Green-boned glass frogs, monkey frogs, toothless toads

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So here we are, back with the anurans. In the previous article on neobatrachians (here), we looked at the basic division of the neobatrachians into the mostly New World Hyloidea, and the mostly Old World Ranoidea. While the characters historically used to differentiate hyloids (an arciferal pectoral girdle and procoelous vertebrae) are now understood to be primitive within neobatrachians, recent molecular studies have revealed good support for a clade that more or less corresponds with traditional Hyloidea. Many anuran workers have included within Hyloidea the Australasian southern frogs (or myobatrachids) and the huge assortment of American neobatrachians conventionally lumped together in the group Leptodactylidae; some workers have found the Seychelles frogs (or sooglossids) to be basal members of the clade as well. This is the scheme I pretty much followed in the previous article.

However, a close association of Seychelles frogs and southern frogs with a group of neobatrachians that we might term the 'core hyloids' is not agreed upon by everyone: Darst & Cannatella (2004) found support from mitochondrial DNA for a 'core hyloid' clade that includes eleutherodactylines, glass frogs (centrolenids), toads (bufonids), phyllomedusine and pelodryadine treefrogs, and horned frogs (ceratophryines or ceratophryids), and they argued that Hyloidea should best be used as a node-based name for the clade that includes these groups, but not necessarily the other groups traditionally included within Hyloidea.

The monophyly of 'core hyloids' seems generally agreed upon, with one interesting area of agreement being the inclusion within the clade of the South American dendrobatids or poison-dart frogs, or poison-arrow frogs, or poison frogs (Hay et al. 1995, Ruvinsky & Maxson 1996, Darst & Cannatella 2004, Frost et al. 2006). Dendrobatids have actually been one of the most controversial groups within neobatrachian phylogeny: like ranoids, and unlike most hyloids, they possess firmisternal pectoral girdles (see the previous anuran article) and Ford & Cannatella (1993), confident of the classification of these frogs among the ranoids, used dendrobatids as one of several specifiers in their phylogenetic definition of Ranoidea. While a reasonably long list of studies have indeed included dendrobatids among the ranoids, a roughly equal number have grouped them with various hyloid lineages, so use of Dendrobatidae as a phylogenetic specifier is not appropriate, and regret about the decision was expressed by Cannatella & Hillis (2004).

The treefrogs

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One of the most speciose and widespread neobatrachian groups is Hylidae, the treefrogs: an immense group of over 860 species from the Americas, Australasia, tropical Asia, Europe and northern Africa. Treefrogs have conventionally been grouped together on the basis of claw-shaped terminal phalanges: they also possess intercalary elements (accessory digit segments located between the distal and penultimate phalanges), though the latter also occur in glass frogs (more on those in a moment). Most treefrogs are green arboreal frogs with expanded toe pads, but many are terrestrial, some (like the American burrowing treefrogs Smilisca and some Australian Litoria species) are burrowers, and some (like the paradox frogs) are aquatic. Several recent studies have looked at hylid phylogeny (Darst & Cannatella 2004, Faivovich et al. 2005, Wiens et al. 2005, Frost et al. 2006): the details differ, but the more recent of these works conclude that Hylidae includes a pelodryadine + phyllomedusine clade, and a far larger and more diverse hyline clade. The most divergent hylids are the bizarre leaf frogs, monkey frogs or phyllomedusines, a group of tropical American taxa that superficially resemble slow-climbing primates like lorises (indeed one taxon is named Pithecopus; another is named Philomantis lemur).

As we saw in the article on horned treefrogs (here), experts disagree as to whether horned treefrogs and other marsupial treefrogs are part of Hylidae or not. While the exact relationships of marsupial treefrogs remain controversial (as does their monophyly), they are almost certainly 'core hyloids': Wiens et al. (2005) found them to be close to eleutherodactylines, and not allied to other hylids. This means that the intercalary elements and claw-shaped phalanges present in marsupial treefrogs are convergent with those of hylids. As we saw earlier, marsupial treefrogs are of course well known for keeping their eggs and/or young in dorsally located pouches. Yes, frogs with pouches.

Treefrogs have a fossil record going back to the Palaeocene, and this and various other lines of evidence shows that most hyloid lineages originated either late in the Cretaceous or early in the Cenozoic. There are very few fossils to show for this though! [image above shows the phyllomedusine Phyllomedusa iheringii].

Paradoxical frogs

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Previously classified in their own 'family' are the paradoxical frogs (or pseudids, or pseudines... or pseudaens). These are slippery-skinned, mostly aquatic South American frogs, best known for the fact that their tadpoles reach sizes that can exceed those of metamorphosed adults (a 250 mm tadpole might metamorphose into a 70 mm adult) [adjacent image shows lar- - small tadpole of Pseudis paradoxa]. Particularly elongate intercalary elements help add length to their long, webbed digits. Though previously thought to have diverged from a common ancestor that also gave rise to hylids and glass frogs (Ford & Cannatella 1993), molecular data now seems to show that paradoxical frogs are deeply nested within Hylidae, and in fact within Hylinae (Darst & Cannatella 2004, Wiens et al. 2005, Frost et al. 2006).

Whence all those 'leptodactylids'?

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As noted a few times in these anuran articles, the large and diverse assemblage of hyloids conventionally grouped together as Leptodactylidae is quite clearly not a clade. Frost et al. (2006) found hylids to be the sister-taxon to a hyloid clade that they named Leptodactyliformes: along with glass frogs, horned frogs, poison-arrow frogs and toads, it includes several clades previously included within Leptodactylidae, most of which consist of obscure South American frogs (I'll be covering at least some of these groups in articles that will appear in January 2008). The term Leptodactylidae was restricted by these authors to a leptodactyliform clade that includes the nest-building frogs (Leptodactylus) and a host of other taxa, most of which are terrestrial, superficially ranid-like frogs that build foam nests [adjacent picture shows the Brazilian Yellow painted frog L. flavopictus].

The eleutherodactylines - a tropical American group of often tiny forest-floor frogs, most of which produce large terrestrial eggs that undergo direct development - were found by Frost et al. (2006) to be basal among the 'core hyloids' (more so than hylids and leptodactyliforms), and similar results were reported by Cannatella & Hillis (2004) and Darst & Cannatella (2004). Eleutherodactylines were conventionally included in Leptodactylidae, but the older name Brachycephalidae Günther, 1858 is increasingly used for them. They're best known for including the smallest of all tetrapods: there are a couple of species from Cuba and Brazil that have SVLs of 10 mm or slightly less (9.8 mm in Brazilian Psyllophryne didactyla). Continuing the superlatives... this is a huge group, with over 820 species.

Green-boned glass frogs

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Glass frogs, or centrolenids, are wide-skulled, long-limbed arboreal little frogs (SVL 20-60 mm) of Central and South American cloud and rain forests. Most lay eggs on vegetation overhanging water, or on rocks above the water surface. Their eyes are set on the tops of their heads, they have adhesive disks on their digit tips, and - while they are generally greenish on their dorsal surface - they derive their common name from the fact that they lack pigment on their ventral surface, meaning that their undersides are essentially transparent. I have no idea why this is, and I'm not sure that anyone else does. Even stranger, most (perhaps all) species have green bones. Green bones. Their terminal phalanges are T-shaped (this is also the case in a few other neobatrachian groups, like poison-arrow frogs), the males of some species possess spines on their upper arms (these are used in territorial combat), and the two uniquely elongate ankle bones that characterise anurans (the tibiale and fibulare) are fused into a single element [adjacent image shows a species of Hyalinobatrachium: note the transparent ventral surface].

This isn't a small or insignificant group: there are about 140 named species (a number that has increased from about 65 since the late 1980s), with multiple additional ones recognised but awaiting description (Cisneros-Heredia & McDiarmid 2006, pp. 12-13). Though often allied with hylids, data from mitochondrial DNA now indicates that glass frogs are more closely related to toads and leptodactylids sensu stricto (Darst & Cannatella 2004, Frost et al. 2006). It has also been suggested that glass frogs are the sister-taxon of Allophryne ruthveni (Austin et al. 2002), a controversial and problematical toothless hyloid that has often been given its own 'family', Allophrynidae (a second species of Allophryne has recently been discovered, but I don't think it's been published yet. Please let me know if you know otherwise).

Poison-arrow frogs and toads

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Finally, 'core hyloids' also include the poison-arrow frogs, or dendrobatids, and the toads, or bufonids. Studies disagree as to whether these two clades are close kin, or whether dendrobatids are closer to hylids. As mentioned earlier, the inclusion of dendrobatids within Hyloidea is now agreed upon, despite earlier ideas that they might be ranoids. Restricted to Central and South America, this clade of about 170 species is best known for its brightly coloured, highly toxic taxa. However, most dendrobatids are dull-coloured and non-toxic. In contrast to other anurans, dendrobatids possess a retroarticular process on the mandible and the degree of parental care that they exhibit is particularly complex, with egg-guarding and transport of tadpoles on the parent's back being characteristic for the group. The taxonomy and phylogeny of dendrobatids is a very active area of research that I'm going to avoid entirely for now [adjacent image shows a Tinging frog Dendrobates tinctorius, often known as the Blue poison-arrow frog D. azureus].

Finally, another huge and highly successful hyloid clade is Bufonidae, the toads. Toads are edentulous hyloids characterised by parotoid glands (large poison glands on the back on the head) and a Bidder's organ (rudimentary ovaries present in males. Don't ask). They include over 480 (probably over 500) species. Toads are pretty much cosmopolitan, having spread naturally to all landmasses except the Australo-Papuan region (except Sulawesi), Madagascar and the polar regions. This distribution strongly suggests that they originated during the Upper Cretaceous, and this is supported by other evidence (Pramuk 2006, Pramuk et al. 2001, 2007), including by fossils that are referable to extant genera but date to the Palaeocene [image below shows 'Toadzilla', a big Cane toad captured in Australia. Previously Bufo marinus, under the new taxonomy the Cane toad is Rhinella marina].

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A huge amount of work has been done on bufonid taxonomy, phylogeny and biogeography, and the largest genus in the group, Bufo (previously containing about 260 species) has recently been split up into multiple smaller genera (Frost et al. 2006). Again, in the interests of getting this series of articles finished I am going to force myself to ignore all of that for now. If toads really did originate in the Cretaceous, and if - as most phylogenies suggest - they are one of the youngest hyloid clades, then we have to conclude that most divergences within Hyloidea, and within Neobatrachia, occurred in the Mesozoic (Marjanović & Laurin 2007). At least some of the clades in question, toads among them, seem to have been very conservative during their history given that the oldest fossil forms aren't that different from extant taxa.

What I've just done is a very superficial skim of hyloid diversity, but I hope you get the picture. For now we can say goodbye to this huge and fascinating group of anurans; there are just the ranoids left to go. They might be next. Might not.

Refs - -

Austin, J. D., Lougheed, S. C., Tanner, K., Chek, A. A., Bogart, J. P. & Boag, P. T. 2002. A molecular perspective on the evolutionary affinities of an enigmatic neotropical frog, Allophryne ruthveni. Zoological Journal of the Linnean Society 134, 335-346.

Cannatella, D. C. & Hillis, D. M. 2004. Amphibians: leading a life of slime. In Cracraft, J. and Donoghue, M. (eds), Assembling the Tree of Life. Oxford University Press (Oxford), pp. 430-450.

Cisneros-Heredia, D. F. & Mcdiarmid, R. W. 2006. A new species of the genus Centrolene (Amphibia: Anura: Centrolenidae) from Ecuador with comments on the taxonomy and biogeography of glassfrogs. Zootaxa 1244, 1-32.

Darst, C. R. & Cannatella, D. C. 2004. Novel relationships among hyloid frogs inferred from 12S and 16S mitochondrial DNA sequences. Molecular Phylogenetics and Evolution 31, 462-475.

Faivovich, J., Haddad, C. F. B., Garcia, P. C. A., Frost, D. R., Campbell, J. A. & Wheeler, W. C. 2005. Systematic review of the frog family Hylidae, with special reference to Hylinae: phylogenetic analysis and taxonomic revision. Bulletin of the American Museum of Natural History 294, 1-240.

Ford, L. S. & Cannatella, D. C. 1993. The major clades of frogs. Herpetological Monographs 7, 94-117.

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.

Hay, J. M., Ruvinsky, I., Hedges S. B. & Maxson L. R. 1995. Phylogenetic relationships of amphibian families inferred from DNA sequences of mitochondrial 12S and 16S ribosomal RNA genes. Molecular Phylogenetics and Evolution 12, 928-937.

Marjanović, D. & Laurin, M. 2007. Fossils, molecules, divergence times, and the origin of lissamphibians. Systematic Biology 56, 369-388.

Pramuk, J. B. 2006. Phylogeny of South American Bufo (Anura: Bufonidae) inferred from combined evidence. Zoological Journal of the Linnean Society 146, 407-452.

- ., Hass, C. A. & Hedges, S. B. 2001. Molecular phylogeny and biogeography of West Indian toads. Molecular Phylogenetics and Evolution 20, 294-301.

- ., Robertson, J. B., Sites, J. W. & Noonan, B. P. 2007. Around the world in 10 million years: biogeography of the nearly cosmopolitan true toads (Anura: Bufonidae). Global Ecology and Biogeography doi:10.1111/j.1466-8238.2007.00348.x

Ruvinsky, I. & Maxson, L. R. 1996. Phylogenetic relationships among bufonoid frogs (Anura: Neobatrachia) inferred from mitochondrial DNA sequences. Molecular Phylogenetics and Evolution 5, 533-547.

Wiens, J. J., Fetzner, J. W., Parkinson, C. L. & Reeder, T. W. 2005. Hylid frog phylogeny and sampling strategies for speciose clades. Systematic Biology 54, 719-748.

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Within the immense anuran clade termed Neobatrachia, we've so far gotten through the hyloids (see previous anuran article here: you'll need to read also the articles on basal anurans, transitional anurans, and ghost frogs and so on). All we have left is Ranoidea, but this is the biggest, most…
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So here we are: anuran diversity part II - you have to have read part I (here) for the following to make proper sense. Yesterday I showed my video of Tiger the secretary bird (filmed at the International Bird of Prey Centre, Gloucestershire, last week) to anybody that would watch, and in the wee…

[adjacent image shows large tadpole of Pseudis paradoxa]

Large? It's 5 cm long, not 25, and hasn't grown any legs yet.

paratoid glands

Parotoid. Next (para) to the ear (oto-).

("Epipophysis" is wrong, too -- epapophysis.)

including by fossils that are referable to extant genera but date to the Palaeocene

Well, all not especially brightly colored toads are referable to Bufo, or were before Frost et al. blew that wastebasket up.

The two Pramuk et al. references are missing.

If toads really did originate in the Cretaceous, and if - as most phylogenies suggest - they are one of the youngest hyloid clades, then we have to conclude that most divergences within Hyloidea, and within Neobatrachia, occurred in the Mesozoic (Marjanović & Laurin 2007).

Well, thanks for citing us ( :-) :-) :-) ), but in our paleontological supertree we find a Cretaceous age for Hyloidea -- and therefore Neobatrachia -- for the sole reason that the Campanian Baurubatrachus is said to be a ceratophryid. The "hyperossified megafrog" from the Maastrichtian of Madagascar (described in some detail in an SVP meeting abstract from this year) bolsters this assignment, but, as shown in our fig. 7, we are not aware of any Cretaceous bufonids, or for that matter any bufonids older than Miocene (except for a crumb from the middle Paleocene of Itaboraí, which has also yielded the oldest hylid crumb). If you know of some, please tell me!

While I am at it, almost all of the Miocene "Bufo" species in our fig. 7 consist of a fragmentary right ilium, and we cite a Syst. Biol. paper that shows that bufonid ilia (even left ones) are not diagnostic, so the large diversity we show in that figure could be spurious. Fossil crumbs of amphibians almost always get referred to a species (whether a known or a new one), no matter how fragmentary they are. It's a bit like with neornithean half coracoids. We accepted all those assignments in our paper, except when there was a published counterargument in the literature.

Wait a little. Campanian? That's what the literature on Baurubatrachus says (i. e. a small mention in a single book chapter), but the whole Bauru is Maastrichtian, isn't it...? Or am I misremembering...?

By David Marjanović (not verified) on 09 Nov 2007 #permalink

Very interesting. I was familiar with those transparent frogs (which are in fact much more transparent than those new frog-breed from Japan), but I really did not know that they have green bones. I once wrote about giant modern amphibians, including paradoxical frogs and their tadpoles. I have a photo which shows very well the huge size of the tadpole in comparison with the frog (I used a euro for size comparison). Sadly all those photos of amphibians I made at the museum of natural history in Vienna are very dark.
Here they are:
BTW, have you ever noticed how monstrous some horned frog species can grow?

David, many thanks as always for the comments and corrections. I've changed dumb mis-spelling of parotoid, changed description of the pseudid tadpole.. but you're wrong about the two Pramuk et al. references, they're there. I thought you'd enjoy being cited :) I could have cited various of Jennifer Pramuk's papers or Bossuyt et al. (2006), but your figs. 6, 7 and 9 showed what I wanted to see.

I agree that some of the fossils concerned leave something to be desired. The Palaeocene bufonid I mentioned is indeed the Itaborai partial ilium; its identification might be doubtful, but an affinity with Rhinella (the cane toad group) was viewed favourably by Báez & Nicoli (2004) and Pramuk et al. (2007). You say you're not aware of other bufonids older than the Miocene. Shock-horror.. does this mean you aren't aware of Báez & Nicoli (2004)? They described Oligocene bufonid material, again belonging to Rhinella-like taxa.

Finally, yes, the Marília Formation (source of Baurubatrachus) is indeed upper Maastrichtian. There's a little more on Baurubatrachus than a single book chapter: Candeiro et al. (2006) recently discussed this taxon. Note that a few other South American bits and pieces from the Los Alamitos, Loncoche and Allen formations have been suggested to be 'leptodactylids'.. Báez has suggested that some of the taxa involved are 'telmatobiines', or calyptocephalellines, or whatever.

Refs - -

Báez, A. M. & Nicoli, L. 2004. Bufonid toads from the late Oligocene beds of Salla, Bolivia. Journal of Vertebrate Paleontology 24, 73-79.

Bossuyt, F., Brown, R. M., Hillis, D. M., Cannatella, D. C. & Milinkovitch, M. C. 2006. Phylogeny and biogeography of a cosmopolitan frog radiation: Late Cretaceous diversification resulted in continent-scale endemism in the family Ranidae. Systematic Biology 55, 579-594.

Candeiro, C. R. A., Martinelli, A. G., Avilla, L. S. & Rich, T. H. 2006. Tetrapods from the Upper Cretaceous (Turonian-Maastrichtian) Bauru Group of Brazil: a reappraisal. Cretaceous Research 27, 923-946.

Pramuk, J. B., Robertson, J. B., Sites, J. W. & Noonan, B. P. 2007. Around the world in 10 million years: biogeography of the nearly cosmopolitan true toads (Anura: Bufonidae). Global Ecology and Biogeography doi:10.1111/j.1466-8238.2007.00348.x

Hi Darren,

About those green-boned frogs, what is it that makes the bones green?

[from Darren: it's their colour that makes them green. Seriously, I have no idea, nor have I read of one.]

By Richard Hing (not verified) on 09 Nov 2007 #permalink

Oh. I'm too stupid to interpret a hyphen. :-)

but an affinity with Rhinella (the cane toad group) was viewed favourably by Báez & Nicoli (2004) and Pramuk et al. (2007).

Ah. That changes things; Rhinella is rather deeply nested in Bufonidae according to Frost et al..

You say you're not aware of other bufonids older than the Miocene. Shock-horror.. does this mean you aren't aware of Báez & Nicoli (2004)?

Nope. It's not in our fig. 7, we had no idea. :-| We relied very heavily on the Salientia volume of the Handbuch, which documents every single fragmentary right ilium known up to 1998. That's where all our "species groups" of Bufo in the old sense come from, for example.

(Hey, I had no idea of the green bones either! :-) )

Candeiro et al. (2006) recently discussed this taxon.

We submitted the second time in mid-December of 2006, though it's true I haven't followed Cretaceous Research as much as I should have in the last 2 to 3 years.

Note that a few other South American bits and pieces from the Los Alamitos, Loncoche and Allen formations have been suggested to be 'leptodactylids'.. Báez has suggested that some of the taxa involved are 'telmatobiines', or calyptocephalellines, or whatever.

That ought to mean they're in any case hyloids and could save the pre-Campanian age for Hyloidea.

Thanks anyway. If we ever do an update... :-)

(We almost certainly won't before the controversy over Frost et al. has settled, which in turn won't happen anytime soon.)

By David Marjanović (not verified) on 09 Nov 2007 #permalink

I asked Linda Trueb about the green bones of glass frogs. She informs me that the substance suspected of being responsible for this is biliverdin, a bile pigment derived from haemoglobin degradation. It's not just glass frogs that have biliverdin-impregnated bones, as green bones are also present in some hylids (Faivovich & De la Riva 2006). After a bit of googling it seems that the standard paper on all this is Barrio (1965). However, I'd still like to know why the bones of glass frogs and some hylids incorporate biliverdin, yet those of other anurans and other vertebrates don't. Weird. Thanks Linda!

Refs - -

Barrio A. 1965. Cloricia fisiologica en batracios anuros. Physis 25, 137-142.

Faivovich, J. & De la Riva, I. 2006. On the taxonomic status of Hyla chlorostea Reynolds and Foster, 1992, and comments on other South American hylids. Copeia 2006, 785791.

How odd, I have read about centrolenids many times, and yet the bit about green bones never registered. The question Richard asked above about what makes the bones green also sprang to my mind. Does anyone know the pigment reponsible?

I suppose that since they are transparent and found amongst plant foliage some kind of camouflage is most likely (but why not just have green non-transparent skin like so many other frogs). I guess I am not the only one to briefly entertain the probably very daft idea that they may have symbiotic algae (like some freshwater Hydra) or better yet their own photopigments. I haven't lost my mind, I do know a frog capable of photosynthesis is obviously absurd, but what a wonderful idea, and all it will take to completely dismiss it is somebody telling us what the pigment is.

Reviewing various papers quickly I find that there are many freferences to green bones (e.g. check �Revision of the characters of Centrolenidae (Amphibia: Anura: Athesphatanura), with comments on its taxonomy and the description of new taxa of glassfrogs� by Cisneros-Heredia & Mcdiarmid which is very usefuland free!), but I can't seem to find anything about what the pigments is.

Further the paper �The stream-dwelling tadpole of Hyloscirtus charazani (Anura: Hylidae) from Andean Bolivia� by Lotters, Reichle, Faivovich, & Bain, states that juvenile Hyloscirtus charazani have green musculature.

Strangely it also appears that at least some species have in their skin pigment cells that reflect infrared radiation at a wavelength similar to that reflected by many plants. This is invisible to us, but may serve as a camouflage from some predators that can detect at least some infrared (eg some birds and snakes).

While on the topic of fossil frogs, what do you make of Tregobatrachus? Since miocene frog faunas seem largely modern even at generic level, this oddity (though the remains are scant) seems interesting. The only significant account of it I have read is that in Holman's book Fossil Frogs and Toads of North America.

By Mark Lees (not verified) on 09 Nov 2007 #permalink

Damn, I post my rambling question, and as soon as I hit post, I see that you have while I keyed merrily away added a comment that answered my point, and in one simple swipe destroyed the beautiful concept of photosynthetic frogs! :)

I'll try and see if I can find Barrio, 1965.

[from Darren: yeah, sorry - not sure if that was good timing or bad timing :) And, sorry, I know nothing about Tregobatrachus.. nor have I even seen the late Alan Holman's book. I did once ask Bob Nicholls if he had a spare copy though (he did the cover art). ]

By Mark Lees (not verified) on 09 Nov 2007 #permalink

What is Tregobatrachus?

By David Marjanovi? (not verified) on 09 Nov 2007 #permalink

Wow. Green bones. Even for the kind of thing one learns here at TetZoo, that's just plain weird.

BTW, it took me about an hour to read this article. Not (just) because I'm dim, but because I kept googling for images of the cast of characters (the frogs, of course).

By Mike from Ottawa (not verified) on 09 Nov 2007 #permalink

I'm still holding out hope for photosynthetic lizards. Of course it would have started with algae growing on the scales, later moved underneath for better access to moisture in dry months, and then been made useful. Has anyone checked? A green-skinned lizard doesn't attract as much attention as a green-boned frog.

By Nathan Myers (not verified) on 09 Nov 2007 #permalink

I have a herpetology journal with an interesting article about possible bioluminiscence in some lizard species. It would be really great if it would turn out to be true.

So Tregobatrachus hibbardi is a fragmentary left (!) ilium from the Miocene of Kansas, and was discussed by Sanchíz (1998). That ought to mean I've seen it. Sanchíz mentions a Bufo (americanus) hibbardi, which we faithfully entered into our fig. 7. I guess that's it. I'll try to check on Monday.

The description also mentions that the last known palaeobatrachid is not early, but middle Pleistocene in age. :-o

By David Marjanović (not verified) on 10 Nov 2007 #permalink

Many thanks to all for further comments. Mike, it makes me happy to know that you went to the trouble of googling for images - I hope you found that rewarding!

I've never heard of photosynthetic lizards (cool idea), but there's quite a lot of discussion in the literature about bioluminescent lizards: specifically regarding the cave-dwelling teiid Proctoporus shrevei from Trinidad. Ivan Sanderson said that this species was bioluminescent in a 1939 article: while some authors have reported this without question, others have expressed scepticism. The possibility was properly tested by Knight et al. (2004) who spent a lot of time looking at Proctoporus in the field. They found no evidence for bioluminescence and confirmed that iridescent scales were to blame for creating an optical illusion. Less well known is the rumoured existence of an African frog supposed to have a bioluminescent snout. The species concerned was encountered by Jon Downes at a zoological convention. He told me, and I told him that this would be incredible if true given that no known tetrapod definitely exhibits bioluminescence. Ok, so the Franciscana (Pontoporia blainvillei) and some other cetaceans sometimes have a sheen of bioluminescent microorganisms... (the Franciscana might even use these to see with, apparently).

Ref - -

Knight, C. M., Gutzke, W. H. N. & Quesnel, V. C. 2004. Shedding light on the luminous lizard (Proctoporus shrevei) of Trinidad: a brief natural history. Caribbean Journal of Science 40, 422-426.

Many many thanks Mark for sending the stuff on Tregobatrachus. I'd missed this taxon because (as David said) it's described in Sanzhiz (1998) as Bufo hibbardi. Holman argued that it might be a non-neobatrachian, and similar in its primitive character states to leiopelmatids and discoglossids. I'm not the expert that he was, but I'm sceptical.

First of all, it's clear that the type Tregobatrachus ilium is quite autapomorphic (large, medially deflected dorsal prominence, particularly large acetabular fossa, prominent and wide groove on ilial shaft). These features mostly explain why it's strange, but they're still consistent with the idea that it's a hyloid, or even a bufonid as originally thought.

Of the features that Holman used to infer possible non-neobatrachian affinities, all are primitive. These features include a large acetabular fossa, relatively unexpanded dorsal and ventral acetabular prominences, and lack of an ilial shaft ridge and dorsal crest. While Holman noted that such features are typical of non-neobatrachians and not always seen in neobatrachians, he didn't draw attention to the fact that many neobatrachians belonging to many different groups also exhibit these primitive features. I have various figures of neobatrachian ilia in front of me now, and I can see myobatrachids, hylids and bufonids that all share these primitive features (large acetabular fossa, unexpanded dorsal and ventral acetabular prominences, no ilial shaft ridge, no dorsal crest) with Tregobatrachus ((e.g., Litoria caerulea, Crinia, Rhinella arenarum).

So, I think Tregobatrachus might be a bit weird, but I don't think there's good evidence bearing on an unusual phylogenetic position.

Most of what you say I can't argue with because (a) it sounds reasonable, and (b) you understand it better than I do.
But I think I should point out that Holman lists Bufo hibbardi as a separate taxon (Bufo hibbardi Taylor, 1936 as opposed to Tregobatrachus hibbardi Holman, 1975). Both are given as Upper Miocene, both from Kansas, and both Ogallala Fm, and both named in honour of the same Claude Hibbard, but the type locality for B hibbardi is from the Edison Beds (Hemphilian), while T hibbardi is from the WaKeeney local fauna which is Clarendonian. In fact B hibbardi is recorded from many remains mostly from Kansas and Nebraska, and from several subdivisions of the Upper Miocene, including being present in the same local fauna as T hibbardi.
Also the material on which each is based is quite different: T hibbardi is a single partial left ilium, while B hibbardi is known from many remains including frontoparietals, various vertebrae, many limb bones (including a substantial number of ilia) and sacra. Some of the material for B hibbardi was originally published as B arenarius Taylor, 1936, which is treated as a synonym.

I don't think this affects the main points you make, i.e. Tregobatrachus is a bit odd, but Holman may have been way overstating the case to place it outside the neobatrachian group; however it is different to Bufo hibbardi.

By Mark Lees (not verified) on 10 Nov 2007 #permalink

Dont Garfish have green bones too?

"Mike, it makes me happy to know that you went to the trouble of googling for images - I hope you found that rewarding!"

It was. I love frogs and found some that I hadn't known existed. But that's just typical for TetZoo. I'm not sure you've ever made a post that didn't have me tracking down some critter that I'd never heard of or looking up some technical term. Even your short posts generate further reading.

Oh, and I've been wanting to ask if there's a good frog book out there. By 'a good frog book' I mean the book that comes closest to doing for frogs what Unwin's Pterosaurs: From Deep Time does for pterosaurs.

I was also wondering about the business of the epicoracoid cartilages you referred to in the previous anuran post. When you say that in the hyloids these cartilages overlap along the ventral midline, I'm wondering which one is 'on top' (you can pick the frame of reference) where they overlap, the left or right (it wasn't clear in the diagram). Also, in the ranoids where the epicoracoids fuse along the ventral midline, do they butt up against one another end on or do they overlap too but fuse where those of the hyloids don't.

And another thing I do frequently at TetZoo is add new terms to Firefox's dictionary. :-)

By Mike from Ottawa (not verified) on 11 Nov 2007 #permalink

Here's an example of what TetZoo does. A remark about "Franciscana", a term I'd not seen before has me googling it and then perusing the species fact sheets at the American Cetacean Society website. I get drawn in reading through all of them and find out that the pygmy right whale (Caperea marginata) is really weird with huge and flattened ribs over its whole torso and has been observed swimming with an undulatory movement of the whole body not just the tail and flukes.

From green bones in frogs to outlandish ribs in a whale. That's just typical of TetZoo.

By Mike from Ottawa (not verified) on 11 Nov 2007 #permalink

Allan Greer published a paper (Novitates, some time in the Sixties as I recall) on green blood in a scincid. Biliverdin retention again, I think. Can't remember anything else about this species, except that it lived on some Micronesian island.

[from Darren: you're thinking of the Green-blooded skinks, Prasinohaema. An episode of Mark O'Shea's series on reptiles was devoted to these lizards: go here for more.]

Bufo hibbardi Taylor, 1936 as opposed to Tregobatrachus hibbardi Holman, 1975

Oh. So they are different, and I really overlooked T..

[from Darren: my excuse is that my copy of Sanchiz (1998) stops at p. 101, so I lack the index and the problematical taxa at the back. Oh well.]

By David Marjanović (not verified) on 11 Nov 2007 #permalink

Thanks, Darren. I really should be paying more attention to these things.

I have a book about reptiles which shows a skink with a deep-blue tail. Interestingly it has a fresh wound on the tail, and it shows that they flesh beyond the skin is actually blue too. If anybody is interested in this, I can search for the name of this skink.

Tregobatrachus is in the Handbuch -- in the nomina dubia section, p. 134sq.:

Comments: This single fossil could also be interpreted as an anomaly, in which the ventral ischial and pubic section of the pelvic girdle are co-ossified [sic] with the iliac acetabulum. In fact, a line that could correspond with such fusion is clearly visible on the acetabulum and pars descendens. If this hypothesis is correct, T. hibbardi could be attributed to a hylid or bufonid. Nevertheless, I am not aware of any description of similar anomalies. The family Tregobatrachidae, proposed by HOLMAN (1974b), remains doubtfull [sic] until more information on this taxon becomes available.

No connection to Bufo (americanus) hibbardi.

By David Marjanovi? (not verified) on 12 Nov 2007 #permalink

I already checked my source about the biolumniscence in reptiles. There was not only this teju mentioned, but also a gecko. The idea was proposed that it could be a result of a diet which consists of much biolumniscent insects.

It seems like the most difficult aspect of photosynthesizing lizards would be passing the algae on to offspring. This problem has been solved in many ways by bioluminescent fishes. If one were to set out to breed a lizard/algae alliance, what would be the most reliable route?

I suppose such lizards might need to eat only dirt, for the mineral content. I picture brick university buildings covered in summer with bright green basking lizards, like rootless vines. What would the sports league be called?

By Nathan Myers (not verified) on 13 Nov 2007 #permalink

I've just been told that gar (Lepisosteiformes) also have green bones (I know, I know, they're fish, but they can be just as interesting as tetrapods). At least, I think it was gar, definitely one of the basal actinopterygians. I know nothing further, so if anyone has any more information please share what you know.

By Richard Hing (not verified) on 13 Nov 2007 #permalink

Is this a confusion between the marine garfish (genus Belone in Belonidae) and the gars (genera Lepisosteus & Atractosteus in Lepisosteidae)north American freshwater fishes?

As far as I am aware the Lepiosteids don't have green bones (I would be interested to hear otherwise) while the garfish Belone belone from the north east Atlantic, and the Med does. I don't know if any other belonids have green bones.

Interestingly the garfish, which was the original 'gar' (prior to the name being applied to the lepiosteids), was also known sometimes as the 'green-bone'.

I remember as a kid a neighbour catching one and showing us it, and particularly showing the bones because of the colour. It is a longtime ago, but my recollection is that the bones were a pale bluish-green, quite peculiar.
I am told the fish tasted very good steamed!

By Mark Lees (not verified) on 13 Nov 2007 #permalink

On topic considering the golden toad:

"Just a little tip: don't ever invite wildlife biologists or conservation ecologists to give talks. They are the most depressing people in the world" -- PZ Myers.

By David Marjanović (not verified) on 16 Nov 2007 #permalink

a frog with transparent skin is about as appealing to me as a hairless cat, no offense to the frog, of course, it's still a cool discovery

awesome close-up of a pregnant glass frog

Awesome indeed!

(BTW, mistake in the first comment: the paper that shows isolated bufonid ilia are not diagnostic is in JVP, not Syst. Biol..)

By David MarjanoviÄ (not verified) on 08 Nov 2009 #permalink

In the Centrolenidae (Glassfrogs) wheather the bones are green or white actually is one of the important characters to identify species. Good thing they have transparent skin. (Might be an adaption to survive being correctly named..). The green boned Hylids you'd find among the genus Scinax.. The Costarican species Scinax eleochroa f.i. has green bones.

By Peter Mudde (not verified) on 27 Aug 2010 #permalink