Temporal range: Pleistocene
|Fossil specimen in Vienna at the Naturhistorisches Museum|
Glyptodon (Greek for "grooved or carved tooth") was a large, armored mammal of the family Glyptodontidae, a relative of armadillos that lived during the Pleistocene epoch. It was roughly the same size and weight as a Volkswagen Beetle, though flatter in shape. With its rounded, bony shell and squat limbs, it superficially resembled turtles, and the much earlier dinosaurian ankylosaur, as an example of the convergent evolution of unrelated lineages into similar forms. Glyptodon is believed to have been a herbivore, grazing on grasses and other plants found near rivers and small bodies of water.
Glyptodon originated in South America. During 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, it migrated into Central America as far as Guatemala. A related genus, Glyptotherium, reached the southern region of the modern USA about 2.5 million years ago. They became extinct about 10,000 years ago, probably from over-hunting. 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.
Glyptodon measured over 3.3 m (10.8 ft) in length and weighed up to 2 tonnes. It was covered by a protective shell composed of more than 1,000 2.5 cm-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.
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. The lower jaws were very deep and helped support massive chewing muscles to help chew coarse fibrous plants; a distinctive bar of bone projects downwards on the cheek, extending over the lower jaw, perhaps providing an anchor for powerful snout muscles. Another suggestion, made by A.E. Zurita and colleagues, is that the large nasal sinuses could be correlated with the cold arid climate of Pleistocene South America.
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- MacPhee, ed. by Ross. D.E. (1999). Extinctions in near time : causes, contexts, and consequences. New York [u.a.]: Kluwer Acad., Plenum Publ. p. 25. ISBN 0306460920.
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- Gillette, David D. (2010). "Glyptodonts in arizona a saga of supercontinents, sea-floor spreading, savannas, and sabertooth cats". Arizona Geological Survey. Retrieved 25 March 2014.