Specimen # F: AM 95737

Photo of a Glyptodont skull with puncture holes made by the bite of a species of fanged cat, probably a western dirktooth.  This fossil is at least 1.8 million years old.

The Frick Collection in the American Museum of Natural History includes a remarkable specimen catalogued as F: AM 95737.  One lucky fossil hunter found this skull of a juvenile glyptodont at the 111 Ranch in Graham County, Arizona.  It’s a complete skull minus a few missing lower molars.  This alone makes it unusual because most excavated fossils consist of disarticulated pieces.  Holes in the skull inflicted by a fanged cat make this discovery all the more fascinating.  This species of glyptodont is Glyptotherium texanus, a species which dates to the Blancan Land Mammal Age, a stage that ended early in the Pleistocene 1.8 million years ago.  G. texanus is believed to be ancestral to G. floridanus, the species of glyptodont that lived in southeastern North America from 300,000-11,000 years BP.  The species of cat that apparently killed this baby glyptodont can’t be determined with certainty, but it was probably a western dirktooth (Megantereon hesperus), a species ancestral to the Rancholabrean era species’ Smilodon fatalis and Dinobastis serum (the scimitar-toothed cat).

The dirktooth evidentally attacked this young glyptodont from the front.  Scientists consider this unusual because most cats assault their prey from the rear.  In addition to their armored skull adult glyptodonts had a tough cephalic shield protecting their skull, but the cephalic shield was undeveloped in the young, explaining how a western dirktooth’s bite was able to penetrate through to the brain.

The glyptodont skull was found associated with other fossils, including those of one and three-toed horses (Equus and Nannihippus), hares, and more tellingly capybaras and giant tortoises.  The latter two species indicate a subtropical to tropical climate.  Climatic patterns were quite different during the Pliocene and throughout much of the Pleistocene.  Southwestern North American enjoyed a wet lush environment then, unlike the desert of today.  Lots of lakes and marshes dotted the landscape.

Illustration of a glyptodont.  More than one description in the literature compares the size and shape of this beast to a Volkswagon.  They weighed up to a ton.  Note the stiff turtle-like shell and wide spreading feet.

The glyptodont was a bizarre mammal resembling a turtle.  It’s closest living relatives are the other edentates–armadilloes, anteaters, and sloths.  Armadilloes also have armor, but theirs is flexible.  Glyptodont armor was stiff and turtle-like.  Scientists don’t know if it could withdraw its head inside when threatened.  They were adapted for living in flat, marshy terrain.  Their feet spread wide enabling them to stand on and traverse muddy marshy ground, but they were unable to climb up hills.  The range map below suggests they inhabited coastal lowlands and flat river valleys.  They expanded their range during warm interglacials and interstadials, and conversely their range contracted during cold arid stadials.  They inhabited dense vegetation in marshes and swamps which predators avoided because of difficulty in gaining traction and perhaps mosquitoes.  Mosquitoes may not have been able to penetrate glyptodont armor.

Map of fossil sites where remains of G. floridanus have been found.  This is from the below referenced paper.  This map was drawn in 1981 before a glyptodont fossil was discovered in Louisiana.  I added that locality to the map.  Note the latitude of some of the inland sites.  This suggests that during warm interglacials glyptodonts colonized wetlands in upper river valleys.  They may have periodically occurred as far north as what’s now Augusta.

Glyptodont fossils are often found associated with fossils of capybaras and giant tortoises, indicating they occupied the same kinds of habitat.  Glyptodont teeth even resemble capybara teeth, though the former lack enamel.  Glyptodonts are in the edentate family.  Edentate translates to toothless, but they aren’t actually toothless–their teeth simply have no enamel.  Of the three only giant tortoises could occupy drier habitat.  Glyptodonts and capybaras required subtropical or tropical climate because they both fed upon succulent green vegetation, and they couldn’t survive on winter-killed or dormant plants.

Photo of capybaras by a lake shore.  Extinct species of capybaras shared the same habitat with glyptodonts.  Capybaras are the world’s largest rodent, but during the Pleistocene in North America they were second to the giant beaver.

The authors of the below referenced paper suspect a commensal species of bird, like an oxpecker, existed during the Pleistocene and it fed on external parasites formerly found on glyptodonts.

Reference

Gillette, David; and Clayton Ray

“Glyptodonts of North America”

Smithsonian Contributions to Paleobiology #40 1981

Note: I mentioned this specimen in my book but couldn’t remember where I read about it and didn’t include it in my bibliography.  I was happy when I finally find this paper which is available online as a pdf download.

Advertisements

Tags: , , , , , ,

5 Responses to “Specimen # F: AM 95737”

  1. J. Says:

    I think I have heard about this specimen before- but it used to be said that the killer cat had been a jaguar. They have the habit of biting directly through the skull instead of the neck and have such a strong bite that they can puncture bone easily. I had never heard about Megantereon being another likely culprit, though.
    That the cat attacked from the front isn´t too strange if we consider that the glyptodont was a slow moving animal (it wasn´t going to run away!) and that its main weapon was probably its heavy tail, so it would be actually safer to launch a front attack!

  2. markgelbart Says:

    Jaguar fossils are unknown from this time period in North America. The oldest jaguar fossils in North America date to about 1.5 million years BP, and this glyptodont skull is at least 1.8 million years old. Jaguars did live in Europe and Asia during this time period and may have already crossed the Bering strait. It may be a jaguar that killed this glyptodont. Maybe jaguars did live here that early and aren’t known because of the incomplete fossil record.

    However, the scientists who wrote the paper I referenced mentioned that the holes were made by long canines, so I assumed it was a dirktooth which was definitely present during this time period.

  3. James Robert Smith Says:

    One thing that only specialists and some of us laymen consider are the associated species that go extinct when a keystone species goes away. We may never know the animals who depended on something like mammoths or megatherium or glyptodonts for their survival. When the “parent” species goes, the others generally vanish with it.

    Today, there are probably a number of species that will wither away by the time the hemlock wooly adelgid has completely destroyed our eastern and carolina hemlock trees. Who knows how many birds, insects, mosses, lichens, etc. depended on hemlock trees for their food and habitat.

    Re: mosquitoes. I doubt the armor did much to protect them from mosquitoes. They’d just target another spot. Some animals have just learned to endure the suffering of the clouds of mosquitoes. I’ve seen footage of caribou trying to tolerate the ceaseless attacks of hideous swarms of mosquitoes on the tundra. It’s said that some of the caribou are actually driven to death by the little monsters.

  4. markgelbart Says:

    Even people can develop immunity to mosquito bites, so it’s more accurate to say they were probably immune to them.

  5. Glyptodonts Clubbed Their Foes (and each other) | GeorgiaBeforePeople Says:

    […] though evidence from 1 specimen suggests a frontal attack by a big cat could prove fatal (See:https://markgelbart.wordpress.com/2011/11/02/specimen-f-am-95737/).  Their shell provided a wonderful defense, but glyptodonts were capable of taking the […]

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


%d bloggers like this: