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:

Drive to the Quarry: Dinosaur Road Trip With Grace Part 3

PREVIOUSLY, ON BATTLESTAR GALACTICA:

-Grace Albers and I are taking a trip down to Dinosaur National Monument in Utah and Colorado.
-We checked out some cool petroglyphs and then camped the night.
-And now....

Grace was up before I was, and got some cool pictures near the Green River that went right by our campsite!

A sprinkler going off on the farmlands across the river!

A golden-mantled ground squirrel back at the campsite!  These things sure can get pesky, especially if there's food around!

After a quick breakfast, we were off to the quarry!  Here are some of the gorgeous scenery shots on the way!  Pyg definitely enjoyed our view of the Green River!

The Green River in the bottom of the shot!

And then....we saw it!  As we were driving, Grace suddenly told me to stop and back up (as there was no one on the road.  I was being safe, mother, don't worry).  Her instincts were right: it was a golden eagle!  Here are a ton of great shots she took!

Pretty awesome pictures, right!  Well, we continued on to the quarry and were met with an enormous Stegosaurus statue out front!  Here is a picture of Grace next to it!

And here's a Pyg pic!

We went inside of the visitors center.  While we waited for the shuttle to arrive to take us up to the quarry, we looked at some of the things that were inside of the visitor center!  First off, we have some fossil lizard footprints from the Chinle Formation, a Late Triassic formation of North America, whose rocks are around 225 million years old!

Next we have part of the jaw of the large Morrison Formation predator Allosaurus!

Now THIS I thought was really cool, and we will talk more about it in later Dinosaur National Monument posts, but pretty much the two pictures below are before and after pictures.  The first picture is what the intersection of the Green and Yampa Rivers looks like today.  The second is a drawing of what the area WOULD look like if a dam had been built downstream in 1950!  Fortunately, the dam plans were averted!  We will talk more about this dam thingy later!

Pyg touches a large hunk of rock that is about 1.2 BILLION years old!

"What do they keep in there, King Kong?"  Nice Jurassic Park reference, Zack.

After a bit of waiting, the shuttle arrived!  Pyg eagerly awaits our departure!

As we were boarding the tram, I noticed a pair of birds of prey soaring above our heads!  Originally, I thought that they were two of the same birds, and it wasn't until after I put the pictures onto my computer that I realized that these were two very different birds, indeed!  However, I had little to no idea what these birds were, so I contacted Anne Price, the Curator of Raptors at the Raptor Education Foundation, who often brings some fantastic birds to the Best Western Denver Southwest!  To see some fantastic pictures of these experiences and to learn more about them, click HERE and HERE!

Anyways, after talking with Anne, she said that the above picture, as well as the two below, are all of an immature red-tailed hawk, "with a very distinct “dash-and-comma” markings on the wings."

Anne got pretty excited about this last picture, though!  Here is what she said in the email:

"I am 99% certain it is an adult goshawk!!  Very rare to see this bird soaring, and totally in an unusual area; this bird is getting ready  to migrate, or has already started to. Of the 3 accipiters in the US (which are known for having short wings and long tails), the goshawk has the longest wings proportionally to the body and tail. You can very much see that in evidence in your photo. The distinct stripes on the tail are a giveaway too."

Pretty exciting stuff, I'm glad we got the chance to see one!

Finally, as the tram started moving, we noticed some ripple marks frozen in the rock face above us, a reminder that most of the surrounding area was under a shallow inland sea!

Next time: The Quarry!

Animal of the Day: Coelophysis

Today's Animal of the Day is Coelophysis!  The picture of the cast you see off to the left (taken by me at the Denver Gem and Mineral Show a few months back) is from the AMNH (American Museum of Natural History) in New York.  I actually know a little bit more about this particular specimen of Coelophysis than I believe was labeled there, as I remembered seeing this specimen in my Dinosaur Atlas book from DK Publishers.  One of around 500 or so individual Coelophysis specimens discovered at a place called Ghost Ranch in New Mexico, this particular specimen was once thought to reveal something interesting about the species: Coelophysis was once thought to probably be a cannibal, as the remains of a baby Coelophysis were found in the area of the stomach!

Dinosaur cannibalism is not unheard of, and almost certainly occurred in the Late Cretaceous Abelisaur Majungasaurus from Madagascar.  However, this was disproven in 2002 by Rob Gay, when he showed that the baby Coelophysis were either crushed by the smaller ones, or that they weren't even baby Coelophysis!  Instead, many of them were found to be other, small reptiles, such as the archosaur Hesperosuchus, a member of the same group as the crocodilians, dinosaurs, and pterosaurs, amongst others.  So for now, it looks like Coelophysis was probably not a cannibal, but future discoveries may force us to change our minds once again!

Another picture of Coelophysis that I took, at the DMNS

Coelophysis is one of the oldest known dinosaurs, inhabiting North America around 220 million years ago (MYA), during the Late Triassic Period.  The site at Ghost Ranch is interesting, because there are just so many different specimens all clumped together.  Some paleontologists have suggested that a flash flood drowned a huge herd of these animals, or perhaps that they died while trying to cross a river.  We might never know what, exactly, killed these dinosaurs, or why so many of them died in such close proximity.  

Top Ten Favorite Dinosaurs by Zack Neher (Part 4.5)

As some of you may know, right now, we are in the midst of a lis of my  top ten favorite dinosaurs.  However, on December 7th, a new dinosaur was announced, and it has immediately made my top ten list if it is, in fact, a dinosaur, which is currently being debated.  Therefore, I have decided to make this guy number 4.5 on my list, as if this creature is a dinosaur, it may very well be one of the most important finds in the history of dinosaur paleontology, as the find, named Nyasasaurus, may be the ancestor of all dinosaurs! Since this fossil dates to the Middle Triassic Period and is estimated to be about 10-15 million years older than the previously-oldest known dinosaurs like Eoraptor and Herrerasaurus, if this animal is not, in fact, a dinosaur, it resides very close to the base of the dinosaurian family tree!  People around the world eagerly await more remains of this animal from being discovered in Tanzania (where the original fossils were discovered in the 1930s) or somewhere else in the world, in the hopes that some more light can be shed upon this controversy.

 TO BE CONCLUDED IN PART 5