|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Strophomenata - Billingsellida - Billingsellidae
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.
|J. R. Laurie 1997||Concavoconvex, outline transversely semiovate to rounded-quadrate, ornament unequally parvicostellate. Ventral interarea orthocline with apically perforate pseudodelfidium partly covering delthyrium. Dorsal interarea catacline to anacline, with large convex chilidium completely covering notothyrium. Ventral valve with subrhombic muscle field. Diductors subpyriform, distally separated by transversely rhombic adductor scar. Teeth small, dental plates weakly developed. Subperipheral rim well developed. Ventral mantle canal system digitate. Dorsal valve interior with broad median rise and well developed subperipheral rim. Socket ridges nearly straight, cardinal process a thin blade. Posterior adductor scars large, anterior adductor scars small. Vascular canal system digitate, unusual in having blind vascula myaria.|