Thursday, July 28, 2011

Parasaurolophus tubicens crest and airway




This is the original prototype of our Parasaurolophus tubicens crest and airway endocasts I built. Here is a compressed version of the sample animation I sent to our multimedia team.

Parasaurolophus has an elongate crest atop the skull that projects several feet behind the skull. Other "crested" duckbill dinosaurs have widely different shaped crests. The airway in many of these species goes from the nostril, through the elaborate crest structures and then enters the choanae and pharynx to go to the lungs. This structure has been interpreted a variety of ways over the years. Two possibilities include display (makes the animal bigger and possibly had colors or patterns) and sound generation. The New Mexico Museum of Natural History CT-scanned their Parasaurolophus tubicens specimen and generated a predicted sound that an elongate structure such as this may have produced. Someone posted this to Youtube a number of years ago. Sound

For our new exhibit hall, we got a license to use this sound file and I reconstructed the airway in detail in 3D. We synced the sound file up to the airway endocast you see in this animation on the touchscreen exhibit. Pressing the sound button causes the sound to play and also the airway to light up in sequence as the air passes through.

video

-JTH

Sunday, July 24, 2011

Paleontology Myths, Part 1: The myth of ultralight bones

Over the next few months we intend to post a series of short commentaries exposing common myths in paleontological research that have biomechanical implications or relationships.  In some cases, these myths extend to work on living animals, as well.  Today's little "myth" is one of those that does, in fact, crop up in both studies on fossil animals and living ones.

Here is a cross section at the midshaft of the humerus of the pterosaur Bennettazhia; the trabecular braces  have been digitally removed to just show the outer shell of bone (the braces are little struts that run from one side to the other inside the bone):


As you can see, this bone is exceptionally hollow.  A similar degree of hollowness is seen in a few living birds, such as pelicans.  Many other birds also have hollow limb bones (though usually not quite as hollow as seen above in Bennettazhia) and nearly all birds have some hollow bones in the core of their body (vertebral column, especially).

The typical conclusion from observing these hollow bones is that birds and pterosaurs have (or had) light skeletons.  It's simple, clean, and intuitive.  Unfortunately, it's also wrong.  In reality, we have known since the 1970's that birds do not have lighter skeletons than that of other terrestrial vertebrates (e.g. mammals), and there is no evidence that pterosaurs had light skeletons, either (see work by Prange and others in 1979).  This may seem rather odd, but there are two key elements here:

Thursday, July 21, 2011

T. rex endocast animation

This is the original prototype of our Tyrannosaurus rex endocast. Here is a compressed version of the sample animation I sent to our multimedia team so we could show them a skull spinning while opaque and transitioning to highly translucent to show a brain endocast inside. The stopped frames in the middle were for labels depicting the olfactory (smell) and optic (sight) portions of the brain to pop-onto the screen in the touchscreen. The current display form has the skull paired with an Archaeopteryx skull and endocast that the Witmer lab was kind enough to let us use. The touchscreen animation has buttons to highlight the olfactory and optic regions and buttons to show the skull visible, translucent and endocast only. Using the touchscreen, visitors can spin the skull in either direction, 360 degrees about the Y-axis.


video

-JTH

Tyrannosaurus rex brain endocast still shots

One of the things Mike and I want to do with this blog is post extra animations and photos for research that we've done, or a colleague has done. There are lots of cool videos and pictures that get created during projects and most people don't get a chance to see anything, but the finished project.

I created a digital version of a Tyrannosaurus rex brain endocast for the LA County Natural History Museum's new dinosaur exhibition that just opened last weekend using CT scans of our sub-adult T. rex that has been nicknamed Thomas. Here are a couple of the still shots I created for our exhibition and multimedia team to work with in assembling the new display.

I posted a series of shots from lateral view (from the side) and from dorsal view (looking down at the top of the skull). The brain endocast is visible in red. I'll post some video of this later tonight.
--JTH

Lateral View



Dorsal View

Wednesday, July 20, 2011

Flying Giants

We spend much of our time working on flying animals, and both Justin and I have something of a soft spot for giant flyers.  What exactly constitutes a "giant" is a matter of opinion, of course, but I think it is safe to say that animals like Hatzegopteryx count as giant flyers (see below).

This excellent illustration by Mark Witton (for which he owns the copyright - no filching!) nicely illustrates the enormous size of the largest pterosaurs.  We get asked quite often how large flying animals could get, and the answer turns out to mostly depend on how they take off.  Big pterosaurs, for example, probably used what we call a "quadrupedal launch" to take off (that is, all four limbs pushing off the ground for the initial takeoff leap).  If you want to see what that would look like, take a look here.

This particular behavior has actually been discussed quite a bit on the web already over the last few years, following my paper in 2008 on the subject in Zitteliana and my paper with Mark Witton in 2010 in PLoS ONE on giant pterosaurs.  The PLoS paper is freely available here.  I posted a summary of the PLoS manuscript on pterosaur.net here.  And of course, don't forget to check out pterosaur.net and markwitton.com for all your pterosaur needs.

I may write another post or two about giant pterosaurs in the near future, but for now, on to a slightly different problem: how do we deal with giant flying birds in the fossil record?  After all, we are pretty certain that they still took off like living birds, using just the legs for most of the launching power, and yet some of them still managed to get very large.  No birds have ever come close to the giant pterosaurs, to be sure, but some of them were still pretty gigantic.

Justin and I have recently turned our attention to one of these groups of giant seabirds: the pseudodontorns.  The name means "false toothed bird", and refers to the rows of nasty sharp false teeth lining the jaws in this enormous flyers (the "teeth" are actually extensions of the jaw).    A nice example is pictured here.

Pseudontorns were marine birds that survived for approximately 50 million years after the extinction of the dinosaurs (well, all the dinosaurs except birds, of course).  We know a lot more about pseudontorns than we did a few years ago, thanks to the discovery of Pelagornis chilensis.  The description was published in the Journal of Vertebrate Paleontology by Gerald Mayr and colleagues, and it's one fantastic animal.  Not only is the fossil largely complete, but it represents one of the largest birds ever to fly, with a wingspan of about 17 feet.

To get a good idea of what that looks like, turn your cursors here and here.

Justin and I have completed phase one of our study of the flight characters and structure of the largest three pseudodontorns, and we will be presenting our results at the upcoming annual meeting for the Society of Vertebrate Paleontology in Las Vegas this fall (what happens in Vegas... oh nevermind).  We can't give all the juicy details until after our talk in November, but in short, the secret to the ability of pseudodontorns to fly at sizes dwarfing any living flying birds may have been in their legs.  This brings us to one of the most common myths regarding how animals fly: contrary to what is often popularly suggested, flying animals do not (with one known exception in the case of hummingbirds) push themselves into the air with the wings during takeoff.  Most of the force actually comes from a run or leap, using whatever limbs are contacting the ground (that would be four limbs in bats and pterosaurs, two in birds, and six for insects).  So understanding takeoff means looking at both ends of an animal.  We've done this for Pelagornis, and the results are pretty interesting.

More to come on this new discovery, but come see the talk in Vegas (on November 3rd) if you're out that direction!  Other than my brief glide analysis back in 2006, this is the first rigorous biomechanical study of locomotion in pseudodontorns ever done.  Good times all around!

--MBH

Tuesday, July 19, 2011

LA County Natural History Museum Timelapse Video

Here is a really cool video on Youtube showing a time lapse of the LA County Natural History Museum Tyrannosaurus rex display being assembled.

http://www.youtube.com/user/NHMLA#p/c/0/40d-8SNQBDc

New LACM Dinosaur Hall

The new series of dinosaur exhibits at the Los Angeles Museum of Natural History have now opened to the public.  The hall contains more than just dinosaurs - there is a wide variety of Mesozoic animals on display, including what is almost certainly the best mosasaur fossil in the world (Mosasaurs were fully marine lizards from the Cretaceous that often grew to enormous size).  Some excellent pterosaur fossils are also on display.  The LACM is one of our "home bases", as it were - Justin works primarily out of their collections and I fly there to do research on our joint projects a few times a year.

Here are some photos from the preview gala on the 14th of July.  This is now easily one of the best dinosaur exhibit halls in the world.  Be sure to check it out if you're in Southern California!






Welcome to H2VP!

This blog is dedicated to discussions and news related to vertebrate paleontology, particularly animals from the Mesozoic (dinosaurs, pterosaurs, and others). This blog links two coasts: it is the work of Justin Hall from the University of Southern California in Los Angeles, and Michael Habib from Chatham University in Pittsburgh.

All fossils, including dinosaurs and pterosaurs were once living animals, rather than just the pile of bones we see today. We are interested in broad scale questions and in trying to understand how extinct animals behaved and looked. While these are difficult questions to answer, we try to formulate questions about behavior and appearance that can actually be tested by hypothesis driven science. We focus primarily on reconstructing the form and behavior of Mesozoic vertebrates, using comparative anatomy and biomechanics. Our blog will feature our own attempts to resolve these questions, plus relevant papers, animations and blogs of our friends and colleagues.

The writing will generally combine both technical pieces and more informal commentary. Expect a light-hearted approach to many topics, but be forewarned that we have both been trained as professional scientists and had any ounce of creative writing ability pounded out of us long since.
-JTH and MBH