GLYPTODONT, an armored edentate mammal of the extinct family glyptodontidæ, which developed mainly in South America during the Tertiary Period. Several genera and many species have been described from Patagonia, the Argentine pampas, Peru, etc., and northward to the southern United States, associated with the great ground-sloths. These glyptodonts were allies of the armadilloes, and some of the more ancient species of the pampean region were very armadillo-like. As time advanced, however, the race developed into huge and grotesque species, the larger ones reaching a total length, including the tail, of 12 or 14 feet, and standing five feet high. Their general appearance must have been that of gigantic, high-backed, long-tailed tortoises; their squarish heads were turtle-like in shape; and their movements must have been slow and heavy, for these animals were massively armored against the big and savage beasts of their time. The top of the head was protected by a bony casque. The body and much of the limbs were enclosed in an immense domed carapace, which almost reached the ground at the sides. “It was composed of very thick polygonal plates of bone (no doubt covered externally with horny plates) immovably fixed together by their rough edges, and ornamented with an elaborate pattern of sculpture which varied with the genus.” The tail, often exceeding the body in length, was enclosed in a defensive sheath of the same nature, and constituted an extraordinary and powerful weapon of defense. In Glyptodon it was made up of a series of overlapping rings, each ring double and bristling with sharp spikes. In Sclerocalyptus there were several rings around the root of the tail, diminishing posteriorly, and then blending into a long, smooth, somewhat flattened tube of bone, blunt at the tip. In Panocthus this tube carried a few heavy, horn-like spikes; and in Dædicurus the very long tube “had its free end greatly expanded and thickened into a huge, club-shaped mass, on the top and sides of which were fixed long and sharp horns.” The skeleton was of the armadillo type, but modified and strengthened, especially in the spine and legs, to enable it to bear the great weight of the carapace; and the hind legs were much longer than the fore legs, giving the hips a humped appearance. The broad feet had five toes in each pair, and in some species these were armed with powerful claws to enable them to dig roots and tubers. All the glyptodonts were plant-feeders, and entirely harmless. “When attacked by the saber-toothed tigers (Smilodon) or the great bears (Arctotherium) they needed only to squat down, bringing the edges of the carapace to the ground, and draw in the head,” says Scott, “to be perfectly protected, while a sweep of the spiny and club-like or horny tail would have been fatal to everything in its path.” The Texan species (Gomphotherium) was smaller, had less armament and a shorter tail, and survived on the Mexican border, according to Osborn, until near the close of the Ice Age. Consult Woodward, ‘Vertebrate Paleontology’ (London 1898): Ingersoll, ‘Life of Mammals’ (New York 1908) Scott, ‘Land Mammals of the Western Hemisphere’ (New York 1913).