|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Craniata - Trimerellida - Trimerellidae
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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. A. Cooper 1956||Exterior of shell not known ; length of beak not known ; shell evidently thin. Valves subequally convex. Impressions of the pedicle interior indicate a transversely oval outline ; lateral margins narrowly rounded ; anterior margin broadly rounded. Lateral and anterior profiles broadly convex and nearly equal; lateral slopes short and moderately steep ; median region depressed convex in anterior profile.
Pedicle interior with a moderately thickened, nonexcavated, diamond shaped muscle area ; sides of muscle area narrowly angulated in the middle ; anterior narrowly rounded. Individual scars not clear, but a depressed track extending from the apex to the anterior angle suggests the growth path of 2 unidentified muscles. Brachial muscle platform similar in outline to the pedicle one ; individual muscle marks not identifiable.
|A. Williams 1962||Pale-blue coloured, transversely oval and subequally biconvex OboMlina with an obtusely angular, slightly incurved umbo bearing a deep pedicle groove, just less than one-sixth as long as the pedicle valve, which is over three-quarters as long as wide and one-fifth as deep as long; brachial valve without conspicuous umbo, slightly greater than one-fifth as deep as long; ventral muscle-scar large and elevated, almost three-fifths as long as the valve and almost as wide as long, anterior border arcuate and slightly pointed medianly at its junction with a narrow median depression, dorsal muscle-scar also slightly raised and depressed medianly, nearly two-thirds as long as the valve and almost three-quarters as wide as long.|