Tiny pterosaurs and pac-man frogs from hell (original) (raw)

It was Beelzebufo that finally made up my mind. Long-time readers will have noticed that I generally fail to discuss the exciting stuff that's being announced in the news, even when it's very much relevant to the Tet Zoo remit. Indeed some of you have even commented upon this fact. What's my excuse for this? Well there are a few actually...

-- For starters, once I've decided to blog about something - say, initial bipedalism or European pumas or liolaemine lizards - I need to stick with it and get it out of the way. Because I have a long list of subjects that I plan to blog about, I am not looking around for things in the news to write about, as seems to be the case for so many bloggers (no disrespect intended). In other words, I'd rather do my own thing thank you very much (incidentally, this explains why I can't be bothered with memes anymore*).

-- Furthermore, let's face it, most of the scientific stuff that's announced in the news isn't really news in the substantive sense: a lot of it amounts to 'we found a new one'. Cases in point are the mummified hadrosaur named 'Dakota' - splashed all over the news and yet to make a debut in the technical literature - and the giant pliosaur from Jurassic sediments of Spitsbergen, informally dubbed 'the monster'. I'm not saying that these announcements don't have merit, just that there is bugger all to say should you wish to try and write about them.

-- Finally, there's also the point that high-profile stuff announced in the media is already going to be discussed by scores of other people, and if you do chose to write about such stuff you're just one in the crowd, nothing special. And, come on, we all know that you come to Tet Zoo because you read stuff that you don't get elsewhere (hmm, that sounds very arrogant. But still true).

* Though I am still sincerely grateful when people think of me when meme-spreading.

So now you know. Sure, there often are new discoveries or announcements that get me excited, and excited enough that I end up covering them here. And in an effort to redress the general lack of newsy-type coverage at Tet Zoo, I made an effort in February to write an article on 'new stuff in the world of Tet Zoo'. Sengis, deinotheres, abelisaurs, lambeosaurs, uakaris, giant frogs. Alas, it then got shelved and hence is no longer new, plus (see above) it's all been splashed around the internet already. But what the hell. Here are assorted thoughts on a few recent discoveries: I also wrote about dinosaurs and fossil and living mammals, but have held those parts back for other articles. We begin with Beelzebufo ampinga, the large Cretaceous anuran described last month by Susan Evans and colleagues.

Beelzebufo: giant Cretaceous pac-man frog from hell

Given that all Tet Zoo readers are now experts on the phylogenetic diversity and classification of anurans (except perhaps for natatanurans, the one group I have yet to finish writing about), it will have been widely realised that Beelzebufo is a ceratophryid hyloid neobatrachian (go here and here). Its identification as such is based on its thickened, rugose skull roof bones, the projecting shelf on the parietal at the rear margin of the skull, and on other characters of the jaws and teeth (Evans et al. 2008). While it resembles the living Ceratophrys and Chacophrys in its interlocking premaxillary-maxillary articulation, it differs from all other ceratophryids (or ceratophryines) in its over-developed pit-and-ridge cranial sculpturing, in the persistence of cranial sutures, and in its much larger size [adjacent reconstruction shows Beelzebufo to scale with... a pencil.. and Madagascar's largest extant frog, the mantellid _Mantidactylus guttulatus_].

On size, large individuals of Beelzebufo are estimated at having been about 20 cm wide across the back of the skull, and with an SVL (snout to vent length) of about 42 cm. This is immense, but note that most specimens are smaller (a mere 8-12 cm across the skull, SVL estimated at 16-27 cm). Evans et al. (2008) noted that, in extant ceratophryids, juveniles and males are commoner and smaller than the really big females, and what we know of Beelzebufo suggests a similar population structure. Beelzebufo was huge, but was it the biggest anuran? That's difficult to answer. An SVL of c. 35 cm has been reported for Calyptocephalella parodii from the Miocene of Argentina (a close relative of the Helmeted water toad [shown below] I wrote about here), 36.8 cm has been published for the Goliath frog Conraua goliath, and 38 cm for the Cane toad Rhinella marina. While cane toads are short-legged and might therefore be similar in weight to a giant Beelzebufo, the proportionally longer legs of Calyptocephalella parodii and Conraua goliath might mean that giant specimens of these species would be heavier than a giant Beelzebufo. Maybe all of these species max out at about the same size: the record-holding Goliath frog (captured in 1989 on the Sanaga River in Cameroon) weighed 3.66 kg (with legs extended it was 87.6 cm long). Of course it would be possible to scale up the weight of an extant pac-man frog to Beelzebufo size to get an estimate, but I'm not exactly the best person to do that so will leave it to someone else.

Note that, in contrast to so many fossil anurans, Beelzebufo is actually pretty well represented: it's not based on a single ilium or a few skull fragments, but in fact on over 60 bones collected from 26 different localities (all within a 1.8 km radius). I wonder if this means that it was relatively common in its environment (Beelzebufo is from the Maastrichtian Maevareno Formation: the Madagascan unit that, among others, has yielded the amazing crocodyliform Simosuchus, the sauropod Rapetosaurus, and the theropods Majungasaurus, Rahonavis and Vorona).

Living ceratophryids (like the Ceratophrys shown below) are lurking ambush predators that bury themselves in the substrate and sit there, awaiting prey. They lunge at passing animals, subduing them with strong, heavily ossified jaws and sharp teeth, and their immense mouths (which have earned them the popular name 'pac-man frogs') allow them to cram reasonably big vertebrates down their throats. It's reasonable to think that Beelzebufo behaved in the same way, and its large size would have made it a formidable predator of small vertebrates. If it was reasonably common, were parts of the Maastrichtian Madagascan forest floor veritable mine-fields of giant pac-man frogs?

Finally, the presence of Beelzebufo in Maaschtian Madagascar opens up questions about anuran biogeography, given that the presence of a ceratophryid there is totally unexpected. To cut a very long story short, ceratophryids on Madagascar provide support for models where a connection between Madagascar and southern Gondwana persisted until the Late Cretaceous: this suggests that ceratophryids were widespread across southern Gondwana during the Cretaceous, and that their restriction today to South America results from extinction elsewhere in the southern continents. Next time you're on Antarctica, try and find a fossil ceratophryid. Incidentally, Beelzebufo - in its original incarnation as the 'hyperossified megafrog' - was first mentioned on Tet Zoo ver 1 back in January 2006 (here). So as usual, you should be able to say that you heard it here first.

Nemicolopterus: alleged ptiny pterosaur

Moving now to something entirely different, the last several weeks have been particularly exciting if you're interested in pterosaurs although, what with a couple of projects that Mark Witton and I are currently working on, I do admit to having pterosaurs on the brain at the moment. Anyway, firstly we have little Nemicolopterus crypticus, a small pterosaur from the Jiufotang Formation of Liaoning Province, China (Wang et al. 2008). Represented by a near-complete skeleton [shown above] that has an estimated wingspan of about 25 cm, Nemicolopterus is toothless, with a subtriangular pointed rostrum and elongate, curved penultimate pedal phalanges. The latter feature strongly suggests arboreal habits for this little animal (Wang et al. cite a study on the toe bones of sloth lemurs here, which is fair enough as I might have done the same).

However, I do admit to being sceptical of many of the claims made by Wang et al., and indeed thoughts similar to mine have been mentioned already by other people in the pterosaur research community. Its small size, proportionally big skull and large rounded orbit suggest that it might be a juvenile of something else, and given that multiple specimens from the same deposit appear to represent growth stages of a rather similar pterosaur (the tapejarid Sinopterus), it is likely that Nemicolopterus is a baby Sinopterus. Wang et al. note that N. crypticus is juvenile-like in displaying unfused cranial bones, and only go as far as saying that it was 'not a hatchling that had just left the egg' (p. 1986). Well, we already know from other taxa that pterosaurs were precocial as youngsters, and that juveniles acted as separate 'eco-species' from their parents (Unwin 2006), so given all of this it seems reasonable to assume that N. crypticus was not a specialised mini-pterosaur as has been inferred, but a juvenile with a lot of growing to do [adjacent image is John Conway's skeletal reconstruction, go here for bigger version].

Furthermore, while Wang et al. (2008) found N. crypticus to be the sister-taxon to a pterodactyloid clade that included ornithocheiroids, dsungaripterids and azhdarchoids, several of its characters (e.g., its proportionally short distal-most wing phalanx, ventrally extending 'pear-shaped' orbit and ventrally deflected rostrum) seem to better support its inclusion among azhdarchoids, and within tapejarids. One claim made by Wang et al. about N. crypticus is downright odd: they state that big ornithocheiroids and so on 'originated from crestless and toothless small insectivorous arboreal forms', like N. crypticus. The re-evolution of teeth would be interesting (do you recall previous comments on this stemming from Michael Fastnacht's talk at the Munich pterosaur meeting?). However, Wang et al.'s cladogram offers no support for this possibility: based on their findings, it is far more likely that N. crypticus is a specialised oddball, as it's off on its own in their cladogram, surrounded by big taxa, some of which (the nyctosaurids, ornithocheirids and pteranodontids) were oceanic.

Whatever, it's still an awesome specimen and I'm happy to see it in the literature [image at top of article was produced by Mike Skrepnick].

Finally on pterosaurs, Andres & Ji (2008) have just published yet another new Liaoning Province taxon: Elanodactylus prolatus (though, unlike Nemicolopterus, it's from the Yixian Formation). Particularly long wing phalanges indicate that Elanodactylus had long, slim wings, and this explains the generic name (Elanus is the black-shouldered kite genus). The big deal about the paper is that it includes yet another new cladistic analysis of pterodactyloids, and it includes some surprises to say the least: among these are the inclusion of lonchodectids among ornithocheiroids and dsungaripterids within the azhdarchoids. Andres and Ji say lots of other interesting things in their paper; not least is their discussion of alleged Jurassic members of Azhdarchidae and what these specimens imply for the azhdarchid ghost-lineage. We'll come back to all of this in the future.

And I have to stop there. I was going to talk about new dinosaurs, but it'll have to wait. I have become horribly ill. Gave a talk last night on fossil elephants, but that wasn't to blame.

Refs - -

Andres, B. & Ji, Q. 2008. A new pterosaur from the Liaoning Province of China, the phylogeny of the Pterodactyloidea, and convergence in their cervical vertebrae. Palaeontology 51, 453-469.

Evans, S. E., Jones, M. E. H. & Krause, D. W. 2008. A giant frog with South American affinities from the Late Cretaceous of Madagascar. Proceedings of the National Academy of Sciences 105, 2951-2956.

Unwin, D. 2006. The Pterosaurs from Deep Time. Pi Press, New York.

Wang, X., Kellner, A. W. A., Zhou, Z. & Campos, D. de A. 2008. Discovery of a rare arboreal forest-dwelling flying reptile (Pterosauria, Pterodactyloidea) from China. Proceedings of the National Academy of Sciences 105, 1983-1987.