Glyptodont shell

Glyptodont shell

NMMNH P-30441

Arizona glyptodont

Cingulatan (armadillo relative)

South of Las Cruces, Doña Ana County

Pliocene, about 2 million years ago

Partial shell

Glyptodonts were the mammalian version of the giant land tortoise; large, slow-moving herbivores protected by a thick bony shell. They are giant relatives of the living nine-banded armadillo and belong to the same mammalian group (Xenarthra, meaning strange vertebrae) that also includes sloths and anteaters. Glyptodonts evolved in South America during the Eocene epoch (about 40 million years ago) and underwent most of their history on that continent. Glyptodonts immigrated to North America about 3 million years ago, after North and South America became connected at the Isthmus of Panama and the Great American Faunal Interchange began. The “Interchange” consisted of an extensive intermingling of faunas and floras between the two continents. Besides glyptodonts, several other mammals of South American origin, including ground sloths, armadillos, capybaras, and porcupines, migrated northward. At the same time, a large variety of mammals of North American origin, including cats, dogs, bears, squirrels, rabbits, horses, tapirs, peccaries (javelinas), camels (llamas), deer, and mastodons, migrated southward across the Panamanian Isthmus into South America.