Giant African softshells - wow!

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If you're a long-time Tet Zoo reader you might remember the article about giant Asian softshell turtles from November 2007. That article - which mostly focused on the several Chitra species - was colourfully titled 'The goat-eating hot water bottle turtles'. As you may recall, the 'goat-eating' bit was inspired by a comment made in a turtle book (David Alderton's Turtles & Tortoises of the World): according to this source, Chitra 'may even attack goats, overturning them' (Alderton 1988, p. 165). That always seemed like a puzzling statement, but I decided to run with it. As kindly pointed out by Jeannot Maha'a, 'goat' in the book is almost definitely a typo for 'boat' (look where g and b are on the keyboard). Oh well, it was a nice idea while it lasted...

Anyway, Asia isn't the only continent with giant softshells. There are also giant African species (or one anyway: the African softshell Trionyx triunguis), and in an October 2009 post on the SA Reptiles discussion board, forum-user Herphabitat posted several photos of a huge, dead softshell he and colleagues discovered on a peninsula in the mouth of the Congo River. From a distance, they first assumed that the carcass was that of a dead sea turtle (perhaps a Leatherback Dermochelys coriacea). On discovering that it was a softshell, they assumed that it had died further up-river and had then been washed down to the edge of the Atlantic. However, this assumption isn't warranted, as T. triunguis inhabits brackish waters in places, and has even been captured 3 or 4 km out at sea (this was close to the mouth of the Gaboon River: Ernst & Barbour 1989). T. triunguis is a widespread softshell, occurring from coastal Turkey, Israel, Lebanon and Syria all the way west to the Atlantic coast of the Congo region.

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As you can see from Herphabitat's photos, the animal was a pretty impressive beast (his photos of the animal's skull [one shown below] confirm, by the way, that it was indeed a T. triunguis). Its length along the curve of the carapace (known as the CCL, or curved carapace length) was 55 cm, and the total length was given as 106 cm. Its mass was estimated at over 60 kg. Very big indeed - and bigger than most measurements given in the turtle books. Ernst & Barbour (1989), for example, give a maximum length of 95 cm for this species. However, some sources give a maximum length of 112 cm. Again, I hope this brings home the point that softshells - which are relatively familiar turtles to many people - aren't all dinner-plate-sized or smaller; some are giants, among the largest of turtles.

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While we're here... it's been suggested that there might be monster examples of T. triunguis whose lengths well exceed 1 m. In his 1987 book on the mokele-mbembe, Roy Mackal wrote about the 'Ndendeki', a giant turtle of Lake Tele (and perhaps the surrounds) in the Congo. Local people didn't know much about it - other than that it was a turtle and that it was very large - but an estimated diameter of a ridiculous 4 or 5 m was suggested (Mackal 1987, p. 267). Mackal and his colleague Marcellin Agnagna both assumed that exaggeration had occurred, and that a more reasonable size might be about 2 m (this is for length and not diameter). That's still pretty incredible - though certainly not impossible - and really needs verification [adjacent Ndendeki reconstruction from Mackal (1987, p. 271)].

Anyway, full credit to Herphabitat for his excellent photos. Please visit the SA Reptiles post to see more images and more information. Thanks to Markus Bühler for bringing this to my attention.

Coming next: the yowie!

For previous Tet Zoo posts on amazing turtles see...

Refs - -

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

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

Mackal, R. P. 1987. A Living Dinosaur? In Search of Mokele-Mbembe. E. J.
Brill, Leiden.

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That illustration bothers me - did the author intend to portray the carapace as domed or is it just an optical illusion?

When I was researching softies for my own devious means (thankfully not this topic...) I came across this link (warning opens Google Books!) which gives Trionyx triunguis a carapace length of 95 cm and a mass of 90 kg! This would seem to imply that the species actually can reach 2 meters in total length, but I'm worried that they mixed up carapace length and total length. The weight figure is far too low (should be more like 300+ kg), but it could have been poorly estimated after the fact.

I just ask me when the first ones will begin to speculate about any correlations between this carcass and the MM (I don´t want to write the full name, and you surely know what I mean, to avoid that this blog post appears in results of searching engines when people search for the MM). Please, DON´T DO THIS FOLKS! There is absolutely no connection with the infamous MM.
But possibly it´s already too late, we will probably anytime read about the MM being a softshell or find the photos of the dead Trionyx as "unidentified monster" or so in the net.

The Turtles of the World entry gives a CL of 101.5 for a captive specimen at the United States National Zoological Park. What is the CL of this one?

-Soft shell turtles get really big in Florida too.

http://keystreasures.tblog.com/

Scroll down to last article. No pictures are available on-line. You could ask Cryptomundo if they still have one on file. Originally, it was assumed to be an alligator snapper IIRC.

Regarding MM 'similarity' (see comment 2), note that the soft tissues around the nostrils were the first to go in the softshell, as in the MM.

Yes, and this carcass has also a real beak. It is also really interesting how fast the tissue of the face region can become decomposed or removed by scavengers and small animals like insects and their larvae. I have seen photos of black bear and gorilla carcasses, which were in the whle still completely intact and showed only slight signs of decomposition, but much of the skull was already nearly completely defleshed, mainly from the facial region on.

Awesome.

Which makes me even more sad that i missed them in Turkey.

Stupid softshell-related question: I assume the bones of the carpace are just covered in ski and not keratin. Are they otherwise similar ot other turtle shells in terms of boney-ness?

@ Zach Miller -

No, not exactly, the shell is much reduced and has large bony spikes projecting to the sides.

By Tim Morris (not verified) on 17 Jan 2010 #permalink

I'm kind of curious about the rather small shell on the large turtle. Is the carapace in this species historically that small? I'm just curious as to whether this may be an exampe of reduction in carapace size?

Jared:

The shell is reduced in the sense of lacking keratinous shields, please see the link above for more information. This morphological condition has been around for a while, at least the Cretaceous.

I'm most familiar with the small Chinese softshell (Pelodiscus sinensis), so the large captive 50cm Malayan softshell (Amyda cartilaginea) I saw in late 2008 was very impressive. This giant African softshell however is just mind-blowing.

I've yet to encounter any Pelochelys or Chitra though.

I read an article a few years back where someone speculated that the "brontosaurs" reported in the Congo were realy misidentified giant softshell turtles. I am not so certain of this as all of the soft shell species that I know of (all American species) are carnivores feeding mostly on fish. Are the African species of softshells herbivorous or could the native reports (that the mystery animals eat fruit)be incorrect? In any case a new turtle seems more likely to me than a living dinosaur.

Darren:

T. triunguis inhabits brackish waters in places, and has even been captured 3 or 4 km out at sea

Taskavak and Akcinar (2009) suggest that this species is actually quite well adapted to seawater, particularly in the Mediterranean. In their paper there is a photo of an adult Trionyx triunguis resting at the bottom of the sea, at about a depth of 15 m.

Regarding the maximum size of this species; Taskavak and Akcinar (2009) claim to have caught in 2002, as by-catch with a bottom trawl in Iskenderun Bay, SE Turkey, a male soft-shelled turtle with a straight carapace length of 108.4 cm. This, according to the authors, is 'likely to be the biggest on record'. (They don't say how much it weighed, though.)

Reference:

Taskavak, E. & Akcinar, S.C. 2009. Marine records of the Nile soft-shelled turtle, Trionyx triunguis from Turkey. Marine Biodiversity Records 2, e9, doi:10.1017/S1755267208000092.

Wow, thanks for that, Dartian :) It's been said that turtles are especially tolerant to variable salinities because they're buffeted by the shell. And then there's softshells, which can happily tolerate high salinities despite a carapace covered in epidermis. Do they have any adaptations for coping with high salinity? There's data on this sort of thing for emydids, but not sure it's been studied in softshells.

Incidentally, the fact that softshells are OK in brackish or even marine waters means that they can't be used as freshwater indicators in palaeo-environmental studies anymore. Sigh - when will these pesky animals start reading the literature?? What next: salt-water salamanders? Oh yeah.

It really sucks that Taskavak & Akcinar (2009), available here by the way, did not at least include a photo. The 101.5 cm CL specimen from the US National Zoological Park is also tantalizing, surely there's some documentation of it?

It should be noted that the Eocene trionychid Drazinderetes tethyensis had a 1.2 m bony carapace with a total diameter of ~2 m, i.e. leatherback-sized!

And then there's softshells, which can happily tolerate high salinities despite a carapace covered in epidermis. Do they have any adaptations for coping with high salinity? There's data on this sort of thing for emydids, but not sure it's been studied in softshells.

Only thing I'm aware of is this:
http://www.jstor.org/pss/1442415

By Sven DiMilo (not verified) on 18 Jan 2010 #permalink

salt-water salamanders?

Nah.

By Sven DiMilo (not verified) on 19 Jan 2010 #permalink

Are the African species of softshells herbivorous or could the native reports (that the mystery animals eat fruit) be incorrect?

One possibility is that one or more species have switched from carnivory to frugivory. This is the case with the Gulf Snapping Turtle Elseya lavarackorum, only (I think) member of a carnivorous family to have switched to feeding on fruit, mainly figs which drop from trees on the banks and circulate in eddies below waterfalls on Lawn Hill Creek, not far from where I am now. One result was that the species remained unknown until recently (to Western Science, not the hunter-gatherers who'd been eating it for millennia and knew its diet) because it doesn't go for the dead fish bait used to find other chelids. Actually it was described from a fossil, just before turning up alive and well.

A similar switch between frugivory and carnivory occurs in the Serrasalmidae; only one or two piranha species are carnivorous, their dentition seems to have originally been an adaptation to nipping bits off floating fruit.

If a giant softshell (with typical narrow sharp beak and strong bite) switched from fish to fruit, but lived in murky, deep or turbulent water so it couldn't easily be herded or speared, it could remain very poorly known in the same way as the Gulf Snapper (former cryptid).

By John Scanlon FCD (not verified) on 19 Jan 2010 #permalink

Thank You John Scanlon

I did not even know about the Gulf Snapper and I think Snapping Turtles are especially facinating. Many Cryptozoology books mention giant American turtles, apparently unaware that their "giants" are perfectly normal sized Alligator Snapping Turtles. This is yet more evidence that the Mokele Mbembe is a turtle, and possibly even a known species.

@23 John Scanlon: I had never heard of the Gulf Snapping Turtle before - how interesting, thanks!

Hmmm, I never considered the possibility of mokele-mbembe as a turtle before this thread ... it seems that this would require some size exaggeration, as isn't mokele-mbembe supposed to be hippo or elephant size? But size exaggeration is very common in "weird animal" stories... food for thought...

@24 Laura Henson: Yes, alligator snapping turtles can get STUNNINGLY big; I remember seeing a picture 10+ years back of one that was supposed to be something like 80 kg. (even Common Snapping Turtles can get pretty big for that matter; I've seen a captive one that must have had a shell over 40cm long.)

By William Miller (not verified) on 20 Jan 2010 #permalink

In case there's any confusion, the Gulf Snapping Turtle lives in Australia and is a pleurodire in the family Chelidae, as opposed to the (currently) New World snappers which are cryptodires in the family Chelydridae.

'may even attack goats, overturning them' (Alderton 1988, p. 165). That always seemed like a puzzling statement, but I decided to run with it. As kindly pointed out by Jeannot Maha'a, 'goat' in the book is almost definitely a typo for 'boat' (look where g and b are on the keyboard).

If you ever read that turtles 'may even attack boas' or 'may even attack boars',
be similarly cautious (look where t and r are on the keyboard) :-D

Its length along the curve of the carapace (known as the CCL, or curved carapace length) was 55 cm, and the total length was given as 106 cm.

To clarify - the length along the curve of the carapace including the 'soft' portions/margins/rim is 106 cm, 55 cm measures the bony portion of the carapace. Estimating from ImageJ, the SCL is about 90 cm and total length is ~1.3 meters.

However, some sources give a maximum length of 112 cm

This is horrendously vague. It should be SCL, but some researchers (unfortunately) may have meant CCL, SCL of the bony portion, CCL of the bony portion, or total length of the animal.

To me, the 4 to 5 m "Ndendeki" was given corresponds more with its total length !

A 2 meters SCL + a 2 m extended neck !