Graeme’s Pleistocene megafrog
I didn’t talk much to people today: I spent most of it sat in front of a PC, dealing with over-due email responses and sorting through manuscripts I’m handling for my editing job. Jeff Liston phoned though, and I also caught up briefly with Dave Martill for a catch-up on the British dinosaurs project we’re working on (deadline end of this month… gack). I need not labour the point that a disturbing amount of time is passing without me working on my phd thesis. And then Graeme Elliott came to see me. He saw that I was printing out Pounds et al’s (2006) recently published Nature paper on global lissamphibian extinctions. Make no mistake, frogs and toads are in big trouble, with populations and species disappearing at a disturbing rate.
What does Graeme think about this? He thinks that there should be a giant Pleistocene frog somewhere out there in the fossil record, the size of a Labrador at least and able (theoretically, were these organisms contemporaneous) to eat puppies and small children. Skull Island should harbour relict descendants of such forms, though I doubt they would fare well among giant V. rexes, terrestrial predatory crocodyliforms and truck-sized arthropods. Are there any particularly big fossil frogs? Not really. Aubrey Smith, Marc Jones and Susan Evans have been giving conference presentations on a Cretaceous Madagascan fossil they’re referring to as a ‘hyperossified megafrog’ - I think I detect a hint of hyperbole. It’s the biggest Mesozoic frog yet reported, but even so it was probably not much bigger than, say, Ceratophrys (the extant Horned frog). I doubt if Cenozoic fossil frogs got much bigger than extant forms.
Indeed the biggest frog of all time, so far as we know, is the Goliath frog Conraua goliath (and not Rana goliath as said in some older sources, though Conraua was included in Rana until Nieden separated them in 1908) of Cameroon. Described in 1906, it’s one of six Conraua species, sometimes called the slippery frogs. I don’t have Mark Carwardine’s Guinness Book of Animal Records by my side right now, but I think they get to about 60 cm (with legs outstretched) and over 3 kg. For a frog, that’s big. Of course there’s always the unverified carn-pnay of the New Guinean highlands – a crypto-frog supposedly bigger than C. goliath.
Why aren’t there frogs the size of labradors? I don’t know if it’s been discussed in the literature, but I’ve always liked the idea that lissamphibians are constrained in size by the fact that most of them rely on cutaneous respiration. Bigger lissamphibians, having a small relative surface area, should find it more difficult to respire compared to their small relatives, and this prediction seems to be confirmed by the fact that the biggest lissamphibians (the cryptobranchid salamanders) are aquatic. Surely there’s stuff in the herpetological literature that covers this. Maybe I should check.
The picture above is taken from the University of California's amphibian pages.
Coming soon on this blog site… Why rabbits are just wrong; Birds in crevices; Transatlantic manatees; and Eagle owls take over Britain. For the latest news on Tetrapod Zoology do go here.
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Pounds, J. A. Bustamante, M. R., Coloma, L. A., Consuegra, J. A., Fogden, M. P. L., Foster, P. N., La Marca, E., Masters, K. L., Merino-Viteri, A., Puschendorf, R., Ron, S. R., Sánchez-Azofeifa, G. A., Still, C. J. & Young, B. E. 2006. Widespread amphibian extinctions from epidemic disease driven by global warming. Nature 439, 161-167.