• Tag Archives reptile
  • It’s over 9,000!

    Last year was a busy year for me. As such the site had to go into dormancy yet again. This year doesn’t look to be any less hectic, but I couldn’t bear to have the site continue to stagnate. So in an attempt to jump-start things again I am going to try and push out some smaller updates.

    Which brings us to our topic.

    The Reptile-Database recently released the current known/generally accepted species count for reptiles. It is now at a whopping 9,952 species! For comparison, when I was growing up the standard species count for reptiles hovered around 6500–6700 species. In fact one can still probably find this widely cited figure in books today. Even when I started the Reptipage some 16 years ago, the total species count was approximately 7,500 species. So in the span of those 16 years, our knowledge of extant reptile diversity has grown by 33%. That’s pretty impressive. Especially when compared to other amniotes. For instance birds are routinely cited as having 10,000 species. The most recent species count for Aves is: 10,530 (IOC World Bird List), an increase of just 5.3%. Mammals were cited as having 5000 species when I was growing up. The most recent (2008) count I could find shows that this class now contains 5,488 species (IUCN Red List); an increase of only 9.8%.

    Part of the reason for the larger spike in reptile species counts vs. mammals and birds is due to a new interest in reptiles themselves. Much of the history of Reptilia is one of revulsion, lumping, and overall wastebinning. However, now with the rise of herpetoculture and the acknowlegement that reptiles represent more than just a “stepping-stone” towards mammals and birds, herpetology has seen a bit of a renaissance in taxonomy. Another reason for this spike in species counts for reptiles can be attributed to the use of molecular techniques to ascertain differences in populations, along with better morphological data (such as those used to help determine that Crocodylus suchus was a real species and not just a variant of the C. niloticus) as well as better ecological data. This spike in species count has come about largely through the elevation of subspecies rather than the discovery of new species (though that is still happening). Herpetology has had a long history of lumping taxa that seem similar enough. This reluctance to split populations into distinct species rather than populations variations had artificially limited the actual species counts. Along with the elevation of subspecies to full species, there has also been a trend to elevate many subgenera to full genus status. This move is somewhat more controversial as the question always pops up of what the ever moving criteria for a genus are. Of course the criteria for species are hardly set in stone either. Ultimately taxonomy is a largely arbitrary affair of biological bookkeeping. Despite this, the need to have these criteria is paramount. The human brain doesn’t work well without categories, even if they are largely self-imposed ones. The appeal of splitting up Reptilia like this is that it reflects a changing attitude about reptiles in general. Though it has been long known that reptiles outnumber mammals, there always seems to be an undercurrent of “but they’re all just the same lizard.” A view that reptiles may be speciose, but are still limited in their body shapes compared to mammals and birds, still pervades today. Hence one reason why there are 29 orders of mammals, some 23 orders of birds, but only 4 orders of reptiles. A move to upgrade subspecies to species and subgenera to genera adds greatly to dispelling the myth that reptiles are the forgettable “intermediate forms” on the tree of life.

    Example of the different “genericometers” of taxonomists. Top left–right: Different members of the Anolis genus: A. proboscis and A. sagrei. Bottom left–right: Different genera of wild cats: Leopardus pardalis and Leptailurus serval. Anolis photos from: Lucas Bustamante and lanare (wikipedia). Serval photo from Giuseppe Mazza. Ocelot photos is unattributed but widely found on the internet

    Regardless of these higher order relationships it looks like Reptilia will officially comprise over 10,000 species by the end of the year [Note: See the comments].

    That is pretty awesome.


  • 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

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

    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.


  • Amazing acrobatic geckos

    wall runner

    High speed pictures of Cosymbotus platyurus running up a vertical surface

    I don’t know why, but for some reason herp news stories always seem to come in twos.

    Announced today (or yesterday by the time I get this posted), scientists at UC Berkeley have found geckos to be one of the most agile climbing animals ever studied.

    Jusufi, A., Goldman, D.I., Revzen, S. and Full, R.J. 2008. Active tails enhance arboreal acrobatics in geckos. PNAS. Vol. 105: 4215-4219.

    Goldman et al studied geckos of the species Cosymbotus platyurus. Lizards were ran on vertical surfaces that had various degrees of traction. To induce slippage, some of the surfaces were equipped with a section of dry erase board which had been covered with dry erase ink.

    Apparently geckos can’t grab onto everything after all.

    By placing the lizards at various sections of these surfaces, the researchers were able to get them to either slightly slip, almost fall, or completely.

    The results were interesting.

    For starters, lizards ran up the surfaces with their tails off the “ground” the entire time. That is, unless they slipped. Immediately upon slipping, the tail would come down and act as a brace to keep the body from tilting back and falling off. The most dramatic case of this came from an experiment in which the researchers had dropped the lizards down straight on the dry erase board. The gecko in question fell backward, caught itself with its hindlegs, and tail. The body fell away from the wall about 60? before the tail fully caught the animal, and it was able to right itself again (see photo above).
    self righting gecko
    By far the neatest test performed involved getting the lizards and placing them in a supine (belly up) position on a light polyethylene foil held together with four fishing lines. Then by gently shaking the platform (or waiting for the lizards to slip), they were able to dislodge the geckos and send them plummeting to their doom.

    Doom, in this case, being an embellishment for safely padded landing area.

    The lizards fell 2 meters down. High speed cameras recorded the first 23cm of that trip. These little guys were able to go from fully upside down to rightside up in only 106 milliseconds.

    Let me make sure I’m getting the full effect of that result across:

    These geckos were able to reorient themselves in 106 THOUSANDTHS of a second, or .00106 seconds!!

    Geckos now hold the record for fasting righting time of a vertebrate without the aid of wings.

    This unique feat is accomplished by rotating the substantial tail on these animals. As they fall, the tail is rotated counterclockwise. Physics does the rest. Conservation of angular momentum takes over and the entire body winds up turning clockwise, thus reorienting the animal. This phenomenon is known as: air righting with zero angular momentum. It’s the same effect that cats are often lauded for.

    Cats, and other air righting mammals (e.g. rats) accomplish their air righting maneuvers by flexing and twisting their backs. Evolution removed the need/use for a large powerful tail in mammals, hundreds of millions of years ago.

    No so with lizards. Thanks to this “fifth appendage” all the geckos needed to do was use their tail like a little propeller. There is, however, a caveat.

    Cosymbotus platyurus, like most geckos, is capable of caudal autotomy (i.e. voluntary tail loss). Would lizards that have lost their tails still be able to right themselves?

    Jusufi et al tested this scenario too. They carefully elicited the loss of the tails in some of their experimental animals, and then subjected them to the same tests as before. The results were striking. Tailless lizards were unable to keep themselves from falling in the vertical slip tests. When they were dropped supine, they still righted themselves, but the rate at which they did it was much slower. Tailless geckos relied on the kind of back flexion and twisting seen in mammals.

    Taking things one step further, the authours decided to see how much of a role the tail plays during free fall. They placed the lizards in vertically oriented wind tunnels and “set them free.” The results were unequivocal; the tail acts as the main rudder in these guys. Geckos would rotate their tails counterclockwise to turn left, and clockwise to turn right, while the body remained a stationary airfoil.

    The overall results demonstrated the incredible importance of tails in geckos. This is interesting given that so many geckos are also willing to part with their tails when in danger.

    It seems that in the natural world it’s better to risk knocking oneself out from a fall, than to risk getting eaten by a bodypart that stubbornly stays on.
    It’s unfortunate that the researchers didn’t test the air-righting ability of these geckos after their tails had grown back. Judging from the videos it appears that all the work is being generated by the proximal tail muscles; which stay even after autotomy. Theoretically then, it should still work in a regrown tail.

    Oh yeah, did I forget to mention, Jusufi et al not only recorded everything, but they made them available for everyone to watch.

    They’re all worth watching. It’s cool to see just how fast these little geckos are.

    And so the “slow, sluggish reptile” stereotype, receives yet another nail in its coffin.


  • New paper on the strangest pterosaur ever.

    Ooh, I’m coming in under the wire this time (see the time stamp).

    So when someone talks about pterosaurs, or flying reptiles, you probably think of something like one of these:


    Pteranodon and Rhamphorhynchus. The two archetypes of pop culture pterosaurs.
    Former image from here. Latter image by Charlie McGrady.


    Few folks would normally think of this as a normal pterosaur:


    Pterodaustro guinazui (pic culled from Wikipedian artist: Arthur Weasley).


    Its name was Pterodaustro guinazui, and unlike other pterosaurs, which fed on fish, insects, or other types of meat, P. guinazui was a filter feeder. It has commonly been compared to a Mesozoic flamingo (thus resulting in more than a fair share of flamingo like drawings). It sifted microorganisms from the waters that it lived near. Unlike today’s modern flamingo (Phoenicopterus), Pterodaustro could filter feed without dipping its head upside down. As far as pterosaurs go, it was certainly one of (if not) the strangest species to have come from this group.As is typical with the weird ones, though they are celebrated for their uniqueness; that is about all that is known about them.

    Well, no more:

    Chinsamy, A., Codorni?, L., Chiappe, L. 2008. Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guinazui. Biology Letters. DOI: 10.1098/rsbl.2008.0004 (online: first cite)

    Life-history parameters of pterosaurs such as growth and ontogenetic development represent an enigma. This aspect of pterosaur biology has remained perplexing because few pterosaur taxa are represented by complete ontogenetic series. Of these, Pterodaustro is unique in that besides being represented by hundreds of individuals with wing spans ranging from 0.3 to 2.5m, it includes an embryo within an egg. Here we present a comprehensive osteohistological assessment of multiple skeletal elements of a range of ontogenetic sizes of Pterodaustro, and we provide unparalleled insight into its growth dynamics. We show that, upon hatching, Pterodaustro juveniles grew rapidly for approximately 2 years until they reached approximately 53% of their mature body size, whereupon they attained sexual maturity. Thereafter, growth continued for at least another 3–4 years at comparatively slower rates until larger adult body sizes were attained. Our analysis further provides definitive evidence that Pterodaustro had a determinate growth strategy.

    Pterodaustro skull

    Pterodaustro guinazui skull (photo from: http://www.pterosaurier.de)


    I have yet to read the full paper, but from what it says here, it would appear that the filter feeding lifestyle took its toll on P. guinazui, as its growth rate was remarkably slow. As this is the first time a growth series has been done on a pterosaur, it probably shouldn’t be assumed that this growth was typical of all pterosaurs (which would have had diets that were much higher in protein, thus aiding growth). Still the results are definitely interesting. Plus any new bits of info on the world’s strangest pterosaur, is a good thing in my book.


  • Owen and Mzee

    Owen and Mzee

    Though their’s is an old story, it’s so unique that I felt it deserved mentioning on my site at least once.Plus it was recently dugg, so I felt a need to respond.

    For those who don’t know the story; back in 2004 during the infamous tsunami disaster, a baby hippo was found stranded on a little piece of land out from the coast of Kenya. The baby hippo, Owen (named after one of the rescuers), was brought to Haller Park near Mombasa. There, the frightened hippo ran from its caretakers and hid by an old, crotchety aldabra tortoise (Geochelone gigantea) named Mzee (MIZ-ZAY). At first, Mzee wanted nothing to do with Owen, but the little (relatively speaking) hippo wouldn’t leave him alone. Eventually he grew to tolerate Owen’s constant harassment.

    Then something wonderous happened. Mzee and Owen became friends. Owen would follow Mzee around everywhere. They would eat together, bathe together, and sleep together. Mzee (the tortoise) invented a way of speaking to Owen. When Mzee wanted to go somewhere, he would gently nibble the tail of Owen. Soon Owen caught on and would do the same, when he wanted to go somewhere. It was an awesome spectacle to behold. This was completely different from what we see with, say, humans and their pet dogs, or cats. It was also different from the agricultural relationship between humans and livestock, or ants and aphids. This was a case of a genuine friendship between two very different animals (separated by over 300 million years of evolution!).

    Owen and Mzee had even developed their own way of talking to each other. They were also very protective. Neither would passively allow a human keeper to get near the other. It was and is one of the most heartwarming, and amazing things to ever be observed in the natural world.

    In 2006, a children’s book was released, documenting the story. Owen and Mzee became world famous, with visitors wanting to see the dynamic duo in person.

    Back in 2007, it was decided that Owen needed to make friends with other hippos. His relationship with Mzee resulted in Owen acting more, and more like a giant tortoise (a hilarious sight to behold). Unfortunately, the friend that they chose for Owen (a female named: Cleo), was too much of a rough houser with the giant tortoises, so they had to separate Owen and Mzee. It’s hard to say if either animal suffered any heartbreak from this separation (I haven’t read any mention of it anywhere). I also don’t know if the two guys are sharing adjacent enclosures, so they might be able to still hang out.

    Nonetheless, the story of Owen and Mzee is one that will live in infamy  for the ages. An amazing case of inter-special friendship between a mammal and a reptile that, prior to this, no one probably ever thought was possible.

    It’s amazing, and it’s all completely documented on their official site: OwenandMzee.com Make sure to watch the documentary. It’s a heartstring puller.