The Function of Cheek Pouches

A possible ancestor of Diprotodon (the largest mammal known from anytime in Australia, as well as the largest known marsupial known from anywhere in the world, and a relative of the wombat), the skull of Euryzygoma dunense, another extinct, megafaunal, eight foot long, quadrupedal herbivorous marsupial, is quite interesting: it has two extended cheekbones.  This gives Euryzygoma the unusual mammalian property of its skull being wider than it is long.  Although to most this probably doesn’t actually seem all that exciting, the extended cheekbones have led to two interesting theories regarding their function in the living animal.  One we will look at in a few weeks (the week of August 3rd to be more precise), but the other one we will look at now.

The hypothesis came about when the skull of Euryzygoma was first described.  The scientists who first described Euryzygoma thought that the lateral extensions of the zygomatic arch resembled those seen in squirrels, gophers and various types of Old World Monkeys, like the macaque and the baboon. 

 In the living animals just described, these lateral extensions function as cheek pouches, which make it so that the animals that possess them can store food in them.  That is why you so often see a squirrel running around with its cheeks puffed out.   

Some scientists think that Euryzygoma might have used its cheek pouches to store water; thus, it would not need to spend so much time near waterholes that were most likely infested with large crocodiles.  This would also help Euryzygoma travel longer distances during a drought, enabling it to move greater distances to reach waterholes that other animals would simply unable to reach, having a much more limited range.

The Fauna of South Carolina: Reptiles and Amphibians

First off, don't forget to look below to see the answer to last weeks mystery animal, and to see a couple of pictures of this weeks!

Recently, my family visited some good friends of ours in South Carolina for a few weeks.  Not only did we have a lot of fun visiting them, we saw a lot of cool plants and animals there that we simply don't have up north!  For some of you, many of these animals and plants will be routine and boring, but hopefully there will be something in here that you will find interesting!  I think I am going to split this post up into at least a few different segments, with tomorrows post devoted entirely to the Black Skimmer, a very interesting bird that I had the good fortune to see hunt!  So today I am going to talk about some of the interesting reptiles and amphibians we saw down there, and over the next few weeks we can take a look at some of the birds, fossils and other things we saw down there!

Due to the increased heat and humidity, coupled with less of a swing between the seasons (i.e. it rarely snows and drops below freezing), the south is an excellent place to see all sorts of reptiles and amphibians.  We saw a number of turtles and a frog/toad or two when we were in the south, but what interested me more were the lizards.

A Carolina anole (Anolis carolinensis).  Despite its name, the Carolina anole is found in both South and North Carolina, as well as Florida, Georgia, Louisiana, Texas, Alabama and Mississippi.

A type of skink, but I have yet to ascertain its species, although I am almost certain its genus is that of Plestiodon

And then, of course, there's the gators.  The American Alligator lives in the same states as the Carolina anole, as well as Virginia, Arkansas and Oklahoma.  While we did see a few in the wild, all of these shots (except for that of the gator footprint) were taken at a place called Brookgreen Gardens, or at a restaurant called the Crab Shack.

This big gator we saw at Brookgreen Gardens

This is a picture of a gator footprint that I took.  You can see three of the toes very well, making it look a lot like a theropod dinosaur track, but you can see the other two toes as little holes in the ground.

This picture, and all the rest, were taken at an awesome (both food- and entertainment-wise) restaurant on Tybee Island in Georgia called The Crab Shack.

 

 

 

 

 

 This post is part of "The Fauna of South Carolina" series.  For the rest of the posts in this series, click HERE.

Sea Pines 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.