interclavicle

The interclavicle is a small, paired bone found in certain reptiles, birds, and some early tetrapods, serving as a key component of the pectoral girdle. It is located between the clavicles (also known as collarbones) and connects them to the sternum, playing a crucial role in supporting the forelimbs and aiding in locomotion. The structure varies among species, often appearing as a single, elongated bone or two separate elements fused or loosely connected.

In birds, the interclavicle is particularly prominent and is known as the furcula or wishbone when fused at the base. This adaptation provides flexibility and strength, contributing to flight mechanics by allowing the shoulder girdle to absorb shock during landing. Fossil evidence suggests that the interclavicle was more widespread in early vertebrates, including some amphibians and primitive reptiles, before evolving into different forms or disappearing entirely in mammals.

Anatomically, the interclavicle is typically cartilaginous in juvenile animals and may ossify in adults, depending on the species. Its presence helps stabilize the rib cage and supports muscle attachments for movements of the forelimbs. Comparative studies of the interclavicle across taxa provide insights into evolutionary transitions, particularly in the development of terrestrial locomotion and later, flight in birds. The bone’s absence in mammals reflects significant changes in skeletal structure during vertebrate evolution.