After I posted this video, Matthew Mossbrucker, the director of the Morrison Natural History Museum, commented on the post, with some very important and interesting information! Here is what Mr. Mossbrucker had to say:
"Quite a few folks have pondered this through the years - myself included. Allow me to put on my Dr. Ruth field hat for a moment. Heinrich Mallison's concept of the African stegosaur Kentrosaurus mating seems plausible to me. I've assumed this myself as a default mating position for these animals. My read of the tail base in Stegosaurus is a bit different than Brian Switek's analysis. While it is true that our North American stegosaurs had limited up-down motion at the base of the tail, stegosaurs do something for ornithischian dinosaurs: they have the ability to twist their tails in a corkscrew-like fashion. I can envision a standing female Stegosaurus twisting her tail to one side and therefore removing obstacles for her mate. Unlike the boated models in your photo, a living Stegosaurus would have been able to stand and even walk on its hind-limbs with grace. So, therefore I see no barrier putting a male into mating position. So, there you have it."
There we have it indeed! I hope you find that enlightening, as well as the video! The dilemma definitely makes more sense after hearing what Mr. Mossbrucker has to say!
The second of a pair of songs that I made especially for Stegosaurus Week! "The Stegosaur Song" to the tune of "The Mexican Hat Dance." Below is the link to the song:
[Chorus:]
Oh, the plates and the spikes like the head of a trike with them you definitely don't want to mess
The stegosaurs lived in the Jurassicbut some lived to the dawn of the Cretaceous
One of a pair of songs that I made especially for Stegosaurus Week! "Bone Wars, Marsh and Cope" to the tune of "Two Black Cadillacs" by Carrie Underwood. Below is the link to the song:
Here are the lyrics to the song:
Full Lyrics:
1800s, Morrison, a big find was made
"If Cope got a bone, Marsh lost," Dr. Bakker say
They devoted their life,
To get the most bones, each other they'd fight
Two rivals fighting over fossils in the dirt and grime
[Chorus:]
And the teacher, Lakes, he was a good man
And Marsh and Cope, they used to be friends
But then the two of them wanted the other to die
Bye, Bye bye, Bye
1,500 species they wrote down
Dug them all out of rock and from the deep ground
They both refused to work together on the same side
Bye bye, bye bye, bye bye
Bone Wars, Marsh and Cope
Eleven years ago researchers found some more fossil bone
123 years they'd been buried there for oh so long Matthew Mossbrucker, from the Morrison Natural History Museum
The site had been reburied, waiting for the right time, right time
[Chorus:]
Even now some of the fossils in rocks and time are still encased
Mystries and new species found in the Quarry
Learning new secrets from the grave
[Chorus:]
Are you diggin' the songs? Well, then check out our playlist below!
Here we will learn 8 Truths About the Stegosaurus.
This is the third video in our "Animal Truths" series. Make sure to check out the other two we have made so far, "8 Truths About the Mountain Lion" and "17 Truths About the Cheetah," below!
Stegosaurus lived in western North America during the Late Jurassic Period, about 150 million years ago (MYA). Today, we find its remains in the Morrison Formation, named after the tiny town of Morrison in Colorado. What was going on in Colorado at that time? What was the depositional environment like, the environment that laid down the sediment that would one day become the famed Morrison Formation?
Well, according to paleontologist Dr. Robert Bakker in an article about the re-discovery in 2002 of some old paleontological quarries (CLICK HERE TO LEARN MORE) in the Smithsonian Magazine, the environment was very much like the kind of environment seen in Uganda today: a “hot tropical woodland that was dry for most of the year.”
What about the animals, though? Dr. Bakker also said in the article that to “understand the Late Jurassic, you need to understand the common animals, which means Apatosaurus.” Most people are familiar with this massive animal: about 100 feet long (around the length of three school buses put end to end to end), and weighing around as much as eight African elephants, Apatosaurus was definitely a heavyweight of the Morrison biota!
What other animals were running around though? There are a great many dinosaurs, as well as many other animals, that were living in this area at that time, but in this post we are only going to look at one more: Camptosaurus and Allosaurus. All right, I lied. We’ll look at two more.
First off, we have Camptosaurus. To be honest, Camptosaurus doesn’t really look all that special. A small- to mid-sized ornithopod, Camptosaurus was only about fifteen feet long, and didn’t really appear to have any obvious defenses. However, discoveries of articulated Camptosaurus skeletons (indicating that the bones were fossilized were they were deposited, i.e. where the animal died, and weren’t washed together in a big mumble-jumble like at Dinosaur National Monument) in close conjunction with articulated Stegosaurus skeletons seems to indicate that these two herbivores liked to hang out together. But why? Why would they open themselves up to competition and potential conflict like that? Well, analysis of the brains and skulls of these two animals suggests that perhaps by hanging out together, the dinosaurian duo could avoid much deadlier conflict. Studies have shown that the sensory organs of Camptosaurus and Stegosaurus would have differed in very critical ways. The sense of Stegosaurus would have been akin to a rhinoceros, or perhaps myself as well (at least without my contacts), in that it would have had a pretty good sense of smell, but not very good vision. Camptosaurus, on the other hand, appears to have had quite acute vision, which has led to an interesting proposition by researchers: that Camptosaurus acted as a lookout for herds of Camptosaurus and Stegosaurus. If a predator was spotted (say, an Allosaurus or a Ceratosaurus), then Camptosaurus would have been able to alert the herd, and Stegosaurus would have been able to move to the forefront to defend them all against attack.
The last dinosaur that we are going to look at today is Allosaurus, a large, meat-eating theropod dinosaur. It occurs to me as I type this that I have done a very thorough job on Allosaurus before, so instead of typing this all again, I am going to be lazy and redirect you to another post that I did awhile back, entitled “23-Fact Tueday: Allosaurus.” Hidden within the post (but not too hard to find) are 23 Facts about Allosaurus. Yeah. Pretty much says it in the title. Anyways, check out that post to learn more about Allosaurus, as well as the rest of the Morrison ecosystem! And make sure to check back tomorrow, as we learn about stegosaurs from the rest of the world!
Want to learn more about Stegosaurus? Well, check out the Homebase for Stegosaurus WeekHERE to partake in more of the festivities!
In 2002, paleontologists from the Morrison Natural History Museum rediscovered an old paleontological dig site that had been missing since the late 1800s. One of many highly-contested sites of the so-called “Bone Wars” (a paleontological competition between rival paleontologists Othniel Charles Marsh and Edward Drinker Cope), this dig site, dubbed Quarry 10, has been the site of many very interesting discoveries, as has another Quarry nearby, Quarry 5.
Quarry 10 had long thought to have been destroyed. Fossil hunter Arthur Lakes had reportedly dynamited the dig site on Marsh’s orders, to prevent Cope from getting any fossil bones out of it. However, it looks like Arthur Lakes was a very good man, and did not actually dynamite the dig site. According to the MNHM paleontologists, it looks like Lakes, not wanting to destroy something that was potentially very valuable, decided to merely cover up the site with some rocks in order to prevent other people from coming across it.
Further excavations at the Quarrys have yielded a number of VERY interesting fossils, including, amongst others, some baby Stegosaurus footprints! Multiple blocks have been uncovered with the footprints of Stegosaurus at all different stages of development, everything from infants to adults. On some of the blocks, multiple age groups are found in close conjunction to each other, and sometimes are found going the same way. This seems to indicate that Stegosaurus would move in groups consisting on members of multiple ages, a very interesting discovery indeed!
Want to learn more about Stegosaurus? Well, check out the Homebase for Stegosaurus WeekHERE to partake in more of the festivities! You can also check out a song that I wrote to the tune of Carrie Underwood's "Two Black Cadillacs" to learn more about the Bone Wars, below!
The horns and frills of Triceratops. The tube-like crest of Parasaurolophus. The two crests of bone on Dilophosaurus. The sail on Spinosaurus. What function do these various bells and whistles that adorned these so-called "Terrible Lizards" serve? For years, most paleontologists assumed that they were for the sole purpose of combat, be it against predators, or the inter-specific variety. But now, more and more paleontologists are looking to birds to answer the question of functionality when it comes to these bony dinosaurian protuberances.
But what, specifically, about birds is it that is helping paleontologists figure out the purpose of these structures? It all boils down to an interesting phenomenon called "sexual selection." Most people are familiar with the term "natural selection." Popularized by Charles Darwin, natural selection essentially states that animals that are unfit to survive and reproduce in a given environment will die, and will be unable to add their genes to the genepool. (Certainly an oversimplified definition, but you get the picture.) Sexual selection, on the other hand, is a mode of natural selection, and introduced by Charles Darwin, as well. Sexual selection states that some individuals in a given population will be more likely to breed than other individuals will because they will stand out above the rest of the population. There are many ways of doing this, and birds are but one example. Horns and antlers are one instance: typically, if an animal has larger horns or antlers, they will be able to not only fend off predators better (i.e. natural selection), but they will be more likely to be able to fend off other males, and be more likely to be picked for the females (i.e. sexual selection). In many animals, form overcomes functionality in this endless quest for a mate, especially on insular (or island) populations. One of my favorite examples of this is the birds of paradise from New Guinea, as you can see in the video below.
That's all well and good, but how does that apply to the dinosaurs that we were talking about above? Well, for years, paleontologists assumed that dinosaurs like Triceratops and its relatives were using their horns and frills to fight off predators. Well, for Triceratops, that makes sense: with forward-facing horns and a two-inch thick frill, fighting off Tyrannosaurus doesn't seem that far out of the realm of possibility. However, upon examination of many of the other relatives of Triceratops (collectively called ceratopsian dinosaurs), you can see that, perhaps, not all of these frills and horns evolved to fight off predators. Below we have just one example. The picture you see is of a skull that below belongs to a ceratopsian dinosaur called Einiosaurus. As you can see, it does not seem anywhere near as well equipped for fighting off predators as Triceratops does. For example, its frill has a pair of massive holes in it. Furthermore, of its three horns, one points downwards, and two point towards the sky at about a forty-five degree angle. Unless Einiosaurus was being attacked by giant woodchuck-like, burrowing dinosaurs, or being dive-bombed by Tyrannosaurs in F-14s (as seen in Calvin and Hobbes!), it is difficult to see how Einiosaurus might have defended itself against its predators using its frill and horns. Another analogy I like to make is this: if you are a knight going into battle, you don't necessarily want to have a pair of giant holes in your shield, and your sword bent and pointing towards the ground.
So how does this all tie in to Stegosaurus? Well, a same sort of discussion has centered around Stegosaurus for many years. Were the plates used for defense? Or were they used for something else? First let's address the idea of defense. IN THE PREVIOUS POST, we discussed the thagomizer, the group of tail spikes, on the rear end of Stegosaurus. These tail spikes were almost certainly used to fend off enemies, and seemed to have done a very good job, too. So, if you think about it, if you were to cover a stegosaur in these spikes, it would be almost impervious to attack, right? Well, what's interesting is that, early in stegosaur evolution, many of these animals actually did have a lot more spikes than Stegosaurus did. As a matter of fact, the plates of Stegosaurus are nothing more than heavily modified spikes! Below, we have a few more primitive stegosaurs, all of whom demonstrate the fact that, prior to Stegosaurus, many of the plates were actually spikes!
So if the spikes were better than plates were at defending an animal against predators (which is the only logical conclusion that I think people can draw from the data at hand), then why did some of the stegosaurs change? For many years, paleontologists thought that they had a pair of answers to this interesting dilemma. The first was the idea that perhaps Stegosaurus used its plates as a thermoregulaton device. If the animal was too cold, then it could turn its body so that its plates faced the sun, maximizing its surface area that was facing the sun, and enabling it to warm up quicker. The reverse would have also worked: when it became to hot, Stegosaurus could turn perpendicular to the sun, minimizing the surface area that was absorbing the sun. Another theory was that Stegosaurus could flush blood to the plates, turning them a brighter color. This could have either frightened off enemies, or instead it could have been used to attract a mate.
These two ideas seem fairly good in theory: however, much like the skull of Einiosaurus, there are a few massive holes in this logic. If Stegosaurus used its plates as a thermoregulatory device, why do close relatives of Stegosaurus have very different plate shapes, or sometimes fewer plates altogether? If there was one design that these animals used to warm up or cool down, one would imagine they would all converge on the same design. But they didn't, which casts some serious doubt on the whole thermoregulatory idea.
There are two theories that seem to hold the most water today. The first one has the same general idea that the "flushing the plates full of blood" idea has: make yourself more noticeable, as these plates were very impressive looking structures. And, since they alternated down the back (SEE THE FIRST STEGOSAURUS WEEK POST HERE), then a side-on look of Stegosaurus would have been a very impressive sight, indeed! Other stegosaurs of the opposite sex would undoubtedly think so, and these plates probably served a large role in attracting a mate! Predators might have thought that the side-on view was impressive, too, and this might have caused them to think twice about attacking Stegosaurus. It also might have caused other members of the same species to back down, too, in cases where inter-specific combat might have otherwise come into play. As Matt Mossbrucker, the director and curator at the Morrison Natural History Museum likes to say, "think a skinny kid in a puffy coat."
Finally, the plates might have helped stegosaurs to differentiate from one another. This is a tactic often used in animals today (again, the birds of paradise and many other birds: see the last paragraph of our post on the cichlids of the Great African Rift Lakes HERE), and is thought to have been a tactic used by many extinct animals, as well. For example, the various horns and frills of the ceratopsian dinosaurs (like Triceratops and Einiosaurus that we were talking about before) are now thought by many paleontologists to have been used to tell each individual species apart, and its possible that that is what the stegosaurs were doing, too.
Want to learn more about Stegosaurus? Well, check out the Homebase for Stegosaurus WeekHERE to partake in more of the festivities!
