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.

Atlanta Metro Area on Dwellable

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 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 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.