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Tau′-bone, a Τ-shaped bone, as the interclavicle of a monotreme; Tau′-cross, a cross in the form of a Τ—also Cross-tau and Cross of St Anthony; Tau′-staff, a staff with a cross-piece at the top like a crutch.—adj.

Episternum, ep-i-ster′num, n. the interclavicle: the epiplastron: the presternum of mammals.—adj.

In the remote predecessor of Anura, Amphibamus of the Pennsylvanian, the pectoral girdle was less substantial than in many of its contemporaries, but it contained the primitive median interclavicle in addition to the clavicle, cleithrum, and scapulocoracoid.

It is clear that the paired elements of such a girdle were held rigid by their attachment to the interclavicle, via the clavicles.

Subsequent elimination of the interclavicle in the Anuran line of descent, and decrease of ossification, left a girdle like that of Protobatrachus, Notobatrachus, Ascaphus and Leiopelma.