The animal kingdom is a dangerous place, full of claws, jaws, stingers, and spines. But when it comes to home-grown weapons, perhaps no collection of animals is as heavily armed as the artiodactyls.

Also known as even-toed ungulates, artiodactyls include everything from llamas and camels to deer, cattle, and goats. And many of these species sport large, powerful armaments such as tusks (elongated teeth), antlers (temporary bone growths), and horns (permanent keratin structures). (See the muntjac and other "fanged deer")

People have been fascinated by these weapons for thousands of years, but scientists still aren’t quite sure why such closely-related animals would evolve so many different strategies for doing damage.

Now, a new study published in the Journal of Mammalian