Okay, I know all I am doing is fueling the perpetuation of this kind of crap on TV.
That said, I was bored, and one of the few cool things about The History Channel is that it allows folks to watch their shows online.
The latest one was called: Bloodiest Battle; the story of the Cleveland Lloyd Quarry.
Well, the JFC version of what happens.
Anyway, there were, as usual, a host of annoying offenses in the show. Besides the ever annoying “loud dinosaurs” (i.e. all the dinosaurs couldn’t stop roaring), there was also the requisite rampant speculation on the social life of Allosaurus, the ecological relationship between Allosaurus and Ceratosaurus, and various anatomical flubs that continue to send out the message that The History Channel only hires the “talking heads” so they can appear scientifically legitimate.
Anyway, the only reason I am bringing this one up is because the most egregious error in the entire program (in my mind, at least) was the absolute statement from “Dinosaur George” Blasing that “all the evidence points to these animals being warm-blooded.”
That is bull-shit with a capital B.
Er…Bull-Shit.
There is no, I reiterate NO consensus on the thermophysiology of dinosaurs. That is true for all dinosaurs. All the evidence used so far has been ambiguous at best.
Furthermore, a “cold-blooded”Allosaurus is going to have the same overheating problem as a “warm-blooded” Allosaurus.
The problem has nothing to do with thermophysiology. It has to do with big animals over-exerting themselves in a hot environment. Dinosaurs were reptiles, and like all reptiles, they had a very limited means of removing heat. No sweat glands, and no real bare skin.
One thing that Allosaurus and other saurischian dinosaurs may have used to keep cool is their air sac system. Air sacs in birds do not lead to their high aerobic capacity. That is accomplished through the flow through system that the air sacs created, where oxygen is sent only one way (vs. the dead end bellows way that mammals and reptiles use). The perfusion of extra air sacs all over the body does nothing to add to endurance in birds. What it does do, though, is lighten the body and provide a spot for heat to dump from deep in the body. It is honestly quite likely that this is was the main impetus for air sac evolution in dinosaurs, and its consequent exploitation by their avian descendants.
This explanation would certainly have been a more scientific answer to how Allosaurus kept cool instead of pulling that antorbital fenestra radiator idea out of wherever “Dinosaur George” found it.
I don’t like absolutism in science programs anyway, but this type of absolutism is what lead to the general public thinking, erroneously, that scientists have discovered dinosaurs to have been warm-blooded. All this winds up doing is creating a false concept of dinosaurs that winds up getting shot down when new students enter the field and find that dinosaurs weren’t the super hot-blooded beasts they thought they were.
Plus, it’s just annoying when some fanboy says that being “warm-blooded” is one of the fundamental differences between dinosaurs and other reptiles.
Okay, I’m done venting.
Next episode involves some mythical beast called a “megalodon” (they must mean Carcharocles/Carcharodon megalodon). I hear that, at 15 meters (50ft) in length, it was the size of a jumbo jet and had to eat a tonne of meat a day to keep going.
Yeah, definitely sounds like something worth missing!
A few weeks ago the History Channel aired their first in a twelve part series on prehistoric creatures.
Now, being the History Channel – a subsidiary of Discovery ChannelA&E Networks – one would expect this series to detail some aspect of prehistoric life. Well that it does…sort of.
The series is called: Jurassic Fight Club. Many of you have probably already watched the first three, or four episodes, but for the uninitiated the premise is as follows:
Imagine all 4.6 billion years of prehistory as being one planet wide cage match somewhat akin to Primal Rage. Each week two animals (usually dinosaurs, but there are the occasional mammals) are pitted against one another.
Each hour long show is supposedly based off of a real fossil site. For instance the first episode was about a Majungasaurus skeleton that was found with bite marks of another Majungasaurus (erroneously referred to as “Majungatholus” despite paleo-consultant disapproval). One of the recent ones involved the infamous Tenontosaurus tilletti / Deinonychus antirrhopus fossils (a find with one large, dead T.tilletti and a few dead D.antirrhopus nearby. One of the first bits of evidence in favour of pack hunting behaviour in some theropods).
The show sets the “battle premise” and then seeks to justify its reasoning by cutting to various paleontologists for their take. The paleo crew is fairly diverse and include: Dr. Thomas Holtz Jr.Dr. Larry Witmer and Dr. Phillip J. Currie.
Okay, so maybe all that doesn’t sound so bad to some of you, but what may seem okay in theory has turned into an utter failure in execution.
Let me state up front that I immediately left this series for suck back when I first heard the title. It sounded like just another useless “documentary” that is little more than an excuse to watch two CG animals fight each other in order to satisfy some sophomoric need to watch things fight.
Still, there were proponents of the series (namely the paleo folks that worked on it) that urged the most skeptical of us to give the show a shot. As such, I refrained from commenting on it until now.
Four episodes in and now even the scientists who helped on it are starting to back away.
Honestly who could blame them. The show uses minimal information from the actual scientists. The shot of Dr. Witmer comparing theropod maxillae is continuously reused, and I could swear the show spends more time on the non-professional guys than they do the actual scientists.
This is a problem because it is the non-professional crowd (one fellow in particular) who really bring the show down.
The show features the likeness of one Dinosaur George Blasing. A quick perusal of his qualifications finds him to be little more than a particularly successful dinosaur fanboy. He apparently makes his living by talking about how cool dinosaurs are, to elementary school children. In effect, he is little different from Dinosaur Don Lessem, who writes books about dinosaurs for children.
Now don’t get me wrong. There’s nothing wrong with being an amateur, or a big, but non-professional, dinosaur fan. The problem I have is with History Channel essentially letting the fanboys run the show. This is supposed to be an educational program. History Channel is supposed to be the repository for all things historical. As such, it should be held to a higher standard than, say ABC, or Fox. Yet, here we get to witness the production of another terrible program that only seeks to snatch eyeballs. It offers practically no educational value.
Frankly that just ticks me off. Jurassic Fight Club is about as terrible as Animal Face Off was (another Discovery Channel property that not only embarrassed the subject matter, but also the scientists involved with it, by forcing them to give trash talk to one another).
The question that shows like JFC leave me asking is: what audience is it meant for? By seeking out professional paleontologists for their input, one would assume that the makers were looking for scientific accuracy. This, in turn, suggests that the goal is to pass knowledge on to their viewers. Yet, if one can slog through the first episode they will find themselves assaulted with absolutes left and right, tonnes of MTV style quick takes and replays, and a metric tonne of speculation. Each episode ends with Dinosaur George giving “his take” on how the whole story unfolded (complete with the CG animation). Now this sounds like nothing more than Godzilla style popcorn entertainment.
So which is it? Is JFC trying to be a documentary, or a popcorn flick?
By trying to do double duty, it comes off as more of mockumentary. A documentary that seeks to mock the subject material in which it presents. When done right, mockumentaries can be great (e.g. This is Spinal Tap), but in cases like this, where the parody does not appear intentional, the result is more of a slap in the face to those of us who do work in the field. To ask for professional advice and then completely ignore it, is a huge insult to both professions. The History Channel people should know better.
One question that is left from all this is: must we sacrifice scientific accuracy for entertainment, in order to get the knowledge across to the viewers?
As one person had mentioned on another forum: if scientists were to get the documentary that they wanted, no one would watch it.
Pardon me if I decide to call bullshit on this one. If one wants to see a documentary that is designed in a way respectful of the subject matter, one need only look at PBS’s NOVA series. Rarely does NOVA falter in their presentation style. Because of this consistent high quality the series tends to be lauded by many in the fields of science.
Okay, so maybe NOVA is a fluke. Besides, it’s on PBS and we all know how small and concentrated the PBS demographic tends to be. Are there any other examples?
Plenty.
David Attenborough – King of great documentaries
If one really wants to see how to make a series of successful and scientifically sound documentaries, one need only to look over to the UK, and the BBC. In the realm of documentaries, the David Attenborough docs reside in the upper echelon of quality. Not only are Attenborough’s documentaries well done, and accurate, but they are also popular. Planet Earth, one of the latest Attenborough docs, was the most watched cable show of all time. Discovery Channel pulled in 100 million viewers when it first aired in the United States. That is huge for a major network, much less a cable network (Discovery’s average prime time ratings are around 5 million viewers).
So not only does a scientifically sound documentary bring in the audience, but it can bring them in droves. When BBC released “Life in Cold Blood,” it was an event in England, bringing in more viewers that the average drama.
If we head back to the states, we can look at an old staple of children growing up in the 1990s; Bill Nye the Science Guy was a show that garnered a large and devoted fan following. Bill Nye was not only a great presenter and funny comedian, but he was/is also a real scientist. Though the show did its best to avoid using large words (for its young demographic), the show repeatedly and successfully showed off how awesome science was and how amazing the real world is.
Bill Nye – Champion of science education
You know why I think these shows did as well as they did? Because they didn’t dumb stuff down. There was no push to show the flashy stuff in order to maintain audience attention (equivalent to showing something shiny to distract a cat). The BBC documentaries, Bill Nye and NOVA all respected the intelligence of their audience, and the audience reciprocated by showing up in droves. People from all walks of life enjoy a good challenge. Today’s current documentarians would benefit from remembering this.
So for all those scientists who are asked to participate in the next big Sci Fi/Discovery Channel/ABC show/ whatever documentary; I say don’t fear speaking your mind on the importance of keeping the science up to snuff. If the filmmakers start bitching about having to “keep things simple” or removing the science for the sake of “the story,” just tell them:
That’s not how David Attenborough would do it.
~ Jura – who will probably never get a consulting job on one of these shows.
Actually, I’ve never thought that sauropods were grey. Mammals in general tend to be rather bland in their colour schemes. Reptiles don’t have that problem. With xanthaphores (yellow pigmented cells), erythrophores (red pigmented cells) iridophores (iridescent cells) and melanophores (dark pigmented cells), the range of colour available to reptiles, and by extension – dinosaurs, is quite vast.
That said, I always pictured sauropods as either a brownish green colour, or maybe a very pale blue (blue is generally rare in tetrapods, hence the thought of it being a weak blue).
But I digress.
I grew up during an interesting time for dinosaur research. Unlike the majority of paleontologists working right now I didn’t grow up learning about dinosaurs being slow and sluggish mistakes of nature. I also didn’t grow up with the “hummingbirds on crack” version of dinosaurs that is currently pervading popular culture. Rather, I grew up during that strange transitory phase of the Dinosaur Renaissance where dinosaurs were sometimes viewed as sluggish beasts and other times as racecars of the Mesozoic.
The result, I think, has been a slightly detached and objective look at how perceptions of dinosaurs have changed over time.
A “Brontosaurus” getting attacked by Allosaurus during a sojourn on land to lay her eggs. Ah, the classics.
One book I remember fondly was the Golden Book of Dinosaurs (shown above). It featured these beautiful drawings of dinosaurs living life as best we thought at the time. One picture that really stuck in my head, was a shot of two Brachiosaurus; one on land and the other so deep in a lake that one could only make out the crest on the head. I found that page to be so immersive and atmospheric. My knowledge of physics was not so good at the time, so it never dawned on me that this poor sauropod was basically breathing through a straw with its lungs separated by at least 2 atmospheres from the air entering (as best it could) the nostrils.
Then around the early nineties when Jurassic Park the book came out I started to note a distinct change in how dinosaurs were being portrayed. No longer were sauropods swamp bound behemoths. Now they were fully terrestrial titans that could not only support their weight on all four legs, but could even do so on 2 (well 3 if one counts the tail). It was around this time that Robert Bakker’s infamous “Dinosaur Heresies” started making the rounds.
Now, admittedly, Heresies came out in 1986 and the changing view of dinosaurs actually started in the seventies. However, it wasn’t until the early nineties that the full effects of Bakker’s work could truly be appreciated. If anything this gives one an idea of the kind of inertia one must deal when it comes to getting scientific ideas out into the public.
Again I digress.
It was around the early nineties when I first read The Dinosaur Heresies. The first few chapters were amazing. I had never seen dinosaurs portrayed this way. They walked better and were more active. In many ways they better fit the concept I had in my head all along.
Then I came up to the end of chapter 3. The thesis of this chapter was to explain why reptiles should not be viewed as inferior to mammals. In order to do so Bakker explained all the various ways in which extant reptiles outshine extant mammals. The end of the chapter features a beautifully drawn shot of the “panzer croc” Pristichampsus snatching a Hyracotherium (formerly Eohippus). The caption read:
Pristichampsus hunted during the Eocene Epoch, about 49 million years ago, but it was very rare, much rarer than big mammalian predators, proof that cold-bloodedness was a great disadvantage.
Predatory Dinosaurs of the World. Available on Amazon
That’s when the real thesis of the book hit me. The argument wasn’t: “Dinosaurs weren’t slow and stupid, because of the following.”
Rather the argument was: “Dinosaurs weren’t cold-blooded because the facts show the following.”
In order to pull dinosaurs out of the mire, Bakker had to change their fundamental thermophysiology. The general concept, that cold-bloodedness is inferior to warm-bloodedness, remained the same. This despite Bakker’s initial attempt to explain how “cold-blooded” reptiles outshine “warm-blooded” mammals.
Bakker’s book was just the start. From there, we had Adrian Desmond’s “The Hot Blooded Dinosaurs” (okay, technically Desmond was first by 7 years, but he largely stole Bakker’s work to make the book so it evens out) and Gregory S. Paul’s infamous: “Predatory Dinosaurs of the World.” Each new book taking the “dinosaurs can’t be cold-blooded” argument a little further. By the time we hit Predatory Dinosaurs of the World, Tyrannosaurus rex was running along at 40mph, dromaeosaurs were practically flapping around and every species of dinosaur was reaching adult size by between 4-10 years of age.
Sadly it was at this point that Jurassic Park was written. As hardcore fans know it was Greg Paul’s erroneous sinking of Deinonychus antirrhopus into Velociraptor that gave us the JP “raptors.” It was also at this point that the pendulum of dinosaur physiology officially swung the other way.
The thing that had always bugged me about this view of dinosaurs was the sheer lack of supporting data for it. The assumption was always that dinosaurs were so vastly different from “typical reptiles” that they had to have been doing something different. Yet when one looked at the actual data dinosaurs came out looking slightly odd at best. For the most part dinosaurs fit the reptile mold quite well. It was these elusive “classic reptiles” that didn’t appear to exist.
Most reptiles don’t fit the “typical reptile” mold at all. Yet despite numerous papers over the past 30 years depicting reptiles doing things normally thought un-reptile like (e.g. caring for their young, competing with large mammals, etc), most of this was dutifully ignored in favour of an older, more outdated view.
It was a problem that Neil Greenberg (1980) aptly called: The “endothermocentric fallacy.” Basically, the assumption that being an endotherm is inherently superior to being an ectotherm. Part of that superiority included the ability of endotherms to do everything faster and “better” than similar sized ectotherms. This problems with this way of thinking warrants an entire blog post to itself. So rather than get bogged down with this particular I’ll touch more on the endothermocentric fallacy at a later date. For now all that one needs to keep in mind is that the thinking of the time was that if dinosaurs were going to be active at all then they had to be endotherms.
By the late nineties we had the first evidence of feathers in a small branch of the theropods (Maniraptora). Birds were officially adopted into the dinosaur family tree and the fully endothermic concept of Dinosauria was completely entrenched.
The funny thing, of course, is that this dogmatic view of dinosaur metabolism was just as bad as the early 20th century’s “cold-blooded” swamp bound view. Sure dinosaurs were more active now, but the data supporting it was just as nebulous as the stuff that was used to keep dinos in the swamp.
Enter the 21st century, and the late…um, 0’s (does anyone have a name for this decade yet?). Biomechanic work on dinosaurs has started to reveal amazing insights into the physical limits of what dinosaurs could do, and the results have started to pull the pendulum back again.
Work by John Hutchinson and Mariano Garcia (2002) on T. rex showed that not only could T. rex not hit 40mph, but it technically couldn’t run either. A biomechanical assessment of theropod forelimbs by Ken Carpenter (2002) has shown that the “bird-like” dromaeosaurs could not fold their arms up like birds after all.
Work by Rothschild and Molnar (2005) on sauropod stress fractures showed no signs of rearing activity in sauropods, while work by Kent Stevens and J. Michael Parrish (2005) pulled the swan-like curve out of sauropod necks, placing things far more horizontally.
Work by Gregory Erickson and others (2001) on micro-slices of dinosaur bone has indicated that very few dinosaurs hit adult size in less than 15 years.
Now we have a new study by Lehman and Woodward (2008) which follows up on Erickson et al’s work and actually shows that even this toned down version of dinosaur growth is probably too fast as well. Lehman and Woodward focused on sauropods and studies on their bone microstructure. What they did was compare bone growth data to a well used equation for growth in animals.
Deemed the Bertalanffy equation; it states that the mass at any given age is an exponential function limited by the asymptote of adult body mass. This equation has been used extensively in studies on bird and elephant growth among others. An example of the equation is given to the right for fish.
When the authors did this they discovered something quite interesting. Instead of taking 15 years to reach adult mass, sauropods like Apatosaurus excelsus took closer to 70 years!!
Other sauropods measured took between 40 and 80 years! This is a substantial decrease in growth rate estimated before. Mind you this is data taken, in some cases, from the same piece of bone that Erickson et al had used. So one can’t suggest anomalous bones being used as the reason behind the surprising results. The authors also went to great lengths to take into account differences in mass estimations as well as allometric growth of body parts. In each case the changes had little affect on the overall outcome (in many cases, it made growth go even slower).
Now keep in mind we are talking about the time it took sauropods to reach full adult size. This is not the time taken to reach sexual maturity. Earlier studies by Erickson et al (2007) had already discovered that dinosaurs didn’t wait to grow up before engaging in sex, so there is no issue here of 80 year old sauropods finally “doing the nasty.”
What this does show is that growth in dinosaurs might not be as determinate as initially thought. An 80 year old sauropod might just have been close to the edge of its lifespan at this point (though the possibility of bicentennial sauropods does still exist). It also shows that dinosaurs had growth rates far closer to the realm of reality (before it was hard to imagine how an Apatosaurus excelsus was able to pound down enough food daily to add 13.6 kg of new mass a day. Especially given their small mouths).
Thermophysiologically what does this all mean? Were dinosaurs “cold-blooded” after all?
That’s one of those questions that will never be fully answered (short of a time machine). What this does do is pull dinosaurs ever further away from the “definitely warm-blooded” category and push them right back into the middle again. When/if the dust settles on this metabolism debate I suspect that dinosaurs will probably remain in the middle somewhere.
Of course while all of this is going on with dinosaurs we have other studies, like those from Tumarkin-Deratzian (2007) showing the existence of fibrolamellar bone growth in wild alligators, that are finally moving the rusty pendulum of reptile metabolism out of the “classic reptile” category and much closer to the middle.
So in the end dinosaurs will still probably wind up being “good reptiles.” Thankfully the exact definition of what that entails will have probably changed by then.
~ Jura
References
Bakker, R. 1986. The Dinosaur Heresies: New Theories Unlocking the Mystery of the Dinosaurs and their Extinction. William Morrow. New York.
Carpenter, K. 2002. Forelimb Biomechanics of Nonavian Theropod Dinosaurs in Predation. Concepts of Functional Engineering and Constructional Morphology. Vol. 82(1): 59-76.
Desmond, A. 1976. The Hot Blooded Dinosaurs: A Revolution in Paleontology. Dial Press.
Erickson, G.M., Curry Rogers, K., Varricchio, D.J., Norell, M.A., Xu, X. 2007. Growth Patterns in Brooding Dinosaurs Reveals the Timing of Sexual Maturity in Non-Avian Dinosaurs and Genesis of the Avian Condition. Biology Letters Published Online. doi: 10.1098/rsbl.2007.0254
Erickson, G.M., K. C. Rogers, and S.A. Yerby. 2001. Dinosaurian Growth Patterns and Rapid Avian Growth Rates. Nature 412: 429?433.
Greenberg, N., III. 1980. “Physiological and Behavioral Thermoregulation in Living Reptiles” in: A Cold Look at the Warm-Blooded Dinosaurs (R.D.K. Thomas and E.C. Olson Eds.), pp. 141-166, AAAS, Washington, DC
Hutchinson, J.R., Garcia, M. 2002. Tyrannosaurus was not a fast runner. Nature 415: 1018-1021.
Lehman, T.M., and Woodward, H.N. 2008. Modeling Growth Rates for Sauropod Dinosaurs. Paleobiology. Vol. 34(2): 264-281.
Rothschild, B.M., and Molnar, R.E. 2005. Sauropod Stress Fractures as Clues to Activity. In Thunder Lizards: The Sauropodomorph Dinosaurs. (Virginia Tidwell and Kenneth Carpenter eds). Indiana University Press. pp 381-394.
Stevens, K.A., and Parrish, J.M. 2005. neck Posture, Dentition, and Feeding Strategies in Jurassic Sauropod Dinosaurs. In In Thunder Lizards: The Sauropodomorph Dinosaurs. (Virginia Tidwell and Kenneth Carpenter eds). Indiana University Press. pp 212-232.
Tumarkin-Deratzian, A.R. 2007. Fibrolamellar bone in adult Alligator mississippiensis. Journal of Herpetology. Vol. 41. No.2:341-345.
As human beings this might come off as somewhat of a “duh” question.
“To free our hands up, of course.”
Ah, but like most things in life, the common sense answer is not the right one.
Consider all the bipedal animals alive today. We have humans, obviously; kangaroos, birds, a few lemurs, and a whole swath of lizards. Of these, the “free up the forelimbs” argument really only holds true for humans, lemurs and birds. What of kangaroos and all those lizards? Exactly what does one benefit from when going bipedal?
Do you go faster, run longer, or gain a better vantage point?
C.kingii during a typical foraging run.
All these questions were asked, and somewhat answered in a recent paper by Clemente et al.
Bipedal locomotion by lizards has previously been considered to provide a locomotory advantage. We examined this premise for a group of quadrupedal Australian agamid lizards, which vary in the extent to which they will become bipedal. The percentage of strides that each species ran bipedally, recorded using high speed video cameras, was positively related to body size and the proximity of the body centre of mass to the hip, and negatively related to running endurance. Speed was not higher for bipedal strides, compared with quadrupedal strides, in any of the four species, but acceleration during bipedal strides was significantly higher in three of four species. Furthermore, a distinct threshold between quadrupedal and bipedal strides, was more evident for acceleration than speed, with a threshold in acceleration above which strides became bipedal. We calculated these thresholds using probit analysis, and compared these to the predicted threshold based on the model of Aerts et al. Although there was a general agreement in order, the acceleration thresholds for lizards were often lower than that predicted by the model. We suggest that bipedalism, in Australian agamid lizards, may have evolved as a simple consequence of acceleration, and does not confer any locomotory advantage for increasing speed or endurance. However, both behavioural and threshold data suggest that some lizards actively attempt to run bipedally, implying some unknown advantage to bipedal locomotion.
The conclusions reached, were interesting and quite unexpected.
I’d say the most surprising part would have to be the discovery that both endurance and speed were found to be inconsequential. Those were the two forces that I figured would have driven the push towards bipedalism. Apparently this is not the case.
In fact, the only correlate that the authors found was that a switch to bipedalism resulted in an increase in acceleration. Short of that, the authors viewed bipedalism as more of a side effect of speedy locomotion, rather than anything else.
As one author put it: “The lizards were pulling a wheelie.”
There are some gripes (niggles if you will) with the paper. For one, the authors assert that a switch to bipedalism allowed birds to incorporate their forelimbs into wing design. While being bipedal certainly allowed for this, it could not have been the cause. Birds descended from dinosaurs, and very, very very few dinosaurs had wings. Theropods were sporting freed forelimbs for some 80 million years, or so (probably longer given the proposed ancestors of dinosaurs). Wings were not the cause, simply a benefit. Something else had to have spurred the evolution of bipedality.
Side note: What the heck were theropods doing with those forelimbs anyway? Most paleo artists tend to draw theropods with their arms tucked to the side, yet work by Carpenter (2002) has shown that there was some considerable range of motion in theropod forelimbs. They weren’t brachiating from tree to tree, or anything, but they could certainly do a heckuvalot more than just tuck their arms to the side. Even T.rex with its embarrassingly short forearms, had a surprisingly large range of motion to them. So what’s up paleo art guys? Let’s see some theropods putting their arms to use.
The largest SNAFU in the paper comes from the cladogram that the authors chose. They chose to go with the broken molecular tree used by Townsend et al, which asserts that Iguanians are actually Scleroglossan lizards. This might sit all fine and well when looking at molecules, but it utterly falls apart upon a morphological assessment. In order for Iguanians to fit in the Scleroglossan family tree, they had to have undergone a tonne of morphological reversals, including the re-softening of the tongue and the re-evolution of both postorbital bars (surprisingly, the latter is actually not out of the realm of impossibility as tuataras have apparently done just that).
Due to this tree choice, the authors erroneously concluded that bipedalism evolved only once in the lacertilian tree and was lost a multitude of times, with a putative re-acquirement in varanids.
Another minor complaint comes from the very slight use of Chlamydosaurus kingii; the only lizard known to be a “true” biped (see: Shine & Lambeck 1989). Given that the authors were trying to spot differences between bipeds and quadrupeds, I can understand the use of lizards like Ctenophorus, with their greater spectrum of gaits. However, in doing so they should have qualified their conclusions better in regards to how lizards obtain a bipedal stance. In Chlamydosaurus, bipedal trotting is attained from a standing start. Quadrupedal stance is only seen when stopping to eat. Furthermore, foraging runs and escape runs use two different gaits, with the latter gait more akin to that of other facultatively bipedal lizards. Judging from the stats given in the paper, it seems apparent that the C.kingii used in this study were mostly running away.
Frankly the movies are just too short. I have to go super slow-mo just to see anything. So that’s a bummer.
Overall the paper is rather good. The authors discovered that Lophognathus gilberti runs bipedally 85% of the time. This suggests that C.kingii is not the only truly bipedal lizard out there.
The authors also observed that, despite any advantage in speed, or endurance, some lizards intentionally push their center of mass towards their hips early on in the running phase in order to more quickly obtain a bipedal gait. The reasons behind this are unclear, but do suggest that bipedalism confers some advantage not discovered during this experiment.
One advantage alluded to, but never really elaborated on, was the faster acceleration noted in bipeds. Though maximum speed was no different than in a quadruped, this speed was obtained faster. Ecologically I could see this being very advantageous. When one is trying to avoid a predator, maximum top speed is probably less important than reaching that top speed as fast as possible.
If one lizard has a top speed of 12km/hr and another has a top speed of 8km/hr, and the goal (burrow) is only 50 meters away, then that extra speed isn’t going to mean much. Especially if the slower lizard is able to hit its top speed faster.
Apparently lizards “pull a wheelie” because in their ecosystem it pays to be a drag racer, rather than a Daytona 500 car.
~Jura
References
Carpenter, K. 2002. Forelimb Biomechanics of Nonavian Theropod Dinosaurs in Predation. Concepts of Functional Engineering and Constructional Morphology. Vol. 82(1): 59-76.
Shine, R., & Lambeck, R. 1989. Ecology of Frillneck Lizards, Chlamydosaurus kingii (Agamidae), in Tropical Australia. Aust. Wildl. res. Vol. 16: 491-500.
Townsend T, Larson A, Louis E, Macey JR. 2004. Molecular Phylogenetics of Squamata: The Position of Snakes, Amphisbaenians, and Dibamids, and the Root of the Squamate Tree. Syst Biol. Vol. 53(5):735-57.
Otherwise known as: “The Shielded Devil Frog,” is a recent discovery made in Madagascar, by scientists from University College in London, and Stony Brook University, in New York. This behemoth was about 4.5 kg (~10lbs) in mass, with a length of 40.6 cm (16 inches). It lived during the late Cretaceous, about 70 mya, and appears to be related to the living genus Ceratophrys; more commonly referred to as: Pac Man frogs*.According to researcher David Krause:
“It’s not outside the realm of possibility that Beelzebufo took down lizards and mammals and smaller frogs, and even — considering its size — possibly hatchling dinosaurs,”
I’m sure Dr. Krause either added this bit in for shock value, or because he was being prodded by the journalist interviewing him. It always seems that any creature from the Mesozoic has to always be compared to dinosaurs.
That said, given the relationship of Beelzebufo ampinga to Ceratophrys, I wouldn’t rule dinosaur eating out of the menu either. The living animals are voracious.
~Jura
* Of course, frogs of the genus: Pyxicephalus, are also referred to as Pac Man frogs, which can lead to confusion. One reason why taxonomic names are preferred over common names.
As I strolled along internet looking for something to blog about, the only thing that I could find was a report that was mentioned a few days ago.
As is typical, it features the world’s most popular reptiles: Dinosaurs.
From left to right: “Fierce eyed Dawn Shark” Eocarcharia dinops and “Old hidden face Kryptops palaios
In this case, it is two theropods that were described by paleontological superstar Paul Sereno, and somewhat paleo-newbie Steve Brusatte. For members of the Dinosaur Mailing List, Brusatte is well known for his previous work on the internet, as a paleo-journalist. This description is credit well deserved for Steve. So good on him for that.As for the report, what is there to really say. It’s the discovery of two new theropods. In the world of dinosaur diversity, dinosaurs are usually broken up into 3 categories:
Theropoda
Sauropoda
Ornithischia
In terms of diversity, the previous categories are essentially in reverse order. Easily the most diverse dinosaur group was the Ornithischia. They included “duck billed” hadrosaurs, crested lambeosaur…hadrosaurs, horned ceratopians like Triceratops horridus, armoured stegosaurs and super-armoured ankylosaurs. Two legged hypsilophodonts, and helmeted pachycephalosaurs. Ornithischians were all over the map in terms of diversity.
Next up we have the sauropoda (or to be more inclusive: the sauropodomorpha). On the outset one might think that these guys weren’t really that diverse. I mean if you’ve seen one long necked, long tailed behemoth, then you’ve seen them all right?
Er, no.
Sauropods ranged in size from the super tiny Mussaurus patagonicus*, which topped out at 37cm (15 inches), to titans like Argentinosaurus huinculensis, Sauroposeidon proteles, and Amphicoelias fragillimus; all of which grew to excesses of 39.6m (130ft), and had masses 1,000 times greater, with some estimates as high as 122 metric tonnes!
Besides this humongous size range, we also had sauropods that had sail-backs (Amargasaurus cazaui), sauropods that had tail clubs and armour like ankylosaurs (Shunosaurus lii, Saltasaurus loricatus). We even had sauropods with strange beaks and short necks (Bonitasaura salgadoi, Brachytrachelopan mesai).
Finally we come to the theropoda. All are bipedal carnivores (one possible exception in segnosaurs). They came in two size classes: Frickin huge, and medium sized. Some had long necks (Coelophysis bauri), some had display crests (Dilophosaurus wetherilli, Cryolophosaurus ellioti). Many show reduction in arm size, with Tyrannosaurus rex and Carnotaurus sastrei taking the cake for tiniest arms. There was also one weird group that had sail-backs and crocodile like heads (the spinosaurs). Still, in terms of overall diversity, a theropod was a theropod.
Oh, and one group spawned birds, if you’re into that angle.
It never ceases to amaze me at how often the Dinosaur Mailing list, or dinosaur related websites, devote so much time to theropods. Even news stories seem to put more focus on the big meat eaters rather than the numerous plant eaters. Heck just look at how often we watched theropods fight in the Jurassic Park movies (do you know there was never a scene in the JP movies where a theropod attacked a plant eater?).
One is forced to ask why that is. I believe the answer lies in the ecology alluded to above. Though sauropods and ornithischians were a highly diverse bunch, they were all herbivores. The only carnivorous dinosaurs were theropods.
To elucidate this hypothesis even further, check out this story on Digg.com:
Psychologists at Yale University found that the human brain is biased towards images of animals. We are more likely to notice a change in an image, if that change involves animals. I’m going to take this one step further and say that not only are we biased towards pictures of animals, but that bias is even stronger for predatory animals. Especially predators that are large enough to pose a threat to ourselves (e.g. lions, tigers, crocodiles, large sharks, and of course: big theropods).
So there you have it. Theropods might be the plane Jane group of the Dinosauria, but they will always hog the spotlight. Evolution would have it no other way.
~Jura
*Technically M.patagonicus wasn’t actually that small. The type specimen was a hatchling. Adults were closer to 5m (16ft) in total length. Still small for a sauropod though.
