• Crocodiles and turtles are not reptiles? CNAH thinks so.

    Posted on by Jura 4 Comments

    For all those playing the home game, here is the story thus far:

    Reptilia, the group, was created back in the early days of taxonomy. Its coiner, Carolus Linneaus (upon whom we get the dominant form of classification today), created the group to house all the critters that were neither mammalian, nor avian. Reptilia was originally a wastebin that housed all extant reptiles, as well as spiders and sharks.

    Over the decades, classification schemes became more refined and the definition of Reptilia became more restricted until it eventually resulted in the definition we have today. Namely that group that incorporates snakes, lizards, turtles, crocodylians, and tuataras. A group defined (or once defined depending on ones systematic leanings) as a collection of animals all sharing epidermal scales, being bradymetabolic (or more erroneously, ectothermic), and sharing a series of skeletal affinities such as a small, or absent tabular, a large post-temporal fenestra, a suborbital foramen and a supraoccipital plate that is narrow.

    This definition worked and served herpetologists and paleontologists well for decades. Then in the 70’s a new classification scheme came along. Deemed cladistics, it focused less on shared characteristics and more on shared, derived characters.

    For example: Humans have hair and five fingers. The five fingers are a shared character with all other tetrapods (terrestrial vertebrates and their secondarily aquatic descendants). Meanwhile the hair is a shared, derived character with mammals.

    Obviously the terms shared and shared derived (or plesiomorphy and synapomorphy, in the technical sense) are going to depend on one’s frame of reference. For instance if one was going to look for a synapamorphic trait for humans compared to rats, then hair wouldn’t work. Fingernails and tailessness would. Compare humans to other apes and now these last two characters don’t work either, so one must look for something else.

    So on and so on.

    Cladistics had a rocky start, but was eventually accepted as the main means of determining evolutionary relationships. Though there are still a few staunch detractors, the overall view on cladistics is that it is the most true way of expressing evolution.

    Since cladistics groups creatures by their shared derived characters, once one is on a branch of the cladistic tree, one stays there. Creatures can split from this branch, but they will always be retained.

    See the following figure for an example:



    Note how even though sharks, crocodiles and rabbits have all split from the vertebrate branch, they are still retained on it.? Since branches can infinitely split, there is no trouble with showing evolutionary relationships this way. It creates a view of evolution as a very thick bush; which is a fairly accurate representation of the results of this process.

    In terms of phylogenetics, this is just fine.? Cladistics kicks butt.

    Unfortunately, some ardent supporters of cladistics thought that this method might work well in terms of classification.

    Now some of you might be shaking your head right now thinking that phylogeny and classification are the same thing. They are not.

    Classification is the act of categorization. It is an arbitrary way for humans to order what they see in the world around them. We classify everything!

    Cars are broken down into their manufacturer and their model. That’s classification.

    Clothing is broken down into seasons, body type and general design. Once again, classification.

    Google breaks search results into web, images, shopping, scholarly texts, etc. That is classification.

    Now there are those liberal arts types out there that like to think that classification only limits our perceptions and creates unwanted stereotypes. While this is partly true, the alternative is a world without order. If our brains worked differently this might be fine, but our current neurological makeup is such that a chaotic hodgepodge of things without names and categories, only results in confusion.

    Like it or not, we will always need to classify things. The trick is not to let the classification completely colour our perceptions.

    Coming back on track, certain systematists felt that the all inclusive nature of cladistics would work well with classification. So new rules were implemented. From now on a group could no longer be defined by its characters. Rather, its definition would now be dependent on a completely arbitrary association of members.

    For instance snakes are no longer classified based off of being limbless, and lacking both temporal bars among other things. Instead they are now defined as being the group that contains all members that evolved between boas and blindsnakes. To put it in a more exaggerated sense: boas are snakes because snakes include boas. This classification is completely circular and meaningless.

    However it is also stable. 20 years from now, the definition of snake will remain the same. For some systematists the stability of the name outweighs its lack of substance.

    Another rule enacted was that only groups that contain an ancestor and all its descendants would be considered a “natural” or “real group.”

    On the outset this might not seem a problem. Humans are hominids. Hominidae includes us and a few other apes. No big deal. Birds, as neornithines, include every single bird you see flying around today. Again no problem.

    But what about larger groups. Especially groups like Reptilia, that were originally believed to have given rise to numerous other groups (birds and mammals). What of Osteichthys, the group that gave rise to every land vertebrate today.

    Starting to see the problem yet?

    The old definition of Reptilia no longer held up. Reptiles excluded one of their descendants; the birds. This made Reptilia paraphyletic (ancestor and some of its descendants). In order to “fix” this alleged problem, birds would need to be incorporated into the meaning. The result: birds are now reptiles.

    Well, in some circles.

    This kind of all inclusive naming scheme has been met with intense resistance. So much so, in fact, that 30 years after its inception, dinosaur paleontology seems to be the only branch of biology that actually follows these rules. Every other field seems perfectly content with paraphyletic groups.

    And hey, why not? Paraphyly makes perfect sense in terms of classification. It is much easier to grasp the concept that whales evolved from cows, rather than calling whales cows.

    Alas this battle appears to be far from over. For whatever reason, Reptilia seems to be at the heart of the argument. Many herpetologists, ornithologists and paleontologists are perfectly happy with leaving birds out of reptiles. Other paleontologists are not, and continue to do away with the old definition. Some have even gone so far as to try and remove Reptilia altogether from classification.

    So back and forth it goes. This continuous arguing has made things a little confusing for students of evolutionary theory. When it comes to classification the bickering between both sides can be enough to turn students away, or at least give them a headache.

    So the Center for North American Herpetology decided to take matters into their own hands and reclassified Reptilia all on their own.

    Idealistic to be sure (I like the idea of a crocodylian and chelonian class), but controversial. CNAH decided that the most accepted version of reptile is one that doesn’t include either turtles or crocodiles.

    What the hell were they thinking?

    Needless to say, I doubt that this will catch on.

    ~Jura


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  • Whedon FTW!

    Posted on by Jura 3 Comments


    As most web savvy “web 2.0” folks out there, I’m a huge fan of Joss Whedon.

    The man gave us the incredible Buffy the Vampire Slayer series, as well as the equally impressive Angel, and the short lived (but well loved) series: Firefly.

    Joss Whedon also has a hefty comic book following, with season 8 of Buffy, and the “spin off” series: Fray.

    Now he gives us: Dr. Horrible.

    It’s a musical…about a supervillain.

    I mean, really, talk about left field…

    Currently there is only a trailer up through vimeo, but the mini-series is set to air on July 15th.

    As a card carrying geek and Whedonphile, I am doing my duty and passing the word on to all other Joss Whedon fans.



    Dollhouse is still a few months away. Till then, let’s help Joss stick it to the man (of course, he sort of is the man, but no matter), and support Dr. Horrible.

    ~Jura


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  • The old grey sauropod just ain’t what she used to be.

    Posted on by Jura 2 Comments

    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.

    Image borrowed from the Old Dinosaur Books site

    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.

    Bertalanffy growth equation

    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.

    This entry was posted in Dinosaurs Uncategorized and tagged

  • So, why go bipedal?

    Posted on by Jura 6 Comments

    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.

    Clemente, C.J., Withers, P.C., Thompson, G., Lloyd, D. 2008. Why Go Bipedal? Locomotion and Morphology in Australian Agamid Lizards.J. Exp. Bio. 211: 2058-2065

    Abstract:

    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.

    The final complaint comes from the supplementary movies given.

    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.


    This entry was posted in Extant Reptiles Lacertilia Uncategorized and tagged

  • Stuff is coming

    Posted on by Jura Comment

    I know what your thinking, and I have no idea what happened to May either.? Things have been busy for me IRL, but I didn’t want to leave the site hanging.

    Anyway, I have some time off coming,? so I’ll be posting something new soon.

    Till then: R.I.P. George Carlin. You will be missed, but never replaced.


    This entry was posted in Uncategorized

  • Lizards prove evolution can happen rapidly.

    Posted on by Jura 4 Comments

    I’m a little behind on this now 3 day old story. It’s been hard to get back into the proverbial swing of things. I believe part of it has to do with the large dearth of nothing that occurred during my “vacation.” The other part probably has to do with being bloody busy. >:)

    Here’s the story.

    And here’s a brief excerpt:

    In 1971, scientists transplanted five adult pairs of the reptiles from their original island home in Pod Kopiste to the tiny neighboring island of Pod Mrcaru, both in the south Adriatic Sea.

    …

    After scientists transplanted the reptiles, the Croatian War of Independence erupted, ending in the mid-1990s. The researchers couldn’t get back to island because of the war, Irschick said.

    …

    The transplanted lizards adapted to their new environment in ways that expedited their evolution physically, Irschick explained.

    The big and most interesting part of this story is how these amazing little saurians evolved new behaviours, a majour change in diet and they evolved a new physical characteristic (cecal valves in the intestine).

    All of this happened in only 36 years!


    Italian wall lizard

    Podarcis sicula; a representative of the species used in the study. Also, a bit of a show-off.

    That’s not just amazing, it’s bloody phenomenal!

    Prior to this study, the only thing that even came close (in tetrapods) was an “earlier” study by Jonathan Losos on Caribbean Anolis. In one study, Losos found rapid evolution of longer hindlimbs in introduced species of Anolis in as little as 14 years. The results were interesting, but were more a case of an amazing case of Natural Selection changing the frequency of a naturally occurring variation. This latest study is a little different. The kind of changes noticed here are normally the ones talked about in insects, or bacteria (i.e. large phenotypic changes).

    It has been argued by some that this finding might be viewed as more fuel for the nutty creationist movement. Proving that evolution can occur quickly, means that creationists can argue better for a Young Earth. However, since the core tenet of creationism is that life does not evolve, this would do quite the opposite for them.

    What this does bolster evidence for is Gould and Eldredge’s theory of Punctuated Equilibria.

    The theory states that most of the time, populations of organisms remain fixed and stable, with very little evolution occurring. Then, when a portion of the population gets segregated and/or are forced to adapt to a different environment, evolution kicks into high gear. Change happens rapidly, and the new population becomes a new species.

    That was a bit simplified, but you get the point.

    Gould and Eldredge used fossil trilobites to support their case. Studies on plants and insects have also shown that this type of speedy evolution can happen. Now we have proof in a relatively large vertebrate as well.

    I think these kinds of observations are good for the biological and paleontological sciences. I think that there is a tendency for paleontologists to “ride the brake” with evolution. Always insisting on measuring evolutionary change in millions and tens of millions of years. I don’t have a problem with this type of thinking when one is looking at changes in whole families and genera, but it seems very unlikely that many of the species seen in the fossil record were evolving so slowly from species to species (e.g. Tyrannosaurs, or mosasaurs). Showing that speedy evolution does happen, helps to better support a more “punctuated” view of evolution. One in which whole genera can arise in as little as a few thousand (or hundred thousand) years.

    Geologically speaking; that’s pretty damned fast.

    ~Jura


    Herrel A, Huyghe K, Vanhooydonck B, Backeljau T, Breugelmans K, Grbac I, Van Damme R, Irschick DJ. (2008) Rapid large-scale evolutionary divergence in morphology and performance associated with exploitation of a different dietary resource. Proc Natl Acad Sci U S A. 105(12):4792-4795.


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  • Stateside and XPed again.

    Posted on by Jura Comment

    The last few days of my Sydney trip were spent in relative internet silence. During my stay Windows Vista had incurred one of those OS crippling problems that it is so often known for. In this case, I was trying to watch a video of something that wouldn’t open in anything short of Windows Media Player. I had had the media player open to play some music at the time (Tool FTW!), and Vista couldn’t seem to decide which application had priority (*Hint* it would be the one that I am repeatedly trying to open).


    Vista

    Long story short, Windows Explorer crashed.

    Then it restarted.

    Then it crashed again.

    Lather, rinse, repeat.

    Somewhere along the lines a registry change occurred that didn’t get put back and so Explorer got stuck in an infinite loop. I had already dealt with this exact same problem when Explorer would keep crashing upon viewing the C drive. This time, though, it was on the desktop. This meant I couldn’t access most of the programs without doing long work arounds (e.g. opening programs in Firefox). It didn’t matter anyway. Even after a registry clean, or two, Explorer maintained its broken status. The only way to fix it would be to go into the registry, find the problem and manually change it. The only way to do that would have been to go through the command line interface (even Safe mode kept repeatedly crashing).

    Well anyone who has hacked around with Windows knows how awkward it is to deal with their token command lines. In the end I wound up reverting back to the factory conditions.

    Now I’m back in the states and my PC is Vista free. Like legions of other former Vista users, I “downgraded” to XP again. Now my PC runs faster, rarely crashes and has more free space.

    Note to Microsoft: You might want to up the development of Windows 7 a little. As it stands now, Vista is pushing to take the crown away from ME as the worst MS operating system in history.

    In other news Australia was a blast.


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  • Killing time in Sydney

    Posted on by Jura Comment

    I was hoping I would have been back in the saddle by now, but not so much yet. I’m spending the rest of this week in Sydney, Australia (beautiful place, even if I did come at the wrong time of year).

    There still hasn’t been much in the way of herp news. Though there was a recent paper that came out on turtle origins that I feel the urge to talk about. We’ll see though.

    For those still in the U.S. David Attenborough’s Life in Cold Blood series should just be starting up on Animal Planet. Sounds like a ripe time for me to pick up the series on DVD now. On the bright side, David Attenborough’s heavy involvement in the series should mean that American audiences should be treated to the same top notch narration that the U.K. got.

    That’s it for now. For the Aussie locals, I’ll be killing time in Randwick Junction, Coogee Bay, and UNSW. If you guys have any suggestions on stuff to do, please feel free to drop me a line.

    ~Jura


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  • Taking a trip.

    Posted on by Jura Comment

    I’ll be off for the next couple of days. I have an overseas trip to take. Once I’ve settled in, things should be back to normal. Till then, the site is going to be slow…

    Not like it hasn’t already been slow. During the past week, the only real news in the herp world seems to be that the news organizations have finally found the tuatara story.

    Maybe I’ll get lucky, and some big herp news will come out during my interim.

    ~Jura


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