United in Los Angeles

A quick update from Los Angeles.  A while back we mentioned that I would be moving to LA to take a job at USC.  That move occurred after the field season in New Mexico, and so both H2VP authors are now residents of Los Angeles (and USC)!  I have a lot to get running and I am terribly behind the schedule I set for myself in late August, so blogging will be rare until I am caught up.

In the meantime, I have posted a slightly longer update at http://aeroevo.blogspot.com/2012/10/updates.html.  You'll see, in short, what I've been up to these last two months...

Back from the Field

Very successful field outing in New Mexico.  I'll let Justin take care of posting about the field trip, as he was our fearless field leader.  Some other highlights from the last few weeks:

- We are both nearing completion of a major manuscript that should make a big splash in the avian flight origins literature

- It looks like I will be adding a swarm motion component to my research base in the near future.  Exciting stuff!

- Data collection underway for some more azhdarchid pterosaur motion and size estimate work.  This will be the best hindlimb cross-sectional work for an azhdarchid, along with some some quite good forelimb data.

- I've been doing the Twitter gig for some months now, particularly contributing to Science140.  My Twitter handle is @aeroevo

Cheers!

--Mike

Field Work

I'm leading my first field expedition ever this summer, taking a crew from the Natural History Museum of Los Angeles County and associated colleagues to New Mexico for two weeks. I've been second in command on a number of expeditions and involved in probably a dozen or so, but this is the first time that I've been the primary budgeter, scheduler, organizer and everything else. It's an amazing experience, but sometimes it feels like trying to herd cats to make it all come together. I have a new appreciation for the complexity and expense of fully managing a field crew now and it's been an amazing experience. It will definitely be easier next time. I'm through the looking glass now. The kind of looking glass that only appears when you've spent time researching and negotiating for a company to drop port-o-potties in the middle of BLM land, 51 miles from the nearest town. It's a truly unique experience. I'm spending nearly two weeks in and around the Bisti/De-Na-Zin Wilderness in northwestern New Mexico. Mike is going to come join the crew for a week, which will be his first time out in the field. Expect lots of exciting (hopefully) updates in a couple of weeks and pictures regardless. This is some of the most stunning geology I've ever seen. -JTH

Pterosaur.net: The Beauty of Big

Greetings all!  Hoping to get some more material up on H2VP soon, but in the meantime, those of you that don't already follow p.net might find my latest post on that site interesting: it involves the possible selective advantages of being a giant flyer. Turn your cursors here.

Aero Evo

Greetings everyone!  Just a quick note that on April 4th I launched a new blog, called Aero Evo.

I will still be posting here to H2VP, of course.  Aero Evo fulfills a different sort of niche.  First and foremost, I will be specifically discussing animal flight - particularly the evolution of flight (as opposed to all manner of biomech topics here at H2VP).

The format is also going to be different from H2VP. I have designed this blog to be a rapid-fire, regularly updated feed.  I expect to post something almost every day (holidays and such excepted, of course). Posts will typically be short - when I have something more lengthy to say, I will link over to H2VP or Pterosaur.net.  In this way, it falls within the realm of so-called "micro-blogging", though not as extreme as things like Twitter (I also have a Twitter account, incidentally, called aeroevo).

No, dinosaurs were not aquatic.

So, as some of you might have heard, a very questionable news item hit the BBC this morning.  In short, they did a news release on the claim by a rather odd individual that all large dinosaurs were semi-aquatic.  I could go on for pages about how many things are wrong with the "research" in question (which isn't actually research because no evidence or data are provided) or the fact that it was given a feeling of legitimacy by the BBC.  I'd just be repeating my colleagues, though, because they have taken care of it nicely here, here, and here.

Now, I'll be honest - I still think that this may have been an elaborate April Fool's Day prank, and others have suggested this as well.  Even if that is true, however, it managed to dupe the BBC, which is pretty scary.

The individual who was interviewed on the program, Brian J. Ford, has a website where he discusses the supposed merits of aquatic dinosaurs, etc.  I was just going to laugh and blow the whole thing off, but it occurs to me that his supposedly "difficult" questions might actually pose some interest to readers.  So, here is my quick debunking of his list.  Enjoy.

"a) How dinosaur limbs could otherwise have borne such weight 

(up to 100 tonnes)"

-- Short answer: easily.  Longer answer: bone is much stronger in axial compression than in bending or torsion.  Sauropods, in particular, had columnar limbs, so the bones were loaded almost purely in axial compression.  Their long bones were also almost solid compact bone at midshaft.  The failure stress of compact bone in axial compression is 170 GPa, which for comparison, is nearly 5x the compressive failure stress for concrete.  Not only could sauropod limbs support their weight, not a single sauropod known to date was at the mechanical limit for the group.  It's also worth noting that the 100 tonnes estimate is pretty outrageous.  Mike Taylor (an expert on sauropods, specifically) estimates Giraffatitan to have weighed in at 23 short tons in life.  That is among the largest known sauropods.  So it's a bit puzzling where the other 80+ short tons are coming from.  Perhaps sauropods were composed largely of metal.

"b) Why they would expend such a large amount of metabolic energy holding tails erect 

(There are no tail drag marks in the fossil footprints; there are for crocodiles)"

--"Why" is presumably because of mobility and balance.  What I think he really means is "how", to which the answer is that holding tails erect is not very energetically expensive when much of the weight support is done by tension.  Besides, plenty of animals hold parts of their body upright for long periods of time.  We hold our entire trunk, upper limbs, head and neck erect.

"c) How they maintained their steady body temperature without the cushion of a huge body of warm water (Isotope analysis shows they maintained a constant body temperature and no reptiles evolved a mechanism to do so)"

--Vertebrate animals are mostly water to begin with; large animals have naturally high thermal inertia as a result (this leads to the possibility of so-called "gigantohomeothermy" for very large ectothermic, organisms).  Even more damning, however, is that Ford has forgotten basic physics here: unless the water was the temperature of the animals, or greater, they would lose heat over time while submerged.  Given that homeoendothermic animals (i.e. "warm-blooded") can be 90+ degrees or more resting temperature, that is some awfully hot water.  Oh, and "reptiles" have evolved endothermy at least twice (see: mammals and birds - the latter, being dinosaurs, likely inherited some endothermic traits from the very sorts of animals Ford implies could not possibly have been truly endothermic).

"d) Why the abundant fossil footprint are proportionately comparable 

(They'd have sunk up to the armpits were they standing on dry land)"

--The depth to which an animal sinks is a product of the shear imposed on the substrate, not simply total mass.  This depends on the stress on each foot, as well as duty factors and substrate conditions.  In short, there is no reason to think that a large dinosaur would sink appreciably deep on dry land.  Elephants, for example, do not leave footprints much deeper than those of humans.

"e) Why they claim that Spinosaurus - and a host of similar dinosaurs! - simply dipped their heads beneath the waves (Their snout glands are like those of crocodiles; clearly they spent most of their lives in water)"

--"Host" here is about three or four, depending on who you ask.  In short, while spinosaurids have cranial features associated with aquatic feeding, the postcrania typically lack any major aquatic adaptations.  Hence, the current best conclusion is that they hunted from the shoreline.

Fun in Georgia

I recently returned from Athens, Georgia, where I gave a talk for Darwin Days at the University of Georgia.  John Gittleman is the Dean of the School of Ecology there, and he was my Masters advisor back in the day (I also worked for him as an undergraduate).  It was great to see John's new haunts (his lab group has some awesome work on biogeography, extinction risk, and mammalian disease ecology rolling).

My talk was basically about new perspectives regarding the origin of flight in dinosaurs/birds, with an emphasis on biomechanics.  What was neat was the crowd - the audience was large, but included only a handful of paleontologists.  Most of the individuals in attendance were ecologists or ornithologists in the neontological sense.  It was interesting to gauge their reactions, and the overwhelming result was that they all find fossil taxa fascinating.  So here's a little commentary: fellow paleontologists, we need to hang out with more folks that work on the living stuff.  Vertebrate biology folks, we need to hang out with invertebrate biologists (I have made it a point to spend time with entomologists over the years - it really helps, trust me).

Happy Darwin Day!!!

Sometimes there's a man... I won't say a hero, 'cause, what's a hero? But sometimes, there's a man. And I'm talkin' about Darwin here. Sometimes, there's a man, well, he's the man for his time and place. He fits right in there. And that's Charles Darwin, in 1850's England.

Thanks Chuck.

-JTH

Happy Holidays!

Happy Holidays from H2VP.  We will be back to blogging soon!

For the New Year, Justin and I would like to invite our readers to submit topics of interest to be covered on the blog.  Please keep it to vertebrate paleontology, of course.  Have a burning question about morphology or biomechanical methods you've been looking to ask for years?  Give it a whirl and we'll do our best to cover it!

Cheers,

--MBH

Air Giants: Does atmospheric density make a difference?

One thing Justin and I have been asked with some regularity is whether or not the somewhat denser Mesozoic atmosphere, particular in the Cretaceous (compared to the modern one), could explain the giant size of Late Cretaceous pterosaurs or large dinosaurs.

There is a reasonably good body of information regarding atmospheric composition during the Mesozoic.  Both carbon dioxide and oxygen concentrations were higher that at present, particularly during the Cretaceous, and the total atmospheric density would have been slightly greater as a result - but the difference would have been relatively mild for large vertebrates.

Here is an example of a paper published on the effects of Cretaceous oxygen concentrations on plants: http://jxb.oxfordjournals.org/content/52/357/801.full, and there is a manuscript examining the effect of paleoatmosphere conditions on insects: http://jeb.biologists.org/content/201/8/1043.full.pdf

As you can see, plants and insects probably felt the effects of slightly higher oxygen and carbon dioxide concentrations, and indeed the insects of the Cretaceous included some relatively large species, as would be expected.  A slight increase in atmospheric density would have relatively little impact on the maximum size of dinosaurs or pterosaurs, however, and there is not actually any need for an extreme explanation for their size, anyway - despite being larger than living animals with similar lifestyles, none of the giant dinosaurs exceeded the expected maximum size for a walking animal, and no pterosaurs exceeded the limits for biological flight.  Quite a few pterosaurs exceeded the estimated limit for continuous flapping flight in a vertebrate animal (limit is roughly 25-30 kg, give or take), but that only means that they could not flap continuously over long distances and would have switched to soaring flight for long trips; it does not forbid them from flying.

Skin Makes the Swimmer: Mosasaur Integument

There is a recent paper in PLoS ONE on mosasaur skin interpretation that falls within the realm of Paleobiomechanics, and which I found absolutely fascinating.  It is by Lindgren et al., and is entitled "Three-Dimensionally Preserved Integument Reveals Hydrodynamic Adaptations in the Extinct Marine Lizard Ectenosaurus (Reptilia, Mosasauridae)".  Because the paper is in PLoS it is open access (three cheers for open access science!) and you can find it here.

Here is the abstract:
The physical properties of water and the environment it presents to its inhabitants provide stringent constraints and selection pressures affecting aquatic adaptation and evolution. Mosasaurs (a group of secondarily aquatic reptiles that occupied a broad array of predatory niches in the Cretaceous marine ecosystems about 98–65 million years ago) have traditionally been considered as anguilliform locomotors capable only of generating short bursts of speed during brief ambush pursuits. Here we report on an exceptionally preserved, long-snouted mosasaur (Ectenosaurus clidastoides) from the Santonian (Upper Cretaceous) part of the Smoky Hill Chalk Member of the Niobrara Formation in western Kansas, USA, that contains phosphatized remains of the integument displaying both depth and structure. The small, ovoid neck and/or anterior trunk scales exhibit a longitudinal central keel, and are obliquely arrayed into an alternating pattern where neighboring scales overlap one another. Supportive sculpturing in the form of two parallel, longitudinal ridges on the inner scale surface and a complex system of multiple, superimposed layers of straight, cross-woven helical fiber bundles in the underlying dermis, may have served to minimize surface deformation and frictional drag during locomotion. Additional parallel fiber bundles oriented at acute angles to the long axis of the animal presumably provided stiffness in the lateral plane. These features suggest that the anterior torso of Ectenosaurus was held somewhat rigid during swimming, thereby limiting propulsive movements to the posterior body and tail.


I found this paper to be a very exciting look at a feature of mosasaur anatomy which Justin and I have both recently developed an interest in, as well.  In terms of critiques, I thought that the general observations and conclusions were quite compelling, though I would have liked to see some consideration of how the specific scale patterns and integument reinforcement might have contributed to boundary layer control.  The authors almost get there - they discuss the importance of keeping a smooth body contour for reducing friction drag, but they never consider the possible effects (and advantages) of microturbulence generation, which is important in living sharks and some other "rougher skinned" swimmers.

For those that do not play with fluid mechanics on a regular basis: the boundary layer is the fluid adjacent to the solid body (the animal, in this case) that has very low velocity as a result of friction drag. Right at the interface, the fluid theoretically has no velocity, which is called the "no slip condition". Creating microturbulence in the layer just beyond the no-slip region creates a bit of extra drag initially, but it helps the rest of the water running along the animal to essentially "stick" to the boundary layer more effectively, so that major flow separation is reduced.  Because large scale separations add more to drag than the microturbulence, this is a net gain: by giving up a small amount of initial drag, the swimmer prevents a big jump in drag under more rigorous conditions.  This also reduces sound production in fluids, interestingly enough, which is probably how owls achieve silent flight (thanks to Dr. Andrea Prosperetti of Johns Hopkins University for point that out to me years ago).

In any case, that's my two cents for now.  A solid paper, all around, and well worth reading.

Cheers,

--MBH

Happy Thanksgiving: Microraptor ate birds

A recent paper in PNAS seems particularly worth mentioning on Thanksgiving (which, of course, is only really relevant to the U.S. readers of the blog, but so it goes), as it involves predation on birds:

http://www.pnas.org/content/early/2011/11/17/1117727108.abstract

The paper is entitled "Additional specimen of Microraptor provides unique evidence of dinosaurs preying on birds", and is authored by Jingmai O'Connor, Zhou Zhonghe, and Xu Xing.  The paper is based on an awesome little fossil that preserves an enantiornithine bird head-first in the gut of a microraptorine.  Because most enantiornithine birds seem to have been arboreal, the authors conclude that the Microraptor individual was likely hunting in the trees, and therefore potentially arboreal.  There are some potential gaps in this conclusion, particularly that modern arboreal birds are actually often predated on the ground (where they are more vulnerable) but it's an awesome specimen, regardless.  Direct evidence of feeding behavior is very rare as fossils, so this is a special case, indeed.

SVP Part 3: More than Looks?

A very brief post this evening.  One of the interesting talks at SVP 2011 was by Ryan Carney, who presented on his imaging study of the original Archaeopteryx holotype feather (it is now, of course, essentially an unidentified Jurassic bird element, as the holotype of Archaeopteryx has been transferred formally to the London specimen).

Most of the talk concerned using microstructure imaging to determine color in the feather, and it was determined that the feather was likely quite dark, possibly black.  This may seem to be purely a matter of appearance, but it turns out to be biomechanically relevant: melanin actually strengthens feathers, so black feathers are stronger than white ones, all else being equal (note that all else need not be equal; there are other ways of reinforcing light colored feathers).  It may be that incorporating pigment effects into structural analyses of basal bird wings will have interesting effects on the results.  I may be doing some of this myself over the next year, but look for similar analyses from multiple authors (Ryan, himself, mentioned the structural importance in passing during his presentation).

SVP Part 2: Water Launching Pterosaurs

I gave a second presentation at SVP this year, as well, in the form of a poster on pterosaur water launch.  Specifically, I presented a model that Jim Cunningham and I have worked out for a plausible water launch strategy in Anhanguera.  If you want to see what this might have looked like, turn your cursors here to Mark Witton's website.  The relevant illustration is on the far right.

I will not give too much detail on this presentation at the moment, as it is shortly bound for PLoS ONE.  However, here are some of the highlights:

- A bipedal water launch model appears to fail for Anhanguera (and other pterosaurs), just as the bipedal model fails for their terrestrial launch.

- A quadrupedal water launch model, in which the wings are the primary mechanism used to free the animal from the surface and to push along the surface to reach launch velocity, seems to check out for all of the parameters we can currently estimate with any confidence.

- Anhanguerids probably took multiple hops across the water surface to launch, but our calculations suggest that most of the actual energy expenditure was spent escaping the surface tension.

- Our model makes testable predictions about comparative anatomy of pterosaurs, which is important when building these kinds of models from fluid theory.  Our model predicts that water launching pterosaurs should have features such as: warped deltopectoral crests or dp crests with flared distal ends, enlarged scapulae, extreme disparity between forelimb and hindlimb lengths, and reinforced scapulo-notarial joints.  We have a more extensive list of features that can be shared a later date, but the primary note here is that these predicted features do indeed seem to show up mostly in marine pterosaurs, and less so in terrestrial taxa, so there is a least a loose, pattern-matching form of validation that can be applied to our hypothesis.

We hope to have animations and a full paper out on the topic of pterosaur water launch in the near future (next few months) so stay tuned!

SVP Part 1: Enormous, amazing, soaring birds

Over the next week I will be posting a bit about some of the talks and poster sessions I attended at SVP.  I am going to begin, however, with a bit about the presentation that Justin and I presented (because heck, it is our blog, after all).

Our talk was entitled "Flight Performance of Giant Pseudodontorn Birds".  As the title suggests, we were working with material from some of the largest flying birds in history.  Our results, in fact, may help explain how they obtained such sizes in the first place.

What are pseudodontorns?

Pseudodontorns were extraordinarily long-winged seabirds with a duration of nearly 55 million years in the fossil record (Paleocene/Eocene to Pliocene) - the wonderful image above is by Greg Paul (he owns the image; don't use without permission).  Some of the California specimens preserve feather impressions which allow us to make a quite good estimate of wing shape.  Typically, the long, narrow wings of pseudodontorns have been interpreted as adaptations to a soaring regime similar to albatrosses.  However, albatrosses have a rather specific specific soaring mechanism that is enabled by their high wing loading.  An alternative, looking at modern birds, would be a frigate bird type flight strategy, but the overall morphology of giant pseudodontorns (span, size, etc) seems at odds with this particular strategy (frigates are highly maneuverable kleptoparasites - they steal fish from other birds).  See the wonderful photo below of a frigatebird, taken by Chris Hobaugh (note the extremely broad wings).

Our answer is a third strategy: Justin and I suggest that giant pseudodontorns, such as Pelagornis, were "globe trotters" - that is, our analysis indicates that they were adapted to extreme flight range.  This update comes, in part, from using new mass estimates from an exceptionally complete specimen found in Chile.  It turns out that pseudodontorns had such elongate wings that mass estimates extrapolated from other seabirds produce overestimated body masses.  The new, lower, body masses suggest that Pelagornis and kin combined a very high aspect ratio wing shape with rather low wing loading.  This would enable highly efficient flight (glide ratio of 27:1 - the highest for any bird) and the ability to use micro-lift sources.  Such an animal would not be able to soar fast like an albatross or turn on a dime like a frigate, but the potential time in the air and maximum range could have been quite extraordinary.

The new mass estimates also modify our thoughts on the limb strengths of pseudodontorns.  It turns out that they had rather strong hindlimbs compared to, for example, a living albatross.  Because launch is hindlimb driven in birds, this might mean that pseudodontorns had more juice over short takeoff sprints, and therefore a larger maximum size for effective takeoff.

All told, a fascinating group of birds that is sorely understudied.

SVP and PLoS ONE

Greetings everyone!

There has been a long hiatus from posting here on H2VP.  Justin and I are back with a vengeance, however, and we have just returned from the annual meeting for the Society of Vertebrate Paleontology.  SVP 2011 was held in Las Vegas, Nevada, and was an exceptionally good time.  We attended some excellent talks (puls some weaker ones) and will be blogging about SVP extensively over the next week.

In the meantime, however, I am a co-author on a new paper in PLoS ONE.  The citation is:

Dyke GJ, Wang X, Habib MB, 2011 Fossil Plotopterid Seabirds from the Eo-Oligocene of the Olympic Peninsula (Washington State, USA): Descriptions and Functional Morphology. PLoS ONE 6(10): e25672. doi:10.1371/journal.pone.0025672

The paper concerns relatively early members of an extinct seabird group call plotopterids.  Some of these grew quite large (up to 6 feet in length, potentially), and all of the known taxa appear to have been flightless, wing-propelled divers.

As some of you may know, I have a bit of a thing for wing-propelled swimming birds, and I published a biomechanical analysis of them in 2010 entitled "The structural mechanics and evolution of aquaflying birds".  One of the primary points in the paper is that the biomechanics and swimming dynamics of penguins are quite different from other living wing-propelled birds.  In particular, penguins have a mirrored stroke, meaning that the upstroke and downstroke produce similar propulsive forces.  In contrast, the other living aquaflying birds use mostly the downstroke to propel themselves through the water (though the upstroke does add some thrust).  The mirrored stroke system appears to be reflected in the particularly broad forelimb bones of penguins (photo above copyright by L. Henricks, 2009).

This raises the following question: are penguins unique in this way because they are flightless?

If so, then other flightless aquaflyers should have similar bone mechanics.  As such, we compared plotopterids to both living alcids and penguins.  We found that plotopterids, while they had similar hindlimb mechanics to living penguins (suggesting lots of walking), did not actually have similar forelimb shape to penguins.  Instead, plotopterid forelimbs are more comparable to alcids, which we take to suggest that plotopterids did not use the penguin-style swimming stroke.

If we are correct, then penguins are unique for reasons beyond simply being flightless wing-propelled swimmers.  The full story on the acquisition of the unique penguin swimming mode will likely be revealed by careful biomechanical study of their fossil history...

Dinosaur Revolution: Anhanguera

Those of you that watched episodes 3 and 4 of Dinosaur Revolution (which aired exactly one week ago) saw the sequence focusing on the large pterodactyloid pterosaur, Anhanguera.  This was one of the sequences I had the most input on, so I thought it might be fun to chat briefly about some scientific background that inspired the sequence.


Parental care in pterosaurs?
The sequence opens with a mother Anhanguera visiting her nest of offspring, whom she then kicks out of the test for their first flights (these end poorly for the first two babies, but the "hero" character survives to fly another day).  We have relatively little evidence regarding the specifics of parental care in pterosaurs.  What we do have is good evidence that pterosaur babies were able to fly very early in life, and that the eggs were of a soft-shelled structure, which implies that the eggs were buried in foliage rather than brooded in the manner of birds.  This manner of egg-laying alone does not tell us much about parental care - "leathery" eggs are laid by some taxa that do guard young (crocodilians) and many that do not (most squamates, though some of those guard nests and young, too).  However, the fact that baby pterosaurs were so well developed, and likely able to fly early in life, is at least suggestive that there was not an extended period of parental care.  Baby pterosaurs probably set off from the nest relatively early (possibly immediately).  Check out Darren Naish's blog post from February on pterosaur babies and eggs for more.


Pterosaur Locomotion
There are three major types of motion shown in the sequence: ground locomotion, launching, and flight.  As it turns out, the first two of these are really the same "mode" of movement.  After speaking with David Krentz, he and I thought it would be interesting to show the baby Anhanguera hopping in a saltatorial fashion.  There are no trackways that show this mode of locomotion in pterosaurs, but we also don't have any trackways that can reliably be mapped to ornithocheirids yet, and the limb proportions of ornithocheirds like Anhanguera are consistent with a saltatorial method of movement.  This observation is noted in the paper that Mark Witton and I published in 2010.  It is published in the highly acclaimed, open access journal PLoS ONE, and is freely available here.

The takeoff mechanism features the quadrupedal launch model that I proposed in 2008, and which was further used to make predictions about pterosaur ecology by Mark and I in the PLoS ONE paper.  Julia Molnar generated a wonderful animation of quadrupedal launch for Anhanguera, and it has appeared across multiple venues, including National Geographic.  She was subsequently kind enough to make it freely available on YouTube.  I have inserted the video below.  You can also pull it up by clicking here.

I have written about quadrupedal launch on other web resources previously, so I won't belabor the point here.  In short, takeoff acceleration in animals tends to be generated mostly by the walking limbs, rather than the wings.  As such, takeoff is really a form of running or leaping (usually the latter).  The strengths of the limb bones in bending and torsion, particularly with regards to the moments sustained for leaping, are therefore highly indicative of launch mode.  Pterosaurs turn out to be much more bat-like in this regard than bird-like: they had forelimbs which were much stronger than the hind limbs across a wide range of body sizes.  By contrast, large birds have stronger hind limb elements (particularly the femur) when compared with the forelimb elements.  Giant pterosaurs, such as Quetzalcoatlus, had very long, thin hind limb elements, which argues against a bird-like launch.  However, because pterosaurs walked on their folded wings, as well, the incredibly robust forelimb musculature and structure could provide most of the launch power (and sustain the resulting forces) during a quadrupedal launch.  Since pterosaurs were quadrupedal while moving on the ground to begin with, this is actually the most simple model, as well.  Modern bats, particularly vampire bats and New Zealand short-tailed bats, use a quadrupedal launch.

There are a host of other problems with a bipedal launch in pterosaurs, including problems with angle of attack of the wing, trailing edge flutter, Wagner effects, insufficient height and time, and pitching instabilities.  Depending on interest, I may do a summary of these observations at a later date.

There is not much to say specifically about the flight patterns.  One nice thing was that the flapping amplitudes used were pretty reasonable.  The wing cycles are probably a bit too large in some cases (particularly the Quetzalcoatlus models that do flybys), but it's usually much worse.  The problem here is that large animals actually tend to fly with more shallow wing strokes, especially if they have high aspect ratio wings.  This tends to make a distant albatross etc. seem a bit smaller to us than it really is, and the same happens when doing pterosaur models - they just don't look as huge if you model them correctly.  In Clash of the Dinosaurs, I tried very hard to get the animators to reduce the flapping amplitude of the Quetzalcoatlus model to no avail - there was a general feeling from those working on the show that the giant size didn't come across with the lower-amplitude wingbeats that are predicted by anatomy and fluid mechanics.  Oh well, such is life.

Dinosaur Institute hiring paid intern. Please pass along.

Feel free to pass this along to any interested parties/mailing lists.

The Dinosaur Institute at the Los Angeles County Natural History Museum is currently seeking applicants for Proyecto Dinosaurios, a 1-year paid internship designed to encourage under-represented students to pursue careers in the geosciences. In order to apply, students must 1) currently be enrolled in a 2-yr community or junior college, 2) be a minority, preferably hispanic, 3) be eligible to work in the US (citizen or permanent resident), and 4) be interested in the sciences.

It's short notice, but if you know of any potential applicants please pass the information on to them. The application is due Sept 16, so passing this along soon would be greatly appreciated. Feel free to contact me with any questions or interest and I'll pass it on.

-JTH

Dinosaur Revolution Part 2

On Tuesday September 13, at 9:00PM, episodes 3 and 4 of "Dinosaur Revolution" will air on the Science Channel.  Note the change in date and venue.  One of the featured sequences involves the Early Cretaceous pterosaur Anhanguera.  Since I was a major consultant on that episode, in particular, I will be posting about some of the science background that went into that sequence (after it airs, of course).  Stay tuned!

--MBH

Dinosaur Revolution

This Sunday, starting at 9:00PM, Discovery Channel will air the first episodes of their new dinosaur miniseries, "Dinosaur Revolution".  I have been consulting on this show for the last 18 months.  The main page for the show can be found at:

http://dsc.discovery.com/videos/dinosaur-revolution-new-series-premiere.html

I appear briefly in a couple of the episodes, but my primary involvement was in advising on the models and animations.  The show primarily uses CGI, with limited "talking heads" and narration components.  There are some well known dinosaurs, but there are also quite a few species that are often overlooked and a number of featured Mesozoic animals beyond dinosaurs (pterosaurs, mosasaurs, mammals, etc).  I was primarily involved with the formulation of the pterosaur models.  The art director, David Krentz, is one of my favorite paleoartists, and an outstanding person to boot - his involvement has really helped shape this production into a stunning show.  Check it out this weekend!

--MBH