Top Five Extinct Crocodilians

As a reward for winning our Winter Trivia Contest, Carla has requested a "Top Five Extinct Crocodilians" post, and I was all too happy to oblige (but sorry it took so long)!  Let's face it: living crocodilians are pretty awesome, and their extinct cousins?  Even MORE so!  And although some of the creatures that we will look at in this Top Five list may not be crocodilians by the strictest sense of the term, those that don't entirely fit the bill are very closely related.  These "almost crocodilians," as well as the actual crocodilians, are all from a group of reptiles that we call the archosaurs.  Archosaurs include many fascinating animals, including the crocodilians, pterosaurs, dinosaurs, and birds, as well as their extinct ancestors.  Some of the members of this list are critters that look a whole lot like crocodilians, but just weren't quite there yet, as most sources state that modern crocodiles did not evolve until the Late Cretaceous.  Some people refer to this large group of crocodile-like creatures, as well as the crocodilians and their ancestors, as "pseudosuchians," which is what is used to describe the first few animals that we are looking at today!

1.  The phytosaurs are the first of these "pesudosuchian" groups.  Although at a glance they look pretty similar to the modern day Indian gharial, the phytosaurs lived in the Late Triassic, right around the time that dinosaurs were first evolving too, about 200-220 MYA.  We still have nearly 150 million years before the appearance of modern crocodiles!  As you can see below, the phytosaurs definitely resembled the later crocodilians in many ways, but they were different, too.  Just look at how far back on the skull those nostrils were!

2.  Our next pseudosuchian is one of my favorites, named Desmatosuchus.  A member of the extinct group called the aetosaurs, Desmatosuchus was actually an herbivore!  As you can see on the back of this animal, Desmatosuchus is yet another one of those fascinating creatures that has evolved dermal armor, similar to the armadillo and the ankylosaurs!  The giant shoulder spikes of Desmatosuchus definitely look a whole lot like those of the ankylosaurs, and served a similar defensive purpose.  If you traveled back to the Late Triassic period, you would have been able to find Desmatosuchus in the southern United States.

3.  While Poposaurus definitely looks a lot like a dinosaur, just like Desmatosuchus and the ankylosaurs, this is simply another fascinating example of convergent evolution!  Poposaurus, just like Desmatosuchus and the first dinosaurs, lived during the Late Triassic Period, about 225 million years ago.  For whatever reason, it was the poposaurs and not the dinosaurs that went extinct at the end of the Triassic Period.  Apparently, the Triassic town wasn't big enough for these two groups of bipedal reptiles.

4.  Postosuchus, a member of another group of pseudosuchians called the rauisuchians, looked a lot like Poposaurus, as this critter also is thought to have been able to walk on its hind legs.  Postosuchus and Poposaurus also both lived at the end of the Triassic, and both disappeared in the mass extinction event that jumpstarted the Jurassic.  Apparently, when it was first discovered, Postosuchus was thought to be a tyrannosaur ancestor, an understandable mistake once you look at the skull of this creature!

5.  This next crocodilian seems like a bizarre medley of different animals and, in some ways, it kind of is!  Meet Dakosaurus, a member of a group of extinct crocodilians called the metriorhynchids.  The metriorhynchids display numerous physiological adaptations that suggest they were quite comfortable in marine environments, such as paddle-like front limbs, hypertrophied nasal salt glands (presumably to help keep the body from getting an excess of salt), and a hypocercal tail.*  Unlike many other crocodilians, the metriorhynchids evolved sharp, serrated teeth, similar to those seen in terrestrial predatory dinosaurs.  These marine crocodilians also lost their dermal armor over the course of evolution, the tough, bony scales and scutes on the backs of modern day crocodiles that help defend them against attack from predators or other crocodilians.  Presumably, this lack of dermal armor would have helped make the metriorhynchids even more hydrodynamic.  Dakosaurus has been discovered in Europe, South America and Mexico, and lived during the Late Jurassic and Early Cretaceous.

*As you can probably tell from the complicated words used in these descriptions, the "hypertrophied nasal salt glands" and "hypocercal tail" are both direct quotes from the paper describing Dakosaurus (click HERE to check it out).  I had a tough time determining the exact meaning of the term "hypocercal," but as I understand it, it is a condition seen in many extinct fish and other marine creatures, in which the vertebral column bends downwards in the tail, (as you can see in the picture of Dakosaurus above), as opposed to where the vertebral column bends upwards, or simply doesn't protrude very far into the tail to begin with.  Amongst other creatures, the ichthyosaurs seem to have a very similar tail design, as you can see below.  I'm not certain what, if any, the distinction is between hypocercal and reversed heterocercal; either way, this sort of tail definitely seems like it would be a good adaptation for swimming!

Works Cited:

Museum Spotlight: Fernbank Museum of Natural History

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.

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Museum Spotlight: California Academy of Sciences

Another really cool museum that my family and I visited in California was the California Academy of Sciences.  They had lots of really cool exhibits!  My favorite was a prehistoric mammals exhibit, but unfortunately, pictures weren't allowed inside, so therefore I don't have any pictures!  We also didn't get to visit the whole museum, but the parts that we did we all really enjoyed!  But I did get a few pictures of some of the other really cool things, so here they are!  A brief overview of the California Academy of Sciences!  Enjoy!  First, we are going to look at what they call "The Living Roof," which is a cutting edge....garden.  However, although it does sound a bit unexciting, it was actually pretty cool, as the cutting edge garden was on the roof!  (Hence the name "The Living Roof," in case you missed that part.)  It actually always reminds me of the Shire from Lord of the Rings!

Although I didn't get any pictures of any prehistoric mammals, I did get a picture of another prehistoric animal!  Does anybody know what it is?

One particular exhibit was called "Rainforests of the World," which, as you can imagine, focuses on the worlds rainforests.  It was really cool, and it was all inside of this enormous dome thing!  But yeah here are some pictures from inside of the dome!

 

 

Finally, the last thing that we saw that I thought was really cool was this: an albino alligator!  Definitely don't see those every day!

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Zoo Spotlight: Gatorland

When my family and I visited Disney World in Orlando, Florida in 2007, my dad really wanted to go to this alligator zoo thing that he had gone to before, called Gatorland.  It was really awesome!  So let's do a Zoo Spotlight on it!  Every photo in here was taken by my mother, so there is no need to do a "Photo Credit" for every single one!  First off is the entrance to Gatorland!

Perched right next to the entrance were a number of black vultures!

And, as you can probably imagine of a place called "Gatorland," there were lots and lots of alligators, all over the place!  Probably some of the coolest alligators we saw while we were there, though, were the ones that were involved in the feeding demonstration!

There were lots more alligators too, though.  Some were sunning themselves....

 

 

Now, what was that bird in the last picture of the alligator sunning itself on a dock?  That was a great blue heron, and not only do we have those here in Colorado, but there were a bunch there too!

The great blue herons seemed pretty comfortable in the murky water, although something sinister lurked beneath....

 

 

 

 

 

And as if that wasn't enough, they had a place where you could feed goats, too!

 

So would I recommend Gatorland to anyone who was going to be in the area?  Heck, I would recommend it to anyone who isn't going to be in the area, too!

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Proterosuchus....or Should I Say "Broterosuchus?"

Before we learn about Proterosuchus, it will be helpful to discuss where this creature comes from.  Proterosuchus is an archosaur, and to understand what an archosaur is, we must first travel back 320 million years into Earth's history: back....to the middle of the Carboniferous Period.  To travel back to that period of Earth's history, click HERE TO SEE A POST I JUST MADE ABOUT THE EVOLUTION OF THE ANIMALS THAT WE ARE TALKING ABOUT RIGHT NOW.  Unless, of course, you are fine with just accepting the idea that the archosaurs are relatives of the dinosaurs, pterosaurs, and crocodilians, in which case you can just skip that post.  I think it's interesting, though, so it might be worth checking out!

Well, that was confusing.  So how does all of this evolutionary rig-a-ma-roll pertain to Proterosuchus?  Well, in his excellent book entitled "Gorgon," paleontologist Peter D. Ward actually talks about that.  Here is that passage from his book:

"During the Triassic a whole new suite of vertebrates populated the land.  The oldest true "ruling reptiles," the stock that would ultimately give rise to the dinosaurs, are found in the oldest rocks of the Triassic.  The most ancient of these is Proterosuchus.  Yet within several million years, there was a variety of these predinosaurs, belonging to a group known as the archosaurs.  From these ancestral stocks the successful lines of crocodiles and crocodile-like animals known as phytosaurs evolved.  From other members of this group came lizards, snakes, and, by the middle of the Triassic, the first true dinosaurs."  

Well, that certainly sums it up quite nicely, don't you think!  Anyways, Proterosuchus was around the size of the extant Komodo dragon, and was one of the largest reptiles alive during its time, in the Early Triassic Period.  Similar in appearance to the modern day crocodiles, it has been theorized that this animal would lie in wait much like the crocodilians, ambushing its prey when it came down to bodies of water to drink.  One bit of evidence that causes some scientists to believe that Proterosuchus hunted like the crocodilians was that the eyes of Proterosuchus were were located on top of its head, again like the crocodilians.

Remains of Proterosuchus are known from both China and South Africa, where it was first discovered by Robert Broom, a famous South African paleontologist, in 1903.  This specimen was discovered in the Karoo Basin, an enormous desert in South Africa where large numbers of fossils have been discovered. 

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The Archosaurs: A Brief Summary of Reptilian Evolution

320 million years ago, during the Carboniferous Period, the flora and fauna looked quite different than it does today.  Oxygen levels in the atmosphere were much higher, allowing insects to grow to enormous sizes.  Centipedes were the size of snowboards; dragonflies were the size of hawks; and spiders were the size of dinner plates.  There were also no mammals.  Not only that, but there were no reptiles, no dinosaurs, and no birds (which, of course, are dinosaurs).  There were, however, amphibians.  Amphibians, like frogs and salamanders, cannot lay their eggs on dry land, and instead must lay them in pools of water.  This is because the eggs that they lay, unlike those laid by dinosaurs, birds, reptiles, and monotremes (the two egg-laying mammals), have soft-shelled eggs, which allows water to move in and out of them.  They would simply dry up on land!

Around 320 MYA, however, something changed.  Some of these amphibians developed what is known as an "amniotic egg," the type of egg typified by the dinosaurs, birds, reptiles and monotremes.

Around 5 million years after that, around 315 MYA, another major split occurred, this time between the amniotes.  This split resulted in two lineages, the first of which, the synapsids, would one day become the mammals.  The second of these two lineages was the sauropsids.   Within the sauropsids was the group known as the archosaurs.  The archosaurs, in turn, suffered two major splits.  The first split was the crocodiles, alligators and their kin.  They joined with the rest of the reptiles contained within the sauropsids.  The second large split within the archosaurs was another large group, off of which the pterosaurs broke off, before the rest of the group became dinosaurs (and, in turn, birds).  If you look at the family tree below, you can see that the group known collectively as the "reptiles" is what is referred to as a "paraphyletic group."  Put simply, that means that a paraphyletic group consists of "all the descendants of the last common ancestor of the group's members minus a small number of monophyletic groups of descendants, typically just one or two such groups." So for reptiles, that means that the group consists of the last common ancestor of all reptiles (which includes both extant reptiles and the extinct mammal-like reptiles, the precursors of the mammals), including all of the descendants of that ancestor....EXCEPT for the mammals and the birds, which are defined separately.  I feel like I have confused you enough, so I am not even going to get into the whole dinosaur debate.

The Denver Gem and Mineral Show Part 2: The Piscivores (Excepting Penguins)

As we started talking about a few weeks ago, my friend Masaki Kleinkopf and I were able to visit the Denver Gem and Mineral Show at the Denver Merchandise Mart.  Last time, we talked about the giant ammonites, the baby eryops that Dr. Robert Bakker was working on, the gliding Indonesian lizards of the genus Draco and the pterosaurs that evolved from creatures purportedly much like this millions of years ago.  Today, we are going to talk about all of the piscivorous animals that we saw there, except for the fossil penguin that I saw there.  Knowing me, that would easily take up one whole post of its own there.  Keep in mind throughout this post that I'm not certain for all of these animals that they actually eat fish, I just know that the large groups that they belong to often eat fish.  Today, we are going to be looking at the mosasaurs, crocodilians, pterosaurs, sea lions, other fish, sharks, and the dreaded piscivorous dinosaur Spinosaurus.  

MESSAGE FROM ZACK FROM THE FUTURE:  Hello, everyone.  This is Zack Neher.  I have travelled to this post from the future.  I wanted to give you a link to the Homebase for these posts.  I am like Rose Tyler, leaving clues in the form of Bad Wolf.  Except this is not quite like that at all really.  Anyways.  The Homebase for the series is HERE.

Myself next to a gigantic mosasaur skull

I am pretty sure that this is the skull of a mosasaur , anyway.....it looks more like a mosasaur skull than the skull of a crocodilian, if you ask me

A mosasaur jaw, from Morocco by the looks of it

A mosasaur skull (Platecarpus, if memory serves, but it is entirely possible that I am wildly off) in front of a fossil ray

Another huge mosasaur skull

We also got to see the teeth of a piscivorous pterosaur.  The teeth of a piscivore are usually different from those of other carnivorous animals due to their conical shape.  The teeth of the fish eaters, like those of crocodilians and dolphins, are usually conical in shape, to prevent prey from struggling out of their grasp.

The teeth of a piscivorous pterosaurs

Below are the skulls of various crocodilians.

 

 

The skulls of these dudes seem like they should be out of a cartoon or something, they are so weird and comic looking!

Here are a pair of photos of fossilized sea lion teeth, both from the extinct sea lion Imagotaria sp., from the Miocene to Pliocene in the Atacama region of Chile.

Imagotaria sp., from the Miocene to Pliocene in the Atacama region of Chile

Imagotaria sp., from the Miocene to Pliocene in the Atacama region of Chile

Next, a picture of a pair of fossil jellyfish!

Fossil jellyfish!

Next are the teeth of the gigantic, fifty to sixty foot long carnivorous (or actually, piscivorous) dinosaur: Spinosaurus.  Also in the picture are the teeth of another enormous carnivorous dinosaur that lived in the same area of Northern Africa as Spinosaurus at this time of the Cretaceous Period: Carcharodontosaurus, who was not a piscivore, at least not primarily a piscivore, like a penguin, or as Spinosaurus is purported to
be.  (Did you see that alliteration?  My language arts teacher would be most impressed).  I discuss both Spinosaurus and Carcharodontosaurus in two previous posts, which you can look at HERE FOR SPINOSAURUS and HERE FOR SPINOSAURUS AND CARCHARODONTOSAURUS.

The teeth of Spinosaurus.  Actually in this shot, it looks as if most or all of these teeth belong to Spinosaurus.

And now for some pictures of the teeth of Megalodon, the largest shark that is ever known to have lived!  I have talked about Megalodon in the past, click HERE to learn more.

 

Now for some random ones.

It's a fish eat fish world out there

A pair of shark jaws.  I am not certain as I don't remember at all and they are unlabeled, but I believe them to be jaws of sand tiger sharks.  Again, I could be totally off on this!