The anatomy of the forelimb in the anteater (Tamandua) and its functional implications

The forelimbs of anteaters play a major role in obtainment of food, defense, and locomotion. The greatly enlarged claws on the manus are used for ripping open insect nests and insect-infested wood; the claws also serve as the animals' only defensive weapons, since they lack teeth. Specialization of the claws for these functions has also had a substantial effect on the ways in which the forelimb is used for posture and locomotion. Modifications of the forelimb in the anteater Tamandua include the following. Attachments of the medial head of triceps are rearranged so as to greatly increase capability for powerful flexion of the claws. Ability to flex the elbow and to retract the humerus is also augmented; these movements would assist digital flexion in applying traction with the claws to material being torn away during food procurement. This traction can be supplemented by a variety of powerful side-to-side and/or twisting movements of the hand, brought about primarily by axial rotation of the upper arm and forearm. The digital joints are reinforced to resist the deviational and torsional loading to which the digits would be subjected during such movements. The morphological modifications of the forelimb in Tamandua are discussed in terms of how they affect the mechanical capabilities of the limb, what functions the limb is best designed to perform, how they may relate to what little is known about the specialized behavior of this animal, and what behavioral predictions may be made based on mechanical design.