The Morrison Biota

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 Week HERE to partake in more of the festivities!  

The Thagomizer of Stegosaurus (Stegosaurus Week)

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!

Another picture that I took at the Denver Museum of Nature and Science of an Allosaurus attacking a Stegosaurus adult and juvenile

Want to learn more about Stegosaurus and it's relatives? Well, check out the Homebase for Stegosaurus Week HERE to partake in more of the festivities!

The Denver Gem and Mineral Show Part 6: Dinosaurs and Their Ancient Relatives

At last: here we go on the sixth post of our Denver Gem and Mineral Show series!  Even though I went with my friend Masaki Kleinkopf a few months ago, I still have a large number of picture that I am eager to share with you.  If you are interested in reading about the other posts in this series, feel free to check out the Homebase for the series HERE, with links to all of the other posts in the series that have been created thus far!  Today we will be looking at the dinosaurs, as well as an ancient relative!  Fasten your seat belts, everyone!

Here we have the skull of Allosaurus!  We have discussed Allosaurus extensively, especially in our 23-Fact Tuesday post, so click HERE to learn more about this fascinating creature!

A dinosaur who needs no introduction, but, as you can see, I am introducing him anyways: Tyrannosaurus rex!  I believe the second picture is of the foot of Tyrannosaurus, but I am not one hundred percent positive.

Psittacosaurus, one of the most primitive ceratopsian dinosaurs known to science.  It doesn't even have a frill or horns!  So how do we know that it is a ceratopsian dinosaur?  It has an extra bone on its upper jaw called the rostral.  It is this bone that distinguishes the ceratopsians from the other groups of dinosaurs.

Another dinosaur foot, this one belonging to Diplodocus, a large sauropod from the Late Jurassic Period, whose remains are found in the Morrison Formation. 

 Some fossil footprints that I am guessing belong to a theropod dinosaur, but I don't actually know.

Some fossil bones of a hadrosaur known as Edmontosaurus.  Here is what the card says: "Edmontosaurus sp.  Cervical vertebrae and bone.  Lance Formation.  Maastrichtian.  Late Cretaceous.  Niobrara County, Wyoming."

Some teeth belonging to the massive carnivorous dinosaur Carcharodontosaurus.  Up at the top of the picture, you can see a few from Spinosaurus, as well. 

Various teeth and claws from the Rocky Mountain Dinosaur Resource Center (RMDRC) booth.

This last guy, Desmatosuchus, is not actually a dinosaur, but a type of archosaur.  Although it looks quite fierce, Desmatosuchus belongs to an order of Late Triassic herbivores called the aetosaurs.  Desmatosuchus in particular has been found in Texas, and was around 15 or 16 feet in length. 

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23-Fact Tuesday: All About Allosaurus!

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!

Allosaurus Vs. Stegosaurus at the Denver Museum of Nature and Science

1.  On Halloween in 1879, Arthur Lakes discovered a tooth from a dinosaur that was later identified as Allosaurus in Wyoming.

2.  In the United States, Allosaurus is found in the Morrison Formation, and lived alongside other animals such as Stegosaurus, Apatosaurus, Ceratosaurus, Camptosaurus, Gargoyleosaurus, and many others. 

A skeleton of Gargoyleosaurus from the Denver Museum of Nature and Science

Allosaurus Vs. Camptosaurus that I saw at a traveling exhibit at the San Antonio River Walk in Texas

Ceratosaurus at the Smithsonian

Stegosaurus at the Utah Field House

3. The claws on the hand of Allosaurus could reportedly grow up to 10 inches long.

The arm and the claws of Allosaurus, mounted at the Morrison Natural History Museum

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.

6.  Allosaurus is the state dinosaur of Utah.

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 Late Jurassic 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.

And remember, if you have a birthday coming up, just email me the date at cuyvaldar123946@gmail.com with the date and your favorite animal, and I will do my best to get a post in!  And remember, if you like what you're reading, make sure you LIKE US ON FACEBOOK, follow us (if you have a google or gmail account), or hit the subscribe button off to the right if you don't!

Top 10 Favorite Dinosaurs by Zack Neher (Part 1)

Just a few days ago, we had our first ever guest blog post by David Church.  Mr. Church did his top ten favorite dinosaurs, which got me thinking about what my favorite dinosaurs were, and inspired me to do this post!  So here is my top ten favorite dinosaur list!

10. Argentinosaurus

Inhabiting South America during the Late Cretaceous Period, the enormous sauropod Argentinosaurus is the heaviest known terrestrial animal and, according to BBC, also has the record for being the longest land animal.  It was, of course, discovered in Argentina, and would have been a contemporary of Giganotosaurus.  

A picture of Argentinosaurus (background) under assault from a Giganotosaurus (foreground) with my parents off to the left at the Fernbank Museum in Atlanta, Georgia, United States

Another shot of the Argentinosaurus at Fernbank

9. Allosaurus

Allosaurus was a thirty or so foot long carnivorous dinosaur from the Late Jurassic Period.  Discovered in the Morrison Formation of Colorado, Montana, New Mexico, Oklahoma, South Dakota, Utah, and Wyoming, this dinosaur (or one quite like it) was also likely found in the Tendaguru Beds of Tanzania.  The Cleveland-Lloyd Dinosaur Quarry near Price, Utah holds the remains of more than forty individual Allosaurus bones.

Assorted Allosaurus bones from our visit to the Cleveland-Lloyd Dinosaur Quarry

8. Spinosaurus

Spinosaurus is an enormous carnivorous dinosaur that we have talked about on multiple occasions, both in our "Biggest Carnivorous Dinosaur" trilogy of posts awhile back, but also in Mr. Church's Top Ten list.  Spinosaurus, despite the fact that it is easily the largest known carnivorous dinosaur, with an estimated length of almost sixty feet, did not eat meat like the other enormous dinosaurs: instead, Spinosaurus was a piscivore, or a fish eater.  This giant creature lived in Africa during the Cretaceous Period.

 7. Parasaurolophus

Parasaurolophus is another one of those dinosaurs that overlaps from Mr. Church's list to my own.  Parasaurolophus is certainly an interesting creature!  A member of the hadrosaurs, or duck-billed dinosaurs, Parasaurolophus, as Mr. Church discussed, is the only dinosaur I know of where paleontologists know with a high degree of accuracy what they sounded like.  The large crest on the back of the head of Parasaurolophus is full of hollow tubing, similar in shape and structure to the trombone, as well as similar in sound, too.  Unfortunately, I could not find a sound file or video of the call, so if anyone has access to a scientifically reconstructed call, let me know!

TO BE CONTINUED IN PART 2

We Interrupt Our Previously Scheduled Programming: Robert T. Bakker

So today I went in for an interview for a volunteer position at the Morrison Natural History Museum (you should check it out, it's pretty cool!).  I went in, and I met Robert Bakker.  He is pretty much like the Michael Phelps of paleontology.  He is really, really cool.  He and John Ostrom were pretty much the catalysts of the so-called "Dinosaur Renaissance," where the ideas of dinosaurs being cold-blooded, sluggish, stupid and slow were turned on their heads.  So that was pretty exciting.  Below is the link to his page on Wikipedia.  Very exciting stuff!

http://en.wikipedia.org/wiki/Robert_T._Bakker

We will get back to the polar bears later in the day, but I had to talk about this first!

Evergreen on Dwellable

The Thagomizer of Stegosaurus

Stegosaurus is a very famous dinosaurs, one of the most famous, along with Triceratops and Tyrannosaurus.  All three of these dinosaurs have been found in Colorado; in fact, the first Triceratops bones were actually found in Denver, and Stegosaurus is the state dinosaur of Colorado!  Stegosaurus has also been found in Wyoming and Utah, in the Morrison Formation, as well as in Portugal.  The row of plates along its back make it very interesting looking, as do the spikes on the end of its tail, nicknamed a "thagomizer."  Holes in the vertebrae of a potential predator of Stegosaurus, Allosaurus, fit exactly with the size of one of the spikes on the tail of the Stegosaurus, showing that there was almost certainly a predator-prey relationship between the two, as was previously suspected.  Studies have shown that the tail end of Kentrosaurus, a close relative of Stegosaurus, also with a thagomizer on its tail, could have been brought around to the side of the dinosaur, potentially swatting at enemies trying to attack the Stegosaur from the side.

Finally, discoveries of articulated Stegosaurus skeletons show that the spikes were actually horizontal from the ground, as opposed to held at an angle, as you can see in the outdated and incorrect picture below.

It's an interesting word, though, isn't it: "thagomizer."  It certainly doesn't sound like a very sciency name; in fact, when I first heard it, I immediately thought it sounded like something out of one of my favorite comic strips, Calvin and Hobbes, by Bill Watterson.  Well, if you thought that as well, then you were actually surprisingly close to the mark, as the term did in fact come from a comic strip, another one of my favorites: The Far Side.

The term wasn't used scientifically until the year 1993, at the annual meeting of the Society of Vertebrate Paleontology, by the one-time Curator of Paleontology at the Denver Museum of Nature and Science Ken Carpenter.  The name has been used multiple times since then, in different mediums; books and television shows (including another personal favorite, BBC's Planet Dinosaur), as well as places such as the Smithsonian Institution and Dinosaur National Monument.  Although an informal name, it is popular, and has amusing origins.

Gary Larson created a great number of hilarious The Far Side cartoons covering all sorts of topics.  However, it seems like a large number of them featured animals, or were in some way nature related.  You will undoubtedly see a great many of them in this blog as time goes on, but here are a few other amusing dinosaur ones.

The Biggest Carnivorous Dinosaur Part 2: Carcharodontosaurus Vs. Spinosaurus

As I promised yesterday, today we are going to take a closer look at Carcharodontosaurus (kar-kar-o-DON-to-SAUR-us).  Carcharodontosaurus was a relative of Colorado's own Allosaurus.  However, Carcharodontosaurus was four times larger, and found in Egypt, Morocco, Algeria, Libya, and Niger.  At around 46 feet long, Carcharodontosaurus was similar in size to yesterday's Giganotosaurus (pronounced jig-a-NOTE-o-saur-us), and longer than Tyrannosaurus, though Tyrannosaurus was undoubtedly much bulkier.  Regardless, Carcharodontosaurus was a monster-sized killer, and almost certainly had a monster-sized appetite to match.  It is almost a certainty that such an animal would have a fairly large territory, and would have needed to eat a great deal to maintain its fast metabolism, similar to your average teenage dude.

Clearly, such a large predator had little competition from other carnivorous dinosaurs.  Or did it?  As a matter of fact, 95 MYA, North Africa was home to not one, but two monster-sized killers, Carcharodontosaurus, and the even longer, 50 foot (15 meter) Spinosaurus.  (Some not so conservative estimates even place the maximum size for Spinosaurus as 60 feet (18 meters) in length, but this does seem extreme.)

Now, in the modern day, predators can inhabit the same area.  Take the plains of Africa, for example; in many places, lions, leopards, cheetahs, wild dogs and hyenas all inhabit the same area.  There is a clear hierarchy amongst the animals, and each seems to get enough to eat.  However, this is partly because each animal exploits a slightly different set of resources, so contact amongst them is less frequent than if all five of the large carnivores all hunted the same animal, say, the Thomson's Gazelle.  This is a phenomenon known as resource partitioning, and it occurs all over the place in nature, arguably one of the most important factors involving ecology and evolution. Scientists believe that a similar sort of partitioning took place between the two mega-carnivores of Mid-Cretaceous North Africa, with Carcharodontosaurus being a terrestrial carnivore, while Spinosaurus took to the water.  We will conclude "The Biggest Carnivorous Dinosaur" trilogy tomorrow with a look at the environment Spinosaurus was able to so successfully exploit.

A fantastic visual representation of resource partitioning amongst large herbivorous mammals in Africa.  The giraffe, the zebra, and the wildebeest will all inhabit the same area and eat plants, but the types of plants can differ.  Photo Credit: Ted and Gail Neher

The Biggest Carnivorous Dinosaur Part 1: Move Over, T-Rex (Kind Of)

Tyrannosaurus rex, the "Tyrant Lizard King," has long been a dinosaurian favorite the world over.  He is quite the interesting animal, and simply massive; the publicity received by him and the giant-sized Velociraptor in Jurassic Park helped a bit, I'm sure!  However, T-rex is no longer thought to be the largest carnivorous dinosaur.  Well, yes he is.  But he isn't.

A picture of the Tyrannosaurus rex specimen Stan at the Morrison Natural History Museum.

Imagine someone who has never heard of the giraffe and elephant asks you which one is biggest.  You might say the elephant, because the elephant is much heavier and has more bulk.  But what if they mean which animal is taller?  Somewhat of a dilemma.  So using words like "biggest" (as I have done here) is not the best way to go.  So Tyrannosaurus still seems to be the heavyweight champion, there are other dinosaurs that, while more slender, were probably longer.  Kind of confusing, I know.

The fact that T-rex has some serious competition has put barely a dent into his popularity, and some of the other larger carnivores are receiving a lot of attention, too. The longest of these carnivores, which we will learn about on Wednesday, was possibly around 20% larger than Tyrannosaurus Rex!  Today, we are going to look at another enormous killer, of South American origin; the massive, the monstrous, Giganotosaurus.

A Giganotosaurus on display at Fernbank Museum, in Atlanta, Georgia

Giganotosaurus is an estimated 46 feet long, comparable in length to the average Tyrannosaurus!  We do have some specimens of Tyrannosaurus that are around the same size as Giganotosaurus, but either way: Giganotosaurus was a massive animal! Of course we don't actually know for sure what the maximum size for any dinosaur is as, unlike for most living animals, we generally have a relatively small sample set, but we can make close estimates based on the finds we have.  And these estimates indicate that Giganotosaurus grew to simply massive proportions.  One of the largest terrestrial animals that we know of is Argentinosaurus (who, like Giganotosaurus, was also found in Argentina), a sauropod dinosaur that lived at the same time as Giganotosaurus.  For Giganotosaurus to prey on even the juveniles of such a large herbivore, it would similarly need to grow to massive proportions.

Giganotosaurus vs. Argentinosaurus at Fernbank Museum, in Atlanta, Georgia

Giganotosaurus vs. Argentinosaurus at Fernbank Museum, in Atlanta, Georgia

This pattern repeats itself all over the world, the pattern of gigantism evolving in sauropods, along with the subsequent evolution of gigantism in the theropods (meat-eating dinosaurs), is a pattern repeated throughout the world, and throughout the Jurassic and Cretaceous Periods of the Mesozoic Era, the two periods in time when the rule of the dinosaurs was absolute.  Here are some more of the predator-prey, giant-sized carnivore/giant-sized herbivore relationships seen throughout the Mesozoic.  The first animal named will be the predator, and the second will be the sauropod.

Asia, 160 MYA: Sinraptor, Mamenchisaurus
Europe, 125 MYA: Neovenator, Ornithopsis
North America, 150 MYA: Allosaurus, Diplodocus
North Africa, 95 MYA: Carcharodontosaurus, Paralititan

In tomorrows post, we will look at the last relationship, and focus on another larger (or longer) than life carnivore, Carcharodontosaurus.