?Early Ordovician, Middle Ordovician – Recent
Pholadomyoida is an extant order of facultatively mobile infaunal suspension feeders
Characteristics of the Order
- Relatively short to elongate
- Nestling to fossorial forms with ventrally fused mantle lobes
- Equivalve to subequivalve; generally approximately isomyarian
- Hinge margin characteristically thickened or enrolled, with lateral teeth absent
Treatise on Invertebrate Paleontology, Part N, Mollusca 6 (2 of 3) (1969):
- Ordinal characters same as those of subclass Anomalodesmata.
- (Characters of subclass) Relatively short to elongate, nestling to fossorial forms with ventrally fused mantle lobes; equivalve to subequivalve; generally approximately isomyarian; hinge margin characteristically thickened or enrolled, edentulous, or with one amorphous tooth and corresponding socket in one or each valve, lateral teeth absent; ligament opisthodetic or absent, where present associated in many genera with separate resilium and lithodesma; many genera said to have nacreous endostracum; living forms eulamellibranchiate; a few, septibranchiate.