Family Cancellothyrididae Thomson, 1926

Shells are biconvex or plane-convex, ribbed or secondary smoothed.There are no hinge-plates. Crura are straight with cylindric profile. In advanced taxa crural appendices join each other to form a ring together with transversal band of short free loop. Lophophore is plectolophous or simplified. Anterior body wall and lophophore are full of spicules.

The family includes no less than 17 fossil Mesozoic-Cenozoic genera and 8 recent ones (Cancellothyris, Terebratulina, Murravia, Chlidonophora, Agulhasia, Eucalathis, Bathynanus, Nanacalathis). Among them the genus Terebratulina is the most usual and rich with species.