Tetrapod Zoology

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ResearchBlogging.org

In the previous few gekkotan articles we looked at the seriously weird and highly distinctive leaf-tailed geckos of Madagascar. There’s another group of especially unusual, highly notable gekkonid gekkotans I want to write about: the flying, gliding or parachute geckos (Ptychozoon) of south-east Asia and India. These geckos are weird: the adjacent pic (widely available online, but only at frustratingly small size; it’s credited to Tim Macmillan/John Downer) makes them look like tiny screaming dragons…

Parachute geckos are cryptic, forest-dwelling lizards. Patterned in greys or browns and possessing blotches and wavy dark lines on their bodies, they are good at concealing themselves on trunks and branches. Like the majority of the 1500-2000 gekkotan species (remember: this is a big, important group), they’re fairly small, with SVLs* of between 58 and 108 mm.

* snout to vent lengths (i.e., not the same as total length, as it excludes the tail).

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As is the case in a few other geckos (like the leaf-tailed geckos), flaps of skin grow from the sides of their heads, flanks, limbs and tails. Despite having known of these lizards for, certainly, the whole of my adult life I still think that the idea of lizards with lateral winglets, skin fringes and massively webbed digits is pretty freaky: look at the photo of the P. intermedium holotype here (from Brown et al. 1997), and hopefully you’ll see what I mean (incidentally, this specimen was destroyed during WWII).

Rounded flaps are present on both sides of the head, there are continuous fringes running along the sides of the body, flaps on the rear surfaces of the thighs, and semi-circular or subtriangular fringes project from the sides of the tail. The fringes are not supported internally by muscles or skeletal structures, and they scale allometrically with the size of the lizard (Russell et al. 2001). Flaps also extend along the leading and rear margins of the forelimbs in some species, and in one species* (P. lionotum, sometimes called the Smooth-backed parachute gecko) a notch – termed the predigital notch – separates the webbing round the thumb from that on the inside of the lower arm [notch presence (in P. lionotum) and absence (in P. trinotaterra) is shown in the diagram below: from Brown (1999)]. I wonder if this serves some aerodynamic function (could it work as a leading-edge slot?), though why it’s seen in P. lionotum alone and not the others is an interesting question.

* Yup, there’s more than one species. We’ll get to that in a minute.

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The digits on both the hands and feet are connected by extensive webbing. You might recall from the article on gekkotan digits that gecko scansor pads and their associated blood vessels and musculature are quite complex. One peculiarity of geckos is that many of them possess accessory, rod-like elements (termed paraphalanges) that project from the sides of the phalanges (the cylindrical bones that make up the digits). Surprisingly – in view of their extensive digital webbing – parachute geckos lack paraphalanges.

If you’ve ever read anything about Ptychozoon (or seen it on TV, or in real life), you’ll be familiar with the idea that these integumentary structures are all used to help these geckos to glide. It’s perhaps somewhat surprising, therefore, to find that it’s sometimes been doubted or even flatly denied that Ptychozoon is truly capable of any sort of aerial activity; to be fair, however, these assertions all date from the early 1900s. Theodore Cantor (in 1847) and Georges Boulenger (in 1890) had noted a parachuting function for the skin flaps somewhat earlier [Boulenger was so confident about this that he had P. kuhli illustrated in a gliding pose: this picture is shown below]. However, the flaps are also used to help break up the body outline and conceal these animals when they press their bodies against bark. Some authors have asserted that, because this cryptic role is used more often than the parachuting one, the flaps and fringes are “primarily cryptic” in function.

Russell (1979) argued that all of the features involved in parachuting – like the enlarged lateral skin folds on the body, jumping behaviour and extensive digital webbing – are seen in related gekkonine gekkonids that use them for crypsis, and not for parachuting or gliding. Hence, the characters allowing the behaviour are, in Russell’s view, ‘protoadaptational’. This makes Ptychozoon an excellent example of exaptation (where structures that initially served one role were co-opted during evolution for another).

Parachuting or gliding behaviour, or both

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Experimental (and photographic) evidence does of course confirm that Ptychozoon definitely does engage in ‘parachuting’ behaviour at least. But does it do more: can it actually glide? ‘Parachuting’ can be defined as falling at a slowed rate and in controlled fashion, while gliding is usually imagined as descending at an angle of less than 45° to the horizontal. The two kinds of behaviour grade into one another (Pennycuick 1972) and parachute geckos seem capable of both.

Heyer & Pongsapipatana (1970) tested the parachuting skills of Ptychozoon by dropping test subjects from 41 m up in a meteorological tower at the Sakaerat Experimental Station, Thailand (they also dropped a variety of non-parachuting geckos, and in their work on gliding snakes also dropped an Agkistrodon pit viper and even a specimen of the aquatic snake Enhydris plumbea). On being dropped, the parachute geckos stretched their legs out, held their tails out straight, and travelled for a much greater distance than did the control geckos. Sometimes the parachute geckos went with the wind, but on other occasions they travelled at right angles to it [P. kuhli below from here]

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Marcellini & Keefer (1976) concluded that specimens of P. lionotum didn’t just parachute, but actually glided. The geckos did this (on average) for about 5 m (one specimen made a glide of 9.35 m) and performed well in terms of the rate of descent. The style of descent seen in parachute geckos is pretty distinctive: they drop vertically for 1.2-3 m, then adopt the characteristic ‘spread-eagle’ posture and parachute/glide in a descending arc. As they approach the chosen landing site, they pull upwards and stall sharply. Young et al. (2002) also regarded parachute geckos as gliders and argued that their feet were particularly important in their aerial movements. In fact, Young et al. (2002) proposed that the geckos might be more similar – in terms of aerodynamics – to flying treefrogs than to other squamates capable of aerial behaviour (like the lacertid Holaspis). Most recently, Vanhooydonck et al. (2009) compared the aerial behaviour of P. kuhli with other lizards: they concluded that parachute geckos are able to generate lift and described P. kuhli as a “true glider” (p. 2479).

Little known is that Ptychozoon is not the only gecko that engages in gliding behaviour. Luperosaurus – identified in some studies as the sister-taxon to Ptychozoon – has similar flaps and folds and glides too, and so do at least some species of Thecadactylus, like T. rapicauda (Pianka & Vitt 2003). Thecadactylus is not at all close phylogenetically to Luperosaurus and Ptychozoon (it seems to be a phyllodactylid, and not a gekkonine gekkonid like Luperosaurus and Ptychozoon). Still other gecko species are able to leap and drop great distances (as much as 6 m) when escaping predators.

As usual, there is more than one

As is so often the case, you only ever ordinarily hear about a single species of Ptychozoon (this being P. kuhli from Java, Sumatra, peninsular Malaysia, southern Thailand, Borneo, the Nicobar Islands*, Sulawesi, and possibly Myanmar) and hence might assume that it’s the only one. But, no, it’s actually one of six. The others are P. lionotum (often incorrectly spelt P. lionatum) from Thailand, Myanmar, peninsular Malaysia and India (Pawar & Biswas 2001), P. rhacophorus from northern Borneo, P. horsfieldii of Thailand, peninsular Malaysia, Borneo, Sumatra, Java and Myanmar, P. intermedium from the Philippines, and P. trinotaterra from Thailand and Vietnam (and only named in 1999). They differ markedly from one another, especially in tail anatomy and in the details of their scalation.

* The Nicobar Islands population was named last year as a new species: P. nicobarensis Das & Vijayakumar, 2009. So, there are currently seven species, not six. See the comments for more.

In the Bornean species P. rhacophorus, the tail tapers to a point (it looks fairly typical for a lizard) and the lateral lobes on the tail are very small. Rather than having regularly spaced, rounded tubercles on its flanks, it possesses randomly aligned large scales (some of which are semi-conical) that are scattered across its sides. The amount of digital webbing present in P. rhacophorus is small compared to that of the other species, and its lateral body fold is also smaller. In fact, P. rhacophorus looks like an ideal ‘intermediate’ between the more extreme parachute geckos and members of the probable sister-taxon to Ptychozoon, Luperosaurus (Russell 1979).

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The tail tip of P. rhacophorus [A in the adjacent composite; from Brown et al. (1997)] doesn’t have any sort of flattening at its tip, but what seems to have happened in other species is that some or many of their lateral lobes have become partially or completely fused, thereby forming a terminal tail flap that might be rounded or squared-off at its tip. P. horsfieldii resembles P. rhacophorus in having a tapered tail [its tail is B in the adjacent composite], but its lateral tail lobes are bigger than those of P. rhacophorus and their shape (like scalene triangles) means that they look ‘swept back’ compared to the lobes of the other species. The lobes are bigger and have more rounded tips in P. intermedium [C in adjacent composite]; three or four of the lobes are fused to form the terminal tail flap in this species, and it also differs from the others in having small, slightly convex tubercles scattered across its sides. P. lionotum lacks tubercles on its sides and has a wide tail [D in adjacent composite] where about eight lobes near the tip are partially fused together, giving the tail a squared off, serrated tip. The weirdest tail is seen in P. kuhli [E in adjacent composite]: here, the lobes at the tail-tip have become imperceptibly fused, forming a rounded, paddle-like tail tip. Two obvious rows of enlarged, rectangular tubercles are obvious on the sides of this species; it also has large, rectangular scales lining its sides (as do P. horsfieldii, P. intermedium and P. lionotum). P. trinotaterra has a tail similar to that P. kuhli, but narrower. This species also has just a single row of flattened tubercles, or lacks tubercles entirely [scale bars in adjacent photos = 5 mm].

As usual, relatively little is known about the behaviour and lifestyle of parachute geckos. They are presumably nocturnal insectivores that frequent tropical evergreen habitats, but there are some indications that they can make a living around places where people live and they may be reasonably good at dispersing through disturbed areas (Pawar & Biswas 2001). Some authors say that parachute geckos sometimes walk around with the tail curled up over the back, perhaps to mimic scorpions (a behaviour previously reported for various other gecko species). How often they engage in the parachuting or gliding behaviour is not entirely clear: do they only employ this behaviour as an escape tactic, or do they deliberately leap from tree to tree while foraging or searching for mates? One of my favourite facts about these geckos is that specimens are sometimes captured in mist nets set for bats (Brown 1999), and this at least implies that their parachuting behaviour is a normal part of their daily life [captive P. lionotum shown below; from here... though note that its mostly smooth-edged tail is rather different from what's shown in D above. Hmm].

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For previous Tet Zoo articles on gekkotans see…

For previous Tet Zoo articles on neat squamates see…

Refs – -

Brown, R. M. 1999. New species of parachute gecko (Squamata: Gekkonida; genus Ptychozoon) from northeastern Thailand and central Vietnam. Copeia 1999, 990-1001.

- ., Ferner, J. W. & Diesmos, A. C. 1997. Definition of the Philippine parachute gecko, Ptychozoon intermedium Taylor 1915 (Reptilia: Squamata: Gekkonidae): redescription, designation of a neotype, comparisons with related species. Herpetologica 53, 357-373 [version below included for Research Blogging purposes].

Brown, R. M., Ferner, J. W., & Diesmos, A. C (1997). Definition of the Philippine parachute gecko, Ptychozoon intermedium Taylor 1915 (Reptilia: Squamata: Gekkonidae): redescription, designation of a neotype, comparisons with related species Herpetologica, 53, 373-373

Heyer, W. R. & Pongsapipatana, S. 1970. Gliding speeds of Ptychozoon lionatum [sic] (Reptilia: Gekkonidae) and Chrysopelea ornata (Reptilia: Colubridae). Herpetologica 26, 317-319.

Marcellini, D. L. & Keefer, T. E. 1976. Analysis of the gliding hehavior of Ptychozoon lionatum [sic] (Reptilia: Gekkonidae). Herpetologica 32, 362-366.

Pawar, S. & Biswas, S. 2001. First record of the smooth-backed parachute gecko Ptychozoon lionotum Annandale 1905 from the Indian mainland. Asiatic Herpetological Research 9, 101-106.

Pennycuick, C. J. 1972. Animal Flight. Edward Arnold (London).

Pianka, E. R. & Vitt, L. J. 2003. Lizards: Windows the Evolution of Diversity. University of California Press (Berkeley).

Russell, A. P. 1979. The origin of parachuting locomotion in gekkonid lizards (Reptilia: Gekkonidae). Zoological Journal of the Linnean Society 65, 233-249.

- ., Dijkstra, L. D. and Powell, G. L. 2001. Structural characteristics of the patagium of Ptychozoon kuhli (Reptilia: Gekkonidae) in relation to parachuting locomotion. Journal of Morphology 247, 252-263.

Vanhooydonck, B., Meulepas, G., Herrel, A., Boistel, R., Tafforeau, P., Fernandez, V. & Aerts, P. 2009. Ecomorphological analysis of aerial performance in a non-specialized lacertid lizard, Holaspis guentheri. The Journal of Experimental Biology 212, 2475-2482.

Young, B. A., Lee, C. E. and Daley, K. M. 2002. On a flap and a foot: aerial locomotion in the ‘flying’ gecko, Ptychozoon kuhli. Journal of Herpetology 36, 412-418.

Comments

  1. #1 Zach Miller
    June 7, 2010

    What strange little lizards. While the answer is likely “no,” I wonder if there are any osteological correlates with all this extra skin? Of course, I’m thinking of the fossil record. Could you diagnose a gliding gecko from its bones alone?

  2. #2 Adam F
    June 7, 2010

    I had a good laugh at the mental image of researchers chucking various reptiles off of that observation tower. I wonder how many of the non-gliders survived the fall though…I imagine most of the smaller things would.

  3. #3 J. S. Lopes
    June 7, 2010

    Maybe proto-birds used enlarged feathers for crypsis too, before adapting them for parachuting or gliding.

  4. #4 Allen Hazen
    June 7, 2010

    Those side flaps along the torso… They’re not like the multiple-times evolved thingies I think of as typical of gliding “reptiles” (Draco, Keuhneosaurus, something whose name I can’t remember) in that they don’t have internal skeletal support. They’re not like they many-times evolved patagia of gliding mammals in that they aren’t stretched between the fore- and hindlimbs.
    The skin can’t be too floppy, or they would be aerodynamically useless.
    I take it these aren’t very big animals. Perhaps at their mass a fairly ordinary degree (for skin) of stiffness is sufficient (and they’d need skeletal support if scaled up). Or do you suppose they some sort of unusual soft-tissue structure (lots of very small collagen rods or fibers or placques?) which functionally takes the place of supporting skeletal structures?

  5. #5 Darren Naish
    June 7, 2010

    Quick responses… So far as I know, there are no osteological correlates for these integumentary structures. Nor (re: comment 4) do they have internal support other than the usual stuff (like collagen fibres and fat). Skeletal material of these animals is scant, as are descriptions. Wellborn included some comments on the osteology of Ptychozoon in her monograph (discussed in the first Uroplatus article), but it’s thought that she was actually looking at Cosymbotus as her observations on parachute gecko digits have proved erroneous (Russell & Bauer 1988).

    Re comment 2: it seems that all of the animals survived, though some performed more poorly in air than others. The water snake, for example, tumbled end over end. Poor things. I’m not sure that this qualifies as ethical research.

    Re comment 3: the idea that feathers originally evolved to aid in crypsis has, surprise surprise, been seriously proposed: Liston (2000) suggested that the similarity present between feathers and the branching fronds of some plants was not coincidental. And, yes, this is Jeff ‘Leedsichthys‘ Liston.

    Allen (comment 4): Russell et al. (2001) looked in detail at the patagium structure and showed that the scales (yeah, remember the scales) and the normal properties of skin provide enough support to allow the flaps and fringes to function aerodynamically. The skin flaps are essentially just flaps of scaly skin surrounding a fatty core (though the arrangement of scales on their surfaces is highly complex and there are both ‘hinge’ zones and specialised sensory structures incorporated… I had to skimp all this in order to get the article finished). They definitely seem to function passively: that is, they’re unfurled and held open by air pressure during a leap.

    Refs – -

    Liston, J. 2000. Archaeopteryx and the evolution of feathered flight: the hidden story. The Quarterly Journal of the Dinosaur Society 4 (1), 6-14.

    Russell, A. P. & Bauer, A. M. 1988. Paraphalangeal elements of gekkonid lizards: a comparative survey. Journal of Morphology 197, 221-240.

    - ., Dijkstra, L. D. and Powell, G. L. 2001. Structural characteristics of the patagium of Ptychozoon kuhli (Reptilia: Gekkonidae) in relation to parachuting locomotion. Journal of Morphology 247, 252-263.

  6. #6 Karl Einum
    June 7, 2010

    The Ptychozoon of the Nicobar Islands was described as a separate species in 2009. I. Das & S. P. Vijayakumar (2009) New species of Ptychozoon (Sauria: Gekkonidae) from the Nicobar Archipelago, Indian Ocean Zootaxa 2095: 8–20

  7. #7 Darren Naish
    June 7, 2010

    Oh!!! I had missed this paper – can anyone send me the pdf please (I lack access to Zootaxa and oh so wish I had it).

  8. #8 Darren Naish
    June 7, 2010

    The species concerned was named Ptychozoon nicobarensis. The first page of the paper (which looks very interesting) is available here.

  9. #9 Sebastian Marquez
    June 7, 2010

    You have mentioned in previous posts that it seems there are large gaps in the field biology with many of these so called “lower” vertebrates. Yet, ironically, a number can be found in captivity in the exotic pet trade. Is there any value to observations of captive animals as it pertains to the wild populations? Or is “extrapolation” in this sense just a dirty word?

  10. #10 Nick
    June 7, 2010

    The last gecko pictured with the smooth-edged tail looks like a regrown tail. You can see the breakpoint in pattern near the base. These are my favorite geckos – this post makes me very happy :)

  11. #11 Albertonykus
    June 7, 2010

    Chucking reptiles out of a tower more than forty meters off the ground sounds fairly amusing… I mean, unethical.

  12. #12 Chris M.
    June 7, 2010

    I’m a little surprised you didn’t cite any of the papers of a few biomechanicists at Berkeley that I know about gliding in general; turns out, a lot of geckos that they’ve studied are able to direct their falls surprisingly well. Not to the point of 1:1 “gliding” as it’s defined above, but a well-directed 1:5 or will land you anywhere in a 5m radius from a high tree, and that’s really quite significant.

    Still, the move from falling in a safe place to actually using it for transportation is major, and these adaptations are just fantastic!

    Anyway, I can report secondhand that the tower or tree dropping is definitely entertaining, but the big problem is recovering the animals afterward. Since most of them can target when given 10+ meters to fall, they aim for good places to hide! Usually it’s limited to several drops per animal because of this, but a long sheet hanging nearby as a target made life easier. The main goal is to stay in the canopy (at least that’s the current guess, since they aim for trunks and branches), so they avoid falling all the way to the ground.

    The comments about them likely being unhurt are also definitely accurate, they reach terminal velocity after much less than the distance they’re falling, and as far as I recall hearing they’ve never seen an injury from the experiments over hundreds of trials. They’re really very light, I’d be surprised if these passed 10-20g.

    Just to math it out, Wolfram Alpha’s got a terminal velocity calculator if you type that in (just click the “with drag” option). Equivalent cross-section for a 15g gecko is not going to be less than 10 square centimeters, and the drag coefficient is going to be much higher than a streamlined body (0.04), call it 0.2 to be irrationally conservative (a sphere is 0.47, cube 1.05).

    At this estimate, they’re going to be going about 8mph/13kph on impact, and carrying extremely little kinetic energy due to their low weight. No worries about the lizards!

  13. #13 Adam F
    June 7, 2010

    It was the snakes, depending on their size, which I might have expected to have some trouble. But I’m not surprised to hear that they survived-it really is amazing the distance that smaller animals can survive falling. I’d hate to be walking under that tower when the viper came down though….

  14. #14 Dartian
    June 8, 2010

    Darren:

    Little known is that Ptychozoon is not the only gecko that engages in gliding behaviour. Luperosaurus – identified in some studies as the sister-taxon to Ptychozoon – has similar flaps and folds and glides too, and so do at least some species of Thecadactylus, like T. rapicauda (Pianka & Vitt 2003). Thecadactylus is not at all close phylogenetically to Luperosaurus and Ptychozoon

    Perhaps worth mentioning here is that Ptychozoon and Luperosaurus are Asian while Thecadactylus is from the tropical Americas, thus making the latter one of the relatively few gliding Neotropical vertebrates. In comparison, tropical Asian rainforests virtually abound with vertebrate gliders and parachuters (while having rather few prehensile-tailed arboreal vertebrates, which, in turn, are more common in the Neotropics).

    I’m not sure that this qualifies as ethical research.

    Well, the paper was published in 1970. In the bad old days that kind of scientific experiment with live animals would have been almost routine. (Imagine if someone had tried to study, say, giraffe floatation dynamics back then. It would probably have been logistics rather than ethics that would have prevented him/her/them from using live animals for that.)

  15. #15 Darren Naish
    June 8, 2010

    Thanks for further comments and neat insights. It’s obvious now that the tail on that P. lionotum (last photo in article) is a regrown one. Still seems slightly odd that lizards with such specialised, valuable tails retain the ability to shed them when the need arises, but I guess this says something about how significant the pressures of predation are.

    Chris M (comment 12): the Berkeley research on how geckos use their tails to help control their falls was discussed in the article on gekkotan tails, so I didn’t want to cover it again!

  16. #16 John Scanlon, FCD
    June 8, 2010

    do they deliberately leap from tree to tree while foraging or searching for mates?

    Well of course. I mean, who doesn’t?

    I do hope it wasn’t necessary to drop the water snake and pitviper from all of 41 m to prove they couldn’t fly very well. Presumably this could be established with reasonable certitude in lower-altitude tests.

    Imagine if someone had tried to study, say, giraffe floatation dynamics back then.

    What surprises me is that (if?) it didn’t happen. Giraffes have occasionally been used in circus acts (still now, some places?), which is not obviously less criminal than gently leading one into a swimming pool or lake. I’m sure that a truly great scientist could ethically justify throwing a giraffe off a 41 m tower if there was a few million dollars in it.

    Oh, nice geckos. Regenerated tails apparently always have more uniform scales than originals, so e.g. in Phyllurus they’re easy to spot: just velvety, lacking the fringe of spine-like scales and scattered tubercles. Also yellow instead of grey, which can’t help with crypsis much.

  17. #17 Chris M.
    June 8, 2010

    True, I don’t know how well the more gliding-focused research ended up getting published, it was fieldwork at Barro Colorado Island that I saw mostly as presentations of preliminary results. The data was difficult to analyze for mechanics, so it may have been primarily used to motivate the tail studies. I’ll ask one of the lab members what ended up happening with that, I likely have the details of what made it into the paper wrong.

  18. #18 Hai~Ren
    June 8, 2010

    Besides Ptychozoon and Luperosaurus, Cosymbotus geckos also have flaps of skin along their flanks; Cosymbotus craspedotus in particular has a noticeable fringe along the sides of its body and tail, and authors assert that this is used more for camouflage than for parachuting.

    I now wonder about the evolution of the flaps in Draco, and whether they first evolved as display structures. I’m also wondering where Draco fits in the agamid family tree, and whether other arboreal agamids have parachuting abilities as a precursor to the gliding seen in Draco.

  19. #19 J. S. Lopes
    June 8, 2010

    Would geckos’ webbed digits provide a good model for the origin of bats’ dactylopatagium? Would proto-bats look like a crossbred between a rhacophorid flying-frog and a tree-shrew.

  20. #20 Jerzy
    June 8, 2010

    BTW, why amazing Namibian fin-footed gecko cannot be found in any zoo?

  21. #21 Darren Naish
    June 8, 2010

    WRT comment 18… I’ve got a half-finished article on Draco somewhere and must finish and post it some time (it’s called ‘Why Draco volans is boring’. All will be revealed). The next squamate stuff (pending more gekkotans, of course) will most likely be on the many new monitor lizards, however. So far, 2010 has been ‘year of ceratopsians’ and ‘year of varanids’.

  22. #22 Nathan Myers
    June 8, 2010

    I hope it’s not too late to post some images from California and Hawaii:

    http://cantrip.org/tets2/

    These are all (hereby) public domain. Click through each for nice 12Mpix images perhaps suitable for cropping.

  23. #23 Nathan Myers
    June 9, 2010

    Incidentally, I found to my surprise that Island (“Brahminy”, “Hawaiian”) Blind Snakes have been in Hawaii since the 1930s. Also known as flowerpot snakes, they are parthenogenetic and are said to live in ant and termite nests and dine on grubs. Our innkeeper said he frequently spots them wriggling smartly out of the way of his lawnmower, so they must have figured out something else to live on. They were too fast for my daughter to catch.

    I doubt this particular parthenogenetic species will go extinct any time soon.

  24. #24 Tim Morris
    June 9, 2010

    Anyone who has attempted to catch Marbled Geckos will know that they will literally leap out of your hands to the ground while you are standing fully upright in order to get away. I imagine this stems from an ability to leap from high surfaces like trees or walls in order to escape spiders and birds, as Darren has said.

  25. #25 Hai~Ren
    June 9, 2010

    Tim Morris: I think that’s the standard escape response for any small arboreal lizard – climb as high as you can, or just leap off and scamper off once you hit the ground.

    Even green iguanas do that.

  26. #26 Sven DiMilo
    June 9, 2010

    Is there any value to observations of captive animals as it pertains to the wild populations?

    Pet-trade animals are used pretty often for studies of functional morphology, physiology, etc. The problem with rarer types, though, is that the lack of locality-of-origin information makes it tough to even know what species you’re working with. And for the same reason, they’re usually useless for systematics work.

    It’s obvious now that the tail on that P. lionotum (last photo in article) is a regrown one. Still seems slightly odd that lizards with such specialised, valuable tails retain the ability to shed them when the need arises

    Agreed, but even more amazing is the ability to regrow a tail with the requisite functional characteristics despite a completely different structural support system. There are fascinating questions about the genetic control of development and regeneration in there somewhere.

    Even green iguanas do that.

    The big ones are aiming for the water though. They better be.

  27. #27 Daniel
    June 9, 2010

    The big ones are aiming for the water though. They better be.

    On river banks, they sure are. Add their crypsis and, when not actively looking for them, you’re up for random scares from their diving splashes :)

    However, they are present in very dry places too (though I’ve only seen them on river banks myself). I’ve never read anything specific about how do they escape there (although someone mentioned thorny bushes once).

    From the noise they make when falling (I assume grasping branches to slow down), I believe they could hit the ground from quite a height ( >5m? >10m?) given enough obstacles.

  28. #28 Darren Naish
    June 9, 2010

    Some surprisingly large animals deliberately fall from great heights, and are (apparently) ok. I am, of course, thinking about tree kangaroos, some of which leap out of trees from as much as 30 m up and land on the ground with a heavy thud. I don’t have Flannery’s book: doesn’t he say that their particularly large cartilaginous joints held them to absorb the impacts?

  29. #29 Dr. Nick
    June 9, 2010

    Darn those pesky neuter names…

    In the Bornean species P[tychozoon] rhacophorus

    Probably should be P. rhacophorum.

    The Nicobar Islands population was named last year as a new species: P. nicobarensis Das & Vijayakumar, 2009.

    This totally unambiguously has to be P. nicobarense.

    Not sure what the intended meaning of trinotaterra is, but it looks like a noun in apposition rather than an adjective and if so wouldn’t have to agree in gender.

  30. #30 Andrew
    June 10, 2010

    In Bangkok we have loads of Cosymbotus platyurus gekkoes, which have plenty of flaps and flanges but aren’t true gliders (though they like to jump!). Never seen a Ptychozoon though.

    However, the gliding colubrid Chrysopelea ornata would appear to be pretty common in the leafier areas of Bangkok. I’ve found skins, seen dead ones on the road, and one even launched itself from a mango tree to land about a metre away from me while I was checking my school’s football pitch. Incidentally, they make a sound like wet rope striking something when they hit the ground, and then they shoot off into the bushes. If you chase them they tend to turn and adopt strike position, though it mostly seems bluff.

  31. #31 David Marjanović
    June 12, 2010

    Draco, Keuhneosaurus, something whose name I can’t remember

    The squamate Draco, the probable stem-lepidosaur Kuehneosaurus, and the stem-diapsid Coelurosauravus (aka Weigeltisaurus aka Daedalosaurus).

  32. #32 Allen Hazen
    June 12, 2010

    David Marjanovic– Many thanks! I was thinking of Coelurosauravus but didn’t remember the name.

    General comment: I suppose the unknown ancestors of the Pterosauria may have gone through a stage with a “flying squirrel” configuration, but it is striking (to me) how rare this is in “reptiles” in contrast to the ?? seven and counting ?? times it has evolved in “mammals” (sensu non strictissimo, sed non latissimo: Volaticotherium is probably not in Crown Theria, may be in Theria+Monotremata, but is certainly more closely related to living mammals than Sinoconodon is!). I think it plausible that this is an example of “phylogenetic constraint”: something about the mammalian versus reptilian bauplans makes different sorts of gliding adaptation likely in the two groups. (I think I’ve gone on about this before — sorry to be a bore.)

  33. #33 Jura
    June 13, 2010

    Draco, Ptychozoon [debatable], Chrysopelea, Coelurosauravis, Kuehneosaurus, Sharovipteryx, Icarosaurus, Mecistotrachelos and possibly Longisquama. Other than the familial relationship between Kuehneosaurus and Icarosaurus, none of the others seem particularly closely related to each other (though I imagine part of this stems from the general lack of interest in non-dinosaur reptile systematics). This is also not counting Microraptor, and possibly Archaeopteryx and Rahonavis as well. I can’t say I really see much phylogenetic constraint here.

    I am rather surprised to learn that gliding forms have shown up so often in mammals. I only knew of flying squirrels, sugar gliders, and Colugo. I didn’t know it extended much further than that.

  34. #34 Hai~Ren
    June 13, 2010

    Don’t forget Xianglong.

  35. #35 Allen Hazen
    June 13, 2010

    Jura–
    I don’t know all the Sauropsid taxa you mention well enough to comment.
    What I had in mind when Italked about “phylogenetic constraints” was that bauplans rendered only certain types of gliding adaptation likely. No requirement that there be only one type of glider available: on the list you give, it seems to me that there are at least two radically different ones for Sauropsids: the feathered hand type (Archaeopteryx et al) and the body-side fin (Draco et al), with the ancestry of the Pterosauria probably representing a third. In contrast to which, on the assumption that the ancestry of bats went through a limb-supported patagial gliding phase, there is apparently only one air ticket available for Theropsids. … The point I am most confident of is that a Draco-style fin, supported by skeletal elements associated with the ribs, is NOT an option for mammals: rib cage to heavily “committed” to respiratory function to allow add-ons to it like this.

  36. #36 Dartian
    June 14, 2010

    Jura:

    I am rather surprised to learn that gliding forms have shown up so often in mammals. I only knew of flying squirrels, sugar gliders, and Colugo. I didn’t know it extended much further than that.

    Gliding adaptations have indeed evolved several times in mammals:

    -In three diprotodont marsupial taxa (the greater glider Petauroides volans, the flying phalangers Petaurus, and the feathertail glider Acrobates pygmaeus, respectively), which almost certainly have evolved their gliding adaptations independently from each other (e.g., Johnson-Murray, 1987; Jackson, 1999).
    -In four rodent lineages: the extant flying squirrels and the anomalurids, as well as the Oligocene eomyid Eomys quercyi (Storch et al., 1996) and the Miocene dormouse Glirulus lissiensis (the latter supposedly congeneric with the extant, non-gliding Japanese dormouse G. japonicus) (Mein & Romaggi, 1991).
    -In colugos.
    -In the Paleogene plagiomenids (e.g., Planetetherium); they used to be considered close relatives of colugos, but later research has suggested that they probably aren’t (Ducrocq et al., 1992).
    -In the Jurassic Volaticotherium.
    -And, most likely, also in the LCA of bats (whatever it was).

    That’s a total of ten or eleven occasions (that we know of) of patagia evolving in Mammalia sensu lato. Most likely new fossil discoveries will increase the number.

    References:

    Ducrocq, S., Buffetaut, E., Buffetaut-Tong, H., Jaeger, J.-J., Jongkanjanasoontorn Y. & Suteethorn, V. 1992. First fossil flying lemur: a dermopteran from the late Eocene of Thailand. Palaeontology 35, 373-380.

    Jackson, S.M. 1999. Glide angle in the genus Petaurus and a review of gliding in mammals. Mammal Review 30, 9-30.

    Johnson-Murray, J.L. 1987. The comparative myology of the gliding membranes of Acrobates, Petauroides and Petaurus contrasted with the cutaneous myology of Hemibelideus and Pseudocheirus (Marsupialia, Phalangeridae) and with selected gliding Rodentia (Sciuridae and Anamoluridae). Australian Journal of Zoology 35, 101-113.

    Mein, P. & Romaggi, J.-P. 1991. Un gliridé (Mammalia, Rodentia) planeur dans le Miocène supérieur de l’Ardèche: une adaptation non retrouvée dans la nature actuelle. Geobios 24(Supplement 1), 45-50.

    Storch, G., Engesser, B. & Wuttke, M. 1996. Oldest fossil record of gliding in rodents. Nature 379, 439-441.

  37. #37 Dartian
    June 14, 2010

    Pedantic self-correction:

    Anamoluridae

    [Sic] in the original reference; it should of course be Anomaluridae.

  38. #38 Allen Hazen
    June 14, 2010

    Thanks for the list! (I knew about Glirulus lissiensis but not Eomys, hadn’t heard that Planetetherium had been separated from the Colugos.) I’ll try to remember at least the number: 10 or 11 and counting!

    I’ve seen a drawing of a gliding Ptilodontid multi, but it was on some alternative history “Speculative Zoology” website… still, the idea is intrinsically reasonable, and I sort of hope someone will find evidence of one. (We need a Paleocene Messel-like site, somewhere in, say, Arizona!)

  39. #39 Dartian
    July 6, 2010

    Marginally on-topic…

    Allen and Jura (and anyone else who might be interested): Later this year, Stephen Jackson and Peter Schouten will publish a book entitled Gliding Mammals of the World. Judging by Schouten’s previous work, it will surely be a visual treat.

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