|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||Age range and collections|
Orthothecida - Circothecidae
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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.
|P. D. Kruse 2002 (Larawidae)||Conch straight, may be slightly curved near apex; transverse section circular, oval, elliptical or oviform; sculpture of transverse growth lines, in some cases with longitudinal sculpture; dorsum and venter poorly differentiated, dorsoventral transition smooth|
|P. Y. Parkhaev and Y. Demidenko 2010||"Shell elongated with circular or slightly oval cross-section, straight or slightly bent. Differentiation of dorsal and ventral sides absent (in shells with circular cross-section) or faint (in shells with oval cross-section), in latter case dorsal side more convex. Shell ornamented by transversal ribs of similar prominence along shell perimeter."|