Lower Ordovician (Llanvirn) – Middle Silurian (Wenlock)
Glyptorthis is an extinct genus of stationary, epifaunal suspension feeders
- Moderately sized, biconvex shell with clear radial ornament
- Many prominent concentric laminae, creates cross-hatched pattern
- Hole under the pedicle opening is triangular
- Shell shape ranges from subquadrate to subelliptical
- Dorsal interarea small
- Muscle scars on the ventral valve are heart-shaped, with the “open” part of the heart shape opening anteriorly.
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- Shell of variable size, subquadrate to subelliptical in outline, unequally biconvex; ramnicostellate to fascicostellate, sometimes frilled; ornamentation concentric, strongly lamellose; rectimarginate to sulcate; delthryium open, triangular; ventral interarea short to long, orthocline to catacline; dorsal interarea small, orthocline to apsacline; subcordate ventral muscle scars, deflecting anteriorly, additional lateral deflection not uncommon; ventral adductor scars sometimes elevated on a raised platform; quadripartite dorsal muscle scars; thickened notothyrium; brachiophores divergent.
Treatise on Invertebrate Paleontology, Part H, Vol. 3 (2000):
- Variable in size and in cardinal extremities, subequally biconvex, ramicostellate, strongly lamellose, ventral interarea of varying length , dorsal interarea short, curved; ventral muscle scars subcordate with adductors commonly raised on median callist extending forward as tongue of secondary shell; brachiophores divergent, rodlike
Fossils of Ohio (1996):
- Medium-sized orthid brachiopod that has an unequally biconvex profile and an elliptical outline truncated by a straight hinge line. The width is greater than the length. The more inflated brachial valve has a sulcus. Numerous branching ribs radiate from the beaks of both valves. The intersection of radiating ribs and concentric growth lines results in a reticulate ornamentation on the exterior surface of the valves. The delthryium is open. The interior of the pedicle valve has a muscle scar consisting of two deep grooves, made by the diductor muscles; this muscle scar is separated by a ridged from the adductor muscle scars. Pallial markings are present beyond the muscle scar. Glyptorthis occurs in the Waynesville and basal Liberty Formations.