umbo swollen with moderately steep sides; flanks gently inflated. Sulcus originating in front of umbo and forming a mesial depression that increases in width to about one-half the shell width at the front. Interarea of pedicle valve short but well defined, averaging somewhat less than one-half the shell width; delthyrium large, open, with small apical foramen usually present through beak resorption.
Brachial valve moderately to strongly convex in lateral profile, displaying the greatest curvature in the posterior half. Umbo inflated, merging anteriorly with a fold which bears four costae, the lateral pair of which are weaker and lower than the median costae; fold becoming moderately elevated at the front and occupying about one-half the valve width. Flanks moderately convex. Dorsal interarea smaller than the ventral one and varying from about four- , tenths to one-half the valve width.