Ancient armadillos were extinct relatives of modern armadillos, often considerably larger. These prehistoric creatures possessed heavily armored bodies, allowing them to thrive across the Americas for millions of years. Their fossilized remains provide insights into a time when enormous, shelled mammals roamed the landscape.
Giants of the Past
Glyptodonts are among the most recognizable ancient armadillos, known for their massive, dome-shaped carapaces. Genera like Glyptodon and Doedicurus reached sizes comparable to small cars. Glyptodon clavipes, for example, weighed up to 2,000 kilograms (4,400 pounds) and measured 3.5 meters (11 feet) long, with a carapace length of 1.7 meters (5.6 feet). These carapaces were formed from hundreds of interconnected bony plates, called osteoderms, providing a robust, immobile shield up to 2.5 centimeters (0.98 inches) thick. This armor covered their torso, and smaller osteoderms protected their heads and undersides.
Doedicurus clavicaudatus was one of the largest glyptodonts, averaging 1,400 kilograms (3,100 pounds) and reaching 4 meters (13 feet) in length. Its distinctive feature was a tail club, up to 1 meter (3 feet 3 inches) long and weighing 40 to 65 kilograms (88 to 143 pounds). This tail had a flexible bone sheath and depressions that may have anchored keratinous spikes, functioning as a weapon. Pampatheres, such as Holmesina, were another group of large armadillo-like xenarthrans, weighing up to 200 kilograms (440 pounds) and reaching 2 meters (6.6 feet) long. Unlike glyptodonts, their armored shells featured three movable lateral bands of scutes, offering flexibility.
Their World and Time
Ancient armadillos originated and diversified in South America, thriving throughout much of the Cenozoic Era. Their earliest fossils date to the late Eocene epoch, about 38 million years ago. Many species flourished during the Pliocene and Pleistocene epochs, from 5.3 million to 11,700 years ago. South America remained their diversity center for millions of years due to the continent’s isolation.
Around 2.7 to 3 million years ago, the Isthmus of Panama formed a land bridge, allowing some armored mammals to spread northward into Central and North America. This event, known as the Great American Biotic Interchange, enabled glyptodonts like Glyptotherium and pampatheres to expand their range. They inhabited various environments, including grasslands, open woodlands, and the edges of forests and shrublands. Different species occupied diverse habitats, from low grasslands to mountainous areas.
From Past to Present: The Armadillo Lineage
Ancient armadillos, sloths, and anteaters belong to the superorder Xenarthra, an ancient lineage of placental mammals found in the Americas. Xenarthrans share skeletal features, including extra contacts in their lumbar vertebrae that strengthen the lower back and hips, aiding digging. Molecular and genetic evidence confirms glyptodonts are closely related to modern armadillos, classified within the armadillo family Chlamyphoridae. Glyptodonts represent an extinct subfamily within the broader armadillo radiation.
Large ancient armadillos, including glyptodonts and pampatheres, became extinct around 12,000 years ago, coinciding with the end of the Late Pleistocene epoch. This extinction event is attributed to a combination of factors. Significant climate change at the end of the last Ice Age led to rapid environmental shifts, altering habitats and food sources. The arrival of humans in the Americas also contributed, with evidence suggesting early Paleoindians hunted these large, slow-moving animals for their meat and potentially used their carapaces for shelter. Modern armadillos represent the surviving lineage, adapted to changing conditions.