Glyptodon

Julius T. Csotonyi Artwork

***Glyptodon*** (meaning "grooved or carved tooth" in Greek) was a large, armored mammal of the subfamily Glyptodontinae, a relative of armadillos that lived during the Pleistocene epoch. It was roughly the same size and weight as a car such as a Volkswagen Beetle, though flatter in shape. With its rounded, bony shell and squat limbs, it superficially resembled turtles, and the much earlier dinosaurian ankylosaurs, as an example of the convergent evolution of unrelated lineages into similar forms. *Glyptodon* is believed to have been a herbivore, grazing on grasses and other plants found near rivers and small bodies of water.

## Discovery

Although Darwin is said to have found the first glyptodonts (the family), the first mention of the genus *Glyptodon* in Europe was in 1823, from the first edition of Cuvier's "Ossemens Fossiles."[3] The then unnamed *Glyptodon* was briefly mentioned in a letter from Don Damsio Laranaga. He had found "a femur... It was about seven pounds, and maybe six or eight inches wide", as well as part of a tail.[3] At the time, the discovery was believed to have belonged to *Megatherium*, a type of giant ground sloth. A man named Sellow found some carapace plates in three-foot deep clay in Uruguay four years later. That discovery only made the professors even more certain that the discoveries were of the *Megatherium*, since the bones of this prehistoric giant sloth were usually found in similar conditions and Cuvier had said that the genus was loricated.

Although some believed that the armor resembled that of the modern armadillo, the popular opinion was the *Megatherium* theory. It was not until Professor E. D’Alton wrote a memoir to the Berlin Academy in 1833 comparing the extreme similarities of these mysterious fossils to that of the armadillo, that the scientific world seriously considered that the pieces of carapaces and fragments of bone could belong to some prehistoric version of *Dasypus*. D’Alton said that “all the peculiarities of the former [*Dasypus*] may be paralleled to the latter [fossil pieces]” He concluded that the fossils belonged to some prehistoric version of an armadillo. However, since a full skeleton was not available at the time, he said that his idea was not conclusive. This uncertainty in the fossil remains continued until a man named Dr. Lund identified the remains as a new genus in his 1837 memoir.

### Naming of *Glyptodon*

When scholars first acknowledged the genus *Glyptodon*, there was not a consensus on its name. In 1837 Dr. Lund, a professor who wrote a memoir on Brazil’s ancient fauna, suggested these creatures be recognized as the new genus “Hoplophorus”. In 1838, another scientist, Professor Bronn, published in the second edition of his book Lethaea Geognostica a proposal for the new genus to be called “Chlamydotherium”. In Professor D’Alton’s 1839 memoir, it was called “Pachypus”. The director at the Museum of Natural History in Dijon at the time, M.L. Nodot, had named the genus “Schistopleuron”.

It was finally given a single name when English scholar Richard Owen noticed the similarities of the genera his colleagues were describing in their publications. Owen realized they were all the same genus from their depictions, from carapace to tooth structure. He decided on “*Glyptodon*”, which means "grooved or carved tooth". The name was originally coined by Sir Woodbine Parish, the man who had sent some *Glyptodon* fossils to Europe. Those fragments of carapace and bones he sent had been heavily studied at the time and had assisted in the recognition of the new genus.

After unifying the name of this genus, Owen continued working on its taxonomy. In 1845, after analyzing the fossils of his colleagues, he named four species within the genus: *G. clavipes*, *G. reticulatus*, *G. ornatus*, and *G. tuberculatus*.

## Evolution and History

*Glyptodon* is part of the superorder of placental mammals known as Xenarthra. This clade of mammals includes anteaters, tree sloths, extinct ground sloths, extinct pampatheres, and armadillos.

*Glyptodon* originated in South America. A related genus reached the southern region of the modern USA about 2.5 million years ago as a result of the Great American Interchange, a set of migrations that occurred after North and South America were connected by the rising of the volcanic Isthmus of Panama. They became extinct about 10,000 years ago. The native human population in their range is believed to have hunted them and used the shells of dead animals as shelters in inclement weather.

## Description and Anatomy

*Glyptodon* was covered by a protective shell composed of more than 1,000 2.5 cm thick bony plates, called osteoderms or scutes. Each species of glyptodont had its own unique osteoderm pattern and shell type. With this protection they were armored like turtles. Unlike most turtles, glyptodonts could not withdraw their heads, but instead had a bony cap on the top of their skull. Even the tail of *Glyptodon* had a ring of bones for protection. Such a massive shell needed considerable support, evidenced by features such as fused vertebrae, short but massive limbs, and a broad shoulder girdle.

The nasal passage was reduced with heavy muscle attachments for some unknown purpose. Some have speculated that the muscle attachments were for a proboscis, or trunk, much like that of a tapir or elephant. Most animals with a trunk, however, have nasal bones receding back on the skull, and glyptodonts do not have this feature. The lower jaws were very deep and helped support massive chewing muscles to help chew the coarse fibrous plants that can be found along river and lake banks.

## Paleoecology

*Glyptodon* and its cousins were likely hunted by early humans, and grazed the open plains in search of low shrubs, and grass. *Glyptodon* used its rounded shell to hide from hungry predators.

## Appearance in other media

### *Jurassic Park*

* *Glyptodon* was added as a rare Cenozoic cavern creature on November 21st, 2017 in *Jurassic World: The Game*.
* *Glyptodon* is a common animal that appears in *Jurassic World Alive*.

## References

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4298209/
2. https://books.google.com/books?id=kUAKgNfiAvoC&pg=PA184#v=onepage&q&f=false
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4760074/
4. https://www.researchgate.net/publication/262718932\_Paleobiology\_of\_Pleistocene\_ground\_sloths\_Xenarthra\_Tardigrada\_Biomechanics\_morphogeometry\_and\_ecomorphology\_applied\_to\_the\_masticatory\_apparatus
5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4580109/
6. https://books.google.com/books?id=vW\_aBwAAQBAJ&pg=PA115#v=onepage&q&f=false
7. https://books.google.com/books?id=UZLuF1YXYTcC&pg=PA17#v=onepage&q&f=false
8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2825778/
9. https://www.researchgate.net/publication/265120808\_First\_evidence\_of\_scavenging\_of\_a\_Glyptodont\_Mammalia\_Glyptodontidae\_from\_the\_Pliocene\_of\_the\_Pampean\_region\_Argentina\_taphonomic\_and\_paleoecological\_remarks
10. https://www.researchgate.net/publication/257931077\_Evaluating\_Habitats\_and\_Feeding\_Habits\_Through\_Ecomorphological\_Features\_in\_Glyptodonts\_Mammalia\_Xenarthra
11. https://palaeo-electronica.org/content/2012-issue-3-articles/305-glyptodont-nasal-anatomy
12. https://academic.oup.com/zoolinnean/article/126/1/41/2684265