[petrovitch (OP)]

What is the purpose of the sharp bones of an armadillo?  As kids we called them a possum in a shell, but their bone structure is very unlike any other animal I've ever seen.  They have blade like bones at the joints.  What is the origin?  What is the purpose?

[Don_1]

Armadillo's have a fine network of veins and arteries in their legs. Warm blood entering the legs transfers it's heat to the cold blood returning to the body. Much of the leg is shaded by the armour, so the leg is probably a good place to regulate the animals body temperature. The flattened leg bones would probably make a better skeletal structure for this network of blood vessels than the conventional round bones. The bony extensions may be to increase the area of this network.

Contrary to popular belief, only the three banded Armadillo can roll into a ball when threatened, others with nine bands cannot do this, so rely on running for cover when threatened. The carapace offers some protection, but the plastron is soft and vulnerable.