Given all the recent stink over a certain other documentary, I’m not exactly itching to jump back into dino docs.
Oh well.
The Public Broadcasting Service’s long running series NOVA, has a new episode out, entitled Arctic Dinosaurs. The episode is about a particularly exciting find in Alaska, and its implications for our view on dinosaurs. The researchers; namely museum Victoria’s Tom Rich and MNS Dallas’ Anthony Fiorillo, came across a fossil bed along Alaska’s north slope, that revealed the existence of hadrosaurs, ceratopians and coelurosaur theropods, all living in far North Alaska.
As I had mentioned previously, NOVA tends to get lauded for its well put together documentaries. I would argue that this doc was no different; though there were some missteps that I feel may be a sign of NOVA’s producers trying to fall more in line with the fare seen on Discovery Channel and the A&E networks.
Secondly, I would like to lambast PBS for what is probably their most egregious error with this, and other NOVA specials. Namely the lack of Firefox love. The only way I am able to watch these NOVA specials is by firing up Internet Explorer. If I use Firefox all that happens is I get a dead loading screen.
The premise of the series is fine, and as in previous iterations, NOVA has done a good job of letting the scientists talk how scientists really talk (i.e. with lots of caution and caveats).
I was far less impressed with the writing for the narrator. There were more than a few instances where the narrator resorted to straight up hyperbole. Especially in the beginning when it is revealed that all these dinosaur fossils had been found in this polar state.
The narrator said:
The startling discovery that these ancient reptiles, “thunder lizards,” lived and thrived in the arctic has taken scientists by surprise.
Then a little later:
According to conventional wisdom, it shouldn’t be here, because this is how dinosaurs are typically pictured: cold-blooded reptiles living in tropical climes, not in cold, arctic environments like this one. And the Hadrosaur is not alone.
Um, no. We have had discoveries of dinosaurs, and other reptiles from polar and paleo-polar latitudes, for decades now. The real neat thing about this find, was the sheer number of animals discovered. This doc served more as a review of what we have learned so far, rather than a breaking news story.
There was another writing snafu that occurred a little further in too that I feel needs clarifying:
Scientists long believed that dinosaur biology resembled that of cold-blooded reptiles like crocodiles, animals that require warmth to survive and cannot withstand prolonged exposure to temperatures below freezing. But not one crocodile fossil has been found along the Colville, which suggests that polar dinosaurs found a way to adapt to an environment that their cold-blooded cousins couldn’t tolerate. But how?
This statement is misleading. We do have evidence of non-dinosaurian polar reptiles. These include Cretaceous crocodylian and turtle fossils found in Victoria, Australia (which would have been closer to the South Pole) and Axel Heiberg Island in Canada, as well as plesiosaur fossils from Antarctica, and at least the assumption that Meiolaniid turtles (large, ankylosaur like armoured turtles that lived from the late Cretaceous through to the Pleistocene) had once lived in Antarctica.
Oh, and also Leaellynasaura amicagraphica was a herbivore; not a carnivore as was stated in the show.
So there were those few writing missteps. The only other thing I can fault the show for was its very lackluster CG work. As NOVA is a mostly public funded series, I can forgive the lower quality CG work, though I still think they could have afforded to make their models at least a tad more realistic (especially since they teased feathers on Dromaeosaurus albertensis before returning to scaly maniraptors (i.e. the Troodon formosus). Plus their Gorgosaurus libratus was just atrocious.
Regardless, most of these complaints are small. The writing flubs were probably the worst offenders. Short of that, the show was well put together. Though the show still fell a little more in the pro-warm-blooded camp for dino metabolism, it was the first and only time I have ever heard a documentary point out that warm-blooded and cold-blooded are opposite ends of a continuum. In fact one of the better writing moments occurred towards the end when the narrator stated:
Dinosaurs likely had their own unique solution to the body temperature problem, which allowed them to survive for millions of years in the toughest seasonal conditions their world had to offer.
It was nice to see a documentary that actually took a more objective stance on the whole thermophysiological debate.
Finally another big plus for this show was the sheer number of paleontologists that rarely seem to make it in front of the camera, including Hans-Dieter Sues and Anusuya Chinsamy-Turan (the latter of whom while being a great scientist, has one of the harder to pronounce names in paleontology).
Overall, this was another fine piece of work from the folks over at NOVA. Though there was a tendency to stray into the realm of hyperbole with the narration, and the CG work is somewhat painful to watch, the show proved informative and interesting.
In the end, that’s really all a documentary should strive for.
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.
So I’ve been working on dragging the rest of my site into the 21st century. While most of this work has been just transcribing of old code to new code, I didn’t want to just wind up rehashing all of my old info.
I mean there are only so many ways that one can remix the same stuff.
As the meat of the site was meant to contain species information, I thought it would be nice if my first revamped species page, was a new one.
I had been meaning to write about Chlamydosaurus kingii (i.e. the frilled lizard) for a long time now. They have been a lacertilian favourite of mine. It’s rather sad that there is not much written about these guys, save for the occasional herpetocultural article, or the rather glib Wikipedia article.
Now, while I could have just gone and updated Wikipedia with this info, I wanted to have it on my site first. I mean, if I’m going to be the person to flesh out this species, then it’s only fair that I give my site first dibs.
Much of the article was culled from data in Shine & Lambeck, 1989. This was, and still is the most comprehensive review of this species. It is interesting to note that this reference is used in the Wikipedia article, but not for any of the more interesting info.
For example, as can be read in the article, frilled lizards are unique in being the only extant reptile that is an obligate biped. You’d think that would get more attention. Hmmph, it must be that distracting frill. 🙂
There you go. A new update with actual new content.
We used electromyography on juvenile American alligators to test the hypothesis that the following muscles, which are known to play a role in respiration, are recruited for aquatic locomotion: M. diaphragmaticus, M. ischiopubis, M. rectus abdominis, M. intercostalis internus, and the M. transversus abdominis. We found no activity with locomotion in the transversus. The diaphragmaticus, ischiopubis, rectus abdominis and internal intercostals were active when the animals executed a head-down dive from a horizontal posture. Weights attached to the base of the tail resulted in greater electrical activity of diaphragmaticus, ischiopubis and rectus muscles than when weights were attached to the head, supporting a role of this musculature in locomotion. The diaphragmaticus and rectus abdominis were active unilaterally with rolling maneuvers. Although the function of these muscles in locomotion has previously been unrecognized, these data raise the possibility that the locomotor function arose when Crocodylomorpha assumed a semi-aquatic existence and that the musculoskeletal complex was secondarily recruited to supplement ventilation.
Scientists at the University of Utah have discovered the unique internal subtleties that allow crocodylians to sink, rise, pitch and roll; all without disturbing the water (much). It turns out that the main muscles used for breathing, are also used to actually shift the lungs within the body!
That’s just crazy awesome. Uriona & Farmer’s work raises the question of how prevalent this ability is in other semi-aquatic animals (e.g. seals, terrapins, manatees). By shifting the lungs further back in the body, crocodylians are able to change their local density. This allows the front, or back of the animal to rise and sink separately from the rest of the body. So too does moving the lungs from side to side allow for rolling in the water. All of this can occur without the need to move any external body parts. This means no extra turbulence gets created in the water, thus allowing crocodylians to better sneak up on their fishy, or fleshy prey.
Baby crocodiles exhibiting their unique pulmonary powers.
If anything, it sure speaks to why crocodyliformes have held dominion over the semi-aquatic niche for over 200 million years. Uriona and Farmer do suggest that the ability of these respiratory muscles to do this might not be an exaptation. Rather, this might have been the initial impetus behind the evolution of these muscles. Only later would they have been exapted to help with breathing on land. Though the authours provide some good parsimonious reasons for why this may be (basically it would take less evolutionary steps to accomplish than the other way around), it doesn’t really jive with the fossil evidence. Part of the reason why the crocodylian diaphragm works, is because the pubis (the forepart of the hip bone in most animals, and the part that juts out so prominently in theropod dinosaurs), is mobile. This mobility occurred early on in crocodyliforme evolution, with the crocodylomorph Protosuchus having a pubis that was almost mobile. The problem arises when one looks at this early crocodylomorph. Protosuchus was obviously terrestrial. If Protosuchus was evolving a mobile pubis already, then it was doubtful that it was being used to allow lung shifting in the body (an ability that is helpful when underwater, but pretty pointless on land). Furthermore, Crocodylia proper is the umpteenth time that crocodyliformes have returned to a semi-aquatic existence. It is doubtful that all the numerous land outings that occurred during crocodyliforme evolution, would have retained the ability to move the lungs to and fro. It seems far more likely that this was an ability that evolved in Crocodylia, or somewhere close by on the evolutionary tree, in some taxa that was still semi-aquatic.
Protosuchus richardsoni. An example of an early crocodylomorph.
Of course it is also possible that crocodyliforme phylogeny is just all f-ed up. With the amount of convergence rampant in that lot, this remains a distinct possibility.
Either way this is a cool discovery, and one worthy of adding to the crocodylian pages.
The second paper also comes from the Journal of Experimental Biology. This one involves lizards.
Foraging mode has molded the evolution of many aspects of lizard biology. From a basic sit-and-wait sprinting feeding strategy, several lizard groups have evolved a wide foraging strategy, slowly moving through the environment using their highly developed chemosensory systems to locate prey. We studied locomotor performance, whole-body mechanics and gaits in a phylogenetic array of lizards that use sit-and-wait and wide-foraging strategies to contrast the functional differences associated with the need for speed vs slow continuous movement during foraging. Using multivariate and phylogenetic comparative analyses we tested for patterns of covariation in gaits and locomotor mechanics in relation to foraging mode. Sit-and-wait species used only fast speeds and trotting gaits coupled with running (bouncing) mechanics. Different wide-foraging species independently evolved slower locomotion with walking (vaulting) mechanics coupled with several different walking gaits, some of which have evolved several times. Most wide foragers retain the running mechanics with trotting gaits observed in sit-and-wait lizards, but some wide foragers have evolved very slow (high duty factor) running mechanics. In addition, three evolutionary reversals back to sit-and-wait foraging are coupled with the loss of walking mechanics. These findings provide strong evidence that foraging mode drives the evolution of biomechanics and gaits in lizards and that there are several ways to evolve slower locomotion. In addition, the different gaits used to walk slowly appear to match the ecological and behavioral challenges of the species that use them. Trotting appears to be a functionally stable strategy in lizards not necessarily related to whole-body mechanics or speed.
I haven’t had a chance to read much more than what was written already. I do take a bit of offense to the authours referring to scleroglossan foraging technique as “slow,” but what are you going to do?
I do find it interesting that lizards seem to have lost the ability to “walk” numerous times. That almost seems bizarre. The study points out that ecology produces heavy pressures on lizards in terms of their locomotion type. This is extremely pertinent given how often one hears the old (and wrong!) adage about “reptiles” being incapable of intense aerobic activity.
According to the above study (among others), it all depends on the animals being tested.
There we go. Two really cool papers on reptiles, being released in one day.
Just announced today on the BBC news website, scientists have unearthed the remains of a giant plesiosaur from the Arctic island of Svalbard.Coming in at 15 meters (50ft), it ranks as one of the largest known specimens of ancient marine reptile. Since there are other plesiosaur and mosasaur specimens that are known to approach 50ft in length, I’m assuming the reason that this species is given the term “monster” is because of its overall size. No species name has been given yet. Judging from past plesiosaur behemoths, I’m thinking that it might be Liopleurodon. Folks who saw the BBC series: Walking with Dinosaurs, might remember the Liopleurodon in one of the episodes. That one was a whopping 21m (70ft) in length. So, to date, it is still an unrealistic size.That said, there sure were a lot of giant marine reptiles swimming around the Mesozoic seas.
It is interesting to note that there has yet to be a fossilized sea animal (or any animal) that approaches the monstrous blue whale (Balaenoptera musculus) in terms of overall size (giant jellyfish [Cyanea capillata] grow longer, but have nowhere near the mass). Off the top of my head, the largest prehistoric fish was the Jurassic giant: Leedsichthys problematicus, which has had length estimates very close to blue whales (~30m, or 98ft). There was one ichthyosaur that exceeded “the monster” in length, but might have fallen “short” in terms of overall mass (Shonisaurus sikanniensis). All in all, B.musculus stands alone in terms of oceanic giants. What was imposing this size limit on all the Pre-Tertiary marine fauna? One possibility that I’ve heard tossed about (and the only one that I happen to think is on the right track) is that the reason for the size of blue whales, is due to the prevalence of krill (order: Euphausiacea).
Liopleurodon swims by Leedsichthys; weighing its options.
Krill are way down at the near bottom of the food chain. They eat plankton and are, in turn, eaten by a huge chunk of the marine ecosystem. Krill are global in their distribution, and their biomass is astronomical (500 million tonnes, according to Wikipedia). So why is this important?Well, if we look back at all the large marine reptiles, or most of the large prehistoric marine vertebrates; all of them were large predators. “The Monster,” Kronosaurus, Liopleurodon and most of the others, all had a taste for meat. The problem with this, is that a large meat eater requires lots of meat in order to survive. This imposes a size limit right away. Either a large marine animal is going to eat shoals and shoals of small fish (which may reproduce rapidly, but probably not rapidly enough to maintain a viable population of large carnivorous marine vertebrates), or it is going to eat any large animal that it can take down. If shoals of fish can’t maintain a viable population of marine behemoths, then anything bigger will certainly not. Large marine animals with big appetites, need something that can take the hit and keep on going.Krill and plankton provide the only real option for giant marine animals. And it just so happens that we are currently living in a time period where most of the oceans are temperate.This is important. Temperate waters mean that there is a section of ocean that is very cold and a section that is warm. This results in upwelling, or the pushing of nutrients from the bottom of the sea, up to the top where it can be used by other life forms (namely: plankton, squid and krill) to make energy. The importance of thermohaline circulation for all of this cannot be discounted either. Both result in the necessary conveyor belt like mixing of oceanic nutrients.
So more nutrients results in greater biomass of krill, which allows for the evolution of large marine animals beyond the 15 meter / 30 tonne mark. Today that niche happens to be filled by mammals. Why?
Is there something special about their physiology that allows only them to grow to this size?
No…not really. Most likely, mammals just so happened to be big enough at the right moment in time.
If Antarctica, or Australia had moved closer to the South Pole and iced over, then we would have had a thermohaline circulation in the Mesozoic, and most likely, giant planktivorous marine reptiles. It didn’t so the best we got was the smaller, yet equally impressive: Leedsichthys problematicus. Incidentally, it probably was a planktivore; though it probably relied on the less productive tropical plankton spawns (not much choice, given the time period).
Nevertheless, these were all truly awesome animals. I look forward to seeing what else these Arctic islands are going to give up.
From UKPets.co.uk, we have this interesting bit of news:
Life In Cold Blood Sells Reptiles
According to the UK pet store chain, Pets at Home, more people than ever are interested in owning a reptile as a pet, thanks to BBC’s Life in Cold Blood series. The company reports that sales of Fire-bellied Newts and Albino Clawed Frogs have more than doubled in some stores.
Following the debut of the Sir David Attenborough series on 3rd February, and its second instalment[sic] the following week, Pets at Home received a surge of enquiries from customers regarding keeping reptiles and amphibians as pets.
Follow the link for more. I think that this is just awesome that a documentary can spark the public’s interest this much. it will be interesting to see if an effect similar to this will be seen when the series hits U.S. shores.
Till then, I wait…and remind folks that while the interest in owning a reptile as a pet is great; do make sure that you have done your homework on the particular species that you are interested in maintaining. After all, we are talking about living beings here; not toys.
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.
Just announced today in the journal PNAS, is the discovery of the world’s smallest pterosaur. Dubbed: Nemicolopterus crypticus, this little guy had a wingspan of only 10 inches (25.4 cm). I haven’t had a chance to read the paper on it yet, but from the abstract, it appears to be a juvenile. I’d like to know how much larger the authours believe N.crypticus got.
Either way, this is big news for pterosaur researchers. It means that either:
A.) Pterosaurs covered a greater size range than previously thought, or…
B.) Pterosaur juveniles lived in different niches than adults.
Given the reptilian status of pterosaurs, I wouldn’t be surprised if it did turn out to be choice B. The large size discrepancy between adults and hatchlings / juveniles, often results in the formation of two size classes per species. This allows the animals to better exploit their given ecosystems.
Anyway, we’ll just have to wait for the paper, and see what the results suggest.
I just found out that David Attenborough’s latest (and possibly greatest) documentary series: Life in Cold Blood is now out on BBC One.
I remember talking to a fellow who was working on this series, about 2 years back. At the time, he mentioned that the goal was to portray reptiles doing things no one had ever seen before. It sounded great, and now I’m looking forward to seeing how successful it was in its portrayals.
Unfortunately, as a citizen of the U.S., I’m going to have to wait until it gets released on DVD here, much like Planet Earth, or Life in the Undergrowth…or Blue Planet: Seas of Life…or…you get the point.
Damn you BBC. Why do you have to make such enticing programming. >:)
Anyway, for those in the same boat as me, make sure to visit the official site. It features clips and interesting behind the scenes shots. We might not be able to watch it yet, but we can at least whet our appetites.
