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South American Mammals

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Top of Case

  • Macrauchenia (real) skull [Recent article on this fossil]
    - Darwin thought it a mastodon relative, but Richard Owen named it as a giant llama.
  • Glyptodont (real) skull and replica head plate
  • Replica Tail ring
  • Doedicurus with reconstructed spikes
  • Pink Fairy Armadillo skull (replica of its closest living relative) also with a bony tail club (replica)

Bottom of Case

  • giant ground sloth skull replica
  • giant ankle bone (mostly real) from sloth that walked on the sides of its feet
  • ankle bone from a flat footed walking sloth
    - with a human ankle bone for size and shape comparison
  • numerous parts from various armadillos of various sizes
    - from the small, softball size Three Banded Armadillo
    - replica skulls of the grizzly bear size armadillos from ice age Florida

There are 20 living species of armadillos. The smallest species of armadillo is the chipmunk size South American Pink Fairy Armadillo. It will fit easily on a hand. It has a fairly flat set of bony armor plates across the top of its back that project laterally a little wider than the body. The plates are covered with a thin layer of fingernail-like keratin, but unlike most armadillos it doesn’t have any special flexion plates to allow curling up into a protected ball. Under the armor the side skin has white hairs that continue around the belly of the animal. It has a tiny, but enlarged terminal tail club. The upper portion of the display case has a replica of its tiny skull and pictures of the animal and a model of its tail club.

The closest living relative of the extinct, giant glyptodont Doedicurus, is the chipmunk size Pink Fairy Armadillo. The former had a dome shaped, rigid, bony shell covering their body with individual plates ¾” to 1” thick and 1 ½” to 2” in diameter. Another set of keratin covered, bony plates capped the head. They lived in South America until about 10,000 years ago. They may have been exterminated by early humans who arrived there. Doedicurus was the longest of the many varieties of glyptodonts. The body was almost as large as a Volkswagon “bug”. Like the Pink Fairy Armadillo they also had a conspicuous tail with a big, straight, bony tail club. The Doedicurus tail made their total length about 13 feet. The last segment of its tail was the one piece club, about three to four feet long and the terminal end had numerous keratin spikes of various sizes, similar in composition to rhino horns. The males probably used the tail clubs in contests for feeding territories and/or mating rights. Some fossils have been found with serious dents in their armor. Estimates of weight are around 2,000 pounds, a ton. Some think the tail club was used for defense, as did the extinct dinosaur Ankylosaurus, but if adults just laid down on the ground and curled their head in they were about as invulnerable to predators as an army tank.

Other species of glyptodonts (e.g. Glyptodon clavipes) had a bony ring with short, conical, bony spikes on the rear portion around each vertebra of the tail and others such as Panochthus had non-spiked tail clubs without the enlarged terminal end.

In the lower half of the display case are parts of various kinds of armadillos and sloths, more close relatives of the glyptodonts. The modern Nine Banded Armadillo has invaded southern North America. They have nine elongated, bony bands (scutes or osteoderms) with flexible connecting skin that allow flexion in the middle of their otherwise fairly rigid anterior and posterior armor.

Armadillos came in various sizes. The extinct Dasypus bellus was about twice the size of our approximately 6-7 pound, nine banded armadillo, Dasypus novemcinctus. They were very closely related. But it was about twice as long and twice as wide and twice as tall, so it weighed about 2 x 2 x 2 = about 8 times heavier or about 50 to 60 pounds. The largest living armadillo is the rare and endangered giant armadillo of northern South America, Priodontes maximus. It weighs up to 120 pounds.

But there were even larger versions in the past. Holmesina floridanus showed up in North America some time after North and South America connected about 3 million years ago. It grew to about 250 pounds. And the larger Ice Age version, Holmesina septentrionalis, grew to about 500 to 600 pounds. Both species of Holmesina had three bands of flexion scutes and were probably closely related to the small living Three Banded Armadillo which can close up so tightly into a cantaloupe or grapefruit size ball that all you can see is the external body armor, head cap and dorsal side of the tail. Despite its three, mid-section flexion bands Holmesina could not curl up that tightly. Many other living and fossil genera of armadillos are known from South America. The largest one known, extinct Chlamytherium, was about half again heavier than Holmesina and grew to about 750 to 800 pounds.

Armadillos, and their relatives the hairy anteaters, are great diggers, and small ones dig for ants, termites, worms and other animals in the soil. They have numerous, very simple teeth. Limb bones from the various sizes of armadillos show their adaptations for powerful digging for food and/or for protective burrows. The larger members of the group have more complicated teeth and probably ate a much higher percentage of plant material.

Tree sloths have permanently curved wrists, ankles and claws to help them hang in the trees. Some of the extinct, giant ground sloths still had that curled ankle structure and walked on the outside of their hind feet. They had unusual shaped ankle bones with a broad shelf that helped support their weight without damaging their curled ankles and a central knob to keep the tibia from sliding off the weight bearing surface. The really BIG partial left ankle bone, with the missing parts restored, was from a giant ground sloth from Florida that was even larger than an Indian elephant’s ankle. Next to it is a human, left ankle bone for size comparison. Some sloths also had small bones (osteoderms) embedded in the skin across their backs. These are small versions of the external bony armor of their armadillo relatives.

Donations:

Stanley Davis - glyptodont skull, glyptodont tail club, Macrauchenia skull 

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