Wright, A.D. 1994 10 15: Mantle canals on brachiopod interareas and their significance in brachiopod classification.

Mantle canals have been located on the internal surface of the interareas in several clitambonitacean brachiopod genera. This indicates that, in contrast to the cardinal areas of Recent terebratulides and rhynchonellides, these surfaces were lined with mantle, with no fusion of the mantle lobes at the lateral ends of the hinge line, and the coelomic cavity confined to a median zone at the posterior of the shell. The discovery provides additional support for the view of Jaanusson (1971; Smiths. Contr. Paleobiol. 3) that the Beecher (1891) classification has considerable merit, and indicates that the calcareous brachiopods may be subdivided into the three subclasses Craniformea, Protremata and Telotremata. Brachiopoda, classification, Clitambonitacea, interareas, mantle canals, Protremata.