|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Rhynchonellata - Orthida - Hesperorthidae
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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.
|A. Williams 1962||Subcircular, piano-convex Hesperorthis with pedicle valve less than one-third as deep as long, brachial valve commonly slightly convex umbonaUy and faintly sulcate antero-medianly, over three-quarters as long as wide; ornamented by a variable number (most commonly 26-30) of narrowly rounded costae with a wave-length of over 0.5 mm. at 5 mm. antero-median of the dorsal umbo, ventral muscle-scar subcordate, about as long as wide and extending anteriorly for about one-third the length of the pedicle valve.|