|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Rhynchonellata - Orthida - Dalmanellidae
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 1963||Subcircular to subquadrate unequally biconvex Onniella with sulcate brachial valve about three-quarters as long as wide and about one-seventh as deep as long and evenly convex pedicle valve over one-quarter as deep as long ; radial ornamentation rather coarsely fascicostellate with modal count of 3 costellae per mm., 5 mm. anterior of dorsal umbo, external branching freely developed in sectors I to IV ; dental lamellae divergent, short, less than one-quarter as long as pedicle valve, teeth massive, crenulated ; adult ventral muscle field subpentagonal, less than two-fifths as long as pedicle valve and over four-fifths as wide as long with submedian diductor lobes extending beyond but not enclosing lanceolate adductor scar ; cardinalia massive, less than one-fifth as long as brachial valve and less than one-half as long as wide, consisting of thick cardinal process commonly bilobed and filling entire notothyrium even in young growth stages and divergent brachiophores so exaggerated by secondary shell deposition in adult shells as to form a solid transverse bar ankylosed with thickened median ridge, adductor scars, subquadrate with posterior and anterior elements subequal, divided by the median ridge and extending forward for over one-half the length of brachial valve.|