More wide-mouthed South American horned frogs

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Yesterday - the day I posted an article on horned treefrogs - there was a peak on the site stats graph. In view of that I'm thinking that weird anurans are popular, so I'll try the same trick again. This time round we're looking at another group of 'horned' anurans: the Brazilian smooth horned frogs of the genus Proceratophrys. This time I really will try and keep it brief: I have ichthyosaurs to deal with...

Like the hemiphractids we saw yesterday, smooth horned frogs are wide-skulled ambush predators that hide on forest floors in tropical South American forests, specifically those of Brazil, Argentina and Paraguay. With fleshy growths that extend from bony frontoparietal crests and with tubercles and nodules on their body and limbs, they mimic the leaf litter that they hide amongst and are highly cryptic. Indeed very little is known of their biology and behaviour. They mostly prey on arthropods, with cockroaches, spiders and crickets proving important in the diet of some species (Teixeira & Coutino 2002). They aren't particularly big, with SVLs ranging from about 25 to 50 mm. 18 species are currently recognised, eight of which have been named since 1990 (the newest is P. paviotii Cruz et al., 2005), but it's been noted that the genus needs revision and that not all the species are close relatives. Indeed they don't all look alike: P. subguttata (shown here: it was only named in 1999 [photo from here]) and similar forms possesses large, horn-like supraorbital growths and are decorated with lichen-like growths on their limbs and sides, whereas species like P. brauni and P. bigibbosa only have small 'horns' and exhibit a granular skin texture. Others, like P. cristiceps, virtually lack horns. In the more elaborately ornamented species, the bony frontoparietal crests are particularly tall and the skull bones are decorated with tiny bumps and spurs (Izecksohn et al. 1999).

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The adjacent photo, from Izecksohn et al. (1999) shows the skulls of P. boiei (top left), P. appendiculata (top right), P. melanopogon (bottom left) and P. laticeps (bottom right). The scale bar is 10 mm.

Smooth horned frogs have conventionally been regarded as part of the huge South American leptodactylid group and they have often been allied with the far more familiar Ceratophrys species (the horned frogs) in a group called Ceratophryinae. This has been contested in some studies however (see Fabrezi 2005) and Frost et al. (2006) argued that the smooth horned frogs were actually allies of Rhinoderma (the amazing mouth-brooding Darwin's frogs) and a number of other genera, all of which they united in a group termed Cyclorhamphidae, a clade close to the origin of dendrobatids (poison-arrow frogs) and bufonids (toads). As you'll know if you've been paying attention, however, there is a little bit of scepticism about Frost et al.'s new phylogeny....

Yay - it's Friday, pass the whisky.

Refs - -

Fabrezi, M. 2005. Morphological evolution of Ceratophryinae (Anura, Neobatrachia). Journal of Zoological Systematics 44, 153-166.

Frost, D. R., Grant, T., Faivovich, J., Bain, R. H., Haas, A., Haddad, C. F. B., De Sá, R. O., Channing, A., Wilkinson, M., Donnellan, S. C., Raxworthy, C. J., Campbell, J. A., Blotto, B. L., Moler, P., Drewes, R. C., Nussbaum, R. A., Lynch, J. D., Green, D. M. & Wheeler, W. C. 2006. The amphibian tree of life. Bulletin of the American Museum of Natural History 297, 1-370.

Izecksohn, E., Potsch de Carvalho-e-Silva, S. & Deiss, I. 1999. O osteocrânio de Proceratophrys boiei (Wied-Neuwied), P. appendiculata (Günther), P. melanopogon (Miranda-Ribeiro) e P. laticeps Izecksohn & Peixoto (Anura, Leptodactylidae). Revista Brasileira de Zoologia 22, 225-229.

Teixeira, R. L. & Coutinho, E. S. 2002. Hábito alimentar de Proceratophrys boiei (Wied) (Amphibia, Anura, Leptodactylidae) em Santa Teresa, Espírito Santo, sudeste do Brasil. Boletim do Museu de Biologia Mello Leitao (nova serie) 14, 13-20.

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I'll pass on the whisky and go with rum or port, but that P. subguttata photo is very weird. The frog looks so flat at first I thought it was a painting rather than a photo. If that flatness is not an artifact of the photographic process or being viewed on a computer, it would be a very effective camouflage technique.

By Mike from Ottawa (not verified) on 19 Oct 2007 #permalink

Very interesting.

Has the SNV measurement been employed in non-anurans, such as miocene apes or chimps or rabbits? I never heard of it.

Snout-vent length is generally used for extant amphibians and "reptiles", but not for anything else, AFAIK. Elsewhere, total length is preferred, except for mammals, where "body length" and "tail length" are given separately.

Snout-vent length has the advantage that it can be applied to legless animals, and the disadvantage that it's not very easy to determine in fossils.

By David Marjanović (not verified) on 21 Oct 2007 #permalink