Glyptodon

Glyptodon (Greek for "grooved or carved tooth") was a large, armored mammal, related to the armadillo, that lived during the Pleistocene Epoch. Flatter than a Volkswagen Beetle, but about the same general size and weight, Glyptodon is believed to have been an herbivore, grazing on grasses and other plants found near rivers and small bodies of water. A large and heavy mammal, it could probably only have moved one or two miles per hour.

Its physical appearance superficially resembled the much earlier dinosaurian ankylosaurs, an example of the convergent evolution of unrelated lineages into similar forms.

Evolutionary History

Glyptodon is part of the placental group of mammals known as Xenarthra. This order of mammals includes anteaters, tree sloths, extinct ground sloths, extinct pampatheres, and armadillos.

Glyptodon originated in South America. A related genus, Glyptotherium, first appeared in the American Southwest about 2.5 million years ago as a result of the Great American Interchange, a set of migrations that occurred after North and South America were connected by the rising of the volcanic Isthmus of Panama. They became extinct about 10,000 years ago. The native human population in their range is believed to have hunted them and used the shells of dead animals as shelters in inclement weather.

Anatomy

Glyptodon was covered by a protective shell composed of more than 1,000 one inch-thick bony plates, called osteoderms or scutes. Each species of glyptodont had its own unique osteoderm pattern and shell type. With this protection they were armored like turtles. Unlike most turtles, glyptodonts could not withdraw their heads, but instead had a bony cap on the top of their skull. Even the tail of Glyptodon had a ring of bones for protection. Such a massive shell needed considerable support, evidenced by features such as fused vertebrae, short but massive limbs, and a broad shoulder girdle.(Lambert, 196)

The nasal passage was reduced with heavy muscle attachments for some unknown purpose. Some have speculated that the muscle attachments were for a proboscis, or trunk, much like that of a tapir or elephant. Most animals with a trunk, however, have nasal bones receding back on the skull, and glyptodonts do not have this feature. The lower jaws were very deep and helped support massive chewing muscles to help chew the coarse fibrous plants that can be found along river and lake banks.