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. 

Denver on Dwellable

The Biggest Carnivorous Dinosaur Part 3: Spinosaurus, The World's Largest Penguin

Spinosaurus quickly smashed its way to the top (literally!) following the success of Jurassic Park III.  At up to 56 feet (17 meters) in length, Spinosaurus (found in Egypt and Morocco) is unquestionably the longest carnivorous dinosaur that has ever been discovered, and by a significant margin, too.  But how could Spinosaurus be so successful when another carnivorous monstrosity, Carcharodontosaurus, lived in such close proximity?  The answer lies in what it ate; in fact, Spinosaurus appears not to have been as carnivorous as we once thought, and seems to in fact have been more piscivorous.  Essentially, it is thought that Spinosaurus might have survived on a diet consisting a great deal upon fish.

There is a great wealth of information that indicates the staple diet of Spinosaurus was fish.  Here we will take a more in-depth look at this evidence.

A picture of Spinosaurus drawn by the talented young artist Sam Lippincott.

1.  POSITION OF THE NOSTRILS:  Spinosaurus, unlike most other theropod (meat-eating) dinosaurs had nostrils situated very high up on its skull.  By contrast, most other theropods, like Tyrannosaurus, had nostrils very close to the front of the skull.  The nostril placement in Spinosaurus would have allowed it to stick its nose into the water quite deep, enabling it to hunt fish more effectively.

2.  SENSORY ORGANS ON THE TIP OF THE SNOUT:  Along with the high placement of the nostrils, Spinosaurus also had a number of small sensory organs at the front of the snout, revealed by CT scans.  These greatly resemble those of the crocodile, who uses them to sense where prey is by "seeing" tiny movements in the water.  Thus, a crocodile can attack its prey without ever seeing them with their eyes.  Spinosaurus appears to have been able to do much the same thing, making its hunting method of choice quite obviously effective, given its immense size.

3.  ISOTOPIC EVIDENCE:  A study of the isotopes in the skull of a Spinosaurus specimen revealed something quite interesting.  Spinosaurus shares a great deal of isotopic overlap with crocodiles, fairly aquatic animals.  By contrast, other carnivorous dinosaurs like Tyrannosaurus have very different isotopic readings, indicating a terrestrial lifestyle.  Given the great deal of overlap possessed by Spinosaurus and crocodiles, it appears that Spinosaurus spent much of its life like a crocodile; semi-submerged in rivers and streams.

4.  THE TEETH TELL THE TALE:  Spinosaurus, unlike most other carnivorous dinosaurs like Tyrannosaurus, Allosaurus, or the famous Velociraptor, possess conical, round teeth.  These other carnivores possess thin, blade-like teeth, made for slicing, crushing or tearing into other animals.  Spinosaurus has teeth much like a crocodile; round and conical.  These teeth are made for gripping and making sure that an animal does not escape. 

5.  THE TEETH TELL THE TALE....AGAIN:  Yet again, we come to the issue of teeth, and this is one of the most damning pieces of evidence of all.  During the time that Spinosaurus lived in North Africa, another inhabitant of these streams and rivers was a saw-toothed fish called Onchopristis.  Two fossils involving Onchopristis have been discovered in conjunction with the remains of Spinosaurus.  One was the skull of a Spinosaurus; imbedded in one of the tooth sockets was a vertebrae from an Onchopristis.  The other discovery was the barb of an Onchopristis embedded in the jaw of the Spinosaurus.

6.  PLUS:  We only ever seem to find Spinosaurus in shallow aquatic environments, where fishy prey would be abundant.

All in all, it seems like an inevitable conclusion to draw that Spinosaurus was, in fact, a piscivore, at least much of the time.  A fascinating example of the crazy turns evolution can take.

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.