Glyptodon: Prehistoric Animal of the Week

This week we are checking out a really heavily-protected prehistoric mammal.  Enter Glyptodon!  Glyptodon was a member of a family of mammals called xenarthra, which also includes modern anteaters, armadillos and sloths.  Glyptodon resembled a gigantic armadillo with a high, dome-shaped shell covering most of its body.  This beast measured ten feet long and would have lived in what is now South America during the Plestiocene era which spanned from a few million years ago up until only ten thousand years ago.  The genus, Glyptodon, translates to "carved tooth" and includes a few different, but similar species. When alive, Glyptodon would have coexisted with many other prehistoric beasties including Sabre-toothed cats, giant, flightless terror birds like Titanis, mammoths, giant ground sloths like Megatherium, and even humans. 

Glyptodon by Christopher DiPiazza.

In life, Glyptodon's shell was comprised of wide sheets of bone under the skin covered in a layer of horny keratin. (same stuff as our fingernails)  Modern armadillo armor is like this as well but varies in thickness and flexibility depending on the species.  Modern armadillos also have segmented shells with bands in the middle.  The number of bands is different depending on the species and the higher the number of these bands, the more flexible and maneuverable the armadillo can be.   

Above are two modern examples of armadillos that I work with.  On the left is the Six-Banded Armadillo (Euphractus sexcinctus) who's armor is thicker and stiffer than the surprisingly fast-running Nine-Banded Armadillo's (Dasypus novemcinctus), on the right. 

Glyptodon, however, had a shell that comprised of one solid dome covering the entire body, except for the head and tail.  When faced with a predator, Glyptodon wouldn't have been able to run away quickly.  Instead it would have simply lowered it's head and stood firm, making it's body into a seemingly impenetrable fortress. The shell was so strong and big that some believe early humans would have used hollowed out Glyptodon armor as shelter sometimes. Glyptodon also had armor on the top of its head like a cap as well as the tail which was covered in rings of armor. 

Somebody is about to get a sexy wake-up surprise!

Glyptodon's body design has evolved separately many times in other kinds of animals throughout history.  This idea of different, unrelated animals evolving similar adaptations for similar purposes is called convergent evolution.  The group of dinosaurs, the ankylosaurs, the crocodile relatives, the aetosaurs, and the testudines (turtles and tortoises) all are examples of other vertebrates that independently developed bony armor for protection.

Glyptodon skeleton.  Note the high shell and the short face.

In addition to being much larger, Glyptodon differed from modern armadillos in other ways, too.  Most notable is the skull.  Modern armadillos all posses long, pointed snouts with small teeth designed for crunching up insects and other food items.  Glyptodon, on the other hand, had a very short, robust skull with a huge lower jaw where a lot of muscle would have been attached in life.  Glyptodon teeth are also more designed for chewing grass, suggesting that this prehistoric xenarthid was a herbivore and not an omnivore or insectivore like its modern relatives.

That's all for this week!  As always comment below or on our facebook page!

References

Fidalgo, F., et al. (1986) "Investigaciones arqueológicas en el sitio 2 de Arroyo Seco (Pdo. de Tres Arroyos, prov. de Buenos Aires, República Argentina)" In: Bryan, Alan (ed.) (1986) New evidence for the Pleistocene peopling of the Americas Peopling of the Americas Symposia Series, Center for the Study of Early Man, University of Maine, Orono, Maine, ISBN 0-912933-03-8, pp. 221-269, in Spanish

Politis, Gustavo G. and Gutierrez, Maria A. (1998) "Gliptodontes y Cazadores-Recolectores de la Region Pampeana (Argentina)" ("Glyptodonts and Hunter-Gatherers in the Pampas Region (Argentina)") Latin American Antiquity 9(2): pp.111-134 in Spanish