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
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!
This Saturday at the Morrison Natural History Museum in Morrison, Colorado, we will be celebrating Stegosaurus Day, in honor of Colorado's state fossil! (To learn more, click HERE to
be redirected to the Facebook page of the Morrison Natural History
Museum!) So, in honor of Stegosaurus Day, The Natural World is going to
have ourselves a little Stegosaurus Week! Each day, we are going to be looking at a different aspect of Stegosaurus, and today, we are going to be looking at the tail spikes on the tail of Stegosaurus, nicknamed the thagomizer! What were they used for? Did they actually use their tail spikes for defense? And how about that funky name: where did the term "thagomizer" come from? Well, learn those answers and more in today's post for Stegosaurus Week!
Remember IN THE LAST POST OF STEGOSAURUS WEEK when we mentioned paleontologist Ken Carpenter and his very complete and articulated Stegosaurus skeleton? Well, in 1993, when Carpenter was presenting his findings, he first used the term "thagomizer" to describe the tail and spikes of Stegosaurus. Without even knowing its backstory, it seems like a fitting name: but its true origin is even more interesting! For those of you who have enjoyed Gary Larson's fantastic "The Far Side" comic strip, then you may already know where we are heading with this! One of my favorite "Far Side" strips is the one above, and, interestingly, it is from this strip that Ken Carpenter got the name "thagomizer!"
Now, one question that has stumped paleontologists for years is, how were the spikes arranged on the thagomizer? Nowadays, we know that there were two sets of spikes, and they are thought to have been about 180 degrees from each other, forming a horizontal line. (For a more complete discussion, see the last post in our Stegosaurus Week series, entitled THE GENUS STEGOSAURUS THROUGH TIME.) But other questions stumped paleontologists, too. For example: what was the thagomizer used for? It definitely looks like a very apt defensive weapon, but for a long time, paleontologists had no clues to help them figure out whether defense was actually the answer.
One source of evidence that Stegosaurus and other stegosaurs were using their thagomizers to defend themselves is that many of the spikes have broken tips. Now, just because a fossil is broken, doesn't necessarily mean that it was broken during the animals life. Paleontologists can tell whether or not a bone was broken during the life of the animal by looking to see whether the bone shows any signs of healing. If the fossilized bone shows signs of "remodeling," then the bone broke during the life of the animal, and then started to heal while the animal was still alive. Following the death of an animal, if somehow a bone becomes broken, it's not going to heal: the animal is already dead! In a study that examined 51 tail spikes of Stegosaurus, researchers found that about 10% of these spikes had broken tips whose bone had started to grow back. So clearly, these spikes weren't just for show, and were actually being used for something.
The best evidence that paleontologists have right now that indicates that Stegosaurus was using its thagomizer to defend itself against predators is an Allosaurus tail vertebrae with a hole in it: a hole exactly matching the kind of hole that a thagomizer would have made! What's very interesting about this fossil is that, while damaged bone in the vicinity of the hole shows signs of healing (indicating that the Allosaurus survived, at least for a little while, following its encounter with Stegosaurus, and that the damage to the vertebrae was not post-mortem), the hole itself doesn't seem to have healed at all. This has caused some paleontologists to hypothesize that part of the tough outer sheath that would have surrounded the tail spikes in life, probably making them sharper and pointier, of a Stegosaurus became stuck in the tail vertebrae, remaining lodged within the tail vertebrae of that particular Allosaurus, until the animal died!
This Saturday at the Morrison Natural History Museum in Morrison, Colorado, we will be celebrating Stegosaurus Day, in honor of Colorado's state fossil! (To learn more, click HERE to
be redirected to the Facebook page of the Morrison Natural History
Museum!) So, in honor of Stegosaurus Day, The Natural World is going to
have ourselves a little Stegosaurus Week! Each day, we are going to be looking at a different aspect of Stegosaurus, and tonight, we are going to be looking at the genus Stegosaurus as a whole, and how our concept of Stegosaurus has changed over time! Let's dive on in! Stegosaurus was first discovered by famous paleontologist Othniel Charles Marsh during the Bone Wars (a paleontological competition from Marsh and rival paleontologist Edward Drinker Cope) in the late 1800s, and was first described by him in 1877. When Stegosaurus was first described by Marsh, he wasn't really sure what it was: he actually thought that it might be a turtle-like creature, as you can see in his illustration from above! This reconstruction explains why Stegosaurus has its name: covered, shingled, or roofed reptile. It wasn't until Marsh and his crew found other, more complete specimens of Stegosaurus that he was able to figure out what the animal looked like with a greater degree of accuracy, which you can see in the reconstruction below.
The reconstruction above, while much closer to what we think Stegosaurus looks like today than the first reconstruction, nevertheless has several key differences from today's reconstructions. One of the main issues that paleontologists face when reconstructing Stegosaurus and its relatives from fossils is that the plates aren't attached to any bones. The plates are modified osteoderms, used in many different animals to protect themselves from attack (a more extreme example of which can be seen in the close relatives of stegosaurs, the ankylosaurs). Like the osteoderms in other animals, such as the ankylosaurs, the osteoderms would sort of "float" in the skin, only attaching to the rest of the skeleton by means of softer tissues, softer tissues that don't typically fossilize. What paleontologists really needed was an articulated specimen of Stegosaurus.
Well, that's exactly what paleontologist Ken Carpenter got in the 1990s! Using this very complete and articulated specimen, Carpenter and his colleagues were able to solve a number of Stegosaurus mysteries. For example: the exact placement of the plates. In Marsh's 1890s reconstruction above, you can see that he had positioned the plates in a single row running down the back. Later reconstructions by other scientists had been created with a double row of plates, which was proven to be correct by Carpenter's specimen. It was also shown that the plates alternated down the back, as opposed to the side-by-side reconstructions sometimes seen.
Another mystery that Carpenter's specimen was able to solve is the number and placement of the tail spikes. As you can see in Marsh's 1890s reconstruction above, he hypothesized that Stegosaurus had four pairs of spikes, and that they pointed upwards at around 10-15 degrees from the vertical. Carpenter's specimen, coupled with further research, has shown that, to the best of our knowledge, no species of Stegosaurus had that many tail spikes: in fact, from what we know, all species of Stegosaurus had two sets of tail spikes, for a grand total of four. We also now know that, instead of the spikes being about 10-15 degrees from the vertical, they were almost certainly horizontal to the ground! This hypothesis is backed up by investigations into the flexibility of Stegosaurus's tail: to successfully bring its tail spikes into play in the 10-15 degree arrangement, Stegosaurus would have had to have a tail much like a scorpion, and all research done up to this point indicates that Stegosaurus had nowhere near that much vertical flexibility in the tail. However, the horizontal reconstruction makes much more sense, as the tail seems like it would have had a great deal of side-to-side flexibility.
The final main difference between Marsh's 1890s reconstruction and our reconstructions of Stegosaurus today lies in the way it held its tail and its neck. Due to the Dinosaur Renaissance in the 1960s and 1970s led by John Ostrom and his pupil Robert Bakker, the perception of dinosaurs as lumbering failures changed dramatically to what it is today: not failures of evolution, but instead, a remarkable success that shaped the evolutionary course of the Earth for millions of years. This change in perception is reflected in how we think dinosaurs moved: we no longer think that they dragged their tails on the ground, barely able to keep their heads from dragging in the mud. Instead, we view them as much more nimble than we once thought. And while Stegosaurus may not have been the nimblest of them all, you can clearly see how our ideas of how we think this animal moved around have changed over the years.
This Saturday at the Morrison Natural History Museum in Morrison, Colorado, we will be celebrating Stegosaurus Day, in honor of Colorado's state fossil! (To learn more, click HERE to be redirected to the Facebook page of the Morrison Natural History Museum!) So, in honor of Stegosaurus Day, The Natural World is going to have ourselves a little Stegosaurus Week! This post will serve as the Homebase for the weeks festivities! Below, we have a schedule of what I hope to have us talk about this week: we'll see whether I end up sticking to it or not! I am also going to be making a few videos, as well, so be on the lookout for those!
In 2006, my family and I went down to Georgia (we were lookin' for a soul to steal) to visit our really good friends the Guinees (we were way behind, and we were willing to make a deal). On our trip, we visited what is now one of my most favorite museums of all time: the Fernbank Museum of Natural History. While Fernbank certainly has a large number of really cool exhibits, easily my favorite one was the one around which most of the museum is built: an enormous room with a Giganotosaurus attacking an Argentinosaurus, one of the largest theropod dinosaurs known to science attacking one of the largest sauropod dinosaurs known to science. It was simply fantastic! In the upper levels of the atrium thing, you could also see fossil skeletons of various pterosaurs, and there was also a fossil crocodile on the ground floor! Fantastic!
Another thing that I thought was really cool was a large, life-size statue of Stegosaurus outside of the museum! Below is a picture of my sister and I acting like dinosaur in front of it!
All of the photos in this post were taken by Julie Neher.
Today we are going to do yet another 23-Fact Tuesday, and this time it is all about a particularly interesting dinosaur known as Allosaurus. But this 23-Fact Tuesday is particularly special, as it is also the birthday post of one of my personal heroes and one of the people who inspired me to take this dinosaur- and animal-oriented path, Mr. "Dino" George Blasing! Happy birthday, Mr. Blasing! Here we go!
4. Some scientists believe that Allosaurus had a very weak bite, around the strength of a leopard. Regardless of exactly how weak of a bite it had, Allosaurus was definitely not a heavy-biter champion, and many paleontologists hypothesize that it instead used its skull sort of like a hatchet to kill its prey, using its razor-sharp teeth to critically injure its prey.
5. The first fossils of Allosaurus that were ever discovered were originally thought to be petrified horse hooves.
A reconstructed skeleton of Allosaurus at the Cleveland-Lloyd Dinosaur Quarry in Utah
7. Allosaurus certainly didn't sit on its rump and enjoy hamburgers and tea, as their skeletons show that they suffered many injuries throughout their lives. As a matter of fact, the Allosaurus specimen that is on display at the Smithsonian Institution has a number of broken ribs, a smashed shoulder blade, and a damaged lower jaw.
A crushed femur belonging to Allosaurus from the Cleveland-Lloyd Dinosaur Quarry
8. The lower jaw of the specimen at the Smithsonian was so damaged, in fact, that it took scientists more than 100 years to figure out that it was, in fact, an Allosaurus jaw!
9. A predator-prey relationship between Allosaurus and Stegosaurus was all but confirmed with the discovery of a specimen of Allosaurus with a hole in one of its tail vertebrae that perfectly matched the shape and size of the thagomizer on the tail of Stegosaurus.
Allosaurus Vs. Stegosaurus at the Denver Museum of Nature and Science
The "thagomizer" of Stegosaurus, mounted at the DMNS. Check out THIS post to learn about how this particular part of the Stegosaurus got its name!
10. "Allosaurus" spelled backwards is "Suruasolla," which means absolutely nothing.
11. The small horns above the eyes of Allosaurus are mostly thought to have been for display, as most scientists believe them to be too weak to withstand much stress resulting from conflict with prey or other Allosaurus.
12. Allosaurus gives its name to the group Allosauroidea, which includes the Chinese theropods Yangchuanosaurus and Sinraptor, and the carcharodontosaurids, which includes one of the largest carnivorous dinosaurs of all time, Carcharodontosaurus, amongst other dinosaurs.
13. Some of the other scientific names that Allosaurus fragilis has
had over the years are Allosaurus lucaris, Allosaurus ferox, Labrosaurus
ferox, Labrosaurus lucaris, Antrodemus, Poicilopleuron valens, Laelaps
trihedrodon, Epanterias amplexus, Hypsirhophus discurus, Hypsirhophus
partim, and Creosaurus atrox, with a few other names under debate right
now. Specifically, some scientists think that the dinosaur known as
Saurophaganax is the same animal as Allosaurus. However, I have talked
with a few people, including Matthew Mossbrucker, curator of the Morrison Natural History Museum, and he says that he has seen the remains of
Saurophaganax and believes them to be distinct from Allosaurus.
A reconstructed skeleton of Saurophaganax that I saw at a traveling exhibit at the San Antonio River Walk in Texas
14. Besides Saurophaganax, Allosaurus was much larger than the other known theropods from LateJurassic Morrison, such as Ceratosaurus and Torvosaurus.
A reconstructed skull of Saurophaganax that I saw at a traveling exhibit at the San Antonio River Walk in Texas
15. We humans actually live closer in time to the famous Tyrannosaurus rex, Triceratops, and other dinosaurs from that time period than they do to Allosaurus!
A Triceratops skull at the Morrison Natural History Museum
16. Allosaurus fragilis was first named by famous paleontologist Othniel Charles Marsh in 1877.
17. The scientific name of Allosaurus fragilis translates to "fragile
different lizard," named such due to the fact that Marsh believed that
the vertebrae of Allosaurus would have been quite weak, and were
different from those of other, previously discovered dinosaurs. Now we
know that vertebrae of this kind were quite common.
18. One of the most famous specimens of Allosaurus is the approximately 95% complete specimen nicknamed "Big Al." Estimated to be only a teenager at his TOD, he is about 26 feet long, which probably helps to explain why so many of my dinosaur books list the estimated length of Allosaurus at around 26 feet.
19. Allosaurus lived during the Late Jurassic Period, around 155.7-150.8 MYA in the United States (Colorado, New Mexico, Utah, Wyoming, Montana, Oklahoma, and South Dakota), Portugal, and possibly the Tendaguru Beds of Tanzania, although many people believe that this is African animal is an entirely different animal from Allosaurus.
20. Work began at the Cleveland-Lloyd Dinosaur Quarry in 1960, and over 40
individual specimens of Allosaurus have been uncovered there since then.
Unarticulated bones of Allosaurus from the Cleveland-Lloyd Dinosaur Quarry
21. Due to the vast number of Allosaurus specimens discovered in all different stages of its growth development (especially from Cleveland-Lloyd), paleontologists have been able to estimate that Allosaurus reached full-size at around 15 years of age, and lived to around 22-28 years old.
A whole bunch of Allosaurus leg bones all put next to each other to show the growth of the animal, largely based upon bones found at the Cleveland-Lloyd Dinosaur Quarry, which is where this picture was taken
22. Fossils of Allosaurus are still being discovered to this day, a fact which I can personally attest to. Blocks of stone are still being excavated at the Morrison Natural History Museum, and bones of Allosaurus, as well as its teeth, are currently being cleaned.
23. Allosaurus is the favorite dinosaur of the famous dinosaur educator, "Dino" George Blasing.
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There are three different types of wombat. There is the common wombat (Vombatus ursinus), the southern hairy-nosed (Lasiorhinus latifrons) and the northern hairy-nosed (L. krefftii). They have been classified by the IUCN, respectively, as Least Concern, Least Concern, and Critically Endangered. Unfortunately, all three wombats face threats that could easily result in their extermination from the wilds of the earth. Fortunately, steps are being taken to prevent such a wombacide.
In Queensland, Australia lies Epping Forest National Park. In just two square miles of this park live the last ninety individuals of the northern hairy-nosed wombat. Surrounding this puny area is a 20 kilometer long perimeter fence, erected after 10 wombats were killed by dingoes a few years ago, which, considering the severity of a ten percent population loss in such a small population, makes total sense.
Although these steps are being taken to protect the northern hairy-nosed, this species of wombat still faces several severe problems. One such problem is the fact that 75% of these wombats are male, making a boom in their population more difficult to achieve. Fortunately for the northerners, the southern hairy-nosed wombat has a very similar reproductive system as the northern hairy-nosed. Scientists are therefore using female southerners as surrogate mothers for the northerners. This method is referred to as "cross fostering," and has been used successfully when it comes to other marsupials.
The other major problem confronting the northern hairy-nosers is the fact that all of the animals are located in the same place. In the event of a disease, wild-fire, or some other similar catastrophe, most or all of these creatures could be exterminated in the virtual blink of an eye. Conservationists think it wise to create a second population of northerners, not too far away from the first, but far enough away to ensure that a disaster could not take out both populations with one fell swoop. Scientists and conservationists have decided that it would be most beneficial to the northerners if they were to assist in their burrow construction.
These burrows, which can be over 100 feet long, would be time-consuming construction projects. Not only that, but a single wombat will often use up to five different burrows, moving to a different one each day. The first wombat doesn't just leave his or her old burrow unoccupied, however, as another wombat, probably the same one every five days or so (I would guess), temporarily moves in. It's really less of a permanent residence, like a house, and more of a time-share condo.
But just how time and energy consuming would it be to dig such a burrow if you were a wombat? Wombats have a problem with keeping cool. If you ask my opinion, I suspect it has a lot to do with their body design. As we discussed a few posts ago, animals that live in hot environments typically adapt in ways to increase their Surface Area to Volume ratio, or SA:V for short. To learn more about why this is, click HERE. However, fossorial, or burrowing, animals, like the wombat, aardvark, marsupial mole, and many, many others, try to keep their bodies streamlined. Like dolphins and sharks, these animals want to be able to glide smoothly through their desired area (be it water or burrows). Having random chunks of body, i.e. the ears of an elephant or a deer, would merely slow the animal down. That is my theory, anyways.
To keep cool in the heat of the Australian day, wombats will take refuge in their burrows. However, to be efficient enough when it comes to trapping moisture (as water can often be very difficult to come by in the habitat of the northerns), it has been estimated that the burrow would need to exceed fifteen feet in length. It has also been calculated that the approximate amount of energy required for a wombat to dig a three foot long chunk of burrow is about the amount of energy that a wombat would expend running twelve miles. That means for the comforting fifteen foot length of burrow, the wombat could instead run about sixty miles. Clearly no small effort.
The way that the scientists actually figured all of this out was really quite interesting. To see how long it takes for a wombat to dig a burrow, experimenters Glen Shimmin and David Taggart put one wombat into a box. (Equipped with breathing holes, of course. As pirates and I like to say, "A dead wombat digs no holes"). The human duo then dug a hole in the ground the same size as the box. Placing the wombat-infested box into the ground, they then opened up one end of the container, allowing the wombat free access to the soil. Instinctively, the wombat would begin to dig. A half an hour later, Shimmin and Taggart ceased the wombat-excavation, and carefully measured how much dirt was displaced by the wombat, as all of the displaced dirt would conveniently be shoved (by the wombat) into the box! Convenient, huh? During the half hour digging session, the wombat moved more than 100 pounds of dirt! Impressive, but the team concluded that, if conservationists were to release a group of northern hairy-nosed wombats into their new territory without pre-dug burrows, it was incredibly likely that the wombats would simply dig themselves to exhaustion, and subsequent death. An undesirable outcome for all parties involved, it was decided to dig man-made burrows, resembling those of wombats, throughout the habitat, prior to the installation of the wombat center-piece.
What are some other problems facing wombats? Well for starters, some of these problems, even when facing the wombats in the face, are virtually invisible to them. Wombats, like Stegosaurus, rhinos, and myself (without my contacts), are virtually blind. You don't need eyes if you are a fossorial (burrowing) creature; just ask the marsupial mole, the golden mole, or many other types of fossorial animals who no longer use, or even have, eyes! However, when it comes to crossing roads, their terrible eyesight really takes its toll. Hundreds, if not thousands, are hit by cars each year.
Other problems include starvation, drought, mange, and other people problems. Starvation can be easily caused by the gradual squeezing out of the native grasses typically consumed by wombats by other, inedible grasses. Drought should be self-explanatory; without water, the food dies. Without water, there is no water. Both are not good for wombats. Mange, for wombats at least, is a fatal skin disease. And as for the other people problems? Let's just say that prairie dogs can relate. (And now, even though I just said "Let's just say," I am going to go into more detail). Like prairie dogs, wombats burrow. And also like prairie dogs, the habitat of the wombat is perfect for ranchers. So it goes like this. Ranchers come along, and bring their cattle. The cattle step in prairie dog/wombat holes, break their legs, and die. The ranchers, enraged, take their rage out on the culprits: the prairie dogs or the wombats. And as we have discussed before, wombat burrows can be quite extensive. Furthermore, the entrance holes would have to be quite fat in order to accomodate such...robust occupants.
As we have also previously discussed, much is being done in order to protect the wombat. Another bit of good news is that a population boom of around 10% was recorded for the sole population of the northern hairy-nosed wombat! Another wee bit of hope in a world that we willfully wish not to become wombatless.
WOMBAT FACTS:
Cooling Off: Besides retreating into their burrows, wombats will also flick dirt onto their bodies to keep cool.
Olympic Runners: Despite its dumpy appearance, the wombat can reach a top speed of around 25 mph. This means that it can outrun an Olympic sprinter, like Usain Bolt!
Cooling Off V 2.0: Besides retreating into their burrows and flicking dirt onto their bodies, wombats are also nocturnal, meaning that they avoid the heat of the day.
Life Span: Wombats can live around twenty years.
Wombat Wesearch: Prior to around fifteen or so years ago, not much research had been done on wombats. Most of what we know has been discovered since that time.
Power House Excavators: For their size, wombats may be the world's most powerful excavators.
