Meet Marshosaurus, Morrison's Mysterious Meat Muncher!

If I were to tell you to picture the environment of the Morrison Formation 150 million years ago (MYA) in the Late Jurassic Period, most of you would probably have no idea what I was talking about.  For some of you, the words “Morrison” and “Late Jurassic” would trigger images of enormous sauropods like Apatosaurus and Diplodocus, with the occasional plated Stegosaurus, and the carnivorous Allosaurus.  For still fewer, images of the ornithopods Camptosaurus and Dryosaurus might appear, the theropods Ceratosaurus and the smaller Ornitholestes, and perhaps another sauropod or two.  Fewer still might picture the theropod Torvosaurus, the ankylosaur Gargoyleosaurus, and the ornithopod Othnielia.  However, very few people indeed would think of the medium sized, 20-foot long theropod Marshosaurus.

Marshosaurus bicentesimus was first named in 1976, and received the second half of its scientific binomial name (bicentesimus) from the fact that it was described during the bicentennial of the United States!  The first part of the name (Marshosaurus) honors the famous paleontologist Othniel Charles Marsh, one of two main participants in the extreme paleontological competition more than 100 years ago!  If you want to learn more about the Bone Wars, be sure to check out a song that I wrote about it below: to the tune of Carrie Underwood's "Two Black Cadillacs!"

Anyways, all silliness aside, I actually got to see what is widely considered to be the most complete Marshosaurus specimen ever discovered about a month back when my friend Sam Lippincott and I got to go on a behind the scenes tour of the Denver Museum of Nature and Science with paleontologist Dr. Ian Miller!  To be honest, even from a paleontologists perspective, the Marshosaurus specimen was definitely not the most exciting thing there, not by a long shot!  Overall, all of the known material attributed to Marshosaurus taken together, there sure isn't much: four fragmentary skeletons, composed of bits and pieces of the spine, skull, and pelvis.

One of two small trays of bones belonging to Marshosaurus that the Denver Museum has on display in the paleo lab for the time being.  Looks like we have some vertebrae and ribs!

One of two small trays of bones belonging to Marshosaurus that the Denver Museum has on display in the paleo lab for the time being.  This box contains the right maxilla of the specimen.  You actually have a right maxilla, too: just tap abut halfway between your nose and your mouth on the right side of your face: that's your right maxilla!

According to a brief article written by paleontologist Dr. Joe Sertich and published in the Denver Museum's magazine, the specimen of Marshosaurus held at the Denver Museum has "large portions of the skull....several vertebrae, bones from the back and neck, and ribs."  Although it doesn't give us a lot to work with, such fragmentary remains are often all that paleontologists have to work with!  It appears to have been enough for some scientists to come to the conclusion that Marshosaurus is a member of the megalosauroids, a distinct group of meat-eating theropod dinosaurs that includes the famous Megalosaurus, the very first dinosaur ever described!  (I would say discovered, but most people suspect that ancient races have been discovering dinosaur bones for hundreds of thousands of years: but more on that later!)  It is thought that Spinosaurus and its relatives are closely related to the megalosauroids as a group.

According to the article, the remains of the Denver Museum's Marshosaurus specimen were discovered at a site in Dinosaur National Monument that, due to a fluke of the law (I would say loophole, but I feel like that's too harsh of a word), allows the Denver Museum to collect fossils and take them back to their collections, as opposed to them going to the collections facility at the visitor's center.  At this particular site, the remains of "at least six other animals made their way back to Denver."  Amongst these remains  includes the small, plant-eating ornithopod Dryosaurus, and the very famous Stegosaurus, as well as a few bits and pieces of a crocodile!

So how likely is it that Marshosaurus will become as famous as Tyrannosaurus and Triceratops?  Not very likely at all!  But it's a cool animal, and I definitely hope we find the remains of more of these guys sometime in the future!

The Morrison Biota

Stegosaurus lived in western North America during the Late Jurassic Period, about 150 million years ago (MYA). Today, we find its remains in the Morrison Formation, named after the tiny town of Morrison in Colorado. What was going on in Colorado at that time? What was the depositional environment like, the environment that laid down the sediment that would one day become the famed Morrison Formation?

Well, according to paleontologist Dr. Robert Bakker in an article about the re-discovery in 2002 of some old paleontological quarries (CLICK HERE TO LEARN MORE) in the Smithsonian Magazine, the environment was very much like the kind of environment seen in Uganda today: a “hot tropical woodland that was dry for most of the year.”

What about the animals, though? Dr. Bakker also said in the article that to “understand the Late Jurassic, you need to understand the common animals, which means Apatosaurus.” Most people are familiar with this massive animal: about 100 feet long (around the length of three school buses put end to end to end), and weighing around as much as eight African elephants, Apatosaurus was definitely a heavyweight of the Morrison biota!

What other animals were running around though? There are a great many dinosaurs, as well as many other animals, that were living in this area at that time, but in this post we are only going to look at one more: Camptosaurus and Allosaurus. All right, I lied. We’ll look at two more.

First off, we have Camptosaurus. To be honest, Camptosaurus doesn’t really look all that special. A small- to mid-sized ornithopod, Camptosaurus was only about fifteen feet long, and didn’t really appear to have any obvious defenses. However, discoveries of articulated Camptosaurus skeletons (indicating that the bones were fossilized were they were deposited, i.e. where the animal died, and weren’t washed together in a big mumble-jumble like at Dinosaur National Monument) in close conjunction with articulated Stegosaurus skeletons seems to indicate that these two herbivores liked to hang out together. But why? Why would they open themselves up to competition and potential conflict like that? Well, analysis of the brains and skulls of these two animals suggests that perhaps by hanging out together, the dinosaurian duo could avoid much deadlier conflict. Studies have shown that the sensory organs of Camptosaurus and Stegosaurus would have differed in very critical ways. The sense of Stegosaurus would have been akin to a rhinoceros, or perhaps myself as well (at least without my contacts), in that it would have had a pretty good sense of smell, but not very good vision. Camptosaurus, on the other hand, appears to have had quite acute vision, which has led to an interesting proposition by researchers: that Camptosaurus acted as a lookout for herds of Camptosaurus and Stegosaurus. If a predator was spotted (say, an Allosaurus or a Ceratosaurus), then Camptosaurus would have been able to alert the herd, and Stegosaurus would have been able to move to the forefront to defend them all against attack.

The last dinosaur that we are going to look at today is Allosaurus, a large, meat-eating theropod dinosaur. It occurs to me as I type this that I have done a very thorough job on Allosaurus before, so instead of typing this all again, I am going to be lazy and redirect you to another post that I did awhile back, entitled “23-Fact Tueday: Allosaurus.” Hidden within the post (but not too hard to find) are 23 Facts about Allosaurus. Yeah. Pretty much says it in the title. Anyways, check out that post to learn more about Allosaurus, as well as the rest of the Morrison ecosystem! And make sure to check back tomorrow, as we learn about stegosaurs from the rest of the world!

Want to learn more about Stegosaurus?  Well, check out the Homebase for Stegosaurus Week HERE to partake in more of the festivities!  

Top Ten: Extinct Sea Monsters (Part 2 of 5)

So why did I split this post up into five parts?  Well, originally it was all just one big post, but it was simply too big, like so often happens.  So I will just post the rest of the parts throughout the next few days.  So here is part number two!

3.  Liopleurodon - A member of the short-necked Plesiosaurs, or Pliosaurs, Liopleurodon was the top predator of the Middle and Late Jurassic shallow seas that covered Europe at that time.  Fossils of Liopleurodon have been found in England, France, Germany, and Russia. 

4.  Shonisaurus - Shonisaurus is a fascinating example of convergent evolution.  When similar environmental and ecological pressures went to work on the ancestors of Shonisaurus, and the rest of the ichthyosaurs, as well as the ancestors of the dolphins and porpoises, they produced very similar results in very different kind of animals.  Shonisaurus and the rest of the ichthyosaurs are marine reptiles, while the dolphins and porpoises are both mammals.  Shonisaurus lived during the Late Triassic Period, right around when the dinosaurs were first making their debut.  At least thirty-seven skeletons of this giant have been discovered in Nevada. In fact, Nevada is still a fantastic place to see some of these creatures, especially Berlin Ichthyosaur State Park in Berlin, a few hours outside of Reno (pictured below)!  This is where the first bones belonging to Shonisaurus were actually discovered!  Definitely high on the list of places that I want to go!

Coming Up:
5.  Elasmosaurus
6.  Dunkleosteus
7.  Archelon
8.  Leedsichthys
9.  Tanystropheus
10. Tylosaurus

This post is part of the "Top Ten: Extinct Sea Monsters" series.  For the rest of the posts in this series, click HERE.  

What REALLY Killed the Dinosaurs?

Today, almost all paleontologists believe in one of two scenarios that brought upon the downfall of the dinosaurs; the Silver Bullet Hypothesis, and the Blitzkrieg Hypothesis.  Proponents of the Silver Bullet Hypothesis consider the asteroid that hit Mexico 65.5 MYA to be the cause of the dinosaurs extinction, while fans of the Blitzkrieg Hypothesis believe that the asteroid worked in concert with other factors, like a number of extraordinarily large volcanic impacts and receding sea levels.  Although both of these hypotheses hold great weight, and stand up well to investigation, I find myself more in the Silver Bullet camp.  (If you are unsure, check out this video: http://www.youtube.com/watch?v=5gqq2rgOmi8 .  It's a bit long, but you can skip parts of it and still get the gist.  I was simply blown away after watching it, and landed smack-dab in the center of the Silver Bullet camp.)

However, this post is not to talk about the merits of the generally accepted dinosaur-death hypotheses; just like the post regarding the oddly named animals (http://thenaturalworld1.blogspot.com/2012/07/masiakasaurus-knopfleri-and-other.html), Scott Sampson's book Dinosaur Odyssey had another especially interesting tale, a tale about the many different hypotheses (over one hundred in all!) about how the dinosaurs died from over the years.  Here are some of the more interesting ones, quoted from Scott Sampson's book:

1.   Disease
2.   Slipped Vertebral Discs:  Because dinosaurs were so big
3.   Loss of Interest in Sex
4.   Poisonous Plants 1:  The consumption of these plants led to a deadly diarrhea amongst the dinosaurs
5.   Poisonous Plants 2:  The consumption of these plants led to a deadly constipation amongst the dinosaurs
6.   Fungal Invasions
7.   Climatic Change 1:  Global Warming
8.   Climatic Change 2:  Global Cooling
9.   Cosmic Radiation From a Supernova
10.  Egg-Eating Mammals
11.  Sunspots
12.  Nasty Aliens
13.  Not Enough Room on Noah's Ark
14.  The Racial Senility Hypothesis:  Dinosaurs, as a group, were young and restless when they first appeared in the Late Triassic Period.  During the Early Jurassic, the dinosaurs experienced "adolescence," as they expanded "in both form and diversity."  When they reached the Late Jurassic and Early Cretaceous, the dinosaurs had "reached their evolutionary peak;" they were middle-aged, and had nowhere to go but down.  Thus, in the Late Cretaceous Period, when the dinosaurs like Triceratops, Parasaurolophus, and Pachycephalosaurus grew interesting crests, frills and the like, these were "the result of hormones gone wild and certainly symbolic of a group on its way out."

Obviously, some of these solutions are more interesting than others, but all of them are, at this point in the study of dinosaurs, outdated.  But who knows: perhaps, someday soon, someone will discover proof that it was aliens, and not an asteroid, that ultimately did-in the dinos.