The clavicle, well developed in humans, is absent or a small rudiment embedded in the brachiocephalic muscle in animals:
Cats: a flat slightly bent 2-5 cm bone
Dogs: rudimentary, 1 cm length, not connected to the skeleton
Horses, ungulates: reduced to a fibrous intersection in the brachiocephalic muscle.
Text by Antoine Micheau, MD - Copyright IMAIOS Veterinary Anatomy of Domestic Mammals: Textbook and Colour Atlas, Sixth Edition - Horst Erich König, Hans-Georg Liebich - Schattauer - ISBN-13: 978-3794528332