Formation of the Coracoid Region of the Anuran Pectoral Girdle

The anuran pectoral girdle consists of the scapular and coracoid regions. The latter is composed of the coracoid, procoracoid, epicoracoid, and clavicular elements. The coracoid and procoracoid enclose a large coracoid fenestra, which is a unique feature of these amphibians. Despite many authors having studied the development of the amphibian pectoral girdles, some mechanisms of its development remain unclear. This paper presents a morphological description of the development of the coracoid part of the pectoral girdle in four anuran species ( Bombina bombina , Bufo bufo , Rana temporaria , and Xenopus laevis ) and proposes a mechanism of its ontogenetic formation. The critical part of this process seems to be the position and size of the coraco-clavicularis nerve, vein and artery complex.