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Roger Weller, geology instructor

Jocelynn Snoozy

Historical Geology
Spring 2005


The glyptodont was a prehistoric mammal the size of a small car.  It had a large shell, resembling that of a turtle and a long armored tail.  “Some of the glyptodonts, such as Doedicurus, had an armored tail which ended in a viciously spiked club, a weapon of defense similar to that possessed by the ankylosaurs” (Norman, 190).


The glyptodont was armored from nearly head to toe.

 Its head had a small cap of armor and its tail was

enrobed in a tube of armor plating.  “The skulls of

glyptodonts were very deep, and housed extremely

powerful muscles which allowed these animals to

grind up abrasive grasses.”  The teeth used for

grinding up plant matter were open-rooted so that

they continued to grow despite being worn down by eating abrasive materials.  The glyptodont was a placental mammal, meaning that it developed inside the mother’s uterus and was born almost fully developed.  Although these animals were extremely large, the glyptodont was most likely gentle because it was an herbivore.  Its large spiked tail was used for protection against saber-tooth tigers.  It may have also been used in mating practices as two males fight over a female (Moss, par. 15). 

There has been question as to whether the force of the glyptodont’s tail may have been enough to produce the large cracks found in some fossil remains of their shells.  Researchers at the University of Leeds performed tests on the fossils and determined that it would take 1,400 joules to crack a glyptodont shell.  After estimating the amount of joules a glyptodont could have created with the strong muscles it was hypothesized to have, it was determined that the force created by an angry glyptodont was enough to cause the spikes of the tail to puncture another glyptodonts carapace (“Giant Armadillos,” 13).








Text Box: This drawing depicts what an ancient glyptodont looked like.





The glyptodont belongs to an animal group called edentates, which means “toothless.”  This name is actually misleading.  All of the members of this group have teeth except for the anteater.  Another name given to this group is xenarthrans, which means “strange joint.”  This term is used to describe the group’s unusual backbones.  According to “Successful in Spite of Themselves,” an article written for Natural History, “In most mammals, the paired overlapping surfaces that prevent dislocation between vertebrae are flat or faintly curved, but in these animals, the surfaces are scrolled into an elaborate set of interlocking ridges and valleys.”  This was to help the glyptodont carry such a large and heavy shell (“Successful,” par. 4 &5).

First Appearance and Location

            The edentates developed following the extinction of the dinosaurs, emerging about three million years ago (Moss, par. 1).  “Among the edentates were armadillos, which first appeared during the Paleocene,” explains author David Norman.  “During the more recent Pliocene and Pleistocene Epoch,” the glyptodonts appeared (Norman, 190).
            The edentates were almost entirely confined to South America until the “Panamanian isthmus reconnected North and South America several million years ago” when the group migrated north (Smith, par. 7).  Because they were confined for so long to one area, “the mammals of South America evolved almost independently and developed into a remarkable indigenous fauna including the edentates” (Sutcliffe, 167).

            Darwin’s Expedition

            Darwin found shells and bones in a sand bank while exploring a bay on his trip on the HMS Beagle.  He had the fossils shipped to England where he identified one as the shell of a glyptodont (Callahan, 101).


            The glyptodont became extinct 10,000 years ago (“Successful,” par. 10) during the most recent Ice Age.  It was one of the three-fourths of the large mammals to disappear in North America and one of the four-fifths of them to become extinct in South America (Norman, 212).  This mass extinction began during the Pleistocene and “by the early Holocene, the glyptodont became extinct in both Americas” (Sutcliffe, 169).

            Modern Descendants

            Armadillos, or armored pigs are the most closely related species of the glyptodont.  They too, have armored plating covering almost their entire bodies, but the modern armadillo is much smaller than the large glyptodont.  Most of the early armadillos died out, leaving about 20 species on Earth today, all of which are in Latin America, except for one.  For a long while, before humans arrived and changed its living conditions, armadillos of the United States were found along the Rio Grande and Rio Brazos drainages of Texas (Smith, par.8).

            The modern armadillo has been nicknamed the “armored pig” because it changed its food preference from only plants to almost anything.  It is now a carnivore, feeding on insects, “small lizards, salamanders, snakes, frogs, and toads” (Smith, par. 13).  The armadillo is becoming more versatile to climate changes and has been increasing its resistance to colder temperatures every year (Haines, 201).

            Glyptodont Links

Some quick information:

Lifelike figurine photo:

Glyptodont Photo:

Link to various glyptodont facts:

Skull replica photo:

Glyptodont shell fossil:

Glyptodont scale samples:

Glyptodont Info:

Glyptodont fossil photos:

Information on Pleistocene animals:




Works Cited

           Callahan, Tim, et al.  “How The History of Life Was Discovered:  Part I.”  Skeptic. 

Altadena:  2000. Vol. 8, Iss. 1, pg. 96-103.  Research Library.  ProQuest.  Cochise College, Sierra Vista, AZ.  13April 2005.
“Giant Armadillos Used Tails as Battle-Axes.”  Current Science Stamford:  Nov 5,

1999.  Vol. 85, Iss. 5, p.13.  Research Library.  ProQuest.  Cochise College Library, Sierra Vista, AZ.  13 April 2005.
Haines, Tim.  Walking With Prehistoric Beasts.  New York:  DK Publishing, 2001.

            Moss, Meg.  “Old Cold:  Living in Ice Age America.”  Ask Peru:  Feb 2004.  Vol.

3, Iss. 2, p. 6-12.  Research Library.  ProQuest.  Cochise College Library, Sierra Vista, AZ.  13 April 2005.
Norman, David.  Prehistoric Life:  Rise of the Vertebrates.  New York:  MacMillan,


            Smith, Dwight G.  “The Armored Pig.” The World & I.  Washington:  Aug 1999. 

Vol. 14, Iss. 8, p. 174-179.  Research Library.  ProQuest.  Cochise

College Library, Sierra Vista, AZ.  13 April 2005.
“Successful In Spite of Themselves.”  Natural History.  1 Apr. 1994: 50.

Research Library.  ProQuest.  Cochise College Library, Sierra Vista, AZ.  13 April 2005.
Sutcliffe, Antony J.  On the Track of Ice Age Mammals.  Cambridge:  Harvard

University Press, 1985.