Reptile Tracks: Past and Present

Recently the folks from the New Jersey Track and Trace Museum paid a visit to my work to gather some data to help them with their fossil research.  John McCauley, the curator of the museum, along with help from Henry Villa and John's girlfriend, Dianne, wanted to get footprints and tracks from some modern day reptiles to compare to trace fossils from Mesazoic animals.  A trace fossil is a fossil that clearly shows evidence of an organism without actually being the organism's remains themselves.  Examples of trace fossils are things like footprints, trackways and skin impressions.  These sorts of fossils are very important because they can give us information on things like how animals behaved, moved, rested, and what their posture would have been like when they were alive.  New Jersey in particular is famous for having a lot of trace fossils from the late Triassic and Early Jurassic periods.  Most of these fossils take the form of footprints from a dinosaur named Grallator.  The name Grallator is given to the maker of the tracks and the tracks alone.  No bones from Grallator have ever been discovered.  However, looking at the shape and size of the tracks plus the time that they were made it is likely that Grallator was similar in appearance to dinosaurs such as Ceolophysis and Dilophosaurus.  For all we know the tracks could have very well been made by either of those two dinosaurs themselves.  The only problem is there is no definite way to link the tracks from New Jersey to either of them yet.    

Dilophosaurus (above) and Ceolophysis (below): possible makers of the famous Grallator tracks in New Jersey

The animal of focus for this day, however, was not a dinosaur at all but an extinct relative to modern crocodillians called Batrachopus that lived during the late Triassic period, roughly 220 million years ago.  Just like with Grallator, Batrachopus is a name given to the maker of the tracks with no actual skeletal remains known to science.  Judging by the shape of the tracks its likely that it was similar to many of the crocodillian relatives of that time, however.  These animals are called Protosuchians.

John and his team came armed with specially mixed mud that was made of same materials to the Triassic mud from the area.  What they intended to do was have a variety of modern reptiles I work with walk through the mud that was set up neatly on slate tiles to make tracks.  They would then allow the track to dry and eventually be able to make a cast from it.  Looking at the similarities between the tracks from various modern reptiles and Batrachopus, a more clear vision of the Triassic reptile when it was alive can be made. 

The first animal to make tracks in the mud was a Dwarf Caiman.  Caimans are close relatives of crocodiles and alligators that are native to South America.  The individual we used for this is named Elvis.  This past summer (2011) a friend of mine had Elvis dumped on her from someone who had him for a pet and (I wonder why) couldn't keep him anymore.  She immediately called me up, knowing that my work could give him a better home than anyone's living room ever could and he has been thriving ever since!

The Dwarf Caiman was a successful candidate and made tracks like a pro.  The next animal we tried was Rocky, the Cuban Rock Iguana.  You may remember him from my first blog post here.  Rocky was a little less cooperative but ultimately still gave us some nice results.

The third animal was Bruno, a Black Throat Monitor.  Related to Komodo Dragons and the long extinct Mosasaurs, he was one of our bigger subjects but pleasantly enough, is also one of the most docile animals I work with. Because of this Bruno was most likely not going to walk for us.  Instead we just took prints of his front and back feet.

 Lastly we got prints from our American Alligator.  Much like the Caimin I had to have his mouth taped shut because...well...he's an Alligator.  Don't worry it was just for this activity.  His mouth is free normally.  No animals were harmed in the making of any of this.

All in all it was a very successful day!  I especially love this kind of work because it really shows how important modern animals can be when studying paleontology.  John is putting coats of latex on the prints last I knew and hopefully he will have some nice casts to study very soon.  For more information about John and his work you can visit his site right here. Farewell until next time!

Works Cited

Weishampel, D.B. & L. Young. 1996. Dinosaurs of the East Coast. The Johns Hopkins University Press

A New Look at Killer Claws

I recently read a scientific paper that really made me think about a certain group of dinosaurs in a new way and hopefully after reading this (and the actual paper which I will link at the bottom) you will as well.  The dinosaurs I am referring to are the ever popular dromaeosaurs, or as they are referred to more casually, "raptors".  I personally hate using the term "raptor" when referring to this type of animal since the word, "raptor", really is supposed to be used to describe modern birds of prey like hawks and their relatives.

The paper had to do with a new theory on how dinosaurs like Velociraptor and Deinonychus (dromaeosaurs) used their trademark switchblade-like killing claw to deal with their prey.  If you are not familiar with what I am referring to allow me to briefly explain.  Dromaeosaurs (and to a lesser extent, Troodontids) have a special modified toe on each of their hind limbs.  Digit two (counting from the inside out.  Digit one is the reduced hallux/dewclaw) of each foot wields a HUGE curved claw that looks like a sickle or a hook.  This toe is also retractable like a cat's claws so when not in use, it can be held up off of the ground as to not get dull while the animal walks or runs around.  Still confused?  Check out my sketch below.

The theory that has been generally accepted with regards to the use of these claws is that the dromaeosaur would use them to stab or slash prey to death.  Many times dromaeosaurs are showcased in art and media hunting in packs to overwhelm much larger, slower animals. Shown below is a quick sketch I did of two Deinonychus doing exactly that to a poor Tenontosaurus.

This article, however, proposes a different theory and it all starts with something I touched on last month: looking at modern animals for reference.  When dealing with dromaeosaurs, the first living animal that comes to mind is a bird.  After all, birds are dinosaurs themselves and further more, are theropods just like dromaeosaurs.  Dromaeosaurs in particular were very bird-like even amongst other extinct dinosaurs in that they have very similar skeletal structures to birds as well has having had feathers according to many fossil discoveries.  So what kind of bird are we talking about here?  Many times when studying extinct dinosaurs, large, flightless birds are used for reference but in this case, because we are dealing with the dromaeosaur's special claws, raptors (birds of prey) take the center stage.  Ever get a close look at the foot of an eagle or a hawk?  Check out this photo below.

Notice anything interesting about the sizes of the talons on this bald eagle?  Okay now check out this other photo.

That one is from a South American bird called a Seriema that is more adapted to walking around on the ground than to flying unlike the eagle.  What they both have in common, however, is that over-sized claw on the toe just like an extinct dromaeosaur has! Now whether this is from the same gene that was present in a common ancestor between some modern birds and dromaeosaurs or just an example of good old convergent evolution I do not know.  (Remember convergent evolution from my post last month?)  Whats important to figure out is how these living birds use their special claws and apply this behavior to animals like Velociraptor and Deinonychus back in the Mesazoic.  As you may know, these modern birds don't really hunt in packs for the most part nor do they hunt prey too much larger than themselves (there are a few exceptions).  This claw is mostly used to pin down struggling prey while the sharp beak, which is hooked in the front and blade-like on the sides, tears off chunks of meat.  Think of it like using a fork and knife to eat a meal.  The fork holds down the food while the knife cuts off a bite-size piece.  Still can't visualize it?  No worries!  Once again my job at Outragehisss Pets comes to the rescue.  Below is a short video of our Eurasian Hawk, Gwen, using this exact method to eat a dead mouse while listening to some sweet tunes.  (She doesn't actually start to do the feeding behavior until about 1 min 50 sec in.  Feel free to skip ahead if you like.)

So what if extinct dromaeosaurs specialized in hunting smaller prey as opposed to pack hunting large prey?  Pretty cool idea I think.  Even though dromaeosaurs didn't have the beak of a modern raptor, they did have serrated teeth which would have worked just as nicely for tearing off small chunks of flesh.  The paper also talks about how they may have used their arm feathers to keep balance while immobilizing their victims much like modern raptors do today. 

Interestingly enough I did a painting of a Troodontid using a technique similar to the one proposed in the paper on an unfortunate boa constrictor (pictured above) before I had actually known about the paper itself.  Pictured below is a quick sketch I did special for this blog post of a Deinonychus using this technique on a smaller dinosaur. 

Hope you found this post interesting because I sure had a lot of fun writing it.  Also be sure to check out the actual article here.  Farewell until next time!

Works Cited

Fowler, Denver W., Elizebeth A. Freedman, John B. Scanella, and Robert E. Kambic. "The Predatory Ecology of Deinonychus and the Origin of Flapping in Birds." PLoS ONE:. Museum of the Rockies and Department of Earth Sciences, Montana State University, Bozeman, Montana, United States of America, 14 Dec. 2011. Web. 27 Feb. 2012. <http://www.plosone.org/article/info:doi/10.1371/journal.pone.0028964>.

Paleo-Art: When Creativity and Logic Marry

I have decided to do a little tutorial on how to use both science and art when producing paleoart (a fancy professional sounding term for drawing dinosaurs and other prehistoric creatures).  The subject that I have chosen to show you today is actually not a dinosaur at all, but a giant marine lizard called a mosasaur.  Mosasaurs lived in the shallow warm oceans of the late Cretaceous and are known from fossils all over the world including many found right here in New Jersey.  

The reasons why I chose a mosasaur today are:

1) They are a well studied kind of animal known from many fossil specimens.  The more complete the fossil data is for an organism, the easier it is to create a reconstruction that’s as scientifically accurate as possible.

2) They have modern day close relatives.  Mosasaurs are very closely related to monitor lizards and snakes, both of which are very much alive today and both of which I can observe to gather any ideas about soft tissue, colors, movement etc. 

3) They are from New Jersey!  Duh!  Believe it or not, the Jersey shore had even scarier characters living on it during the Cretaceous than it does today (I’m looking at you, Guidos). 

When I reconstruct dinosaurs (or in this case, mosasaurs) I like to start from the skeleton and work my way out.  This is simple enough since the science community has plenty of mosasaur bones to look at for reference.  Remember reason #1- well documented animals are much better to illustrate than ones that are known from only a few fragmentary bits.  The less you have to make up, the more accurate your reconstruction can be.  Luckily for me I have the Rutgers Geology Museum in New Brunswick, NJ to go to for observing mosasaur remains.  It’s always best to use references from real life rather than a picture (easier said than done, I know.)  If going to an actual museum is out of the question then I would opt for photographs of actual fossils rather than another person’s illustrations.  If and when you do get the chance to visit a museum where there are fossil bones on display, I highly recommend taking many photographs of them to store and use as reference for future art projects.  

Mosasaur skull from the New Brunswick Geology Museum in New Jersey

If I plan on drawing the whole animal and not just the skeleton, I don’t draw every bone.  I prefer to lightly sketch a rough plan of the animal’s body just so I can get the proportions right.  For my drawing tool I just use a simple mechanical pencil.  I like this because it’s easy to do fine lines for details and I never have to sharpen it.

Next I add the flesh to the frame.  This can get a little confusing since nobody has actually seen a living breathing version of this animal before.  This is where reason #2 starts to come in.  We DO know what monitor lizards and snakes look like so looking at their body plan is a decent starting point.  However, it is important to keep in mind that despite being related, mosasaurs were still quite different from their modern relatives in that they were marine animals.  Consider this; fish and whales are not closely related at all (whales are air-breathing, milk-drinking mammals and fish are…fish).  However, they both possess very similar body plans because they both live in the same environment.  So despite the fact that a whale is actually more closely related to something like a bat or a porcupine, it still superficially more resembles a fish because of its lifestyle.  This concept is called convergent evolution where two unrelated animals have similar body plans because they live similar lifestyles.

Tuna: fish

Beluga: whale

So let’s apply this to to our mosasaur drawing.  Despite the fact that it’s more closely related to modern squamates (fancy scientific term for lizards and snakes), mosasaurs probably behaved and may have at least from a distance resembled large fish as far as their body shape is concerned.  We know for a fact that unlike monitor lizards, mosasaurs had very short necks with respect to their bodies according to fossil skeletons that have been discovered.  This is consistent with the bodies of other large marine animals like sharks and whales.  It can also be inferred that mosasaurs had modified hands and feet in the form of flippers.  Again, something observable in whales and to some degree seals, sea lions and certain turtles.  Finally, it is known from one very well preserved fossil discovered recently that mosasaurs carried the ends of their tails at a steep decline.  Looking at other marine fossil reptiles that have been discovered holding their tails the same way like ichthiosaurs it can be inferred that mosasaurs probably had some sort of fin-like projection or fluke on their tails as well.  Once again this is also a feature seen in animals like whales and sharks.   All this being said I decided to make my mosasaur have a body shape similar to large marine animals rather than land reptiles. 

  
Next details such as eyes, teeth, scales and such should be added to the drawing.  Generally there is a fair amount of creative freedom for the artist when doing this but there are certainly options that are more logical than others.  I first like to start with the head and move my way down the animal.  Let me draw your attention to the mouth.  We know for a fact that mosasaur teeth were huge and sharp because of the skulls that have been discovered.  As an artist my first instinct would be to emphasize this in my drawing.  However let’s go back to the modern relatives, the squamates for reference.  Monitor lizards and snakes both have large teeth as well and like mosasaurs probably did, use them for holding prey in the mouth when feeding.  However, when looking at a living monitor or snake, the teeth aren’t visible at all when the mouth is closed.  Even when the mouth is opened the teeth are barely visible.  

Komodo Dragon: a monitor lizard

Komodo Dragon Skull

 Let’s look at our convergent evolution animals too while we are at it.  Toothed whales and sharks are also predators much like mosasaurs were and likewise also possess large pointed teeth.  Yet looking at the living animal, it can be observed that the teeth are safely hidden inside the mouth. 

Orca Whale

Orca Whale Skull

Despite the fact that it was an ocean animal, mosasaurs were still reptiles and therefore had scaly skin like their living relatives.  Plus thanks to that same fossil I mentioned earlier, there are mosasaur skin impressions known to science and it should be no surprise that indeed they are scaly.  Drawing scales on an animal’s body can seem intimidating at first for a lot of artists.  There are so many little individual scales how is one expected to draw them all without going insane!  Well in some cases there is really no way around this especially when the subject is viewed up close and the scales are relatively large (this is the case with animals like ceratopsids but I’ll save that for another post).  In the case of the mosasaur, thanks to the fossilized impressions, we know that mosasaur scales, at least those on the parts that left impressions for scientists to observe, were quite small.  Chances are looking at this animal from a distance not every scale would even be visible.  To help me prove my point let me show you a photograph of my buddy, Rocky, whom I work with at Outragehisss Pets.

Add caption

Rocky is a Cuban Rock Iguana and is therefore a lizard, and thus a reptile complete with scales all over.  Looking at this photograph you can see that rocky has some very large scales on his face and neck but on other parts of his body, especially as it gets farther away from the camera the scales aren’t really individually visible at all.  It’s not until I get my camera a few inches away from his body that I can get a shot where you can see individual scales.

Like the iguana, the known mosasaur skin impressions show scales that aren’t very big and really can only be spotted clearly when viewed up close.  That being said I don’t need to draw every single individual scale on my mosasaur.  It should be noted, however that not all scaly animals are the same.  If we were looking at something like a crocodile, the scales would me much more prominent and therefore need to be drawn as such.  On the other end of the spectrum most snakes, despite being scaly as well, appear totally smooth at most distances. 

There are other things that can be applied too but I would be writing forever if I were to include them all.  Like I said earlier there is freedom with this just make sure you think about what you are adding and why. 

Next I apply color.  I’m going to color this drawing with simple colored pencils you can get at any craft store or anywhere that sells art supplies really.  Color is probably where the paleoartist has the most freedom with creativity (with a few exceptions but again lets save that for a future post).  I still like to stay logical with my color choices though.  For instance I would never make an animal like this hot pink.  It simply doesn’t make sense.  Do I know for a fact that living mosasaurs weren’t hot pink?  No I have never seen one alive but I’m pretty sure there are a lot of other more likely color schemes out there that they could have been instead.  Once again I decide to look at animals that live the same lifestyle instead of family ties when looking at colors.  Monitors and most snakes live on the land and therefore have colors and patterns that help them live there.  Mosasaurs lived in the ocean and should probably be colored as such.  Even so, there is plenty of freedom here.  Could it be black and white like an orca?  Perhaps brown with light spots like a whale shark?  The possibilities go on and on.  One thing seems to be consistent with pretty much all ocean dwellers is having a light colored ventral side (belly) and darker colored dorsal side (back).  This is so when being viewed from either above or below the animal can camouflage with either the darker water below or the light from the surface of the water.  This camouflage adaptation is called countershading and is utilized by many animals that swim often.  

Lastly I add shading.  Shading can be done many different ways to produce a myriad of effects.  When using colored pencils some artists prefer to press harder with the colors already used or perhaps mixing colors with darker shades of blue or black.  I prefer to go back to the graphite pencil.  There is no right or wrong way though.  At this point I also like to go back with the graphite and make any details that may have been lost in the colored pencil bold again. 

So that ends my little tutorial on drawing a mosasaur!  I hope you learned some things about both science and art and strongly encourage you to try producing some paleoart of your own!  The only way to get better is to practice of course.  Every month I will be writing something for Gary but it may not always be about art.  Working at facilities with so many wonderful exotic animals I plan on doing some posts on dinosaur’s modern day relatives as well!  We’ll see how things pan out and I will write accordingly.  Farewell until next time!

Works Cited

Klappenbach, Laura. "Counter Shading - What Is Counter Shading." Animals Wildlife - Animal Facts, Animal Pictures, Habitat Facts, Evolution and Zoology. Web. 12 Jan. 2012. <http://animals.about.com/od/zoology12/f/countershading.htm>.

Lindgren, Johan, Caldwell W. Michael, Takuya Konoshi, and Luis M. Chiappe. "Convergent Evolution in Aquatic Tetrapods: Insights from an Exceptional Fossil Mosasaur." Plosone. 9 Aug. 2010. Web. 12 Jan. 2012. <http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0011998>.

Stearns, S. & Hoekstra, R. 2005. Evolution: An introduction.