All About Allosaurus
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Hello and welcome to I Know Dino. Keep up with the latest dinosaur discoveries and science with us. I'm Garrett. And I'm Sabrina. And today in our 542nd episode, it's all about Allosaurus. Or maybe A is for Allosaurus. Although I don't know if we'll do a series like this. We're talking about new species, old species, everything we know about Allosaurus so far. Yeah, because there are multiple species of Allosaurus now. Yes. So...

It's news and dinosaur of the day all wrapped up into one. And our fun fact is that the first Allosaurus fossils found, which were by Ferdinand Hayden, a geologist, they were thought to be petrified horse hooves. That's really interesting. Horse hooves. Yes. That is a mistake I haven't heard between a dinosaur fossil and a living animal before. We've heard about bison, whales, bats.

Turtles. Mystical creatures like dragons. Mm-hmm. But never a horse or especially a hoof. Yeah. Although that happened a long time ago. It happened in the 1800s. Understandable. Just because we didn't hear about it. Yeah. So we could also call this episode Allosaurus Revisited as we sometimes do. Yes. Maybe that'll be the title. Who knows? I like the alliteration. A is for Allosaurus? Mm-hmm. Or all about Allosaurus. Triple A. Mm-hmm.

All right. And before we get into all of that Allosaurus goodness, of course, we want to thank some of our patrons. And this week, we'd like to thank four new patrons. They are Sally, Kiani, Acrofan Owen, and Tyrannosaurit. Thank you all very much for joining. And then rounding out our shoutouts, we have Ayrton and Everett, The Howard Family, Koukanosaurus, Joao, Fognite, and Stevaseratops.

Thank you so much for being a dino at all. We hope you're enjoying all of the perks like our bonus content that we've been dropping in between episodes. Yeah, we did two episodes of I Know Paleo last week. That was a little bit of an accident as it turns out. We both thought we were behind by a week or a cycle of I Know Paleos, but it turned out that we were just confused because

Behind the scenes, we had one of our daughters got admitted to the hospital for a really bad virus called human... Metanuma virus. There you go. That was quick. And so she actually had to go to the ICU and a feeding tube and like breathing support and all that stuff. So we were not sleeping very much and got very confused about our timing. Yes. Well, also we had planned it, I guess, for one of the inopaleos to be a little late and then...

One of them ended up a little early, but it's all sorted now. Yes. But there are two episodes of I Know Paleo, long story short, that you may not have heard yet. So they are both there. One of them is on dire wolves and the other is on...

The end Eocene extinction. Thank you. I couldn't remember which extinction event it was. Not a mass extinction. A minor. Yeah, very interesting specific event. Yes, but thank you again to our community and all of our patrons because without you we could not keep this show going and it is especially heartening to know that we have this community when we're going through tough times like this.

dealing with a infant in the hospital for a few days. Yep. And she's back and healthy and smiling and everything now too. Yes.

All right. Before we get into all about Allosaurus, I'm really pushing for that one, Garrett. All about Allosaurus? Before we get into AAAs, I just want to do a quick mention that there is a free dinosaur event with the Colorado Northwestern Community College Paleo Crew on June 28th. So thank you to our Dino It All patron, Eric, for sharing with us. And oh, I forgot to mention, if you want to become a Dino It All, that's at patreon.com slash inodino.

So if you're in the area in Craig, Colorado, it's happening between 1.30 and 2.45 p.m. Dr. Logan King is going to be giving a presentation about CNCC Paleo. And if CNCC sounds familiar, we did advertise a while back their excellent summer field and lab programs. Yeah, we've done it at least two years now, maybe even three years. Mm-hmm. Because they have such a cool program, and we know some of our patrons have gone on those programs before. Plus, they're finding cool stuff. So like Emerald Bender is going to give insights on Walter the Hadrosaur. Mm-hmm.

And then it's going to be followed by a Q&A and an Ask a Paleontologist roundtable. And there will be snacks. Wow, cool. And it's free. Yes. Free snacks plus free dinosaur discussion. Yeah. What more could you want? So if you want to know more, we will have a link to a little bit more information in our show notes. Yes, the link is very long. So we will just post it rather than reading out all 190 characters or whatever it is.

And if you're not familiar with where Craig, Colorado is, it's in Northwest Colorado, which you may have been able to guess from Colorado Northwestern Community College. So you could potentially get there from Utah, maybe Nevada. Yeah. Idaho. Fun day trip. Wyoming. Yeah. Or maybe make a weekend of it. For sure. Yeah. I think if we lived in Denver and we didn't have kids, we might try to make it out there. Or even if we just lived in Denver, we might make a weekend out of it. True.

We're just a little too far for this one. Yes. With an infant and a toddler. Yeah. They do have Allosaurus in Colorado. Yes. So that sort of ties in. You could probably see some sort of Allosaurus thing. I don't know exactly what Allosaurus stuff they might have on display there. At the very least, you could make a side trip over to Dinosaur or Vernal. Oh, yeah. In Utah. Yeah. And see Dinosaur National Monument. They have some really cool Allosaurus stuff there. Mm-hmm.

So if somebody does do all that, let us know. All right. Allosaurus, we're revisiting. This is a request as well from Tyrant King via our Patreon and Discord. So thank you. The request was actually about Allosaurus gemmadsini and Allosaurus tendagurensis. But it turns out a new Allosaurus species was named recently.

Another new species? Yes, another one. And there's also more debate around an existing Allosaurus species, Allosaurus europaeus. So...

seemed like a good time to dig in. Yeah, I don't remember hearing about that one. I'm sure we did Allosaurus very early on in I Know Dino since it's a very well-known dinosaur. And back then our dinosaur of the days were what, like five, 10 minutes? They still are sometimes. Yes. Depending how much information is available. This one, I think it was like episode 25 or something when we first did Allosaurus, but a lot of new stuff has come out because

Three of the papers I'm talking about, this stuff has come out in just the last few months. Good time for a All About Allosaurus episode. It's catching on. Or Allosaurus Revisited. Triple A. Okay. So Allosaurus is an allosaurid theropod. It lived in the late Jurassic in what is now North America, found in the Morrison Formation. It's also been found in Portugal and teeth have been found in Germany. Okay.

Allosaurus has been given several fun titles like the quintessential Jurassic theropod or the most iconic Jurassic theropod. Yes, I do think Dilophosaurus might be up there with them. Well, the reason it's got these titles is because so many skeletons have been found. Yeah, that's true. It's more than Dilophosaurus. I guess I split it in half. Dilophosaurus early Jurassic, Allosaurus late Jurassic in terms of...

biggest coolest most well-known theropod I think Allosaurus was bigger oh yeah it was definitely bigger physically but like in its ecosystem Dilophosaurus was like ahead of its time so Allosaurus is a theropod that means it's distantly related to Tyrannosaurus but it was built very differently

It was a large predator. It did walk on two legs. It had powerful arms and large hands with big, sharp, curved claws. It also had a narrow head with short, crest-like horns above its eyes, strong legs, and a large tail. Yeah, I think those crests above its eyes are partly what makes it so popular. It gives it this really menacing, angry look to it, which is so cool. Yeah.

And those hands too, I love. That was the first real dinosaur replica we ever bought. Actually at Dinosaur National Monument, we bought a replica Allosaurus hand. With the three fingers? Yeah. Because you look at it and you're just like, that claw is almost as big as my hand. And it's got two other smaller claws and these huge powerful fingers. It's just really extremely menacing. Yes. So there's multiple species of Allosaurus, as you might've gathered when I talked about how there's new species named. Yeah.

There's some variation in size. The type species is Allosaurus fragilis. That could grow up to like 32 feet or almost 10 meters long.

And I'll get into other species sizes later because we're going to break down some of the species. Nice. Now, Allosaurus had a large skull and a short neck. The skull was light but robust. It had a narrow snout and, of course, a pair of short crest-like horns above and in front of the eyes, like you were saying, Garrett, that made it have an angry look. I think it's funny that you say it has a short neck because, yes, compared to a sauropod, but not compared to something like a ceratopsian or something. I think it was pretty typical for a theropod.

Yeah, and theropods had short necks. They're not long necks. Yeah. So the horns above the eyes, they varied in shape and size. They were probably covered in a keratin sheath too, so that means they would have been bigger in life. So cool. And the horns may have been for display or help as sunshades for their eyes. Maybe they held glands, like salt glands. Or they could have been used in combat against other allosaurus, although they were fragile. Yeah.

Yeah, they're not bashing them together like a... Like a Pachycephalosaurus? Yes. Which may or may not have also bashed heads? Yeah. Now, a Halosaurus had a wide gape. It could open its mouth pretty wide. It had a good sense of smell. We know it had large olfactory bulbs, typical for its size. Its inner ear was like a crocodilian, so it could hear lower frequencies.

It also had a ridge on the back of its skull roof for muscle attachment. As a side note, one species, Allosaurus amplis, which was named in 2015 by Galton, Carpenter, and Dahlman, but is now considered to be a nomodubium, in that paper they found strong contacts between the cheekbones, quote, probably allowing little if any movement. Okay, so it had a pretty rigid skull compared to some other, say, Dilophosaurus, which might have had a more flexible skull. Yes.

There are also hollow spaces in the neck and backbones. It had a round, large chest, a barrel chest, if you will. Also gastralia, those belly ribs. Yeah, that tells you about the chest shape too, because you can put the puzzle piece together of the bottom of the chest. It's not all guesswork of where it would have been. Yes. And it had large hips and a wishbone.

I love when we talk about wishbones with large dinosaurs because that's one thing they have in common with modern birds. Yeah, and it's just funny to think of a wishbone like bigger than a modern bird. Yeah. If you broke that wishbone, would you get twice as many wishes come true? I don't know. I don't know if you could. Yeah. You'd need like quite a lever on it. Well, skin impressions of Allosaurus have been found and there were small scales around the ribs of one juvenile.

It also had small scales around the lower jaws and on the neck. It had short arms compared to, you know, its body. And as we mentioned, three fingers in each hand. It had three weight-bearing toes and then one small duquois and a long muscular tail and powerful legs. It was probably pretty fast, like faster than other predatory dinosaurs of its time.

It's been estimated to be as fast as 19 to 34 miles per hour or 30 to 55 kilometers per hour. Wow, that is fast. Those are powerful legs. Although I think it's interesting that you mentioned that it had short arms because to me, when I think of Allosaurus, I think of it having long arms. Well, compared to when you're looking at T-Rex and you can see proportionally. Yes, I think compared to pretty much any of the Cretaceous large theropods that people are familiar with, it had pretty long arms. But compared to the earlier stuff...

Like your prosoropods and all that stuff, they were getting a lot shorter. Yes. I don't think it was able to reach down and touch the ground while it was standing kind of thing. Who knows if it was flexible enough. That's true. There are some adult humans who can't reach down and touch the ground easily. Myself included. Yeah.

So like I mentioned, so many Allosaurus skeletons have been found that we have a growth series from babies to adults. I love when that happens. Yeah. And the juveniles had different hunting, feeding strategies from adults, which we've talked about that with other theropods too, like T-Rex.

The juvenile's legs were longer than adult legs, which may mean that they were faster and then they had the different hunting strategies compared to adults. Proportionally longer. Yes. It'd be pretty funny if they were longer on an absolute scale. Oh, that would be funny. Now, as Allosaurus aged, the thigh bone got thicker and wider and the muscles became shorter.

A study of Allosaurus growth, they did histology on a number of individuals, which means they cut into the bones. They estimated that the max growth happened around age 15, and it increased its body mass by 148 kilograms per year. That's about 326 pounds. Okay, so that's a similar sort of teenage growth spurt that you see in Tyrannosaurus. Mm-hmm. They also estimated an upper age limit of between 22 to 28 years of age, which is

It is not as old as some of the Tyrannosaurus specimens that have been found. Close though, because those are like early 30s. Nowhere near some of the Carcharodontosaurs that were in the 50s. Yeah. I think recently you were talking about sauropods maybe even reaching into the, you know, almost approaching 100, like 70 or 80 years old. I'll have to look into that more because that fascinates me. Yeah. It's really hard to estimate because you don't get the good lags in most sauropods the way you do in a lot of these theropods.

So they found that the lengths of the allosaurus legs and arms grew more slowly over time, which makes sense. A 2010 study examined allosaurus growth and individual variation based on specimens from the Cleveland Lloyd Quarry, which is a site famously full of allosaurus specimens. And I will talk a little bit more about that now. I got ahead of myself in the notes. There's at least 46 individuals from the Cleveland Lloyd Quarry. Wow, there were that many? Yeah.

There's a lot of variation in the skull, which is cool. They found that growth is mostly isometric. It grows equally, the different body parts. That's good for identifying different species because if it's just a literal scaled down version and there's not different proportions changing, it makes it easier to identify different species. Yeah.

I'll get more into the history of the Cleveland Lord Quarry a little bit later because it plays a big role in Allosaurus species. But a 2021 study found that Allosaurus fragilis, again, that's the type species, likely had sexual dimorphism based on a statistical analysis. It depends on the size and shape, though the study said that it's also difficult to test. Yes. But there are differences in the femoral head, that's at the top of the thigh bone,

the top ball-shaped part of the thigh bone. And it makes sense to have differences in that part of the body because that's near where the cloaca would be. And presumably, the females, while laying a bunch of eggs, might have some slightly different stuff going on near their hips. That's true. And yeah, some are bigger than others.

There's a possible caveat that some of the specimens in the study were probably sexually immature. That would make a difference. Though in some modern animals, there's differences right from birth. Like apparently male chickens have more muscular mass than female chickens, even at hatching. I didn't realize. It's hard to tell under all those feathers. Yes. They're so fluffy. So there's possible sexual dimorphism based on the width of the head of the femur compared to its length.

Medullary bone was found in one shin bone from the Cleveland Lloyd Quarry. And medullary bone forms in female birds laying eggs, so it's often used to determine if a fossil is female. Well, that's cool because if you could determine that there are two sets, you can figure out which set is the female. Yes, but in this case, there's debate about whether this is medullary bone or a bone pathology, some kind of injury. Yeah, this case and basically every other case with medullary bone. Yeah, it's hard to tell.

In just a minute, we'll get into the Allosaurus history and species, but first we're going to pause for a quick sponsor break.

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So getting into Allosaurus, the history and the species. Allosaurus has been found in Colorado, Montana, New Mexico, Oklahoma, South Dakota, Utah, and Wyoming in the U.S., as well as in Portugal. And like I mentioned, teeth have been found in Germany. It's funny that you started with Colorado. We're just talking about Northwest Colorado. Yes. Well, I think I went in alphabetical order there. But yeah, that works out. It was all on purpose. I probably would have started with Utah. That's where I think, because that's where the Cleveland Loy Quarry is. Yeah.

Well, multiple species have been named. There are three, I'm going to say three undisputed species. Undisputed? Yeah. Bold claim. Yes. But I think time will tell because maybe there's only two. The third species was named so recently, just in the last few months, that other recent studies have

haven't been able to incorporate it. They said that there was only two species. They probably didn't even know about this third one. Yeah. It might've been submitted for publication before that other paper was even finalized. Exactly. But the three undisputed species are Fragilis, Gemadcini, and Anox or Anix. I'm not entirely sure how to pronounce that one. That must be the new one. That is the new one.

So again, that type species is Allosaurus fragilis. That was the one that was named first.

The genus name Allosaurus means different lizard. It refers to its concave vertebrae, which was unique when it was first discovered back in the 1800s. Something that is not even remotely unique now. Yeah. Super common. But it's such a cool sounding name. Allosaurus sounds cool, but it's such a really lame, different lizard. Well, and then the species name for Gillis means fragile. So the full name is different delicate reptile. Yeah.

And that fragilis part refers to the features of the bones that made it lighter. Yeah, basically it was pneumatic. And it was more of a description of the fossil itself than it was over, you know, the animal in general. Something like seven species have been named. Well, there might have been more, but the ones I have stories for. We've got anex, amplis, atrox, europaeus, fragilis, gemmadsini, and lucasi.

In alphabetical order again. Was it? I think so. Oh, I guess I just do that. All right. Well, this was a bone wars dinosaur. And as you can imagine, that led to it being a wastebasket taxon, which means a lot of dinosaurs got named Allosaurus that weren't necessarily Allosaurus. And there's a lot of confusion. So O.C. Marsh named Allosaurus fragilis back in 1877 based on fossils found in Colorado in the Morrison Formation.

Marsh and Cope named other bone wars dinosaurs that turned out to be Allosaurus. So Marsh named Creosaurus and Labrasaurus and Cope named Epontarius. All three of those turned out to be Allosaurus. Those first Allosaurus fossils, even though it was named in 1877 based on fossils in Colorado, the first fossils, they were found in Colorado, probably the Morrison Formation, but they were found back in 1869 by Ferdinand Hayden.

And Hayden sent the fossil to Joseph Leidy, the unsung hero of the Bone Wars. Yeah. Yeah. He was sort of the... He was the third wheel. Or the neutral party. Oh, okay. He was just doing his paleontology. Didn't want to get caught up in all the drama. Yeah, but then he kind of did on accident. He wasn't trying to. Despite his best efforts. Yeah. Anyway, Leidy said that it was half a tailbone and he assigned it to Pochilopluron and then later named it Antrodemus.

And the name Antrodemus means chamber-bodied. He named Lady, named Antrodemus Valens back in 1870 based on a set of vertebrae found in Colorado in the Morrison Formation. Charles Gilmore later in 1920 compared those bones to Allosaurus fragilis and found them to be the same. And since Antrodemus was named first, he gave them all the Antrodemus name. So really, we should be saying Allosaurus is Antrodemus. But...

Madsen in 1976 proposed Antrodemus Valens to be a junior synonym of Allosaurus fragilis because the Allosaurus was more well-known. And I will get into that. That has to do with the Cleveland Lloyd Quarry. So in 1920, Gilmore wrote a monograph of Allosaurus, well then Antrodemus, and said because Antrodemus was named first, we use that name. And we did for more than 50 years until James Madsen died.

Some of the problem here was that Allosaurus was described from fragmentary material from Marsh in 1877, which is not surprising, being a Bone Wars dinosaur. It was named from a specimen that includes three vertebrae, a rib fragment, a tooth, a toe bone, and then part of the upper right arm. Yeah, not great. Not great. We've seen worse. We have. Shortly after, there was an almost complete skeleton and several skulls referred to Allosaurus, so that's good.

But that holotype, that specimen with the vertebrae and rib fragment and everything, is not diagnostic. So a neotype was proposed, a new specimen to represent the species, because you want a good specimen.

A lot of bones to be able to compare other individuals to. Yeah, because again, at the time, look, it's got concave vertebrae. This is such a unique animal. We should name it. Flash forward to, wait a second, tons of these dinosaurs have concave vertebrae. Yes. Not really the most useful criteria. So yeah, Allosaurus in the past was considered potentially dubious because the type specimen was so fragmentary.

But then in 2010, Gregory Paul and Kenneth Carpenter petitioned for a neotype, the more complete skeleton, and then that was ratified in 2023. So Allosaurus is safe. Yeah, which is a good choice because you want a nice, complete animal, as complete as you can get, to compare new fossils to, to tell if it's a new species or genus or if it counts as this existing one. Yeah.

And Allosaurus is one of the first well-known theropods. That's partly because of the Cleveland-Lloyd Quarry, which I keep bringing up. Again, that's in Utah. It's full of Allosaurus individuals. It's the most common dinosaur in the quarry.

And it could have happened like maybe there was a pond where large herbivores died in drought and then attracted allosaurus scavengers. And then as food became more scarce, the allosaurus individuals died as well. Yeah. That's called a predator trap. Yes. Some people think Labrade harpets might have been something similar. Yeah. The Cleveland Lloyd dinosaur quarry in Utah was first excavated in 1927, but nothing big happened there until 1960. Okay.

Nearly 40 institutions worked together and they found thousands of bones between 1960 and 1965. And this was led by James Madsen. 40 institutions. That is a lot. Yeah. And now it was mostly, it turned out to be Allosaurus fragilis fossils. At least 46 individuals, they were disarticulated. And that's 46 Allosaurus fragilis out of at least 73 dinosaurs. Yeah. So you get that at least number because it's...

If I remember right, it's one of the leg bones that they counted up and it's like, oh, there's 43 left femora and therefore each one of them only has one. Or 46, yeah. Yeah, so there's got to be at least 46 allosaurus. But there could be more because there could be some where the femur didn't get perfect.

preserved. I'm just making up that it was the femur. I can't remember which bone, but yeah, likely more than 46. Yes. So some suggestions as to why this happened. There's the predator trap, or maybe they got stuck in a bog. They got trapped in deep mud. They died around a watering hole during a drought, or they got trapped in a spring-fed pond. Yeah. And if you go to the

Utah. Natural History Museum of Utah. Yes. You can vote on which one you think it is. They have a little recreation of it there. Oh, yeah. That was cool. In North Utah, right next to Northwest Colorado. So, yeah, it could also be allosaurus is drawn to feed on dead allosaurus. And then the juveniles and subadults there are.

were killed, like what happens at Komodo dragon feeding sites when they have feeding frenzies. Yeah, because I think there was a paper a couple years ago about some tooth marks on an allosaurus foot, if I remember right. Shoulder blade, possible tooth marks. Oh, I see. Yeah, so there's some evidence for cannibalism, like also shed teeth among rib fragments. Yeah, because usually if you're just fighting, you don't get your teeth in deep enough to damage a shoulder blade. Mm-hmm.

A lot of Allosaurus specimens have survived, well, show that they survived serious injuries, famously so. And that fact may mean that they were gregarious and helped each other out. Maybe.

Because of the Cleveland Lloyd dinosaur quarry, Allosaurus is very well known and one of the best known theropods. So James Madsen wrote a monograph of Allosaurus. This is in 1976, and that made the dinosaur even more well known. And in the monograph, he said the name Allosaurus should be used instead of Antrodemus because Antrodemus was based on fossils with few, if any, unique features, and it was unclear where exactly the bone was even found. So it just made more sense with Allosaurus, and everyone went with it.

All right, getting into the different species of Allosaurus. Allosaurus fragilis. At least 60 individuals are known. Wow. And 46 of them are in the Cleveland Lloyd Quarry? Yeah. So that's like almost 80%? Yeah. Now, Allosaurus fragilis is estimated to weigh around one metric ton, but some individuals are larger. In the paper that named Allosaurus, it said the vertebrae, quote, are peculiarly modified to ensure lightness. Hmm.

And that's where you get the fragilis part. There was a paper in 1879 that noted, quote, in addition to the huge sauropoda and the small species of the genus Lausaurus described in the previous article, numerous remains of carnivorous dinosaurs occur on the same beds and indicate the natural enemies which kept in check their herbivorous contemporaries, end quote. Those natural enemies. Mm-hmm.

Then we've got our second species, Allosaurus gemmadsenii. That was named in 2020 by Dan Schur and Mark Lowen. We probably covered it as a news item in our podcast. Yeah, and we interviewed Dan Schur at one point, so we probably talked about it then too. Yeah, Dan first informally described that second species in an unpublished thesis back in 2000, so that was 20 years in the making. Maybe longer, depending on how long it took him to write that thesis.

The species name Jim Madseni is in honor of James Madsen for his work on Outsource. It's fitting. So the full name means Jim Madsen's different reptile.

They said they spent 20 years studying, quote, virtually all North American Allosaurus material, which sounds like there's a lot. Yes. Now, they said in the paper that 19 species of Allosaurus had been erected since 1877. I think we're up to a higher number now. That's why I just stuck with seven that I had stories about. There's got to be at least 20 because you've got another one. Yeah.

Now, Allosaurus gemmatsinai and Allosaurus fragilis skulls are different. Gemmatsinai had a weaker skull than fragilis, and fragilis has a deeper, more blunt snout, and the cheekbones go downwards, whereas with gemmatsinai, it had a fairly straight cheek region and a shallower, narrower snout. It's funny that the one named Fragile is stronger than the one named gemmatsinai. Yeah. So it could be that these two species had different feeding habits.

Because both species lived around the same place in time, although Allosaurus fragilis tended to be more south in the Morrison Formation compared to Allosaurus gemmatsinai.

The Gemadzeni fossils were first found in the early 1990s in Dinosaur National Monument in Utah. Which is where Dan Chur was the... Paleontologist. Yeah. Yeah. The in-house paleontologist. So obviously he would be the one to talk about it. Yes. And that first Allosaurus gemadzeni skeleton was excavated between 1990 and 1994. The block was so heavy, they used explosives to remove the surrounding rock and they had to have a helicopter fly it out. Although the head was missing.

Some of the right foot and vertebrae was on the surface and then the rest was buried deep in a cliff. Nice. That's what you want. That's why they use the explosives. It's a nearly complete articulated body with a wishbone and complete gastralia and a complete articulated left hand.

Now, the fossils were slightly radioactive. And so in 1995 and 96, they used a radiation detector and found the skull, which was about two meters away from the body. And the left half was in perfect shape, including eye bones from the sclerotic ring. The little eye bones. Yeah. Yeah. That's so cool that they use radiation detectors to find the skull. Yeah.

Yes. And it's called the Mona Lisa of the Morrison Formation because it's in such good shape. Nice. It took seven years to prepare all of the bones. This is at the Natural History Museum of Utah, NHMU. And that museum has the world's largest collection of Allosaurus fossils, which makes sense. More specimens were found later of Allosaurus gematinae. There's Big Al. That was found in 1991.

Big Al was featured in BBC's Walking with Dinosaurs Ballad of Big Al in 2001. I think that's one of the reasons Allosaurus is so popular, actually, at least with modern dinosaur fans. Could be. Also, poor Big Al with all those injuries. Yeah. But at first, Big Al was thought to be Allosaurus fragilis, and then it became assigned, or it was reassigned to Allosaurus gemmatsini. Huh. I never knew that.

That big owl was found, again, 1991 in Wyoming. It's a 95% complete specimen, and it's about 26 feet or 8 meters long. It was only a sub-adult, estimated to be 87% grown. So big owl wasn't so big. Yeah, that's true. So yeah, it was almost fully complete, and we can see from the skeleton all the diseases, infections, and injuries.

Which, there were at least 19 injuries, broken bones, or signs of serious infection. About 2% of all the bones had pathologies. That's a lot. It's rough. Yeah. There's also signs of a severe bone infection. There's pathologies in five ribs, five vertebrae, and in the feet. A lot of injuries and infections. And you see it with these extra bone growths.

It had infection and trauma in its right foot that probably affected how well it could walk and it probably couldn't hunt. And that infection lasted up to six months.

The osteomyelitis on the right foot, which is a bone infection, may have been what led to its death. Yeah, because if your foot is infected and you can't move quickly and you're a predator, that is big trouble. Yeah, and that infected toe kept rubbing against the other toes. That was probably pretty painful. So it was probably in a lot of pain when it died. Poor big L. And it died in a dried up riverbed and it might have been driven there by desperation.

Yeah, and those are, it might have had other injuries too. These are just the ones that preserve on the bones. We don't know what was going on in the soft tissue because that didn't preserve. Yeah. Now there's evidence of beetle burrows on Big Al's carcass, which may mean that thousands of beetle larvae dined on it after it died. About 12% of the skeleton was damaged by beetle activity. And Big Al, the body was exposed for a few months and then covered by a series of flooding events, which is...

Probably why it's in pretty good shape as a fossil. But I mean, because we could study it. Not that it was in good shape at all. I mean, it's in pretty good shape because you can see these details of it. But yeah, it's full of beetle burrows. So you have to recognize that. Oh, I meant the injuries. Oh, that way. Yeah. It wasn't in good shape health wise. Yeah. I mean, I guess every fossil is a dead animal. So.

And then 1996, Big Al 2 was found. That one's also Allosaurus gemmatsinai. Oh, at least it has that going on. Also had a lot of injuries. So we've got Big Al, Big Al 2, including skin impressions from the tail, and a juvenile and adult Allosaurus found in Wyoming. Those are all considered to be Allosaurus gemmatsinai. And Allosaurus gemmatsinai is estimated to be about 26 to 29 feet or 8 to 9 meters long and weigh around 4,000 pounds or 1.8 metric tons.

So just to recap kind of what it looks like, it had horn-like bumps over its eyes and crests on the top of its snout that point more upward, giving it a pinched look. And it also had a pointier tip of its snout compared to Fragilis. Yeah, and you said it had a little bit more robust of a jaw, I think, too. I think it was the other way around. You're right, because the Fragilis one was the one that was stronger. Mm-hmm.

That brings me to the next species of Allosaurus, Allosaurus europaeus. Now three specimens have been found in Portugal.

Europaeus is the one from Portugal. It makes sense. Euro, Europe. Mm-hmm. Allosaurus was first found in Portugal back in 1988. It was reported on in 1999 during construction of a warehouse. It's known as the Andres specimen. And that discovery helped show a land bridge between North America and Europe. Because we don't think it would swim across the ocean. Yeah.

Now, it's a partial skeleton. It includes part of the skull, several vertebrae and parts of the tail, several dorsal ribs and gastralia, part of the hips, most of the legs, and other fragments. And at the time, it was named Allosaurus...

Like just a species of Allosaurus. We don't know which one. We can tell this is Allosaurus, but I don't know where it goes. Then a hatchling Allosaurus species, also SP, it was a right upper jaw, aka an isolated maxilla, was found in a coal mine in Portugal and described in 2005. That's the youngest Allosaurus specimen found so far. It's also the oldest Allosaurus fossil found in Portugal. It's funny to be both the youngest and oldest species.

So like it's the youngest in terms of its age, but the oldest in terms of chronologically in the Jurassic. When it lived, yeah. So then in 2006, Octavio Mateus and others named the new species Allosaurus europaeus. This species...

has been debated. Some researchers say it's actually Allosaurus fragilis. And yeah, there's just a few, a couple of new papers that go back and forth on this. The lumper versus splitter, how many differences qualify as a difference? Yes. And could they just be individual variation? All of the above, yes. So,

Allosaurus europaeus was named on fossils found in a beach in Portugal. It includes part of the skull, three neck bones, and cervical ribs. Sounds a lot like the original Allosaurus fragilis. A little bit. So that's the third Allosaurus specimen that's been found in Portugal.

The Andres specimen was described in the doctoral thesis of Elisabeth Malafeya. The fossils were collected between 1988 and 2010, and that includes parts of the skull and skeleton. And that was tentatively assigned to Allosaurus CF Europaeus, but the thesis said we need more fossils to compare it.

Allosaurus europaeus is estimated to be up to 23 feet or 7 meters long and weigh one metric ton, so a little on the smaller side for Allosaurus, although there's another estimate of 33 to 39-ish feet, 10 to 12 meters long. That's a wide range. That is. But we don't have very complete specimens, at least for adults, to go with here, so that kind of makes sense. Yeah. Yeah.

Now, at the end of 2024 last year, Andre, Borigo, and Octavio Mateus re-examined Allosaurus europaeus and found that it was, in fact, valid, and that Allosaurus europaeus was more closely related to Allosaurus gemmadsini than to Allosaurus fragilis.

Which I guess further cements it being its own species since other researchers said, no, it's Allosaurus fragilis. In their paper, they winnowed Allosaurus down to three species because they didn't take into account a paper that named the new species Allosaurus annex, which came out right around the same time. So I don't think there was a chance for them to read it or incorporate it into their study. So those three species, according to them, are fragilis, gemmadsini, and europaeus.

They found nine features in Allosaurus europaeus that made it unique. A lot of details in the skull and neck bones. They also said it had a pinched crest on the edge of the nasal bone and very pronounced lacrimal horns, kind of the eyebrows. But then a study that came out in May 2025, so just a few months later, examined the skull material and fossils and found that there's only two species of Allosaurus europaeus.

Fragilis and gematinae. So they found that the Portuguese Allosaurus specimens were Allosaurus fragilis and not Allosaurus europaeus. Again, they probably didn't get a chance to factor in Allosaurus annex because that paper was published in December of 2024.

So that's why I say there's still a debate and there's only three-ish undisputed species. And that third one could be because it's so new. So two really well-established ones. Well, yeah, but we'll go with three now because...

That paper is solid. Yeah, for Gillis and Jim Mantsenai. Oh, and Annex. The paper is pretty solid. Oh, I see. Yeah, I think I remember Greg Paul talking about Jim Mantsenai and saying like, how come this counts as a new Allosaurus, but my new Tyrannosaurus species don't count? So that might be the only...

dispute that I've seen, but he wasn't using it to say that Jim Manson and I wasn't valid. He was using it to say that these new Tyrannosaurus species should be valid. So depending on how you take the responses to that Tyrannosaurus paper, you might think, oh, maybe the Allosaurus one shouldn't be either, but I haven't really seen anybody take that approach.

So that brings me to Allosaurus Annex. That was named the end of 2024 by Andy, Danison, and others. And see, we're catching up on our new dinosaurs as we go along here. So I've got to give some background.

In the past, Saurophaginax maximus was speculated to be a species of Allosaurus, and that's a large theropod, Saurophaginax. This latest paper found that the fossils attributed to Saurophaginax were a chimera. They're actually possibly from a sauropod, specifically a diplodocid. Wow. Although some of the fossils are also from Allosaurus.

So now, Saurophaganax is a nomum dubium. Wow. I did not know that. Yeah. Well, the paper just came out. I thought Saurophaganax might get lumped in with Allosaurus as just being a large individual of Allosaurus. The reason we thought it was so large is because of the sauropod bones. That would do it. Saurophaganax was our dinosaur of the day back in episode 58. This is the beginning of 2016. We

We talked then about how the lizard eater was considered by some to be Allosaurus Maximus instead, and this chimera mix-up explains why. It was large, estimated to be like 34 to 43 feet or 10.5 to 13 meters long and weigh around 3 tons. It would have lived in the late Jurassic in what's now Oklahoma in the U.S., the Morrison Formation.

The fossils were found in 1931 and 1932, and they were named Saurophagus maximus in a magazine article, but they weren't described or officially published. And it turns out that the name Saurophagus was already used for a bird, although that bird is now known as Patangus. So the name Saurophagus isn't really being used anymore. But since it was used and abandoned, it's like a synonym for that and you still can't use it. Yes.

So Dan Cher again formally described the bones and he named it Sorophaginax maximus in 1995. The fossils found were fragmentary and weathered. There's 227 associated elements from four different quarries that have been referred to Sorophaginax. Quite a few. Yes. And those areas also had mostly sauropod fossils. Oh, I see where the problems are coming in. Yeah. Not much has been found of the skull.

Saurophaginax was originally considered distinct from Allosaurus because of three features, from part of a neural arch that's part of a vertebra, an atlas bone, the first neck bone, and then fragmentary chevrons, the bones on the underside of the tail bones, just had different features. And then more fossils and features were added later on, and more vertebrae, part of the skull, parts of the legs and feet.

So in this new paper, the authors compared all of these unique features to other theropods and large dinosaurs from the Morrison, including sauropods. They found that some of the bones belong to a Diplodocid sauropod instead of a giant theropod. It's a little different.

and they found the holotype neural arch could not be, quote, confidently assigned to a theropod, end quote. So sorphaginax is now a nomodubium. Although on SVPAL, one of the authors, Matthew Waddle, said that they were convinced of many things at different points of the study from the fact that at first they thought it was theropod, then they thought it was a soropod, then it was back to being a theropod, then back to being a soropod, and then they agreed to it being a nomodubium was the

best move. And they also said maybe they overlooked things or more fossils might be found later and our viewpoint on Saurophagin X may change.

But, like I said, some of those bones seem to represent a new species of Allosaurus, the ones that are not belonging to a sauropod. The fossils that were previously Saurophaginax, and now considered to be Allosaurus, had enough subtle unique features, so that's why they named a new species, Allosaurus anax. Some of the features are like being smooth in areas that have ornamentation on other Allosaurus species, meaning it didn't have skull ornamentation the way that other species did.

Which is interesting because we usually see cranial ornamentation on larger theropods. Yeah, especially allosaurus. I was saying that's sort of the key feature is those angry eyebrows. Yeah. Well, I think the ornamentation is more the top of the skull. Oh, I see. So the species name annex means king, lord, or chieftain. And it, quote, honors the updated name given to the Kenton Quarry I allosaurid by Churr.

1995, when he renamed Saurophagus to Saurophaganax. Thus, Allosaurus Annex means different lizard king, end quote. On SVPAL, the co-author, Matthew Waddle, he wrote that even though they came to a different conclusion from Chur, they like and respect him and his work, and they didn't want this paper to be seen as criticism of his work, which is kind of how Chur honored Stovall, who found the fossils, and he honored his intent with the name Saurophaganax after it turned out that Saurophagus was taken. Yeah.

I mean, Dan Scherer is a great guy. We had so much fun talking to him. He's very inviting and so much fun to talk to. Yes, and very knowledgeable. Very passionate about education too. Yeah, so that was nice. The holotype of this species is a post-orbital bone. It's a piece on the top of the skull.

And then there's some referred material that includes a neck bone, a part of another vertebra, and thigh bones. And these bones are from about 153 to 145 million years ago. Now this species of Allosaurus is capable of getting much larger than other Allosaurus species. It's estimated to weigh between 4,600 kilograms on the higher side and 3,700 kilograms on the lower side. That's based on three femora or thigh bones.

So you're talking about roughly four to five tons if you were going to break it down, which is a lot heavier than the other estimates that you had for other ones. Well, yeah. Fragilis, by comparison, is estimated based on its femur to weigh closer to 2,600 kilograms. It's like almost half the size. Yeah.

And the foot bones referred to this species, Allosaurus annex, have some structures. They did some histology, so they cut into the bones that suggest that the individual was skeletally mature. So it wasn't just big because of those sauropod bones. It was fully grown. Oh, yes, that's true.

There is also some large theropod material from the quarry without any distinguishing features that have been referred to Allosaurus species, SP, although the authors say it likely belongs to Allosaurus annex. They also said, quote, it is possible that future studies will show that the holotype neural arch of Saurophagin X belongs to a theropod, in which case Allosaurus annex will be considered a junior synonym of the former. I guess that's not quite as solid as I was thinking. Ha ha ha.

So maybe we'll revise that. There are two undisputed species of Allosaurus and then a third one that's being debated and a fourth one that the authors think might change. And then, of course, there's the former species of Allosaurus. Since this request was for Allosaurus tendaguransis, I did some digging into this one. That species was named back in 1925 by Werner Genensch.

It was named based on a partial shin found in Tanzania in the Tendigaroo formation, a weft tibia. That's how it got its species name, Tendigaruncis. The tibia was described as different from the American Allosaurus in being so thin and also as significantly slimmer than Megalosaurus because we're back in the days where everything is being compared to Megalosaurus. Yep. And...

When taking into account the weathering and peeling, the tibia is almost the same in pattern and proportion to a tibia of an Allosaurus in the AMNH, known in this paper as the New York Museum. It's the only museum in New York you got to worry about. Just the one. Just the one. Oh, man. I don't think the other museums would be happy to hear that. I'm not the one that said it. Yeah. Well, in the paleontology field. Yeah. Now, the middle section of the tibia is missing.

But it was large. One piece was 40 centimeters or almost 16 inches long. Another piece is 26 centimeters or a little over 10 inches long. However, in the paper, he said it was impossible to know the exact length of the whole tibia because of the missing middle piece. And this is our only bone? Yes.

So now Allosaurus tendigrinsus is considered to be an indeterminate tetanurin. Oh, geez. Yes, because that tibia or shinbone is isolated and poorly preserved. So the species is a nomodulium. That's barely more specific than just saying it's a theropod. Yeah. And that was based on a 2011 paper by Oliver Raoult.

But even in the 1925 paper, it was referred to as Allosaurus question mark Tendaguransis. They gave it a species name even though they weren't sure about the genus. Yeah. It's funny. Although it also said just before naming it using the question mark that, quote, the tibia from Tendagur is so close to the American genus Allosaurus that I have no hesitation to use the same name, end quote. So I'm a little confused. Yeah. Why? Why?

There should just be Allosaurus SP at that point. Yeah. But anyway, it was estimated to be possibly around 33 feet or 10 meters long, even though we don't know how long that tibia is. You could do a diameter of it and get a weight and, you know, or just compare the diameter of it to the diameter of another tibia, I suppose. Yeah.

Okay, being a wastebasket taxon, there are, of course, other species. So Marsh named Camptonotus amplis in 1879 based on a right foot found in the Morrison Formation. But then a 2015 reanalysis examined that right foot and other bones referred to the dinosaur, including a partial skull. And the partial skull referred to question mark Allosaurus amplis, but said it needs to be studied more.

Then we've got Allosaurus atrox, which was named in 1878 by Marsh. That's a dubious species. The howl type was found in Wyoming in the Morris information and originally described as Creosaurus atrox a year after Marsh had described Allosaurus because, of course, he had to name a new dinosaur. Yeah, one year later.

And Gilmore in 1920 referred Creosaurus atrox to Allosaurus, although he called it Androdemus. It was thought to be a separate species at first because it had a bigger, more rectangular skull with less triangular horns above the eyes compared to Allosaurus fragilis. But an analysis in 2000 by Chur found it was a case of distortion. And the skull of Allosaurus was reconstructed incorrectly, and it was thought to be highly convex and with a short snout.

He also found individual variations, so he considered Allosaurus atrox to be a synonym of Allosaurus fragilis. And then a 2024 study said, well, maybe atrox is possibly valid. Then we've got Allosaurus lucaris that was named by Marsh in 1878. It was originally Labrosaurus found in Wyoming. There's one backbone. It's not enough to be a species, so now it's considered to be a junior synonym of Allosaurus fragilis.

There's also Labrosaurus ferrix, considered to be Allosaurus fragilis, named by Marsh and Bone Wars. This was in 1884 based on a jawbone. The lower jaw had a gap in the teeth at the tip of the jaw and the back part was expanded and turned down, but it's possible this is a pathology. The 2024 study said that this species deserves a new study.

So it seems like there might be more going on with Allosaurus in the future. Then we've got Eponterius Amplexus, named by Cope in 1878, based on three vertebrae, part of the shoulder and a foot bone. But the 2024 study said that we need new analysis to see if this one's valid.

There's some debate on Amplexus. It was named Allosaurus Amplexus by Gregory Paul, but now it's considered a synonym for Allosaurus fragilis. There's debate around this. The specimen might be too young to be Allosaurus fragilis, meaning it lived too far after other Allosaurus to be Allosaurus. Yeah. And that's the other thing with all these species, the odds that they are all more closely related than all these other Allosauroids...

They're kind of low. Yeah. So you might want to have new genus names for some, if not all of them. Oh, you're talking about splitting. Yeah. Just because whenever you have a family tree, in order for them to be in the same genus, they can't have other genera that are in between them and something else. Right. So if there are other allosauroids that are

more closely related to Fragilis than Jim Madseni is to Fragilis, for example, then you got to split it out and give it a different genus name. Or you could bring in the other one, I suppose, and make it yet another Allosaurus species. And then we've got Allosaurus lucasii, not to be confused with Allosaurus lucaris that I just talked about. That one was named in 2014 by Dahlman and others based on two partial skeletons. There was an adult and a juvenile found in Colorado in 1953.

It's from the Morrison Formation. The holotype was a fragmentary partial skeleton of the adult that was parts of the skull and jaws and parts of the body. Interestingly, it included part of the right lower jaw of an adult and part of the right splenial that's found on the inner side of the lower jaw from a juvenile.

It's known for its short, deep upper jaw bone, the maxilla, and other details in the bones. But in 2020, Chur and Lowen considered it a nomadubium, and the 2024 study agreed that it's Allosaurus species SP. It's just too fragmentary to tell. So that 2024 study considered Allosaurus atrox, amplis, and leukocyte to not have distinct features and be nomina dubia.

And they also found there was apparently an Allosaurus species SP found in Japan, but they said that is a Cegnosaurus species of some sort. There's also other species named due to errors like Allosaurus agilis, but that was just a typo for Allosaurus fragilis. Agilis does sound more exciting than fragilis. Yeah, very different meaning. And it's appropriate too. You're talking about it running, you know, on the upper end of the estimates up to 30 miles an hour. Yeah. That's agilis. Yeah.

And in just a moment, we will get into Allosaurus the carnivore. But first, we're going to take a quick break for our sponsors. So we know that Allosaurus was a carnivore. It probably preyed on ornithopods, stegosaurs, and sauropods. Poor sauropods. Not poor stegosaurs or ornithopods. Nope. Nope.

There's debates over whether Allosaurus hunted in packs or hunted alone. It's hard to prove hunting in packs, though, and it seems unlikely. There's also debates over how much Allosaurus scavenged. So yeah, there's little evidence of hunting in packs. There's some bite wounds to skulls have been found, so it seems like they fought each other at least sometimes. Allosaurus may have been eaten by other theropods. There was one hip bone found with teeth marks from another theropod. That was probably scavenged.

Allosaurus had a lot of sharp serrated teeth with saw-like edges. Sometimes it's been described as steak knives. These teeth were up to about three inches or 7.6 centimeters long. They were shorter, narrower, and more curved toward the back of the skull. And it shed and replaced its teeth continually.

Not surprising. A lot of theropods did that. Yeah, pretty much all dinosaurs, in fact. Except for the toothless ones. Well, yeah. Now, Allosaurus did have a strong skull, but a relatively weak bite. It could handle a lot of pressure on its jaws. It had a large gape, like it opened its mouth really wide, like 92 degrees. Yeah, we've seen some estimates that were even wider, but I think those have been... The most recent study was 92 degrees. That's still really wide. Yes.

There's evidence of Allosaurus attacking Stegosaurus, including an Allosaurus tailbone with a partially healed puncture wound that looks like it came from a Stegosaurus tail spike. Yeah, it's so cool. It's like a hole, a puncture hole, like you hole punched it with a Stegosaurus tail. That thagomizer. Yep. There's also a Stegosaurus neck plate with a U-shaped wound that fits an Allosaurus snout.

So maybe Allosaurus slashed its prey to weaken it. There's some debate. There's one study that found the skull of Allosaurus fragilis was designed in a way that it could have a quote slash and tear mode of prey attack and feeding. That would explain the lightness of the skull. Based on a study of its endocast, the brain case, it probably kept its head level. And that light head also means Allosaurus could move its head and neck around fairly quickly in a controlled way. It was more flexible, but a little less powerful.

There was a 2013 study that found Allosaurus tugged at its prey, similar to a falcon. That's very different from how Tyrannosaurus went after prey. Yeah, rather than crushing, it's more like a little more surgical. Yes. Yeah, they simulated the head and neck movements when Allosaurus attacked prey. They reconstructed partly based on birds and crocodilians.

And it had this neck muscle low on the skull, much lower than on Tyrannosaurus, that would allow it to drive its head down into the prey, hold it, and then pull its head up and back with the neck and body, tearing flesh from the prey. Similar to small falcons, which has been compared to a backhoe ripping into the ground. Which doesn't sound that pleasant. No. Allosaurus may have also used its claws to hook things.

There's one study suggested Allosaurus used its skull like a machete or hatchet, attacking with its mouth open, slashing the flesh with teeth, and then tearing away. Again, different from Tyrannosaurus, which was the bone crusher. I remember that from the early days of our podcast. I don't remember if that came out, but...

during our podcast or if it was shortly before, but that was the vision I had it as the most scientifically accurate version for a while. Right. But there's debate on this because there's no modern animals that use the hatchet attack method. It is a little strange to just like slam your face into something. Yeah. Seems unpleasant. Yeah.

It's possible Allosaurus was a flesh grazer and then it took bites out of living sauropods and got enough food without needing to kill. Like a cookie cutter shark. Kind of, yeah. And then the prey could recover and then later the Allosaurus could eat part of it again. That reminds me of the restaurant at the end of the universe. Yeah. Eat my rump. Yeah. Now Allosaurus had strong arms and it may have used them on ornithopods by grasping them like modern big cats do and then biting the throat multiple times.

There was a 2024 study by a team of researchers in China that looks at the flexibility of Allosaurus. Speaking of, you know, we talked about being the quintessential Jurassic theropod and iconic and everything. It's also been called Jurassic overlord by some.

Late Jurassic for sure. Yeah. There we go. They studied a shoulder injury of Allosaurus to see how well its arm could move. And then they laser scanned the 3D fossil model and they found there was a lot of flexibility. Like the shoulder and elbow joints could go beyond 70 degrees and the finger joints could flex up to 90 degrees. There's limited range of motion for the shoulder joint. And that may mean it used its arms to capture prey.

Like maybe it used its mouth first, the first contact with prey, and then used its arms to grasp the prey's chest or neck or hook onto objects. Hmm. That's an interesting idea. Yeah. And for the specimen they studied, the shoulder injury had healed before it died, which is a common thing we see with these allosaurus specimens, a lot of healed injuries. Yeah.

I'll get into the injuries in a little bit, but first there's the scavenge debate we have to talk about. Like maybe Allosaurus scavenged, you know, eight dead sauropods, sauropod carry on. Oh yeah. A lot of bite marks found on sauropod bones. And we've talked a lot on our show about Allosaurus potentially scavenging or how much it scavenged.

So a study of pathologies in theropods found that allosaurs were more likely to survive and heal even with bad injuries, which may mean they could live off of scavenged sauropods. Again, lots of debate and critiques and back and forth in this one. Wasn't widely accepted really at all. Well, the thing was the paper that we mostly talked about on our show said that they were obligate scavengers.

That was the only way that they ate. And that's, I think, is why there's so much debate. Yes. Yeah. Obligate meaning they were obligated to do it, whereas facultative is they could do it. And like we talk about, pretty much any predator will go after something to scavenge. An easy meal. Yeah. If it's fresh enough and they're hungry or whatever. Right.

But not very many animals are obligate scavengers. Very, very few. You've got vultures and just a handful of others, especially when you're talking about vertebrates. Yeah. So if you want to go back to those episodes, episode 353 is when we first talk about it. We have an interview with the author of that study, Cameron Paul, in episode 357. And then there's more debates around it in episode 432. So it keeps popping up.

And then, of course, I'm going to talk about it here. It is a fun thought experiment. It is. Which was the original proposal about T-Rex being a scavenger, too, as a thought experiment. Well, so the gist of the paper was that Paul and Ruettas built a computer model to see if Allosaurus could have survived exclusively as a scavenger, the way vultures live today. Part of that is Allosaurus had a relatively weak bite force. It had bad binocular vision, poor hearing. It was relatively slow, even though...

We talked about how fast it was, but anyway, they didn't test all these things in the paper. It was more about the model. They also mentioned that Allosaurus could bite and rip quickly. It could swallow a lot of meat in one gulp, and it had head ornamentation that might scare off prey, which are all good things for scavengers. And the Morrison Formation, of course, is known for all the sauropods. And when those sauropods died, that would mean there was a lot of meat available. Yeah.

It's very interesting to think about an ecosystem where suddenly you have tens, dozens of tons of meat for animals to eat. Right. Because when we, well, when you talked about this paper before, you mentioned how sauropod carcasses could weigh 45 tons. Just so much meat. And those carcasses could last months, possibly up to six years. That's based on pig carcasses. Yep. It depends how good your...

gut is at handling semi-rancid meat. Yes. And Allosaurus could probably detect the carcass from far away, one to 10 kilometers away. It could survive on 11 kilograms of meat a day. That's not a lot compared to 45 tons. Anyway, there's a lot of refutes for this paper of it being exclusively a scavenger. Like,

The jaws weren't that weak. Having good binocular vision wasn't necessary for a predator. There's examples of animals with bad binocular vision like Komodo dragons, crocodiles, and sharks. Sharks have done all right for a while. For a while. For a long time. Yeah. There's also evidence of allosaurus fighting herbivores like the stegosaurus plate with an allosaurus bite mark and the adult allosaurus hip bone with a stab wound that matches the stegosaurus thagomizer spike. It's hard to get that scavenging. Yeah.

Also, a lot of dinosaurs in the Morrison were small enough and not armored for allosaurus to go after. It wasn't all sauropods, even though it was a lot of sauropods. There's benefits for allosaurus to hunt young and or weak prey. And eventually the sauropod meat would also get too rancid. So it seems just difficult to be a pure scavenger. Mm-hmm.

Now there's other arguments on both sides. The original authors stuck to Allosaurus relying on sauropod scavenging. And that does seem likely that Allosaurus would eat sauropod carrion like we were saying when the opportunity arose. But the question is how much Allosaurus relied on them versus prey it hunted.

So 2023 studies suggest that Allosaurus was not an obligate scavenger. It could get its food elsewhere. I like that way of putting it because all you need to do to refute it is that it could get its food elsewhere and that it's not an obligate scavenger anymore. Yes.

And that study questioned the plausibility of some of the assumptions that the model made for the scavenger model. They said that Allosaurus may have been an efficient scavenger, but it still takes a lot of energy to forage. There are lower risks going after young or weak prey. There's likely competition with other scavengers for carry-on. And there's the fossil evidence of Allosaurus fighting other dinosaurs. So it suggests a predatory lifestyle with some scavenging for Allosaurus. Yeah, I think a big piece too is

How many dead sauropods were laying around for how long and how long could Allosaurus actually eat that meat? Yes. And they also said that all terrestrial vertebrate carnivores scavenged, but only vultures have become obligate scavengers.

So land carnivorous animals do scavenge for food, but only vultures exclusively scavenge and do not hunt. Yeah. And it helps being able to soar, right? They sort of coast around really long distances and they have that bird's eye view one might say of the landscape so they can spot and smell things from a really long distance and get there quickly.

Stick their head in the carcasses.

Yeah. But that 2023 study said that they still see value of the model to explore how much Allosaurus scavenged and how much it went after prey. Yeah. It was very interesting. It is. Yeah. I really liked the thought that went into it.

I'm mostly interested in thinking about the ecology of an environment where sauropods die. Because on land today, you've got elephants, which are kind of similar in being a huge animal that dies and now there's a bunch of meat available. But really, the only close example is like a whale fall where you have dozens of tons of meat suddenly available to the ecosystem and all the animals that come to get as much of it inside their body as possible. Yes.

So that brings me to our next section on allosaurus. Well, allosaurus, the pathologies just seems to go hand in hand with hunting or even scavenging. You can get injuries. So a lot of pathologies have been found in allosaurus specimens. Broken ribs, fractures, arthritis, physical trauma, amputation possibly from being bitten, lesions, bone spurs, and more. These dinosaurs have been through a lot.

There's a number of Allosaurus specimens with pathologies, and the high number of pathologies on those specimens may mean that Allosaurus was active and predisposed to injury.

Because multiple specimens have injuries all over their bodies. And even when severely injured, allosaurus specimens heal. So maybe they had gregarious behavior or they scavenged or maybe they didn't need to eat much or frequently. Maybe they were more ectothermic than endothermic that way. A 2001 study of theropod injuries found that allosaurus had a lot of stress fractures. Based on where the foot bones, the stress fractures were found, it seems likely they happened while interacting with prey, like holding on to struggling prey with its feet.

Allosaurus infections tend to be locally restricted and scarce, which may mean, like birds, allosaurus could prevent the spread of pathogens through clotting. There's evidence of severe infections seem to be localized on single bones, and they're relatively rare.

A 2022 study examined an Allosaurus for Joe specimen and found 10 pathologies, some from trauma, possible infection, tumors, and spondyloarthropathy, which is inflammation of the joints, which extended to its shoulder. This is the first dinosaur known to have spondyloarthropathy involving the shoulder, and it may be the first known theropod to have it.

Nine of the 10 pathologies were not fatal to this specimen, but that inflammation at the shoulder would have affected how well it could go after prey and it might have died from not having enough food. It survived nine out of 10 things with that last one. Now, where Allosaurus lived, we talked about it's the most common predatory dinosaur found in the Morrison Formation. It's the most common theropod. It's about 70 to 75% of theropod specimens.

And the Morrison Formation was kind of like the African savanna, but with no grass. That's an interesting way to describe it. Yeah. The habitat was warm. It was mostly dry. There were short wet seasons. There were rivers, forests of conifers, cycads, ginkgos, and ferns. And then in between were flat areas. Some other dinosaurs that lived around the same time and place in the Morrison include theropods like Ceratosaurus and Torvosaurus, sauropods like Camarasaurus, Brachiosaurus, Apatosaurus, Brontosaurus, Diplodocus.

And then ornithischians like Camptosaurus and Stegosaurus. And again, there were just so many sauropods. The Morrison Formation might be my favorite formation. It's a good one. Yeah. Some other animals that lived around the same time and place include snails, fish, frogs, salamanders, turtles, lizards, crocodilomorphs, pterosaurs, and early mammals. Now in the Portugal Formations, it was actually similar to the Morrison, but with more marine life. The Allosaurus lived along Ceratosaurus and Torvosaurus in both parts of the world.

Now, Allosaurus had longer legs but was more compact and may have preferred the dry floodplains compared to Ceratosaurus and Torvosaurus, which were thinner and may have spent more time in the forest and around waterways. I never realized Allosaurus was bulkier than Ceratosaurus and Torvosaurus before. It's interesting. Yeah. And some other similarities in the types of animals found in both the Morrison and the Larinha in Portugal are you've got Stegosaurus.

like Stegosaurus and Myrragai slash Dicentrurus, and then theropods like Ceratosaurus and Taurosaurus. There are more allosaurus specimens out there. In Wyoming, one adult and one juvenile were found together. They were auctioned off together. The adult was excavated between 1994 and 1995, the juvenile in 2002. Then they were auctioned off in December of 2024, and it ended up selling for 10.2 million US dollars.

And then I'm not sure what happened to them after. But we're probably going to learn even more about Allosaurus in the not too distant future because there's a team from the Children's Museum of Indianapolis and the Naturalist Biodiversity Center in the Netherlands that's found this nearly complete Allosaurus skeleton from the Jurassic Mile.

That's part of the Morrison Formation. It's located in Wyoming. And there's a lot of great fossils there, plants and animals. They've been digging in that location since 2017. And this Allosaurus skeleton was first found in 2020. They got the last bits, the snout, out last summer in 2024. And they have most of the tail, ribs, belly ribs, the gastrula, hips, neck, toes, legs, as well as skin impressions all over the body. The legs, the hips, the chest, the neck,

It was laid on its right side and skin up in the mud. So those skin impressions are well preserved and it was found articulated and the teeth are all preserved inside the mouth, which is slightly open.

There are some pathologies, some gnarled bones. It seems like you can't get an allosaurus specimen without pathologies. Yeah. It's currently being prepped in the fossil prep lab at the museum. It's going to take a few years. There are some parts that are still missing. The arms, only one hand claw has been found so far, but they might find more while they're prepping. And actually, it sounds like pretty much only the arms are missing.

Now Allosaurus is the state fossil of Utah as of 1988. That's not surprising considering all the Allosaurus individuals that have been found there. It is where I think of, although you had quite a bit of Colorado history. The first one and some other significant ones that came out of Colorado. Yeah.

Well, they're close. You can see an Allosaurus at the Salt Lake City International Airport, thanks to the Natural History Museum of Utah. It's called Allie, that Allosaurus. It's an Allosaurus fragilis. It's about 30 feet long and 15 feet tall, and they unveiled it at the end of 2024. So something fun to check out if you're at that airport. Yeah, I like that airport. Me too. Except in the winter. Give me a challenge.

Most places can be outside of California. Yeah, parts of California can be too. That's true. And our fun fact for this AAA episode, thanks for sticking with us, is that the first Allosaurus fossils found by Ferdinand Hayden, who was a geologist, he led geologic surveys of the West for the US government, were thought to be petrified horse hooves.

And thanks for sticking with us because I already said that fun fact at the beginning of the episode. And that's it. It's literally just a fun fact, not a whole story like I often do. Well, I figured we had enough. Yeah, fair. And how much can you really expand on that? That's all I could find about it. Otherwise, I would have. I expanded a little bit on Ferdinand Hayden. Well, that wraps up this episode of I Know Dino. Thank you so much for listening.

Our next episode is going to be about new ankylosaurs, but it's not going to come out for a couple weeks because we are biweekly now. In the meantime, for our Dino It All patrons, we'll have a special bonus episode on the anagenesis of dinosaurs when one species evolves into another. So stay tuned, and if you want to hear that, join our Patreon, patreon.com slash inodyno. Thanks again, and until next time.

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