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Ankylosaurus

ANKYLOSAURUS MAGNIVENTIS


Image modified from Wikipedia.
Original image by Tim Evanson
Dinosaurs! Like most children, I devoted a sizable portion of my brain activity between the ages of 6 (when Lost World: Jurassic Park came out) and 10 (when the light finally died from my eyes) to thinking about dinosaurs. For whatever reason, Ankylosaurus was not one of my favourites or even one of the dinosaurs I thought about a lot (probably because it was not prominently features in the Jurassic Park movies). How do I feel about them now? Let's find out.

Appearance

Ankylosaurus was a heavily armuored, and heavily armed, motherfucker with plates on the back and sides, and a club-like tail. Their skulls were covered with small bones, and they had horns on both the top and bottom of the head because having only one pair of horns is for dorks. The knobs on their bodies, as well as their clubs, were made of bony protrusions called osteoderms, which, incidentally, are present on modern crocodilians. These are called osteoderms because they are bony growths on the skin ("osteo" = bone, "derm" = skin). In alligators, they are used for protection of the vital organs and heat regulation - their osteoderms are full of little blood vessels, allowing the animal to cool down quickly. Because Ankylosaurus had more and larger osteoderms than alligators, they were probably much better at regulating temperature.

In addition to being covered in cool bone armour, Ankylosaurus was also an absolute unit. No complete fossil of Ankylosaurus magniventris exists, but by comparing Ankylosaurus bones to the complete skeletons of related species, dino-scientists estimate it was around 8 meters (26 feet) long. Dino-scientists also considered the circumference of the leg bones and asked a computer how much weight they could reasonably support, and came up with 4.78 metric tonnes (over 10,000 pounds), which is ridiculously huge.

Points: 1/1

Behaviour

So Ankylosaurus had a big fuck off club at the end of its tail, made of big fuck off osteoderms. Ever since the first Ankylosaurus club was discovered in 1910, people assumed that it was used for beating the absolute tits off of other dinosaurs, like Tyrannosaurus rex. It wasn't until the 2000s that somebody (specifically, Victoria Arbour) did a science to find out if that was even possible. They found that yes, ankylosaurids with large clubs could probably do some serious fucking damage, likely enough to break bones. Only one club specifically belonging to Ankylosaurus has ever been found, and it's a lot smaller than the biggest ones examined in the analysis, so it's possible that it was used for ritualized self-defense (threat displays) as opposed to explicit self-defense (bashing the other guy's brains in).

Points: 0.5/1 for ambiguity

Distribution

Ankylosaurus fossils have been found exclusively in what is now midwestern North America, from Alberta to Wyoming. At the time it was alive (around the end of the Cretaceous, right before the extinction event that turned dinosaurs into birds), North America was mostly boreal forest and home to a multitude of gigantic herbivore species. The handful of Ankylosaurus fossils that have been uncovered were from what were once the coasts of shallow seas, although that only means that's where they were most likely to fossilize. Anyway, the climate changed around 65 million years ago and everybody got fucked. Even though Ankylosaurus succumbed to climate catastrophe, I can't really fault them for it because the fuckening was so widespread.

Points: 1/1 I guess?

Ecology

Dino-scientists determined that ankylosaurids were herbivores, because they had flat, non-threatening teeth. They also had funky beaks, possibly for eating fruit - but they also don't have any external nares (AKA nose holes) so they may have been specialized for digging up tasty roots. Either way, they would have had to eat a shitload of vegetables in order to sustain their tremendous mass. They were about the weight of a small elephant, so consider how much an elephant has to eat and it's probably comparable. However, unlike elephants, Ankylosaurus appeared to be solitary, so they probably didn't do as much damage to the landscape as elephants do.

Points: 1/1

Evolution

A. magniventis was just one species in a broader group of heavily armoured dinosaurs, the ankylosaurids, many of which we know a lot more about because their fossils are more complete. Thus, a lot of what we think we know about Ankylosaurus actually comes from other ankylosaurid dinosaurs. However, there is some evidence to suggest that Ankylosaurus was kind of weird among its relatives. For example, it had a smaller club than other ankylosaurids so, like I said earlier, it probably used its club for ritualized threat displays rather than outright bone-breakin'. As well, it seems to have more feeding specializations, suggesting it had a narrower diet than other ankylosaurids.

Points: 0/1 for non-conformity

Life History

Almost everything we know about dinosaur life histories comes either from trace fossils (fossils of things other than bones, like footprints and nests - these are obviously sort of sketchy because it's a lot harder to tell what animal left the trace), or the way bone-fossils are arranged together - for example, social animal remains are often found in groups. Since there are hardly any Ankylosaurus fossils, we know approximately dick about what they got up to when they were alive. No adult ankylosaurid fossils have been found together, so we assume that they were solitary animals, but other than that? Total mystery.

Points: 0.5/1 mysteries are cool but also infuriating

Interaction with Humans

Like most other dinosaurs, Ankylosaurus had the good sense to go extinct several million years before humans were ever invented.

Points: 1/1

Final Score: 5/7
Though mysterious, Ankylosaurus magniventis is a lot cooler than I thought, and I regret not giving it the attention it deserves when I was a dino-obsessed kidlet

References

  • Arbour VM. 2009. Estimating impact forces of tail club strikes by ankylosaurid dinosaurs. PLoS One. 4(8): e6738. Open Access
  • Arbour VM, Mallon JC. 2017. Unusual cranial and postcranial anatomy in the archetypal ankylosaur Ankylosaurus magniventris. FACETS. 2: 764-794. Open Access
  • Chen IH, Yang W, Meyers MA. 2014. Alligator osteoderms: mechanical behaviour and hierarchical structure. Materials Science and Engineering: C. 35: 441-448
  • Koch CF, Hansen TA. 1999. Cretaceous period. Encylopedia Britannica. Last updated Oct 16 2018. Link
  • Seidel MR. 1979. The osetoderms of the American alligator and their functional significance. Herpetlogica. 34(4): 375-380

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