In our 98th episode, we had the pleasure of speaking with Dr. Victoria Arbour, a NSERC Postdoctoral Fellow at the Royal Ontario Museum/University of Toronto, Canada and an ankylosaur expert. You can follow her on twitter @VictoriaArbour
Episode 98 is also about Homalocephale (Prenocephale), a pachycephalosaurid that lived in the late Cretaceous in what is now Mongolia.
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In this episode, we discuss:
- The dinosaur of the day: Homalocephale (Prenocephale)
- Homalocephale name means “even head”
- A pachycephalosaurid that lived in the late Cretaceous in what is now Mongolia
- Described in 1974 by Osmólska & Maryañska
- Only one species, type species is Homalocephale calathocercos
- May be a synonym (and juvenile form) of Prenocephale
- Type species is an incomplete skull and postcranial material. Had large openings on the top of the skull and a large, round eye socket. Scientists described it as an adult, even though it has juvenile traits (like a flat skull). Then in 2010 Nick Longrich and others said it may just be a juvenile version of another adult pachycephalosaur (Horner and Goodwin also suggested that in 2009). Longrich suggested it was a juvenile or sub-adult of Prenocephale
- Herbivore, about 6 ft (1.8 m) long
- Had a flat, wedge-shaped skull roof, though the skull was pretty thick (this is similar to Dracorex and Goyocephale, and not similar to other adult pachcephalosaurs)
- Had a broad pelvis (some paleontologists think it may have had wide hips to give live birth, others think the wide hips helped protect organs during flank-butting)
- Had long legs and was fast
- Had a very rigid tail
- Can see Homalocephale in the game Jurassic Park: Operation Genesis (you build your own Jurassic Park)
- Maryanska and Osmolska described Prenocephale in 1974
- Name means “sloped head”
- Lived in Mongolia in the late Cretaceous
- Fossils found include skulls and fragmentary post cranial remains
- Three species: Prenocephale prenes, Prenocephale brevis, Prenocephale edmontonensis
- Type species is Prenocephae prenes
- Another suggested synonym to Prenocephale is Sphaerotholus buchholtzae
- Herbivore, about 7.8 ft (2.4 m) long, weighing 280 lb (130 kg)
- Prenocephale had a round, sloping head, with a row of smally bony spikes and bumps
- Thought to have a stout body with a short neck, short forelimbs, and long legs (based on other pachycephalosaurs, since all that’s been found is mostly skulls
- Some scientists think Prenocephale may have been an omnivore (ate plants and insects), though many think it ate leaves and fruit
- Probably a selective browser, since it had a narrower snout than other pachycephalosaurs
- Pachycephalosaurs may have head butted or they may have used their domes to attract mates
- Teenage or young adult pachycephalosaurs were best equipped to handle head butting (skulls had radiating structures that compressed, provided cushion during a fight)
- Adults don’t have these structures
- Common Functional Correlates of Head-Strike Behavior in the Pachycephalosaur Stegoceras validum (Ornithischia, Dinosauria) and Combative Artiodactyls published in PLOS ONE June 2011, by Eric Snively and Jessica M. Theodor
- Snively and Theodor compared Stegoceras and Prenocephale skulls with head-butting mammals (like elk and musk ox) with CT scans. They found Stegoceras and Prenocephale domes were most similar to musk ox and duiker
- Stegoceras was most able to head butt
- Distributions of Cranial Pathologies Provide Evidence for Head-Butting in Dome-Headed Dinosaurs (Pachycephalosauridae) published in PLOS ONE July 2013, by Joesph E. Peterson, Collin Dischler, Nicholas R. Longrich
- Peterson and his team studied 109 domes from 14 species to see if there was evidence of head butting. 22% of those domes showed evidence of osteomyelitis, which often comes from skull trauma. Because there was a lot of evidence of this, they concluded it was consistent with the idea of intraspecies combat
- They also looked at 30 skeletons of head-butting mammals and found that “Comparisons with injuries in extant bovids illustrate the variation in injury and lesion distribution related to behavior and suggest that the distribution of injuries in extinct animals can therefore be similarly used to infer behavior in extinct taxa”
- Pachycephalosauria is a clade of ornithischians
- Name means thick headed lizards
- Lived in the late Cretaceous in North America and Asia
- Bipedal with thick skulls
- Fun fact:
This episode was brought to you by:
The Royal Tyrrell Museum. The Royal Tyrrell Museum is located in southern Alberta, Canada. One of the top paleontological research institutes in the world, the entire museum is dedicated to the science of paleontology. It’s definitely a must see for every dinosaur enthusiast. More information can be found at tyrrellmuseum.com.
For those who may prefer reading, see below for the full transcript of our interview with Dr. Victoria Arbour:
Garret: Victoria Arbour is a Postdoctoral Fellow at the Royal Ontario Museum/University of Toronto in Canada, and she is one of the world’s leading experts on ankylosaurs, which is why I really wanted to talk to her. So personally my favorite dinosaur is Ankylosaurus. Is that your favorite dinosaur too, or do you like a different ankylosaur better?
Dr. Victoria Arbour: Oh it’s hard to decide because I like a lot of them a lot, but Ankylosaurus is definitely cool, it’s definitely one of my favorite of the ankylosaurs. Yeah, I’d be hard pressed to pick a very favorite one that I can love a lot like cool things, there are a whole bunch of different ones.
Garret: Very cool, yeah your bio on the University of Alberta says that you’ve identified four new species of ankylosaurs before you got your PhD, is that true, that seems too incredible to be?
Dr. Victoria Arbour: Oh well it’s kind of true although maybe I need to update some of those things. So one of the projects that I worked on while I was a PhD student at the University of Alberta, was taking a look at the diversity of ankylosaurs in Alberta especially by sort of broadly in North America and Mongolia. And one of the ankylosaurs that’s one of the best known ankylosaurs is called Euoplocephalus. It might not be a really easy name to say but most ankylosaurs toys are actually Euoplocephalus not Ankylosaurus. So it’s like a really common one to see reconstructed, but they often just call it Ankylosaurus even though they are different animals. But I can’t really blame them, because it’s not a really easy name to say.
This is one of the dinosaurs that—or one of the ankylosaurs that we have the most specimens for, but it also has like a really long stratigraphically. So it has like a long time range that it was found in, and the more that we learn about Alberta dinosaurs in particular, the more that we know that they tend to have relatively restricted stratigraphically. So we find them sometimes just in one part of the geologic formation, and not very often do we find them in more than one geologic formation within Alberta, so that’s pretty cool.
So I took a look at whether or not all these different specimens that we were calling Euoplocephalus actually were all one specie, because there were some variation and I wanted to know whether or not that was just like normal variation, to see whether the species, or whether or not if it really had growth or sexual dimorphism, or even just squishing during fertilization.
So some of the work that I did actually sort of, I didn’t name these species, but I resurrected old species that had been bumped in with Euoplocephalus. There actually had been a couple of different species in Alberta, and back in the 1970s another really common Ankylosaurus researcher Walter Coombs decided that probably all of those represented one species. But now with this new framework of looking at dinosaur species, which is in Alberta, I was able to find that we had actually four different species had been lumped in with Euoplocephalus.
That was really fun, so we had an animal called Dilophosaurus which is represented by a pretty good skeleton at the Royal Ontario Museum, and it has a really skinny tail club and a [inaudible 00:03:09] which is found in younger segments than most of the Euoplocephalus specimen that are found in that show park. It has a really cool pointed ax-like tail club. And Scholosaurus, which is known from a really great skeleton that’s on display at the British Museum of Natural History that has skin impressions and all of it, osteoderms, and [inaudible 00:03:29] which is really cool.
It’s also known from specimens from Montana. So it’s one of the few that crosses the Alberta mark gender board. So yeah—so I didn’t get to name those new ones because they are pretty hard names, but I did get to show that they actually were distinct. And that we actually had a much greater diversity of ankylosaurs, and that not all of the variations that we saw in Alberta was just like intra-specific variation that really was different. That was a really fun project to work on.
Garret: Yeah that sounds really cool. So when you are doing that kind of research where did you come up with the old species names? Were they—all those ones—those specific ones had been previously identified with different species names, and then lumped back together under the same species?
Dr. Victoria Arbour: Yeah.
Dr. Victoria Arbour: Yeah, it’s a funny story; we don’t really talk about sort of synonyms and resurrecting all things, because it’s easier to talk about new names, like identifying a new species. But that’s when a lot of Alberta dinosaurs were being named; it sort of was like every new specimen got a new name. And then as people found more and more specimens, they would look at things and be like, oh I’m not really sure that these are all that different. There is a lot of variation; we can’t have like 30 different species of ankylosaurs in like 2 million years in Alberta.
But maybe all of these are really just one, but like I said now that we sort of got like a new framework for how we think of those species and how we understand their distribution in Alberta, we have a much better sense of—but there is kind of different like cohorts of dinosaurs, specifics sort of groups that get found together at the same time. And then they kind of shift and get a new group of dinosaurs, which is pretty cool.
Garret: Got you, so it’s a little bit of splitting after a whole bunch of lumping?
Dr. Victoria Arbour: Yeah, and I have thought really it’s really fun. I really like doing it, I like figuring out what species we have. But it’s always changing too because new specimens lead to new information that make you look at things in a new light. So I think it’s one of these things that’s always a little bit in flux even though you kind of want it to stay stable as much as possible.
Garret: Yeah, and I think at that level where you are looking at whether they are different species is a little bit easier than the whole like should they be in the same genus or not. I have been reading a bunch about that, and that is such a mess trying to define what a genus is.
Dr. Victoria Arbour: Yeah, it’s really tricky. So what I did in my project was I looked at all the old genre. All the old genus things because I didn’t want to make something really complicated called a new combination, where you like take a new genus name and take an old species name and put them together, and they sort of like a whole like hybrid name out of everything. And the definition if you know what a genus is, is a little bit flexible and especially different taxonomies working on my very different groups.
We’ll have sort of different concepts of what makes a genus versus a species. So if you work on beetles your idea of the amount of differences that you use to call something a different genus rather than different species is quite different from what dinosaurs really focus to. But that’s okay; everybody sort of understands that there is a little bit of flexibility in there and that it’s not really a hard and set rule. So the main thing is that we try to be consistent within our own groups, and just kind of recognize the work that we are all doing together.
Garret: Nice, so as far as when you are saying an ankylosaur, that’s actually a level up from a genus right, is that like…
Dr. Victoria Arbour: Yeah, it’s actually a couple of levels up from a genus depending on how many levels do you like to recognize. So one of the things—so ankylosaurs are a pretty big group of dinosaurs. They are not like the biggest group, they are not as quite as diverse as say like the [inaudible 00:07:13], the things that include like [inaudible 00:07:16] dinosaurs and the ground [inaudible 00:07:17] and all kinds of interesting creatures like that, but they are pretty diverse and they kind of have two main groups.
There is one group that’s called the nodosaur ankylosaurs, and that never involves a tail club that kind of pull like ax structure on the end of their tail, but they often have like really big shoulder spikes. They keep this sort of a long snout that really ankylosaurs had, and they are pretty cool animals in their own right as well. The other main group of the ankylosaurs are – those are the ones I spend most of my time with, and that’s the group that eventually evolves a tail club.
They tend to have sort of a squash, like a squash snout, a more sort of bold long kind of face; they don’t have as long as [inaudible 00:08:00] has. So that’s sort of like the two main groups, and most of the ones that I’ve worked on are in that tail club group.
Garret: Cool, so speaking of tail club evolution, I read your paper on the tail evolution and it’s one of my favorite papers. And you talk about how they went from a flexible tail in early ankylosaurs, and they got a stiff tail a little bit later with some fused vertebrate or vertebrae. And then you had the club eventually forming with osteoderms at the end of the tail.
So I was kind of curious when I was reading this, what’s the—just how useful having just the stiff tail without the osteoderms on it would be? Would it be kind of like having a bat or something on a tail or…?
Dr. Victoria Arbour: Yeah, that’s how I like to picture it. To me that’s one of the most interesting questions is that we’ve seen in the photo actually to have this pattern like you said where the tail becomes stiff well before they get like a really large part of bone at the tip of the tail. They have osteoderms that go down the tail, but they probably like peferred [ph] all the way down to the tip. And then only much later do they get that sort of huge like massive ball of osteoderm at the tip.
So I kind of picture having just the handle, sort of the handle of the axe, the handle of the tail club is a bit like having a baseball bat on the end of the tail. So maybe it’s not quite as effective a weapon as having that full axe head on it, but if someone is chasing you around with an axe or chasing you around with a baseball bat, you are going to probably run away from both of those things, even if like a baseball bat can’t like chop your leg off or something.
I guess that would be too grave [inaudible 00:09:39] I don’t want someone to like smash a baseball bat, so yeah so I think it could have functioned like that. I haven’t done any bionic chemical studies of what an ankylosaur tail with no sort of no bone at the end, how it would function. But I think that’s a really cool area that we could look at in future and try to understand sort of like the function in biomechanics of sort of these hack tail clubs.
Garret: Yeah, because you did write a paper about the biomechanics of a tail with the club right? And you showed that…
Dr. Victoria Arbour: That’s right.
Garret: What was the conclusion you had there; I forget exactly what you learned?
Dr. Victoria Arbour: So what I was trying to pass in, I have a sort of a pair of papers, one where I do some mathematical modeling to see how fast it occurs an ankylosaur completes its tail. And then I took that information and used finite element analysis, which is like a special engineering technique where you can apply force to a digital model of whatever you want, and see what happens to it when you say smash it or something.
And so what I wanted to know was whether or not ankylosaur is specifically could even like build their tail club with any significant amount of force. And then more importantly whether or not they could withstand that estimated force without a break. Because if they can swing it really fast and hard but then it breaks as soon as it touches something, probably they would not have used their tail clubs in that way, because that seems like poor design.
So yeah so the thing that I did was I also modeled sort of a range of assumptions. It’s really tough in some ways to view some of the biomechanical analysis, because we don’t have like the muscle of the soft tissues that really influence how animals move especially in a tail where there’s lots of different bones and lots of muscle that help move the tail in many different directions.
So I used a range of different assumptions like how much muscle there would have been on the tail, different sort of rates of muscles contractions, different like masses of bone and things like that. And we also have different sizes of tail clubs. So some tail clubs are quite small, maybe only like 15 or 20 centimeters wide, but then some are really, really massive. The biggest one I think I’ve ever measured is about 61 centimeters wide.
Dr. Victoria Arbour: Which is really big especially when you consider like the volume represented by that, wow. They are really heavy and I’m not totally even sure like how an animal eats something that heavy up off the ground when it’s so far away from its body. I think it has a lot to do maybe with the tendons that they have sort of ossified tendons that run along the tail. I’m getting off track here, so the question—so the thing that I wanted to know was whether or not they would break under those estimated forces that I did.
And the short answer is probably not. The longer answer is it’s really hard to tell sometimes. So under some of my model assumptions the really big tail clubs would break under like the highest incurred forces. But under the sort of more conservative estimates that I did about impact, speed and mass and all of those fun things, they probably could withstand it. Their tail clubs were pretty good at dissipating the thrust through the knob and through the handle of the tail club. And maybe only the very biggest one that they hit them really hard would actually break their own tails.
Garret: So how fast did you think that they would be swinging these tails? Was it just like as fast as you’d need to break something or were just about …
Dr. Victoria Arbour: I think it would really depend. I think that for some of the really big ankylosaurids with really big tail club nodes, I think that that probably would have been like enough of a visual signal to opponents not to even approach. In the same way that like for example a lot of like heavily armored animals today like porcupines, like a lot of animals won’t even approach those. They are just not prey and they are not bigger ear with bigger [inaudible 00:13:40] kind of intimidate smaller ear with smaller [inaudible 00:13:42], and they don’t even have like—because they’ve got a signal there, a visual signal that says I’m going to win.
So I think that some of the ones with the really huge tails probably didn’t actually even use them a whole lot if we kind of think about them like modern animals. And then for some of these, the sort of like more reasonable size one, say the ones in sort of 40 cm range. I’d have to look, I always forget exactly what the impact velocity, and impact force exactly is. But it’s a lot; it’s enough to break bone definitely. If an ankylosaur tail club smashed into like a [inaudible 00:14:22] ankle or maybe another ankylosaur’s ribs, it definitely would have cracked that bone. That’s so much force behind them.
Garret: Yeah, that’s a good measuring stick to have, if it’s strong enough to break bone you might not even go near it.
Dr. Victoria Arbour: Right, yeah especially like thin bones like ribs and like ankle bones, I think it would have been quite vulnerable.
Garret: Yeah, I think that’s actually why I like ankylosaurs the best, because it’s kind of like one of those pacifist animals. My wife and co-host Sabrina loves sauropods, I think for the same reason where it’s like, well it’s so big everything just leaves it alone.
Dr. Victoria Arbour: Yeah, so I think that’s very true. I think in particular a lot of ankylosaurs were probably using their tail clubs mostly against each other really. When we see like weapons in most modern animals, weapons are really for fighting members of your own species. A lot of weaponry evolves through sort of male to male combat, and interestingly often when you need to defend a resource, so that seems to be the driving sort of selective pressure in modern animals that evolve weapons. It’s almost always males starting some sort of resource related to reproduction.
So there is really cool research out there especially on beetles, sacred beetles, rhinoceros beetles, where the males are defending [inaudible 00:15:49] and sort of using their weapons to shove other animals, like other members of that species away, so that they can mate with the females in that world. So that seems to be the main reason that weapons evolve, but certainly weapons can be used to protect yourself from the predators as well. But that’s probably not really like for driving selective pressure behind a lot of weapons.
And so I suspected it’s probably something similar with ankylosaurs and it’s something that I’m hoping to investigate in a bit more detail as I keep doing my research. So a lot of what I’ve been doing lately is looking at how weapons evolve in ankylosaurs and other dinosaurs and other extinct animals like glyptodonts. So that’s been a lot of fun as well, but it’s tricky to see some of these things out in extinct animals.
Garret: Yeah, glyptodonts, those are those like giant armadillos with a spiky type tail club thing?
Dr. Victoria Arbour: Yeah, that’s exactly right. One of the papers that I’m working on right now is taking a look at what sort of correlations are there associated with having a tail club. So what do ankylosaurs and glyptodonts have in common that might help us understand why they evolved these really bizarre tails. The tail weapons are really rare. Not very many animals ever really use their tails in combat especially in modern animals, and there aren’t really any modern animals that have a specialized weapon without a tail. So something like a tail club or say like a spike on [inaudible 00:17:19] tail.
So it’s really only in a couple of things and they are all extinct. So that makes it a sort of fun challenge to try to figure out like what’s driving like tail weapon evolution, and what sort of led to this very similar structuring to totally unrelated groups of animals, because of course like you said glyptodonts are—they are just big armadillos. They are just really big eared armadillos. Eared armadillos that like have inflexible tail pieces and short skulls, and they are herbivores, but they’re just giant armadillos. And they evolve these really weird tails that are similar to ankylosaur tails even though they sort of do their tail clubs in a slightly different way. It’s still a really similar structure in totally different groups of animals.
Garret: Yeah, do you have any opinions on why more animals don’t have these tail defense mechanisms?
Dr. Victoria Arbour: Yeah, so this is still research that’s kind of in progress, so it might change a little bit as I finish it up. But some of the things that seem to be sort of statistically significant for having a tail club that really correlated with it and need to be there first in order to have a tail club are things like being really big and armored. So that’s probably not surprising, but those things seem to be in place first before tail weaponry can evolve. And today we don’t really have any big armored animals.
Dr. Victoria Arbour: There are armored animals out there are like armadillos and turtles, but none of them really get this sort of truly gigantic sizes. And so that might be like a major reason that we don’t have tail clubs, or other tail weaponry around today, because we just don’t have like big armored animals at all.
Garret: Interesting, are there more ankylosaurids or are ankylosaurids generally bigger than nodosaurids?
Dr. Victoria Arbour: No actually if I have to really guess and I need to double-check this. But I think that nodosaurs actually are often a little big bigger than ankylosaurs.
Garret: Oh interesting.
Dr. Victoria Arbour: But they are all really big, so perfect, it’s sort of like splitting hairs a little bit there I guess. So the very biggest ankylosaur ever I’m pretty sure is Ankylosaurus out of all ankylosaurs. It’s a really big animal, it just has a huge head, and it probably had a huge body as well although we don’t have any skeletons of it. But some of the nodosaurs that we find in the lake group features like [Adventomania] are also really big animals. And I think they are probably at least a little bit bigger than the ankylosaurs that lived at the same time. Things like Euoplocephalus. Yeah so if I had to guess I would say that nodosaurs might have edged out most ankylosaurs except Ankylosaurus.
Garret: Okay, that’s interesting. Is there—you mentioned a little bit about the keeping the tail off the ground. I’ve noticed that recreations of ankylosaurs or whatever you know articulations have been presenting the tail like slowly, higher and higher off the ground.
Dr. Victoria Arbour: My favorite illustrations of ankylosaurs are when ankylosaurids are shown with their tail like a scorpion position.
Garret: How nice.
Dr. Victoria Arbour: Like over their body, like whooping, like a tyrannosaur on the face or something. I have some really—I have a really, really funny collection of images of ankylosaurs fighting. Other animals had really weird ways that don’t really make any sense. But yeah, so I’m not sure if they get higher. I think ankylosaurs are really interesting because yeah, like the tail is really heavy, and it’s heavy far away from your body, but if you think about—if you ever do like weights or anything and you try like holding images, well I figure this is just me, but if I just hold like a 15 pound weight like away from my body like out from the side, I usually can’t do it for very long.
Garret: I don’t think very long.
Dr. Victoria Arbour: Okay that’s good, so it’s really hard. I give you like one and I’m like, “Oh God I’m tired,” [inaudible 00:21:21]. So yeah, so it takes a lot more like muscular energy for us to hold a heavy weight like further away from our body. And it kind of makes you wonder if it’s the same thing in an ankylosaur tail, because these tail [inaudible 00:21:33] are really heavy and their tails are pretty long, not as long as like a [inaudible 00:21:38] tail, but they don’t have like—even really straight [inaudible 00:21:40] have kind of short tails, and ankylosaurs still have like proportionately long tails.
So one thing that I think might be helping a little bit with them not having to use like muscular power to keep the tail off the ground is this really intricate series of ossified tendons that run along the tail club. So ossified tendons are tendons like we have in our bodies, but they become ossified like [inaudible 00:22:06]. So a good example of something like that is in turkeys. This is great because in Canada, we are having Thanksgiving next weekend. In turkeys, if you ever ordered like a chicken, when you eat the sort of drumstick piece, and there is always that like really thin, like toothpick bone in there.
Part of that is an ossified tendon, so, and I think it’s all—Oh no sorry, that’s part of the—that’s the fibula really reduce, but there are ossified tendons in [inaudible 00:22:31] and a lot of bird legs actually. So yeah so ossified tendons is something that we find in a lot of dinosaurs, especially a lot of herbivorous dinosaurs, but usually they are more sort of like over the back, and over the front of the tail. And in ankylosaurs all way down at the tip of the tail, and running along that steep part of the tail, the tail part of the tendon.
So I think that what’s probably happening is the ankylosaurs uses sort of like muscles to keep the tail in the front above the ground, but then it’s probably relying at least a little bit on those ossified tendons to keep the tail from dragging like really heavily on the ground, and maybe also using it a little bit in terms of swinging the tail from side to side, because the ossified tendons sort of store elastic energy as well. And that’s something that’s a little bit harder to model when you are doing mathematical model of the tail bone. Yes, so I think the ossified tendons probably play a pretty key role, although it’s a little harder to actually like test that and study it in a meaningful way.
Garret: Yeah, it makes a lot of sense. I figured there had to be some kind of internal structure. I have a background in engineering, so like I’ve always looked at things and imagining the stresses and forces involved, and yeah.
Dr. Victoria Arbour: Right, it’s like doing this kind of work then, it’s really fun.
Garret: Yeah, it’s interesting.
Dr. Victoria Arbour: Yeah, so it’s a—I’m also not totally opposed to the idea of ankylosaurs maybe having their tail club touching the ground sometimes. We don’t have any evidence for that, although there are ankylosaur [inaudible 00:24:00] there’s probably mostly nodosaurs or at least ankylosaurs without tail clubs, and they don’t drag their tails. You don’t see tail drag marks in nodosaurs track leads.
So it is a little bit up in the air whether or not ankylosaurs could have done that, but I don’t think it’s too crazy that they fight about things like rested them on the ground sometimes. Again because they are like pretty heavy, and especially if they get bigger and bigger, they might droop a little further.
Garret: Yeah interesting, just out of curiosity, why do you think more animals or dinosaurs don’t have osteoderms or some kind of armor?
Dr. Victoria Arbour: That’s a good question. So osteoderms are bone, and bone is really expensive to maintain in your body. Osteoderms are like special bones that form in the sort of lower level of the skin, they are like the dermal layer, so that’s where osteo means bone and dermis the skin, they are simply skin bones. Humans don’t really have anything like that, but it is not uncommon in other animals, so it’s the same thing that forms the shell of armadillos, turtles have osteoderms often times in their arms and legs, but their shell is not osteoderms, it’s actually their ribs.
Crocodiles have osteoderms and some lizards like gila monsters, and gila monsters have osteoderms as well, but [inaudible 00:25:25]. So it’s something that we see sort of in lots of different groups, but not in every member of those different groups, because again like most mammals do not have like osteoderms. So it probably has to do with the trade offs in sort of maintaining a lot of extra bone on your body, and all of the like minerals, and like resources that it would take to both grow those and keep them maintained.
So it’s sort of a trade off between the cost you have to put into it, and the benefit that it does for you in terms of say like not being human, or whatever other function that osteoderms have. So osteoderms have a couple of different functions that we know of in modern animals. They do offer protection against predation essentially when you are very small. It makes sense, but there’s actual evidence behind that for like certain lizards, like the thicker and more osteoderms you have, the less likely you are to [inaudible 00:26:19].
Dr. Victoria Arbour: In crocodiles they seem to also have a thermoregulatory function, so they seem to have a bit of a function in both like absorbing and dissipating heat which is very interesting, because they have blood vessels in them, so that makes sense. And then a paper that was published recently also shows that they act as calcium storage sites. So when crocodiles are getting ready to lay eggs, they pull calcium out of their osteoderms before they pull it out of other bones in their body. So they can also seem to act a little bit as like calcium reservoirs for animals that lay eggs.
So osteoderms probably have a lot of different purposes, and in certain dinosaurs, they probably also served as again visual diploids, so it is hard to argue that the plates of a stegosaurs which are osteoderms don’t have any kind of like visual signaling system or function, because they are so big and like flamboyant. They surely must have some sort of like – that’s really, that’s probably what those are for.
And even some ankylosaurs are similar, so some ankylosaurs have very like flamboyant [inaudible 00:27:24] osteoderms like huge spikes at the front of the shoulder. They are like large, big, triangular plates along the sides of the hips. So those probably have a little bit of a defensive function, a little bit of a thermoregulatory function, maybe they are also working as calcium reserves, but they might also be visual signals as well. So they probably have lots of different functions, and then it’s just sort of a matter of like the trade offs of any one or all of those functions combined versus again the energy after [inaudible 00:27:54] maintained.
Garret: Okay, yeah that makes sense. That kind of reminds me there is this paper, I think it was this year that talked about these large pits that ankylosaurs would get in their osteoderms, did you happen to see that?
Dr. Victoria Arbour: I’m not sure I’ve seen that one, but ankylosaur osteoderms do often have like really weird texture, they are really like bubbly and nobly. Some of them seem to have pathologies in them. But yeah some of them sometimes get these really big [pepsederm 00:28:24], and I think that it’s really interesting, but I haven’t read the paper with that yet.
Garret: Okay, I was wondering if maybe that was part of it like there is a risk for infection that comes with osteoderms, or something that would make it so that not all animals wanted them.
Dr. Victoria Arbour: I don’t know, I mean osteoderms are still covered so their bones are not like exposed at all. So they still would have been covered by like a scale, like a sort of like a horny like virgin scale in life. Not very many animals have just like straight up like exposed bone. I think one classic example is armors, but armors are really huge. So, yeah like they would have been covered by some sort of like horny covering. So I don’t think they’d be at risk of infection like more than other parts of the body unless of course maybe they are harder to heal if they get bitten or damaged or something like that, but that I’m not sure about.
Garret: Yeah, I think in the paper there were some particular bacteria or something that they were guessing might have gotten into it through like either a bite or some other mechanism, and then it spread or something like that.
Dr. Victoria Arbour: Interesting.
Garret: It is interesting. Yeah it was in, I just found it. It was in the Journal of Paleopathology.
Dr. Victoria Arbour: Oh that sounds fun.
Garret: Yeah, I think it’s the only article I’ve ever read from that journal, but I need to check it out more often. So, on a lighter note, getting away from paleopathology, I know that you helped out the group making the game Saurian on their virtual ankylosaurs model?
Dr. Victoria Arbour: Yeah.
Garret: Are there any features that you kind of encouraged them to include or that you are particularly excited about that are in their version?
Dr. Victoria Arbour: I’m really excited about Ankylosaurus because I think that together we came up with like the best, most accurate reconstruction of it that’s out there today. It was really nice working with them because the first draft they sent me, I had a lot of comments about it, they were totally really—and like not because they had done a bad job, just it’s hard because there is not a lot of information out there and knowing Ankylosaurus is such a household name. There isn’t a lot of information out there. There is a couple of papers, but they are like skeletons and [inaudible 00:30:38] to go with that.
So I had a lot of comments, and they were really great about just running with it, and we sort of totally retold it like gave it a whole new sort of osteoderm arrangement, like new interpretations. So I’m really excited because I think it just looks great. I think it looks like a real animal, not like some kind of merged together monstrosity that Ankylosaurus sometimes look like because they are hard to interpret, and they don’t really look like anything around today. So it is kind of hard to like — they are not like intuitive animals to reconstruct, and osteoderms are a lot of work for artists to work on.
Yeah, so I’m really excited about that, and then it also was voted one of the new playable characters. After they release the sort of first release of the game, it’s going to be the next one that becomes one of the sort of characters you can play from a baby up to an adult. I’m really excited to be working with them on sort of teaching what I know about Ankylosaurus [inaudible 00:31:36] and growth in general, and applying that to make sort of like a cool story for Ankylosaurus, so I’m really looking forward to it.
Garret: Yeah me too, I voted for Ankylosaurus with our kick start of votes.
Dr. Victoria Arbour: Oh nice, I did too, but I’m probably a bit biased. Yeah, so I think it’s going to be really fun, and I think—I’m actually not someone who plays all the video games because I tend to get like very motion sick from a lot of like, especially like 3D video games, but I’ve been really excited to work on this and sort of try this new medium of scientific storytelling, because it’s a little bit different than say like a television documentary or even like a university course, because the players get to make decisions about what they are doing as those dinosaur characters.
I think it’s a really neat way to get people sort of more immersed in the science behind dinosaur research as it is today. And it’s just like a cool medium to be helping out with, so I’m looking forward to it.
Garret: Definitely, it’s too bad that you say you get motion sick, because they are going to make a VR version too.
Dr. Victoria Arbour: I definitely will not be able to play that one I know, but I’m looking forward to trying this one out then. I might just have to do it a little bit, but I think it’s going to be really good. I think it’s going to be a lot of fun.
Garret: Yeah, I like the colors that they chose too, or did you have any impact on the orange and brown theme that they kind of put?
Dr. Victoria Arbour: Yeah, a little bit. So they came up with a couple of different like alternative options and then asked for my feedback on them, and yeah I like going with sort of a brightly colored ankylosaur. I sort of like the high sort of contrast that like it’s sort of dark, but then it got things like bright patches on the rest of the body. So I think that looks pretty cool.
I wanted to move us away from like brown ankylosaur. Because they don’t necessarily need to be like neon colors, but I think they are real animals, and you know animals have different kinds of color patterns in some features, and environment all kinds of things. So yeah why not have a nice colorful ankylosaur.
Garret: Yeah, and especially when you mentioned the porcupine analogy. If animals are just going to avoid it because they recognize it as something you can’t really mess with, it makes perfect sense for it to be brightly colored, because then you get the meeting display to go along with it.
Dr. Victoria Arbour: Right, and yeah a lot of animals use like warning coloration or at least warning patterns, sort of bright contrasting patterns to sort of indicate danger. We don’t really have any evidence for this in ankylosaurs, but I think it seems pretty plausible and reasonable, yeah and nicer than just having sort of like a regular like just brown ankylosaur, people believe so.
Garret: Yeah, or green like a lot of pattern depictions.
Dr. Victoria Arbour: Right, yeah and then I’m sure some were green, and that’s fine, but a lot of ankylosaur art doesn’t sort of portray ankylosaurs in very like favorable light. They often do like just kind of standing there not looking particularly smart or falling off cliffs is a thing that is just happening also in ankylosaur art. I have like multiple examples of Ankylosaurus just like falling off of hills. And I’m like, “Oh man, they’re not that,” I mean they are probably not like super smart animals, but they probably could avoid falling off the cliffs like some would have thought.
Garret: Yeah they have a low center of mass; they’d be good at like not falling.
Dr. Victoria Arbour: Right, yeah it’s just like a funny thing that keeps showing up. I don’t really think I’ve seen that with other dinosaurs very often. It’s just like a weird, I don’t know, it’s just a weird thing, a weird thing about Ankylosaurus.
Garret: That is weird, cool, so just like a kind of final research-y question, is there anything else that you are excited about, that you are researching or looking forward to?
Dr. Victoria Arbour: I have really cool things on the go that I can’t really totally talk about yet, but I hope that any listeners will stay tuned for cool ankylosaur stuff in the next couple of years. I just started a new post doc at the Royal Ontario Museum, I was pretty useful at the North Carolina Museum of Natural Sciences trying some really cool things, I’m finishing up there really huge weapons research at how dinosaurs brought weapons. And some of my focus at the Royal Ontario Museum is going to be a bit more of like patterns in dinosaur bio geography.
So looking at Ankylosaurus, but also looking at like groups of 5 ankylosaurs and sort of understanding like how sea level, and climate, and land bridges, and different things like that influenced how they dispersed between North America and Asia during the [inaudible 00:36:13].
And I think that is going to be really cool because I think we are going to be able to learn some really interesting things about what sort of like environmental and biological factors influenced broad scale migrations between [inaudible 00:36:25]. I think that’s going to be really […].
Garret: Does that tie into your research about the Ankylosaurus swimming?
Dr. Victoria Arbour: Yes a little bit. I hadn’t totally decided to take this direction when I wrote that paper, but that paper sort of gave me the impetus to further invest some of these things. In that paper I had taken a look at a pattern that had been noted by other affiliate […] before that nodosaurid ankylosaurs seemed to wind up in marine settlements more than ankylosaurid ankylosaurs.
I took another look at that with some of the new species that we have identified, the new specimens, and did some statistical analysis and found out that, yeah they do wind up in marine settlements more often than ankylosaurids, but not everywhere and not always. It’s mostly in North America that we see that particular pattern, and that’s probably because North America keeps getting flooded by the huge Western interior sea way.
So that seaway has a really big influence on ankylosaur diversity during the [inaudible 00:37:28] period, because at least from the data that we have right now it seems like North America had it’s sort of own like home grown, like group of ankylosaurid ankylosaurs and nodosaurid ankylosaurs. But the ankylosaurs actually got extinct as the sea level gets really, really high, and then lost the species. And so most of the ankylosaurid is the one with tail clubs that are really famous from North America like Ankylosaurus and Euoplocephalus are actually Asian immigrants that came in much later and sort of re-colonized North America.
So it’s really interesting to see how things like sea level, and hopefully we will take a look at say like temperature or maybe even things related to my diet or body mass might sort of influence sort of like extinction events in different place or dispersal events in different place, and just try to help us understand like the pattern of dinosaur evolution in North America, and maybe we will even learn a little bit about what is in store of us as climate changes and [fear of horizons 00:38:29] nowadays. So I think it’s going to be a really cool project.
Garret: Yeah that sounds really interesting. I have to keep my eyes peeled.
Dr. Victoria Arbour: It’s going to be a little while though because I just started, but I am excited.
Garret: Great, well thank you so much for talking to me. If people want to learn more about you or your research or follow you, should they go to Twitter or where should they go?
Dr. Victoria Arbour: Yeah, I think Twitter is probably the best place, and my Twitter handle is really simple. It is just my name, so @victoriaarbour.
Garret: Great, yeah you post lots of things. I think I re-tweeted something you posted today that I liked a lot.
Dr. Victoria Arbour: Oh yay!
Garret: Part of your—what did you call—hollow…
Dr. Victoria Arbour: Oh drooling.
Garret: Drooling that’s sort of about this.
Dr. Victoria Arbour: Yes that’s something that I’m doing, mostly just for fun, but a lot of them are winding up having dinosaur too [inaudible 00:39:20].
Garret: Yeah, and kudos on the great art work. I liked your—all of them so far actually.
Dr. Victoria Arbour: Thanks, that’s so nice of you, thanks.
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