Tetrapod Zoology

i-9b105653263e57598b6928ebcc6d3a88-Glasgow Chitra indica.jpg

That weird little face was, indeed, that of a turtle – but it wasn’t that of a matamata Chelus fimbriatus, it was instead that of a softshell turtle (a trionychid), and specifically that of a narrow-headed softshell Chitra indica (though read on). Well done Lars, Johannes and Emile, and particularly Hai-Ren. Chitra has to be one of the most amazing turtles: a big to enormous, long-skulled rubbery animal that hardly ever leaves the water.

Unlike all other turtles, softshells have reduced the bony carapace to such an extent that the margins of their shell are flexible: in some species, the bony carapace only occupies half of the entire, errr, carapace, and the rest is cartilage and skin (trionychids are unique in that they’ve lost the peripheral bones that normally form the bony carapace margin). While Chitra has big, flipper-like forelimbs, its hindlimbs are often obscured by the flexible rear margin of the carapace. All in all, it reminds me a giant rubber hot water bottle… and if you grew up in the tropics and don’t know what a rubber hot water bottle is, one is shown below with a Chitra chitra. Striking resemblance.

i-10144b159f695bb445d29fa197ad6679-testudine-hot water bottle convergence.jpg

A predator of fish, molluscs and crustaceans (though it also may eat plants on occasion), Chitra is noted by some authors as having a particularly nasty bite. Others say that captive individuals are really quite nice when you get to know them (Ernst & Barbour 1989). As is the case with all big freshwater turtles, some fantastic anecdotes are attached to these turtles. My favourite is that they can catch and overturn goats (Alderton 1988). Quite what the significance of the ‘overturning’ is I’m not sure. As is clear from the skull you can see at the top, the orbits of Chitra are placed unusually far forwards, even for a softshell. In life, a short mobile proboscis extends from the bony nostrils and is used as a snorkel. Females lay 60-110 eggs in a go. Despite this fecundity, they are – like so many Asian turtles – declining due to their use as luxury food items and in Chinese medicine, and they are also endangered by habitat loss, pollution and the construction of dams. Some species are critically endangered and will probably follow other Asian turtle species into extinction in the near future. About half of all Asian turtle species are endangered.

i-dedb8b55a5a6dd214b4ded5b20813182-Hoan Kiem turtle.jpg

Not only are narrow-headed softshells notable in looking so bizarre, they’re also well known for reaching huge sizes. If, until now, you’ve been imagining softshells to be little things perhaps only 30 or 60 cm long, prepare to be shocked, as the biggest species exceed 100 cm in carapace length and 200 kg in weight. A female Siamese narrow-headed softshell C. chitra (aka Striped narrow-headed softshell or Nutphand’s narrow-headed softshell) captured in 1967 had a carapace length of 123 cm (carapace length, not total length) and a weight of 152 kg, and another caught in Thailand in 1986 weighed 202 kg (Kitimasak et al. 2005). For photos of some real big ones, go here. You will doubtless have heard of the reportedly immense softshells from Hoan Kim Lake in Vietnam. They’re not narrow-headed softshells: instead they belong to Rafetus, another genus of big Asian softshells. A lot of claims have been made about these turtles: that they approach 3 m in length and are as big as a double bed, that they live to be over 500 years old, that they are the same turtles mentioned in a story from the 1400s, and that they represent a new species (R. leloii). We await more information. The head of one of these turtles is shown in the adjacent image: there aren’t many good photos of these turtles, and this one gets used a lot, so apologies if you’ve seen it before.

Finally, while the skull shown above was labelled C. indica, we can be confident that this is correct because I know the skull comes from India. The narrow-headed softshells from Thailand and Myanmar, previously included within C. indica, have recently been shown to represent separate species (Engstrom et al. 2002, McCord & Pritchard 2002). C. chitra, which you’ve seen mentioned and pictured above, was separated from C. indica and named in 1986. The Myanmar population was only named as a new species, Van Dijk’s narrow-headed softshell C. vandijki, in 2002 (McCord & Pritchard 2002).

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Softshells have a pretty good fossil record, and in fact Chitra is reasonably well represented in, for example, the Pliocene deposits of the Indian Siwalik Hills (Chitra-like fossils come from rocks as old as the Eocene, but whether they’re specifically allied to Chitra remains unsure). Softshells as a whole have a fossil record extending back to the Cretaceous, and in the past they were present in Australia (Gaffney & Bartholomai 1979); today they don’t occur there, but are ‘limited’ to North America, Africa and Asia. Crown-group softshells have conventionally been divided into two groups, the trionychines and the Afro-Indian flap-shelled turtles, or cyclanorbines (Meylan 1987). These differ from trionychines in being able to hide their feet under flaps of skin that extend from the plastron. Among trionychines, Chitra has conventionally been regarded as closely related to the Asian giant softshell Pelochelys bibroni, and a recent analysis by Engstrom et al. (2004) confirmed this, grouping them together in a trionychine clade dubbed Chitraina (Engstrom et al. (2004) followed the PhyloCode convention of putting all clade names in italics. I appreciate that this is all to do with abandoning ranks, but it so jars with traditional taxonomy that I’m still not keen on it). The next closest relative to Chitraina was Trionyx, and all of these taxa were then found to form a well-supported clade for which another ridiculous-looking new taxon name was created: Gigantaestuarochelys, the giant estuarine turtles (though they mis-spelt it Gigantaesuarochelys [sic] in their Fig. 5, the first place it appears in the paper). Incidentally, the adjacent image shows Pelochelys bibroni to scale with a lady. Remind me to elaborate one time on the noble tradition of using Oriental ladies as scale bars for assorted large animals, seriously.

And, dammit, once more I failed to produce a short 100-odd words.

For previous Tet Zoo turtle pieces, there’s the Green turtle article here, and the famous turtle phallus article here. The ver 1 series on snapping turtles starts here, and the hololissa article is here. Still araripemydid pleurodires, meiolaniids and tortoises to come at some point in the future.

Refs – -

Alderton, D. 1988. Turtles & Tortoises of the World. Blandford, London.

Engstrom, T. N., Shaffer, H. B. & McCord, W. P. 2002. Phylogenetic diversity of endangered and critically endangered southeast Asian softshell turtles (Trionychidae: Chitra). Biological Conservation 104, 173-179.

- ., Shaffer, H. B. & McCord, W. P. 2004. Multiple data sets, high homoplasy, and the phylogeny of softshell turtles (Testudines: Trionychidae). Systematic Biology 53, 693-710.

Ernst, C. H. & Barbour, R. W. 1989. Turtles of the World. Smithsonian Institution Press, Washington, D. C. & London.

Gaffney, E. S. & Bartholomai, A. 1979. Fossil trionychids of Australia. Journal of Paleontology 53, 1354-1360.

Kitimasak, W., Thirakhupt, K., Boonyaratpalin, S. & Moll, D. L. 2006. Distribution and population status of the Narrow-headed softshell turtle Chitra spp. in Thailand. The Natural History Journal of Chulalongkorn University 5, 31-42.

McCord, W. P. & Pritchard, P. C. H. 2002. A review of the softshell turtles of the genus Chitra, with the description of new taxa from Myanmar and Indonesia (Java). Hamadryad 27, 11-56.

Meylan, P. A. 1987. Phylogenetic relationships of soft-shelled turtles (Family: Trionychidae). Bulletin of the American Museum of Natural History 186, 1-101.

Comments

  1. #1 Hai~Ren
    November 29, 2007

    W00t!

    I remember Chitra particularly well, because I was reading a book on turtles of the world once as a teenager, and there was a photo of what was labeled Chitra indica. I remember staring at the photo for a very long time, wondering, “where’s the eyes??” Took me a while to realise that what I’d thought were the nostrils were in fact the eyes. (The real nostrils were just tiny dots in the picture)

    Besides, Chitra is a very easy name to remember.

    And I’m not complaining that some websites use lovely Japanese ladies to provide some sense of scale when showing how big some creatures are/were. =)

  2. #2 Kenneth McFarlane
    November 29, 2007

    That is definitely one of the more interesting turtles I’ve seen, and I can definitely agree with the waterbottle comparison.

    Also, just wanted to add how much I’ve enjoyed your blog since discovering it (I think I came here through zooillogix, but it was a while ago and I don’t remember exactly). Some of what you put in goes over my head, but I’m keeping up much better now than when I started reading. Kudos to you for the effort you must have to put in to keep us all entertained and informed.

    And lastly: that bikini looks photoshopped :P

  3. #3 Stevo Darkly
    November 29, 2007

    The photo of the face in life, emerging from the water, kind of looks like a seal! And also kind of like Rip Taylor.

  4. #4 Zach Miller
    November 29, 2007

    Soft-shells are awesome, but I didn’t realize they got so big! That’s bigger than some sea turtles I’ve seen!

  5. #5 Cameron
    November 29, 2007

    Well, can’t win ‘em all, or, um, I’ll win one eventually.

    These are far more interesting than the mata mata anyways. Softshells are the finest of turtles in my opinion, and you definitely saved me a lot of time writing this :)

    You’ll have to enlighten me about the asian women posing. If I recall, you had a picture of a lady posing next to a Supersaurus scapula…then there’s this page:

    http://post.baidu.com/f?kz=165501403

    The head shape of this particular group does tend to be very eccentric; the head of Amyda looks like something that would be more home on some weird fish than a turtle.

    http://www.chelonia.org/AmydacartilagineaTR3.jpg

  6. #6 Mark Evans
    November 29, 2007

    I first came across a Chitra skull while trying to identify part of our osteology collection – IDing it wasn’t helped by the premaxillae being missing – but they do look truly wierd. I seem to remember that the figure of the type skull actually had the orbits labelled as nares!

  7. #7 Mike from Ottawa
    November 29, 2007

    TetZoo doesn’t disappoint for weirdness. That skull could be passed off as the Alien or, taking the eyes for nostrils, a dragon’s skull.

  8. #8 arachnophile
    November 29, 2007

    “that bikini looks photoshopped :P” LOL – most are.

    So what do the experts consider to be the evolutionary advantage for these species to have the softer and often diminished shell.

    If I read things correctly, the soft-shells are considered to be “derived” from hard-carapced ancestors? Im sure there is a more terminologically-correct way of saying that *shrug*

  9. #9 Cameron
    November 29, 2007

    I remember a paper talking about why soft-shelled turtles have the shell they do.

    Alibardi, Lorenzo and Toni, Mattia. 2006. Skin structure and cornification proteins in the soft-shelled turtle Trionyx spiniferus. Zoology vol. 109 is. 3 182-195

    Or right here: (if you have access)

    It appears that the shell is not actually “soft” at all, but mechanically as hard as those of a normal turtle. It’s also an adaption for a life in water (streamlining), is lighter, and more easily manipulated by muscle.

  10. #10 Lars
    November 29, 2007

    …they can catch and overturn goats…

    I seem to recall that Macrochelys has a reputation as an ambush predator of larger terrestrial mammals also – can’t lay my hands on the reference at the moment, but I recall that stomach contents of some larger individuals (~100 kg) featured bits of deer and dog. These could have been the result of scavenging but there was reason to believe that the turtles indulged in crocodilian-like tactics – lurking underwater and grabbing the nose of the drinking prey, then dragging it in and drowning it. Then eating it, of course.

    Nice post on big softshells, Darren. Like bags of suet concealing pairs of sharpened bolt-cutters. I have fond memories of leaping about to avoid a full-sized female Florida softshell loose on an office floor in my old zoo dept. – I was wearing sandals and this was a real liability with such an unexpectedly limber and aggressive big turtle. Nobody felt brave enough to try and corral her.

  11. #11 John Scanlon, FCD
    November 29, 2007

    Welcome back! I missed yesterday’s puzzle-post, but like to think I would have guessed Chitra as I knew about these freakin’ big softies. A couple of years back I had a guy named Eric Chitra working in my lab, but he was rather more brachycephalic than C. indica.
    Re. the Hoan Kim head-shot above, my thought was that it looked like an Amazonian giant otter, rather than a seal (those whitish patches on the face add to the resemblance).
    Also it’s nice to know the legendary origin of goat-tipping (related to cow-tipping, which I believe had a rash of populkarity in New Zealand).

  12. #12 M. Randolph Kruger
    November 30, 2007

    Indeed the favorite softshelled pancake turtle of the slackwaters of the Mississippi have been observed in the larger ones to latch onto cats, birds and rodents and drag them under. Its a food fight after that as catfish, snapping turtles and others fight over their kills. Biggest one I ever saw was recently near a casino dock, about a foot across and probably 20 lbs. One quick snatch and the prey is in the water and their environment. cant get away if the prey isnt able to swim very well.

  13. #13 Emile
    November 30, 2007

    Yay! :D

    For some reason, softshells seem to be the most aggressive turtles alive. I’ve had hatchlings gape threateningly at my finger. I suppose that’s what happens when people call you a softie…

    Re snatching animals at the water’s edge: alligator snappers probably do that on a smaller (?) scale. And the pleurodire Pelomedusa subrufa apparently grabs and drowns doves.

  14. #14 Randy
    November 30, 2007

    Regarding the function and structure of trionychid (soft-shell turtle) osteoderms, there is also this recent paper:

    Scheyer, T.M., P.M. Sander, W.G. Joyce, W. B�hme, and U. Witzel. 2007. A plywood structure in the shell of fossil and living soft-shelled turtles (Trionychidae) and its evolutionary implications. Organisms Diversity & Evolution 7(2):136-144.

  15. #15 Darren Naish
    November 30, 2007

    I always learn something new from the comments! On predation in Macroclemys, the alligator snapper, I’ve read about carrion-feeding (see this ver 1 article), but not about active predation of terrestrial mammals. It’s certainly feasible though. Someone should try and film a Jurassic Park ‘where’s the goat’ sequence involving a hungry alligator snapper and an unlucky victim, in the name of science of course.

    On Emile’s comment about African helmeted turtles Pelomedusa subrufa (Branston belongs to this species), a National Geographic documentary called ‘Etosha: Place of Dry Water’ includes footage where a displaying male dove is grabbed and drowned by a helmeted turtle. The turtle walks out of the water, and the dove is too busy trying to woo a female to notice. The dove gets grabbed, pulled back to the water, and then gets to enjoy being drowned and dismembered at the same time (by a group of several of the turtles).

    Regarding John Scanlon’s comments on goat-tipping and cow-tipping, I know the latter well thanks to the movies Barn Yard and Cars, which (I’m sorry to say) I’ve watched many, many times. In Cars, it’s tractor-tipping, but same principle :)

  16. #16 johannes
    November 30, 2007

    > “that bikini looks photoshopped :P” LOL – most are.

    I hope that either the lady or the turtle are photoshopped into this image. Otherwise, somebody took a highly unnecessary risk to shoot this. A softshell of this size is dangerous even on land, leave alone in its own environment. As a rule of the thumb (or as a rule of keeping your thumbs, or other fingers and toes): Keep one carapax-length away from the head!

    > So what do the experts consider to be the evolutionary
    > advantage for these species to have the softer and
    > often diminished shell.

    I’m not an expert on tryonychids or turtles in general, and this is just speculation on my side, but tryonychids are said to have a limited degree of skin-breathing (see here)
    Perhaps the lack of horny scutes helps their skin-breathing abilities?

  17. #17 Mark Evans
    November 30, 2007

    I was mistaken. It wasn’t the figure of the type (Gray was, of course, too good). To quote Gaffney in his encyclopaedic 1979 work:

    “…Prasad, 1958 (Chitra indica, an incredibly bad figure in which the orbits are labeled nares and the temporal fossae are labeled orbits)…” [page 243].

    This is available with lots of other AMNH goodies from their site (go to http://hdl.handle.net/2246/565). Takes an age to download though – 120MB!

    Gaffney, E.S. 1979. Comparative cranial morphology of recent and fossil turtles. Bulletin of the American Museum of Natural History 164:1-376.

    Prasad, J. 1958. The cranial peculiarities of mud turtle, Chitra indica (Gray). Jour. Vikram Univ., vol. 2, pp. 97-100.

  18. #18 Cameron
    November 30, 2007

    Johannes, the paper that randy mentioned (and I discovered after I posted) appears to speculate that the lack of a carapace enables more efficient cutaneous breathing. My access to it is currently down so I’m not able to see if they directly studied that or not.

    Photoshopping women next to monsters seems to be the past time of a few Japanese image boards such as: here

    And on strange head morphology, Amyda is so eccentric looking that it looks more like some sort of bizarre eel than a turtle.

    My apologies to Darren for that horrendous URL I posted previously…

    [from Darren: it's ok, I'm used to editing them]

  19. #19 David Marjanovi?
    November 30, 2007

    Remind me to elaborate one time on the noble tradition of using Oriental ladies as scale bars for assorted large animals, seriously.

    Not all of them are to scale. I remember seeing one (years ago) that was way too small.

    BTW, the message board in question is Chinese, though some of the photos are labelled in Japanese (so most likely copied from elsewhere).

  20. #20 Jerzy or Jurek
    November 30, 2007

    Strengh of bite of assorted turtles is legendary. Anybody tested it vs bite of lion and others? ;-)

  21. #21 Jerzy or Jurek
    November 30, 2007

    Strengh of bite of assorted turtles is legendary. Anybody tested it vs bite of lion and others? ;-)

    BTW, in C/S Europe, quite popular urban horror story is overgrown Chelydra serpentina pets captured in city pond after biting toes of some child…

  22. #22 DDeden
    November 30, 2007

    Great post, chitras can get much bigger than I’d thought, and I didn’t think they were quite so dangerous. I thought they were just scavengers (goats/deer washed downriver) and benthic feeders in freshwater. The emerging head photo does remind me of both the giant otter and seals. And I also thought the smaller carapace and/or more external soft tissue related to underwater breathing.

    For anyone interested in aquatic adaptations, theres a Spanish language nature blog with some English, including a reference to “Aquatic Adaptations in Amniotes” in English, can be found here:

    link

  23. #23 Hai~Ren
    December 1, 2007

    That link Cameron posted is definitely in Chinese (thread title loosely translates to “Beauty and the Monster”, and it ripped off a bunch of photos and artwork from various Japanese sites. Off the top of my head I can think of two of them:

    http://big_game.at.infoseek.co.jp/: Most of the pictures with lovely Japanese ladies photoshopped in with the beasts come from there. (Although it’s been down lately)

    http://www.geocities.co.jp/NatureLand/5218/: The drawing of random bikini-clad beauty calmly sitting next to the Dunkleostus doing a headstand comes from there; there’re similar ones featuring the Orodovician cephalopod Cameroceras here and Leedscithys here. It’s a general overview of animal evolution throughout the Earth’s history from the Cambrian onwards (and even some speculative future animals); sad to say, not all the creatures featured have a person standing next to them for scale.

  24. #24 JW Tan
    December 1, 2007

    Hoan Kiem Lake is right smack in the middle of busy polluted Hanoi, and pretty small (you can walk around it in less than forty minutes, even at a tourist stroll). I’m not sure that a couple of big turtles could survive in there… How much food do big softshells need to survive anyway?

  25. #25 David Marjanovi?
    December 1, 2007

    Hoan Kiem Lake is right smack in the middle of busy polluted Hanoi

    That explains it! They’re mutants!!!1! I shudder to think what might come out of any bodies of water in the industrial regions of China…

    How much food do big softshells need to survive anyway?

    Being turtles, not much, I suppose…

  26. #26 Hai~Ren
    December 1, 2007

    I realise that the two links I posted up there have some problems; anyone who wants to visit the two sites I mentioned should remove the colon at the end of the URL. (Although it might not work for the infoseek site, which is down anyway)

    I find it interesting to point out that Pelochelys too has undergone some taxonomic revision as well, with three separate species (bibroni, cantorii and signifera).

  27. #27 arachnophile
    December 1, 2007

    My thanks to Cameron and johannes for the links. Cutaneous breathing would not have been my first, or tenth, guess on that one. Interesting stuff.

  28. #28 pough
    December 2, 2007

    I was dying to know what the text was about, so it’s very handy to be living with a Japanese woman. It says “marusuppon”. Those turtles are called suppon in Japanese. Supponpon means naked. Maru means completely. It’s a pun, with nudity and turtles. Doesn’t get much better than that, does it?

  29. #29 Christophe Thill
    December 3, 2007

    That turtlehead picture is crazy. It does look like a seal. I thought it was one, and that it was there for comparison. I even mistook the creases above the mouth for whiskers ! And those eyes… definitely not very reptilish…

  30. #30 David Marjanovi?
    December 4, 2007

    Well, it’s not really the head of a turtle. It’s the skull of a turtle. Whiskers wouldn’t be there for that reason alone. And what, except the position, is not “reptilian” about the eye sockets? Look like ordinary eye sockets to me.

  31. #31 johannes
    December 4, 2007

    David,

    I think Christophe meant the third picture (counting from above), the head of the Hoan Kim turtle emerging from the water, not the first one depicting the skull.

  32. #32 David Marjanovi?
    December 4, 2007

    Oops! :-] While I still don’t think that one looks like a seal, it does look rather mammalian. The beak especially is very bizarre.

  33. #33 knitting5
    August 29, 2008

    oh my gosh! that third picture looks weird! it looks like a seal or something. and that second picture really does look like a water bottle.

  34. #34 Jeannot Maha'a
    March 3, 2009

    I only just found this fun little post and thread while searching the wed for articles about the turtle genus Rafetus.

    “…overturn goats…” let’s try “boats.” Now look at your keyboard and locate the letters G and B. There have long been reports of large softshells overturning small boats. Alderton’s book is a great and hasty rehashing of previously published material. I think haste turned “boats” into “goats.”

  35. #35 Darren Naish
    March 3, 2009

    Ha! I’m sure you’re right, thanks for pointing this out.

  36. #36 Monado, FCD
    July 1, 2010

    The chitrachitra.com link doesn’t work for me, but here’s a picture from Turtles of the world: Chitra chitra.

    I once visited a zoo that had alligator snappers from the Mississippi. As I held up my 8-month-old baby to see them, one of the turtles slid over to our side of the pool and looked up hopefully.

  37. #37 Surroundx
    April 21, 2011

    [from Darren: sorry, held up by spam filter]

    The individual soft-shelled turtle in Hoan Kiem lake has been confirmed as new species (Rafetus leloii) after DNA analysis was recently performed:

    http://english.vietnamnet.vn/en/science-technology/7350/hoan-kiem-turtle-is-a-new-species.html

    The article states its binomial name as R. vietnamensis (are they unaware it already has a scientific name?), which I presume is what they intend to name it in an upcoming paper. However, as it already has a scientific name, a redescription is warranted instead.

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