Lower Ordovician (Arenig) – Middle Silurian (Wenlock)
Platystrophiidae is an extinct family of stationary, epifaunal suspension feeders
Characteristics of the Family
- Transversely subquadrate to semioval
- Elongately oval ventral muscle scar
- Blade-like brachiophores joined to hinge line by concave fulcra plates
- Visually similar to spiriferid brachiopods rather than orthid
- Dorsibiconvex with Spirifer-like shells, uniplicate shell; interareas low, weakly concave in cross-section, ventral interarea apsacline, dorsal interarea anacline; radial ornament costate; lateral margins of ventral sulcus and dorsal fold not covered by costae; fine hollow spines of high density covering the entire shell surface except interareas; ventral interior with teeth supported by long subparallel dental plates to define thickened elongately oval muscle field; cardinalia of two types: with well-developed notothyrial platform or with sessile septalium; cardinal process simple, blade-like; median septum variously developed; dorsal muscle field quadripartite.
Treatise on Invertebrate Paleontology, Part H, Vol. 3 (2000):
- Transversely subquadrate to semioval, dorsibiconvex, normally strongly uniplicate, medium-sized plectorthoids; interareas proportionally long and curved; teeth normally with crural fossettes supported by subparallel dental plates flanking poorly differentiated, elongately oval ventral muscle scar with broad adductor track impressed on thick callist, pedicle callist rarely preserved; divergent, bladelike brachiophores joined to hinge line by concave fulcra plates and supported by plates converging posteromedianly to form small septalium, cardinal process bladelike; scars of quadripartite dorsal adductor field variable in size, bisected by median ridge, mantle canal systems rarely impressed.