Mechanical analysis of the malformed, yet functional, mandibular joints of a wild timber wolf, Canis lupus

In spite of grossly malformed jaw joints, presumably from birth, the animal survived in the wild for at least 3 years. Instead of a deep glenoid fossa folded over a cylindrical condyle to form a hinge, both joints had freely open articulating surfaces and a mandibular condyle without neck. The neckless condyle produced a shorter moment arm of resistance in all biting positions. The moment arm of the masseter, the jaw-adductor tending to disarticulate the jaw, was longer as a result of an elongated angular process. The combined effect at the carnassials was a 36 per cent improvement in the efficiency of the lever for which the joint is the fulcrum and thus an equivalent reduction in the disarticulating force. The joints were held together by an extra stout ligament about 5 mm in diameter and 8 mm long, linking the lateral pole of the condyle to the zygomatic arch.