|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Orthothecida - Tetrathecidae
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||Conch transverse section trapezoidal, dorsum with two keels separating median and two lateral facets and with median facet planar to convex, venter concave; external sculpture absent on dorsum, absent or of transverse rugae or venter|