• Mechanics of bipedalism suggest dinosaurs had to be warm-blooded. Or: Why the aerobic capacity model needs to be retired.

    The old "cold blooded or warm blooded" argument once again rears its ugly head.

    [Editor’s note: A response from the authors can be found here. It answers many of the questions I had about the paper, though I feel the biggest question remains open for debate. I appreciate the authors taking their time to answer my questions, and PLoS ONE for allowing this type of open communication.]

    This post has taken an inordinate amount of time to write up. Mostly because it required finding enough free time to sit down and just type it out.  So I apologize ahead of time for bringing up what is obviously old news, but I felt this paper was an important one to talk about, as it relied on a old, erroneous, but very pervasive, popular and rarely questioned hypothesis for how automatic endothermy (mammal and bird-style “warm-bloodedness”) evolved.

    Back in November, a paper was published in the online journal: PLoS ONE. That paper was:

    Pontzer, H., Allen, V. & Hutchinson, J.R. 2009. Biomechanics of Running Indicates Endothermy in Bipedal Dinosaurs. PLoS ONE.Vol 4(11): e7783.

    Using muscle force data for the hindlimbs of theropods, and applying it to a model based on Pontzer (2005, 2007), the authors were able to ascertain the approximate aerobic requirements needed for large bipedal theropods to move around. Their conclusion was that all but the smallest taxa had to have been automatic endotherms (i.e. warm-blooded).

    Time to stop the ride and take a closer look at what is going on here.

    In 2004, John Hutchinson – of the Royal Veterinary College, London UK – performed a mathematical study of bipedal running in extant taxa. He used inverse dynamics methods to estimate the amount of muscle that would be required for an animal to run bipedally. He then tested his models on extant animals (Basiliscus, Iguana, Alligator, Homo, Macropus, Eudromia, Gallus, Dromaius, Meleagris, and Struthio). The predictive capacity of his model proved to be remarkably substantial and stable (Hutchinson 2004a).  A follow up paper in the same issue (Hutchinson 2004b) used this model to predict bipedal running ability in extinct taxa (Compsognathus, Coelophysis, Velociraptor, Dilophosaurus, Allosaurus, Tyrannosaurus and Dinornis).  Results from this study echoed previous studies on the running ability of Tyrannosaurus rex (Hutchinson & Garcia 2002), as well as provided data on the speed and agility of other theropod taxa.

    The difference between effective limb length and total limb length in the leg of Tyrannosaurus rex

    Meanwhile in 2005, Herman Pontzer – of Washington University in St. Louis, Missouri – did a series of experiments to determine what was ultimately responsible for the cost of transport in animals. To put it another way: Pontzer was searching for the most expensive thing animals have to pay for in order to move around. One might intuitively assume that mass is the ultimate cost of transport. The bigger one gets, the more energy it requires to move a given unit of mass, a certain distance. However experiments on animals found the opposite to be the case. It actually turns out that being bigger makes one “cheaper” to move.  So then what is going on here?

    Pontzer tested a variety of options for what could be happening; from extra mass, to longer strides. In the end Pontzer found that the effective limb length of animals, was ultimately the limiting factor in their locomotion. Effective limb length differs from the entirety of the limb. Humans are unique in that our graviportal stance has us using almost our entire hindlimbs. Most animals, however, use a more crouched posture that shrinks the overall excursion distance of the hindlimb (or the forelimb). By taking this into account Pontzer was able to find the one trait that seemed to track the best with cost of transport in animals over a wide taxonomic range (essentially: arthropods – birds).

    This latest study combines these two technique in order to ascertain the minimum (or approx minimum) oxygen requirements bipedal dinosaurs would need in order to walk, or run.

    As with the previous papers, the biomechanical modeling and mathematics are elegant and robust. However, this paper is not without its flaws. For instance in the paper the authors mention:

    We focused on bipedal species, because issues of weight distribution between fore and hindlimbs make biomechanical analysis of extinct quadrupeds more difficult and speculative.

    Yet this did not stop the authors from applying their work on bipeds, to predicting the maximum oxygen consumption of quadrupedal iguanas and alligators. No justification is ever really given for why the authors chose to do this. Making things even more confusing, just a few sentences later, it is mentioned (ref #s removed to avoid confusion):

    Additionally, predicting total muscle volumes solely from hindlimb data for the extant quadrupeds simply assumes that the fore and hindlimbs are acting with similar mechanical advantage, activating similar volumes of muscle to produce one Newton of GRF. This assumption is supported by force-plate studies in other quadrupeds (dogs and quadrupedal chimpanzees)

    The force plate work cited is for quadrupedal mammals. However, mammals are not reptiles. As Nicholas Hotton III once mentioned (1994), what works for mammals, does not necessarily work for reptiles. This is especially so for locomotion.

    In many reptiles (including the taxa used in this study) the fore and hindlimbs are subequal in length; with the hindlimbs being noticeably longer and larger. Most of the propulsive power in these reptiles comes from the hindlimbs (which have the advantage of having a large tail with which to lay their powerful leg retractor on). The result is that – unlike mammals – many reptiles are “rear wheel drive.”

    The last problem is by far the largest, and ultimately proves fatal to the overall conclusions of the paper. The authors operated under the assumptions of the aerobic capacity model for the evolution of automatic endothermy.

    It is here that we come to the crux of the problem, and the main subject of this post.

    Continue reading  Post ID 516

  • 2.9 upgrade

    Recently went through the hoopla involved with getting WordPress upgraded (needed to upgrade the MySQL database). Everything appears in working order, barring some strange “?” symbols. I’ll have to figure that out later.

  • The dangers of documentaries.

    I just had to post a link to the current discussion on the treatment of science in current documentaries.

    SVPOW’s Matt Wedel was on the recent Discovery Channel docu-travesty: Clash of the Dinosaurs. While scientists who work with the media, have gotten used to having their data distorted a bit and hyperbolized for the alleged sake of “entertainment,” Matt actually had his words chopped up and edited in such a way as to make it sound like he was advocating a now well outdated view of dinosaur anatomy.

    This blatant case of slander has raised the question of what one should do in this situation. It has also brought up the broader question of how scientists should handle the media. Should we just sit back, hoping that the interviewers will present the facts as best they can, and then deal with any possible blowback if/when that fails? Should scientists demand tighter editorial control over what is shown in videos like these? We are their scientific consultants after all. Theoretically they need us for legitimacy; which gives us a bargaining chip.

    I don’t know what the right answer is. The least I can do is help Matt pass this info along so future researchers who are asked for an interview, can ask the production crew for assurances that they won’t be slandered in the final product.

    Post your thoughts over on SVPOW, and pass the story on.


  • New study suggests that group nesting should be the norm – not the exception – in reptiles.

    A colony of _Eumeces fasciatus_ brood their eggs.
    A colony of Eumeces fasciatus brood their eggs.

    Continuing my trend of “catching up,” an article in the November issue of Natural History magazine, talks about a new study in the Quarterly Review of Biology, that finds group nesting to be very common place among extant reptiles.

    That study would be:

    Doody, J.S., Freedberg, S., Keogh, J.S.? 2009. Communal Egg-Laying in Reptiles and Amphibians: Evolutionary Patterns and Hypotheses. Quart. Rev. Biol. Vol.84(3):229-252.

    In the paper, Doody et al (no laughing) did a massive search through the herpetological literature (both technical journals, and hobbyist magazines) to look at instances of communal egg laying in reptiles and amphibians (herps). I’m not being hyperbolic here either, as the paper states:

    In total, our assembled database was gathered from 290 different sources, including 176 different scientific journals, 72 books or book chapters, 29 unpublished reports, and 13 unpublished theses. We also have included a number of reliable personal communications from herpetologists.

    What the authors found was that group gatherings of herps are vastly more common than previously believed. Group egg laying was found to be present in 345 reptile species. Now you might be thinking 345 really isn’t all that much for a group composed of some 8700 species.

    Well then aren’t you a Debbie Downer?

    _Ophisaurus attentuatus_ brooding her eggs.
    Ophisaurus attentuatus brooding her eggs.

    Seriously though, the authors address this by mentioning:

    Although the difficulty in locating nests hampers our ability to determine the actual frequency of communal egg-laying among species, we can better estimate this proportion by dividing the number of known communally egg-laying species by the total number of species, excluding those for which eggs have not been found. We conducted such a calculation for the three families of Australian lizards known to include multiple communally egg-laying species—Gekkonidae, Pygopodidae, and Scincidae—as gleaned from the Encyclopedia of Australian Reptiles database (Greer 2004). Proportions of these lizard families known to lay communally were 4–9%, but, when we exclude species for which nests are not known, these values rise dramatically to 73–100%

    The biggest take home message to get from Doody et al’s review, is just how much we don’t know about extant reptiles.

    …the present review highlights our inadequate knowledge of the nests and/or eggs of reptiles. For instance, the eggs or nests are known in only 7% of Australian lizards of the three families that commonly lay communally (N = 411 oviparous spp.) (Greer 2004).The extent of this knowledge for Australian lizards is probably similar to that for reptile eggs on other continents, particularly South America, Africa, and Asia, where the reproductive habits of reptiles are poorly known. This is in stark contrast to other vertebrates such as birds, for which complete field guides to the eggs and nests are available for several continents

    Indeed, just by doing the brief research run needed to compile this blog post, it was apparent that communalism is much more common in reptiles than anyone ever thought. However, because so many of these reports are either anecdotal, or buried in obscure journals, it is easy to miss all the many cases where it is known.

    This discovery lead the authors to the inevitable follow up question of: “why?” What benefit do mothers gain by nesting communally?

    Numerous hypotheses for why animals nest communally, have been proposed.

    • Saturated habitat (only so many suitable nest sites)
    • Sexual selection (choice of males that live in a particular area)
    • Artifact of grouping for other reasons
    • Attack abatement (easier to hide a bunch of eggs in one site, than in multiple sites. Less chance that your eggs will be the ones that are eaten).
    • Maternal Benefits (save time and energy finding a suitable nest site by “freeloading”)
    • Reproductive success (if the nest site worked once before…)
    • Egg insulation

    The authors reviewed all of these possible reasons for communal egg laying in herps. In the end, they found evidence for both the maternal benefits hypothesis, and the reproductive success hypothesis, though they felt a mixed model better explained things.

    Python brooding her eggs.
    Python brooding her eggs.

    Sadly, though the authors mentioned how a lack of information on the natural history of most reptiles is largely responsible for this sudden revelation about their nesting behavior, they nevertheless make repeated mentions of how “social interactions are generally less complex in reptiles and amphibians than in other tetrapods” or how herp sociality forms “relatively simple systems“.

    The reality is that the old view of simplistic “loner” reptiles that only come together to mate, is not accurate. This is especially true for parental care in reptiles.

    The popular view (among the public, and the scientific community) is that reptiles are? “lay’em and leave’em” types when it comes to reproduction. Despite all the herpetological knowledge to the contrary that has been acquired in the past 50 years, it is still popular to spout the party line about reptiles being “uncaring parents.”

    Zoologist Louis Somma took issue with this view of reptilian (in particular, chelonian and lepidosaurian) parenting. He conducted a literature search to see how often mentions of parental care in reptiles are recorded. In the end he wound up finding 1400 references to parental care in reptiles (Somma 2003)!

    Somma’s survey covered various aspects of parental care. He found reported evidence of nest building and / or guarding in tortoises like Manouria emys (McKeown 1999), Gopherus agassizii (Barrett & Humphreys 1986) and 4 other species of chelonian.

    Turning to lepidosaurs, Somma found parental behaviour to be present in 133 species of lizards and 102 species of snakes. Even a species of tuatara (Sphenodon punctatus) is known to guard its nests (Refsnider et al. 2009). Though these numbers appear small compared to the total amount of species that have been described; much like the Doody et al. paper, this is just based off of species whose nesting behaviours we do know. That these taxa all span a wide phylogenetic range, suggests that parental care is more commonplace than initially thought.

    Nest guarding is usually a maternal trait, but some squamates exhibit nest guarding behaviour in both parents, such as some cobra and crotaline snakes (Manthey and Grossman 1997) , as well as tokay geckos (Zaworski 1987).

    Not only active guarding of the nest, but actual brooding of the eggs is also commonly reported in squamates such as various python species (Harlow & Grigg 1984, Lourdais et al. 2007), and skinks (Hasegawa 1985, Somma & Fawcett 1989). Some species are even known to groom their newly hatched young (Somma 1987).

    More interesting still are various reports and observations of parental feeding in some reptile species, such as the skink Eumeces obsoletus (Evans 1959), and the cordylid lizard Cordylus cataphractus (Branch 1998). Not to mention recent evidence of parental feeding in captive crocodylians.

    This leads me to the only reptile group where parental care is well publicized: that of the 23 extant crocodylian species. I could, at this point, list references for parental care in crocodylians. However because this behaviour is so well documented for this group, it would seem unnecessary. It is? better to shed light on the many (MANY) examples of parental care in other reptile species. I also didn’t include related examples like placental evolution in the skink genus Mabuya, or instances of egg binding in captive reptile mothers; due to a lack of appropriate substrate to lay their eggs.

    In the end, the paper by Doody et al. adds to a growing body of evidence which suggests that the “lay’em and leave’em” reptile species of the world, are the exceptions? and not the rule.

    ~ Jura

    Next time: Biomechanics of running suggest “warm-blooded” dinosaurs. Or: why the aerobic capacity model needs to die already.


    Barrett, S.L. & Humphrey, J.A. 1986. Agonistic Interactions Between Gopherus agassizii (Testudinidae)
    and Heloderma suspectum (Helodermatidae). Southwestern Naturalist, 31: 261-263.
    Branch, B.. 1998. Field Guide to Snakes and Other Reptiles of Southern Africa. Third revised edition. Sanibel Island: Ralph Curtis Books Publishing.
    Doody, J.S., Freedberg, S., Keogh, J.S.? 2009. Communal Egg-Laying in Reptiles and Amphibians: Evolutionary Patterns and Hypotheses. Quart. Rev. Biol. Vol.84(3):229-252.
    Evans, L.T. 1959. A Motion Picture Study of Maternal Behavior of the Lizard, Eumeces obsoletus Baird and Girard. Copeia, 1959: 103-110.
    Harlow, P and Grigg, G. 1984. Shivering Thermogenesis in a Brooding Python, Python spilotes spilotes. Copeia. Vol.4:959?965.
    Hasegawa, M. 1985. Effect of Brooding on Egg Mortality in the Lizard Eumeces okadae on Miyake-jima, Izu Islands, Japan. Copeia, 1985: 497-500.
    Lourdais, O., Hoffman, T.C.M., DeNardo, D.F. 2007. Maternal Brooding in the Children’s Python (Antaresia childreni) Promotes Egg Water Balance. J. Comp. Physiol. B. Vol.177:560-577.
    Manthey, U. and W. Grossman. 1997. Amphibein & Reptilien S?dostasiens. Natur und Tier Verlag, M?nster.
    Mckeown, S. 1999. Nest Mounding and Egg Guarding of the Asian Forest Tortoise (Manouria emys). Reptiles, 7(9): 70-83.
    Refsnider, J.M., Keall, S.N., Daugherty, C.H., & Nelson, N.J. 2009. Does nest-guarding in Female Tuatara (Sphenodon punctatus) Reduce Nest Destruction by Conspecific Females? Journal of Herpetology. vol.43(2):294-299.
    Somma, L.A. 1987. Maternal Care of Neonates in the Prairie Skink, Eumeces septentrionalis. Great Basin Naturalist, 47: 536-537.
    Somma, L.A. & Fawcett, J.D. 1989. Brooding Behaviour of the Prairie Skink, Eumeces septentrionalis, and its Relationship to the Hydric Environment of the Nest. Zoological Journal of the Linnean Society. Vol.95: 245-256.
    Somma, L. 2003. parental Behavior in Lepidosaurian and Testudinian Reptiles: A Literature Survey. Krieger Publishing Company. 174pgs. ISBN: 157524201X
    Zaworksi, J.P. 1987. Egg Guarding Behavior by Male Gekko gecko. Bulletin of the Chicago Herpetological Society, 22: 193.
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  • Bone histology says ectothermic goats, but does it?

    Once again the blog has taken a backseat to my real life work. It’s unfortunate too as there have been at least three really interesting news stories / technical papers that I feel the need to tackle. The first story I want to talk about is the news of the ancient Mediterranean goat: Myotragus balearicus, and its alleged “reptilian” physiology.

    Myotragus balearicus reconstruction.
    Myotragus balearicus reconstruction.

    On the outset M.balearicus appears like your standard goat; complete with horns, hooves and (likely) a penchant for eating practically anything. The part that makes M.balearicus stick out the most? is that it was a native inhabitant of small islands in the Mediterranean.? Modern goats reach islands through human intervention. There, they become invasive elements that often damage the native flora and fauna. Without human intervention, it is hard for goats – and indeed? most mammals – to become established on islands. Both getting to the islands, and surviving on them tend to require animals that are more metabolically adaptable. Despite their catholic diets, goats are still limited by the “always on” nature of mammalian metabolism.

    At least, that’s what we thought.

    Researchers at the Institute of Paleontology at the Autonomous University of Barcelona, looked at microslices of the bones in this goat. What they found was a pattern of bone deposition that is unusual for ungulates. Rather than have layers of bone strewn about in an interwoven pattern, the bone of M.balearicus was laid down evenly in concentric layers. The latter formation is often assumed to be a hallmark of reptiles and other “slow growing” animals. With this in mind, the authors suggest that M.balearicus had evolved a more plastic metabolism.

    These findings lend support to the model that posits a shift in life history strategies to a lower end of the growth rate spectrum, in areas where mortality remains low.

    The results, while interesting, bother me a bit, as they rely on certain views on reptile growth strategies that are known to be false.

    For instance:

    Ectotherm vertebrates have slow and flexible growth rates…

    Ectotherms are characterized by lamellar-zonal bone throughout the cortex.

    True zonal bone with growth marks deposited seasonally throughout ontogeny is a general ectotherm characteristic. In ectotherms, the bone matrix consists of slow growing lamellar bone.

    While it is true that there are ectotherms that grow in a cyclical manner like this (especially animals from temperate regions), this is not a given for all ectotherms. In fact, it has since been well documented that fibrolamellar bone deposition occurs normally in crocodylians, as well as turtles (Reid, 1997).

    It is a tad strange, as the authors do cite the Turmarkin-Deratzian gator paper, but they erroneously use it as an example of slow growth and contrast it with the fast fibrolamellar growth seen in most ungulates.? There is even a figure in the paper that shows, and even labels fibrolamellar growth in a crocodile, yet appears to get completely glossed over when it comes time to talk physiology.

    Which brings me to my next point. The authors argue that the presence of lamellar zone bone in M.balearicus is suggestive of an ectotherm-like growth strategy. But does lamellar zone bone really indicate slow growth?

    Work by Tomasz Owerkowicz on varanids (Owerkowicz 1997),? found that even the sedentary animals in his control group, could lay down bone at the same rate as his sedentary mammals (Morell 1996). Presumably this bone was lamellar zonal, though without the figures on hand, I can’t say for sure.

    A more prominent example comes from Lieberman and Crompton (1998), who did a stress study on goats and opossums. The authors were looking at the remodeling response of bone to stress, and accidentally came across an interesting growth difference between these two taxa. They found that their opossums grew at a significantly faster rate than their goats, despite both taxa being of a developmentally equivalent stage. The interesting part is that the goat’s were depositing fibrolamellar bone, while the opossums were producing lamellar bone.

    So no, lamellar bone need not be a hallmark of slow growth. Rather, it might be a response of the bones to specific stresses. Lamellar zonal bone is structurally stronger than fibrolamellar bone, so there might have been a more functional need for this type of bone.

    Lastly, I have some issues with the final conclusions asserted by the authors in their closing comments:

    The reptile-like physiological and life history traits found in Myotragus were certainly crucial to their survival on a small island for the amazing period of 5.2 million years, more than twice the average persistence of continental species. Therefore, we expect similar physiological and life history traits to be present in other large insular mammals such as dwarf elephants, hippos, and deer. However, precisely because of these traits (very tiny and immature neonates,low growth rate, decreased aerobic capacities, and reduced behavioral traits), Myotragus did not survive the arrival of a major predator, Homo sapiens, some 3,000 years ago.

    Now I’m sure that there was a need to inject some melodrama at the end (as is typical for many papers), but the assertion that a “reptile-like physiological life history” must also incorporate a small aerobic scope, small neonates and reduced behavioural repertoire, is just uncalled for. All of these are frustratingly common misconceptions about reptiles, and bradymetabolic animals in general. Further, none of these assertions are based on any facts for M.balearicus. The only assertion that could really be tested is the small neonate one, and that appears to be falsified, as data on newborn M.balearicus show that newborns were large and precocial animals; pretty standard fare for an ungulate.

    Overall the results of this study are interesting, and I look forward to seeing if pygmy elephants and hippos also display this apparent “slow growing” bone type. Comparing M.balearicus to reptiles based off this one similarity appears unjustified, and only goes to further perpetuate some common reptile misconceptions.

    Needless to say, Myotragus balearicus was probably not “cold-blooded,” despite what the news headlines would have one believe.

    Next up: Destroying the “uncaring parent” myth.



    Lieberman, D.E., & Crompton, A.W. 1998. “Responses of Bone to Stress: Constraints on Symmorphosis.” Principles of Animals design: The Optimization and Symmorphosis Debate. Weibel, E.R., Taylor, R.C., and Bolis, L. (eds). Cambridge U. Press. Pgs: 78-86. ISBN: 0521586674
    Morell, V. 1996. A Cold, Hard Look at Dinosaurs. Discover. December. Available online.
    Owerkowicz, T. 1997. Effects of Exercise and Diet on Bone-Building: A Monitor Case. Journal of Morphology. V. 232(3): 306
    Reid, R.? 1997. ?Dinosaurian Physiology: The Case for ?Intermediate? Dinosaurs.?? The Complete
    Dinosaur. Farlow, J.O. and Brett-Surman, M.K. (eds.)? Indiana U. Press. Pgs: 449 – 473. ISBN: 0253333490

  • Land lubbing crocs get their day in the sun. Also, there’s a varanid special on NOVA.

    Dr. Paul Sereno stands with others at a meeting for the American Association for the Advancement of Science in Chicago. Note the wheelbarrow like retroarticular processes on the "boar croc."
    Dr. Paul Sereno stands with others at a meeting for the American Association for the Advancement of Science in Chicago. Note the wheelbarrow like retroarticular processes on the "boar croc."

    After spending? a few years collecting and looking at the weirdness that is Gondwanan crocodyliformes, Dr. Paul Sereno has finally started to unveil stuff. With the help of National Geographic comes When Crocs Ate Dinosaurs. It appears to be a special that focuses on the remarkable – and often underrated – diversity seen within this group of animals. The highlight of the program (at least in my opinion) is the focus on all the very un-crocodile like crocodyliformes.

    The National Geographic website has a special section that shows off the various, apparently unnamed, taxa. For now, there are just placeholder names that will likely hurt the eyes and ears of anyone who had to deal with the aftermath of The Land Before Time.

    The artwork is by artist Todd Marshall. I’ve always enjoyed his portrayals of prehistoric reptiles (he tends to get almost too fanciful with dewlaps and spikes though). Sadly the accompanying animations do not do Marshall’s incredible artwork justice.? It will be interesting to see how it all gets integrated into the television show.

    Also airing tonight is a special on NOVA entitled: Lizard Kings. It features the work of Dr. Eric Pianka; a well known and respected lizard ecologist who has focused on monitors for much of his career.? The special looks to be very interesting. Especially given that it appears to have taken years for the film crew to get the footage they needed. As you read this the special has already aired. However, PBS does make their shows avaialable to watch online for free, on their website. The show should also be viewable on Hulu by tomorrow.

    A perentie monitor (_Varanus giganteus_) poses for the camera.
    A perentie monitor (_Varanus giganteus_) poses for the camera.

    I realize that both of these options are only available in the states. To date there seems to be no international options. At best there are some workarounds.

    Still, for those that can get them, both shows should prove to be entertaining.


  • Turns out Komodo dragons aren’t all that unique afterall.

    This might have been a common image for early human settlers of Australasia. Image from Baxterking.com
    This might have been a common image for early human settlers of Australasia. Image from Baxterking.com

    A new study on Komodo dragon phylogeny has found that the mighty ora was, in fact, one of many.

    The paper in question is:

    Hocknull, S.A., Piper, P.J., van den Bergh, G.D., Due, R.A., Morwood, M.J., Kurniawan, I. 2009. Dragon’s Paradise Lost: Palaeobiogeography, Evolution and Extinction of the Largest-Ever Terrestrial Lizards (Varanidae). PLoS ONE 4(9):1-15 doi:10.1371/journal.pone.0007241

    Since this is in PLoS ONE, that means it is freely available. Hooray!

    The authors looked at the skeleton of Varanus komodoensis, V.salvator, and V.priscus (Megalania).? By carefully examining the various bones of the skeleton, the authors were able to determine the taxonomic placement of various large Varanus fossils found in Australia, Indonesia, and Asia.

    In the end their results showed that contrary to popular belief, Komodo dragons are not examples of island giantism, but rather were already large migrants from Australia during periods of low sea level.

    So much for the pygmy elephants scenario.

    Along with finding strong support for the close association of V.komodoensis with V.priscus, the authors also showed that Australia was actually home to many large varanids during the Pliocene/Pleistocene. So while Meglania was certainly the biggest, it wasn’t unique. The authors showed that giantism evolved at least twice in varanids. Once in Asia, and again in Australia.

    The paper also gives support to the statements of Molnar (2004), that the old belief that Komodo dragons (and reptiles in general) only got big because they were isolated from mammalian competitors, is completely false.? The authors point out that both data for the ora, and for another large (though now extinct) varanid – V.silvalensis – show that they existed contemporaneously with large mammalian competitors (hyaenas and tigers). Not only that, but it was on the mainland that they appear to have gotten large in the first place. So not only could large lizards hold their own against “sophisticated” mammalian predators, but they even appeared able to grow to competitive size despite the pressures.

    Finally, the authors also discovered yet another large varanid that lived in Australia before making its way towards Timor. This one was intermediate in size between Komodo dragons and Megalania.

    So it would appear that Australia was not unique in having reptilian megafauna during the Pliocene/Pleistocene.? It seems? that much of Australasia was rife with large, voracious varanids.

    Must have sucked to be an Aborigine back then. >: )


    Hocknull, S.A., Piper, P.J., van den Bergh, G.D., Due, R.A., Morwood, M.J., Kurniawan, I. 2009. Dragon’s Paradise Lost: Palaeobiogeography, Evolution and Extinction of the Largest-Ever Terrestrial Lizards (Varanidae). PLoS ONE 4(9):1-15 doi:10.1371/journal.pone.0007241
    Molnar, R.E. 2004. Dragons in the Dust: The Paleobiology of the Giant Monitor Lizard Megalania. Indiana University Press. 210pgs. ISBN: 0253343747/978-0253343741

  • WordPress upgrade

    If one has noticed a slight change to the blog, it has to do with an upgrade to WordPress. I had been trying get the auto-update to go through, but it was being very stubborn. I have since learned that it was a 1and1 problem (my host), and that I needed to switch to php5.

    Needless to say, the problem has now been solved. If anyone else out there has been having the same problem, or just general issues getting the dashboard to work, consider the php version you are using. It might be what is causing the weirdness.

  • New paper says dinosaurs were endomorphs.

    From left to right: Endomorphic Jay Cutler, Mesomorphic Arnold Schwarzenegger, and Ectomorphic poster-child Frank Zane
    From left to right: Endomorphic Jay Cutler, Mesomorphic Arnold Schwarzenegger and Ectomorphic poster-child Frank Zane

    Endo-what now? Allow me to explain.

    If one studies physical fitness (academically, or practically), then one is bound to come across the three main human body types. The endomorph, mesomorph and ectomorph.

    Endomorphs are characterized by their ability to easily gain weight (be it fat, or muscle).

    Ectomorphs are characterized by their ability to easily lose weight (fat, or muscle)

    Mesomorphs are the middle ground group that appear to have the most malleable bodies.

    In general, endomorphs have lower metabolisms than the other two, while ectomorphs tend to “run hot” all the time. Few people are all one way, or the other, but a notable dominance of one type, or another is usually prevalent.

    The endo/ecto part can get confusing; especially if one is used to these prefixes in the context of endotherm/ectotherm. The names seem to be reversed from what one might normally hear (ectomorphs being more “warm-blooded” than endomorphs etc). The names have nothing to do with thermophysiology. They were coined after the germinative layers of the body during embryonic development. Endoderm forms the digestive tract, and endomorphs are usually stereotyped as fat. Ectotoderm forms the skin, and ectomorphs are usually stereotyped as being “all skin and bones.”

    The reason I went with these specific bodybuilders (Jay Cutler, Arnold Schwarzenegger and Frank Zane) was partly to buck these stereotypes, but also to point out something that the news outlets are missing. Namely that having a lower metabolic state, does not mean one is a “couch potato” or has “forgone exercise.” Bigger, means more massive. That may mean fat, but as one can see above, it also can mean muscle and bone. Dinosaurs were not fatter than mammals. They were bigger.

    So what am I rambling on about?

    Grab a calculator and come along for the ride.

    Continue reading  Post ID 516

  • New paper dispells Komodo myth. Also Megalania may have been the world’s largest venomous animal.

    Megalania chasing down Genyornis newtoni. Illustration by Peter Trusler for Wildlife of Gondwana
    Megalania chasing down Genyornis newtoni. Illustration by Peter Trusler for Wildlife of Gondwana

    Just announced today in the journal: PNAS, is a new comprehensive study on Komodo dragon feeding ecology. The comprehensive nature of the paper is the result of the contributions from around 28 individuals from all over Australia, as well as the Netherlands, and Switzerland.

    The paper in question is:

    Fry, B., Wroe, S., Teeuwissed, W., van Osch, M.J.P., Moreno, K., Ingle, J., McHenry, C., Ferrara, T., Clausen, P., Scheib, H., Winter, K.L., Greisman, L., Roelants, K., van der Weerd, L., Clemente, C.J., Giannakis, E., Hodgson, W.C., Luz, S., Martelli, P., Krishnasamy, K., Kochva, E., Kwok, H.F., Scanlon, D., Karas, J., Citron, D.M., Goldstein, E.J.C., Mcnaughtan, J.E., and Norman, J. 2009. A Central role for Venom in Predation by Varanus komodoensis (Komodo Dragon) and the Extinct Giant Varanus (Megalania) prisca. PNAS Early Release. doi:10.1073/pnas.0810883106

    *catches breath*

    The paper is only six pages long, which downplays just how much work must have gone into this project. The authors used Finite Element Analysis, MRIs, and traditional biochemical and dissectional techniques to look deep into the venom apparatus of the living Komodo dragon (V. komodensis).

    For those who may have missed it on the first go around, it has recently been discovered that venom is more widespread among squamates than previously thought (Fry et al 2005). The authors of that paper (a few of whom are on this paper) found the presence of specific glands at the base of the mandible in numerous lizard species. These glands were found to release salivary proteins that were, in fact, venom.

    It was a “primitive” venom for the most part, with little denaturing, or tissue destroying properties, but enough that it seemed to warrant the construction of a new clade of squamates named: Toxicofera (Fry et al 2005, Vidal & Hedges 2009). Though the discovery of incipient venom production in many squamates, was an intriguing surprise, the resultant cladogram has proven problematic, and controversial. The authors found iguanians (iguanas, chameleons, most pet lizards) to be deeply nested within scleroglossa (skinks, snakes, varanids); a view that flies in the face of every morphological study ever done on this group (e.g. Romer 1956, Pianka and Vitt 2003). In order for Toxicofera’s current associations to be valid, iguanians would have to have re-evolved both their temporal bars, as well as a fleshy tongue. While possible (few things in evolution are impossible), it is extremely unlikely; kind of like expecting snakes to re-evolve limbs.

    Despite this contentious relationship, the discovery of venom glands in animals like monitor lizards, was a surprise. This new study by Fry et al is the first to really look at the venom secreting abilities of this gland, and what it means to Komodo dragon ecology.

    Photo by: Jeff Werner [Fauna vol.1 number 3 Mar 98]
    Photo by: Jeff Werner Fauna vol. 1 (3). March 1998.

    It turns out that the mandibular venom gland in V.komodoensishas six different compartments that open between the teeth of the lower jaw. Unlike venomous snakes and helodermatid lizards, the venom does not travel through any grooves in the teeth. Rather, it appears to pool at their base; bathing the teeth of the lower jaw prior to biting a prey animal. It’s a crude method of venom delivery, but one that might explain why Komodo dragons have such thick gums (which the teeth erupt through during a bite).

    According to the authors, the mandibular venom gland of a 1.6m (5.25ft) Komodo dragon has enough fluid to produce 150mg of venom; 30mg of which would be available for delivery. That’s a fair amount of venom, but how does that translate to toxicity?

    Though the delivery method is crude, the venom is fairly potent. According to the authors it only takes 0.1mg/kg of venom in the blood stream to cause pronounced hypotension, and only 0.4mg/kg to cause hypotensive collapse (fainting).

    To put this into perspective, I weigh approximately 76kg (168lbs). It would take approximately 7.6mg of Komodo dragon venom to make me light headed, and 30mg to knock my arse out.

    Hmm, maybe I should reconsider that Komodo island trip?

    Fry et al go on to discuss how V.komodoensis goes about using this venom delivery system during predation. It was at this point that I became a bit hesitant.

    Komodo dragon feeding ecology has been the subject of much misconception. Much like dinosaurs, earlier work on these beasts was more accurate than the work that soon followed. When Komodo dragons were first discovered, they were thought to be scary top predators of their respective habitat. This was quickly downgraded to obligate scavenger; possibly due to the animal’s willingness to eat prekilled meat, but more likely from general incredulity that a large reptile can actively hunt mammals (see table 10-2 of Auffenberg 1981 for examples). It really wasn’t until Dr. Walter Auffenberg spent some 13 months in the wild with Komodo dragons, that this myth was officially dispelled, and some 20 years after for it to become common knowledge. However, once it was discovered that animals lucky enough to escape from an initial V.komodoensis attack were found to die hours/days later, the view of Komodo dragons as “bite and release” predators was born (e.g. Bakker 1986).

    Auffenberg’s work did show that there is something septic about the bite of oras. This was originally attributed to bacterial flora living in the fairly dirty mouths of these predators. Indeed one study (Gillespie et al 2002) found 54 potentially pathogenic bacteria living in the mouths of oras!

    However, and this is the part that always seems to get glossed over: there has never been a reported case of a komodo monitor using this “bite and release” killing strategy. Despite spending over a year living with these animals, Auffenberg never once found an animal bitten, released and then later tracked down after it died. Komodo dragon attacks were quite the opposite in fact. Small, to relatively large prey (goats, boar) were often killed on the spot using violent side to side shaking to snap the neck, while large prey like water buffalo were hamstringed (Achilles tendon severed), followed by abdominal evisceration of the now paralyzed (and often still alive) animal.

    Despite the gruesome detail in which Auffenberg described ora attacks, as well as the sheer lack of evidence for a viper style feeding strategy; one can still read about how Komodo dragons “avoid confrontation with their prey” by allegedly employing this method of killing (for instance).

    So one can forgive my trepidation over what was to be written about next in the Fry et al paper.

    The authors do discuss the alleged “bite and release” hunting style posited for V.komodoensis, but are quick to point out (as I just did) that there has never been a documented case of this hunting strategy being used on dragon prey.Dr. Fry went went one step further in an interview for Science News:

    What’s more, rare sightings of the lizards hunting didn’t fit with this method. Victims typically died quickly and quietly after going into shock, the authors say. “No one’s actually seen a Komodo dragon track a prey for three days until it dies of septicemia,” Fry says. “It’s an absolute fairy tale.”

    This was very comforting to see. One can only hope that the other news outlets don’t miss this point when doing their write ups (Edit: so much for hope).

    Fry et al then went on to dispel the myth that the mouth of dragons contain toxic microflora. Though there have been studies that have shown the presence of potentially pathogenic bacteria in wild oras, none of these studies found a consistent microflora between individuals. In fact, the authors point out that some of the bacteria found in Komodo dragon mouths, were the same bacteria found in the guts of most lizards.

    That venom must be playing an important role in predation was determined by looking at the evolution of venom in squamates. The authors point out that:

    We have shown that in the species that have developed secondary forms of prey capture (e.g., constricting) or have
    switched to feeding on eggs, the reptile venom system undergoes rapid degeneration characterized by significant atrophying of the
    glands, reduction in fang length, and accumulated deleterious mutations in the genes encoding for the venom proteins (9, 26,
    27). This is a consequence of selection pressure against the bioenergetic cost of protein production (28). The robust glands
    and high venom yield in V. komodoensis thus argue for continued active use of the venom system in V. komodoensis.

    So, while the venom of Komodo dragons is not the primary means by which dragons dispatch their prey, it still must play a pretty important role in prey acquisition. Since envenomated prey tend to become docile and quiet (Auffenberg, 1981, and this paper), it may just play a role in initiating shock, and reducing retaliatory actions by prey. It may also serve as a good “failsafe” in the event of a missed kill. Bitten prey that are “lucky” enough to escape an initial attack, tend to find themselves easily preyed upon shortly thereafter. This is similar to hunting tactics seen in Canadian lynx (the only mammalian carnivores known to have a septic bite) when hunting caribou (Auffenberg 1981).

    Komodo dragon FE skull made by the Computation Biomechanics Research Group. UNSW, Sydney Australia.
    Komodo dragon FE skull made by the Computation Biomechanics Research Group. UNSW, Sydney Australia.

    Using Finite Element Analysis, the authors compared the bite and skull strength of V.komodoensis with that of a similar sized saltwater crocodile (Crocodylus porosus). The results they obtained agreed with previous FE work on Komodo dragons (Moreno et al 2008), which found the bite of oras to be remarkably weak on its own, thus requiring the aid of the postcranial musculature in delivering much of the force. Ora skull strength is at its greatest during bite and pull behaviour. This data agrees well with field observations showing oras biting and pulling back on their prey. Coupled with their recurved and serrated teeth, this results in the creation of large, gaping wounds, which would aid in venom delivery as the ora’s venom would be spread throughout; quickly entering the bloodstream and speeding up shock.

    Finally the authors extrapolated their work to the monstrous lacertilian behemoth Varanus (Megalania) prisca. Using the extant phylogenetic bracketing method (Witmer 1995, 1998), they were able to determine the likelihood of venom being present in Megalania. If true, this would make Megalania the largest venomous carnivore to have ever lived.

    I’m not sure I buy this part. As Fry et al mentioned in the paper, the venom apparatus tends to degrade quickly when not used. Megalania was a big animal (over 2,000 kg according to the authors, though Molnar 2004 places it as just under 2,000kg for the largest individuals). Any hole that V(M)prisca would create when attacking its prey, would have been devastating enough without the need for anticoagulating venom.


    Like the other members of this unique varanid lizard clade, the jawbones of V. prisca are also relatively gracile compared with the robust skull and the proportionally larger teeth similarly serrated (Fig. 3).

    I’d be careful about this assumption, as there is only one fairly complete maxilla (upper jaw bone), and portions of the dentary (tooth bearing lower jaw bone), known for Megalania. This makes comparison with extant monitors, rather hard to do. What little skull bones do exist, show that the skull of Megalania was stronger (or at least, less flexible) than that of other monitor lizards (Molnar, 2004).

    As it stands right now, there are frustratingly too few fossils of Megalania (especially the skull) to accurately say one way, or the other in regards to venom delivery.

    Of course that doesn’t make it any less interesting to speculate about. 🙂



    Auffenberg, Walter, 1981, The Behavioral Ecology of the Komodo Monitor, Florida University press, pgs: 406.

    Bakker, R. 1986. The Dinosaur Heresies. William Morrow. New York. ISBN: 0821756087, 978-0821756089 pgs: 481.

    Fry, B.G., Vidal, N., Norman, J.A., Vonk, F.J., Scheib, H., Ryan Ramjan, S.F., Kuruppu, S., Fung, K., Hedges, S.B., Richardson, M.K., Hodgson, W.C., Ignjatovic, V., Summerhayes, R., Kochva, E. 2005. Early Evolution of the Venom System in Lizards and Snakes. Nature. Vol.439:584-588.

    Gillespie, D., Fredekin, T., Montgomery, J.M. 2002. “Microbial Biology and Immunology” in: Komodo Dragons: Biology and Conservation. James Murphy, Claudio Ciofi, Colomba de La Panouse and Trooper Walsh (eds). pgs: 118-126. ISBN: 1588340732/978-1588340733

    Molnar, R.E. 2004. Dragons in the Dust: The Paleobiology of the Giant Monitor Lizard Megalania. Indiana University Press. 210pgs. ISBN: 0253343747/978-0253343741

    Moreno, K., Wroe, S., Clausen, P., McHenry, C., D’Amore, D.C., Rayfield, E.J., Cunningham, E. 2008. Cranial Performance in the Komodo Dragon (Varanus komodoensis) as Revealed by High-Resolution 3-D Finite Element Analysis. J.Anat. Vol.212:736-746.

    Pianka, E.R., and Vitt, L.J. 2003. Lizards Windows to the Evolution of Diversity. U.Cal.Press. 333pgs. ISBN: 0520234014/9780520234017

    Romer, A.S. 1956. The Osteology of the Reptiles. Krieger Publishing 800pgs. ISBN: 089464985X/978-0894649851

    Vidal, N. and Hedges, S.B. 2009 The Molecular Evolutionary Tree of Lizards, Snakes, and Amphisbaenians. Biologies. Vol.332(2-3):129-139.

    Witmer, L. 1995. “The Extant Phylogenetic Bracket and the Importance of Reconstructing Soft Tissues in Fossils” in: Functional Morphology in Vertebrate Paleontology. Jeff Thomason (ed). Cambridge Univ. Press. Cambridge, UK. pgs 19-33. ISBN 0521629217/978-0521629218

    Witmer, L. M. 1998. Application of the Extant Phylogenetic Bracket (EPB) Approach to the Problem of Anatomical Novelty in the Fossil Record. J.Vert.Paleo. Vol.18(3:Suppl.): 87A.