Saturday, December 30, 2006

When eagles go bad, one more time... part II

Oh, and just for those who still don't accept the idea that a Golden eagle can kill a wolf...

Image again courtesy of Steve Bodio: for more see his post on wolf-killing eagles in Kazakhstan.

Kirghiz tribesmen of central Asia have long been known to use Golden eagles to catch wolves, and in fact Marco Polo (c. 1254-1324) wrote of ‘a great number of eagles, all trained to catch wolves, foxes, deer and wild goats’. This would have been some time in the 1270s, when Polo was in his twenties. John Love, in his 1989 book on eagles, wrote of a Kirghizian eagle that had captured 14 wolves in a day. A Kirghizian wolf-hunting eagle was termed a berkut, and there is some disagreement as to what a berkut’s role was in wolf-killing.

Some authors state that the eagle’s job was not to kill the wolf, but to hold it down until its trainer was able to arrive (on horseback) and dispatch the wolf with a knife. However, as is illustrated by the fact that Golden eagles can kill mammals bigger and heavier than wolves by a powerful strike directed at the back of the skull (go here), a trained eagle would in fact be able to kill even an adult wolf if it approached quickly enough and struck the wolf, from behind, in the right place. Accordingly, other authors state that the berkut’s role was to kill – rather than just pin down – the wolf. Wikipedia’s entry on this subject states that ‘These eagles are so fast and powerful that they are capable of killing a fully grown wolf by diving at speed and striking the wolf on the back of the head or neck’.

Some wolves proved particularly challenging quarry, however, and there is the tale of one that foiled the attempts of 11 eagles – killing each one – until it was finally dispatched thanks to the efforts of a twelfth eagle. Love (1989) intimated that wolf-hunting with eagles is all but extinct in modern times but, as you can see from Steve’s blog post alluded to above, and from his 2003 book Eagle Dreams: Searching for Legends in Wild Mongolia, this is certainly not true.

Oh, and while Im here: check out the recent discovery of a female Golden eagle from Buffalo Valley, Wyoming (NOT New York as I said previously!), captured by Bryan Bedrosian and colleagues, that apparently weighed at least 7.7 kg. This wouldnt be the biggest Golden eagle ever - that record goes to a 9 kg Spanish female (though I dont know if this size was ever authenticated and must find out) - but it would be a record for North America.

To those who check the blog regularly, youll note that this post has just been updated. I should note that I add updates, where relevant, to various of the posts. For other recent examples see Time wandering cynodonts and The first new mammal in 100 years?.

Ref - -

Love, J. A. 1989. Eagles. Whittet Books, London.


Friday, December 29, 2006

When eagles go bad, one more time

A little Christmas season/New Year’s present for all my regular readers. The second article ever posted to this blog discussed the fact (note: FACT) that big eagles, most notably the Golden eagle Aquila chrysaetos, are able to attack and kill mammals substantially bigger than they are (go here). Wild individuals will attack and kill deer (including reindeer, roe deer and white-tailed deer) and pronghorn, and there are ridiculous, authenticated cases where Golden eagles have killed domestic calves exceeding 100 kg in weight. Trained individuals in Kazakhstan kill wolves.

I note that those who are ultra-sceptical of the idea that a 6 kg eagle might be able to kill a 30 kg wolf, or a 100 kg baby cow, are never even aware of any of this stuff, let alone familiar with it. Incidentally, I have tried for a while to get TV companies interested in this issue (and in other arcane, fascinating aspects of tetrapod zoology), thus far without any success. In fact Ill come clean now and tell you that I spent some considerable time during 2006 trying to get various television companies to do some sort of TV spin-off of this blog site. I had in mind something along the lines of Mark O’Shea’s excellent series on dangerous reptiles, and I did actually get quite some interest, but evidently not enough.

Anyway, while surfing recently I noticed Birdchick’s two posts (two links there) devoted to this issue. She was particularly interested in the awesome image shown at top, but had some concerns about its authenticity. I was first sent this image by Steve Bodio of Querencia, and have since used it to death in powerpoint presentations and so on (in my recent ‘Evolution and diversity of the tetrapods’ course I used it as the opening slide). It shows a Golden eagle attacking a Red fox Vulpes vulpes (not a coyote or other canid as some people have suggested) and was taken in Finland in February 2006 by wildlife photographer Pekka Komi of Steve first discussed this image here. While a lot of people have seen the best image (the one at top), less appreciated is that it’s part of a series, five of which are posted on the site (go here). We see the two predators confronting each other at a carcass, with the eagle eventually winning the conflict, kicking the crap out of the fox, and the fox then running away. It is not an attempt at predation, and in fact the carcass had been specially laid out to attract raptors.

The fact that the image is part of a sequence of course rules out the whole issue of the best image being mocked-up, and to be honest this thought never occurred to me given that I’m familiar with the idea that a big eagle is well able to tackle a fox. If that seems like a strange or radical idea, then I can understand that the image might be difficult to accept at face value. The trump card is an exciting video clip (from youtube) viewable here on Birdchick’s site: it shows a Golden eagle attacking a fox, though it’s not possible to work out how the whole event ended.

Many thanks to Steve for the supplementary info. This time I will state with confidence that this post is going to be the last one for 2006, and it is kind of ironic, yet satisfactory, that I have figuratively gone full circle, and have ended the year by discussing one of the year’s first blog articles (indeed, one of my first blog articles ever). I can confidently state that something about my blogging will be different in 2007, but as for what that is… you’ll have to wait and see [UPDATE: to see what I was getting at, go here].

Saturday, December 23, 2006

Happy Christmas, from gigantic Spanish sauropods... or, alas, poor ‘Angloposeidon’

I said the last post would likely be the last before 2007. I lied, as while checking my emails this morning, something came up that I just can’t resist commenting on. As regular blog-readers will know, back in 2004 I and colleagues described a large cervical vertebra from an Isle of Wight sauropod dinosaur (see ‘Angloposeidon’, the unreported story: part I, part II, part III and part IV). Belonging to a large brachiosaurid closely related to the Upper Jurassic Brachiosaurus and Lower Cretaceous Sauroposeidon, the Isle of Wight specimen is 745 mm long, which suggests a total length exceeding 20 m. That made it the largest published European dinosaur (Naish et al. 2004). However, when the time came to talk to journalists about the discovery, I mentioned on several occasions the fact that even bigger European dinosaurs were due to the published in the near future. As I said in part IV

During the long period of time in which the [‘Angloposeidon’] manuscript was in preparation I spoke to several European colleagues who told me of new sauropods from Portugal and Spain that would easily outclass MIWG.7306 in terms of size. I had this on my mind all the way through the submission process, and at any time I expected there to be some report of a new European sauropod that had a total length exceeding 30 m. But even today such discoveries have yet to materialise, and having now seen some of the specimens in question I know that they fail to come close to the 20 m + estimated for MIWG.7306.

The news, of course, is that one of these Iberian giants has just been published (Royo-Torres et al. 2006): its the new taxon Turiasaurus riodevensis from the Villar del Arzobispo Formation (Jurassic-Cretaceus boundary) of Riodeva (Teruel Province, Spain) [many thanks to those who have sent the pdf!]. And it doesnt fail to meet the hype: it really is immense (so, the other Iberian giants that Ive seen were mere pretenders). Turiasaurus has a humerus about 1.8 m long and an estimated weight of over 40 tons. This makes it quite bigger than ‘Angloposeidon’ and in fact one of the biggest sauropods in the world, almost on par with immense titanosaurs like Argentinosaurus and Paralititan. Furthermore, phylogenetic analysis indicates that Turiasaurus belongs to a new clade located close to the origin of Neosauropoda (the macronarian-diplodocoid clade). Galveosaurus (named in 2005, and previously regarded as a cetiosaurid*) and Losillasaurus (named in 2001 and regarded as a diplodocoid, but since suggested to be a mamenchisaurid**) also seem to be turiasaurians. Thats pretty interesting, though it has to be said that the statistical support for turiasaurian monophyly is not overwhelmingly impressive.

* And later renamed Galvesaurus by a different group of authors. I will cover the Galveosaurus-Galvesaurus issue some time in the future.

** The correct term for the group dubbed omeisaurids by some.

Furthermore, the fact that Turiasaurus is represented by good, associated remains means that it might help clear up some of the mess represented by isolated remains (see previous post: Obscure dinosaurs of the Kimmeridge Clay). Scattered throughout the European Jurassic and Cretaceous record are assorted sauropod teeth that roughly resemble the teeth of better known forms, such as camarasaurs and brachiosaurids, but also have a unique look about them. Examples include the huge, beautifully preserved tooth named Oplosaurus armatus (from the Isle of Wight*) and the unusual specimen Cardiodon rugulosus from the Middle Jurassic Forest Marble Formation of Bradford-on-Avon, Wiltshire. It now turns out that these teeth are similar to those of Turiasaurus, which raises the interesting possibility that they are further representatives of this newly-recognised group. That would be cool.

* For more on Oplosaurus and other Lower Cretaceous English sauropods go here.

Anyway, Ill have more to say on turiasaurians and other Iberian sauropods in the future. And it really is relevant as I and colleagues (Barbara Sánchez-Hernández and Mike Benton) currently have an article in press on dinosaurs (including sauropods) from the Villar del Arzobispo Formation. Maybe some of the material we have belongs to Turiasaurus? Well see...

Finally, in other dinosaur news, youll note from the big picture above that Tom Holtzs big dinosaur encyclopedia is finally being advertised. I discussed it previously here.

All the best for Christmas and the New Year. My new year’s resolution? To finish writing all those blog posts I’ve been promising for the last year. Controversial mammals from Borneo, the passerine supertree, rhinogradentians, giant Australian feral cats, temnospondyls, more on tupuxuarids, agamas and sea snakes, the biggest slow worms, fake Chinese turtles, amphisbaenians, and loads more on sauropods, theropods, pneumaticity, flightless birds, bizarre pterosaurs, and giant eagles. And keep an eye on Tetrapod Zoology’s 1st Birthday... Goodbye 2006!

Refs - -

Naish, D., Martill, D. M., Cooper, D. & Stevens, K. A. 2004. Europe’s largest dinosaur? A giant brachiosaurid cervical vertebra from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 25, 787-795.

Royo-Torres, R., Cobos, A. & Alcala, L. 2006. A giant European dinosaur and a new sauropod clade. Science 314, 1925-1927.

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Tuesday, December 19, 2006

Obscure dinosaurs of the Kimmeridge Clay

Someone – I forget who it was – once described dinosaurs as ‘the most American animals that ever lived’. Well, with all due respect to North America’s endemic dinosaurs (Tyrannosaurus, Triceratops and so on), and to the worthy history of North American palaeontological discoveries, this is crap. Dinosaurs are no more American than they are Patagonian, Nigerian or French. Or at least that’s the politically correct version. Reality is rather different: dinosaurs are in fact British, and – what’s more – specifically English, having been discovered in England by English scientists working on English fossils. Ok, lest some flag-waving patriot of any nation gets offended by this, let me assure you that this is all tongue-in-cheek and not to be taken seriously. Dinosaurs no more ‘belong’ to any country than do rodents or grasshoppers.

England has a rich dinosaur record, and many of the taxa first named from English rocks (e.g., Hypsilophodon, Cetiosaurus, Baryonyx) have proved globally important in terms of what they’ve told us about dinosaur evolution and diversity. Furthermore, these taxa and others (e.g., Scelidosaurus, Mantellisaurus, Neovenator) are represented by excellent remains that sometimes consist of near-complete skeletons. Also noteworthy is that English dinosaurs span most of the Mesozoic, from the Upper Triassic to about the middle of the Cretaceous (there is no dinosaur-bearing Upper Cretaceous in England). So as a gross generalisation of the worse kind, England’s dinosaur record is ‘good’.

Partly because the study of dinosaurs began in England, there is an extensive and voluminous literature on scrappy English dinosaur fossils. Furthermore, these early finds were usually given binomial names, but as our knowledge of these animals has improved, it is understandable that many of these remains are today considered inadequate in terms of establishing taxonomic validity. Ideas on British taxa were sometimes revised several or many times as knowledge improved, and the results are convoluted synonymy lists. As I’ve now mentioned several times on this blog, a major effort to review this mess has recently been produced by Dave Martill and myself, and is currently in press for a special bicentennial issue of Journal of the Geological Society. More on that when it appears. In an unrelated project, Dave, I and Sarah Fielding recently reviewed the English dinosaurs of the Kimmeridge Clay Formation, and as it’s only recently been published (Martill et al. 2006) I figured I may as well blog about it.

The Kimmeridge Clay

The Kimmeridge Clay Formation is an Upper Jurassic mudrock, deposited within a shallow marine environment, that crops out in a narrow strip from Dorset in the south-west to Yorkshire in the north-east. There are also a few outcrops in Scotland, and a contemporaneous equivalent that crops out in northern France. Like the older Oxford Clay Formation (go see Life in the Oxford Clay sea), the Kimmeridge Clay has yielded numerous ichthyosaurs, plesiosaurs, marine crocodyliforms and fish. Excepting the fish of course, those animals are all very interesting and worthy of discussion, but of more interest right now are the many dinosaurs that have also been discovered in the Kimmeridge Clay.

Why have so many dinosaurs been recovered from a geological unit deposited in a shallow sea? Despite the title of our paper, I don’t think this means much. The dinosaurs we find in these marine rocks don’t exhibit any features suggesting that they were aquatic or amphibious, and it appears most likely that the carcasses of the relevant species were washed out to sea on a fairly regular basis. This is well supported by the fact that other fossils, such as plants, and the sediments themselves, have clearly been derived from terrestrial sources. At a time when shallow seas covered the better part of the European continent, it makes sense that an unusually high number of terrestrial animals living on the archipelagos of the region found their way into the marine environment.

Kimmeridge Clay dinosaurs belong to most of the major groups living in Europe during the Upper Jurassic. There were large and small theropods, several types of sauropod, herbivorous ornithopods, and both stegosaurs and ankylosaurs.

Kimmeridge Clay sauropods

Perhaps the most interesting of the Kimmeridge Clay sauropods was named by John Whittaker Hulke* in 1874. Based only on a big humerus (1.3 m long, though perhaps 1.7 m long when complete: see adjacent image) discovered at Weymouth, Hulke named it Ceteosaurus humero-cristatus: note that he used a spelling of the generic name that later fell out of favour (the original, and thus favoured, spelling is Cetiosaurus), and used a hyphen in the specific name (an action that is illegal under today’s nomenclatural rules). This animal is quite certainly not really a species of Cetiosaurus (hence the quote marks used from hereon), as it is highly different in detail from the humerus of Cetiosaurus oxoniensis, the type species of the genus (well, actually, C. oxoniensis is not yet the type species of the genus, but that’s a long and complex issue that I can’t go into right now). So what is it? Its length, slender proportions and particularly prominent deltopectoral crest show that it is a brachiosaurid and, among brachiosaurids, its particularly long deltopectoral crest makes it unique and diagnosable. ‘C.’ humerocristatus is therefore one of those annoying fossil tetrapods that clearly needs a new name. So why doesn’t it have one?

The problem is that most workers who encounter problems like this prefer to err on the side of hyper-conservatism (Peter Dodson’s advice is that ‘the practise of naming genera on [the basis of isolated remains] is a highly undesirable one, greatly to be discouraged’ (Dodson 1996, p. 240): for more on this subject see Cryptic dinosaur diversity). Some therefore opt not to name something that they themselves have said deserves a name. In their review of sauropod species referred to Cetiosaurus, Upchurch & Martin (2003) concluded that ‘C.’ humerocristatus ‘is regarded as a distinct taxon referable to the Brachiosauridae’ but went on to state that ‘[w]e prefer to wait for more complete material before proposing a new name for this taxon’ (p. 213). Similarly, Upchurch et al. (2004) regarded ‘C.’ humerocristatus as ‘a potentially distinct taxon … [but] it would be unsafe to erect a new generic name given the material available’ (p. 309). This perpetuates the cycle, and the taxon goes unnamed for even longer.

I’m equally as guilty of this as are Upchurch and Martin: in an earlier draft of the Kimmeridge Clay manuscript, my co-authors did actually come up with a new generic name for ‘C.’ humerocristatus (it has to be said, a pretty awful one), but I managed to get it removed. While I think it would be useful if this apparently diagnostic brachiosaur were named, I guess I’m bowing to peer pressure. Presumably, ‘C.’ humerocristatus was built much like better-known brachiosaurids (such as Brachiosaurus: adjacent image is Greg Paul’s old restoration of Brachiosaurus with Ceratosaurus and pterosaurs), but it was surely different in various of its details. A few additional bones have been suggested to belong to it, but there’s no way of knowing whether these really do belong to the same animal as the diagnostic humerus.

* One of the most prolific dinosaur workers in England during the latter half of the 19th century, Hulke (1830-1895) was a renowned ophthalmologist and firm ally of Huxley. Elected Fellow of the Geological Society of London in 1868, he was President by 1887 and, later, Foreign Secretary. Hulke was elected to the Royal Society for his work on the retina and received the Wollaston Medal in 1887. Research on prehistoric reptiles was only his hobby, but he published multiple papers on them, with 25 appearing in the Quarterly Journal of the Geological Society of London alone.

Various other sauropod remains have been reported from the Kimmeridge Clay. ‘Ornithopsis’ manseli was named in 1888 for another isolated humerus, and again it appears to be from a brachiosaurid. In fact it might be the same animal as ‘C.’ humerocristatus. Yet again it was originally placed in an inappropriate genus: Ornithopsis is a Lower Cretaceous sauropod (first named for dorsal vertebrae), and there’s no reason at all to think that an Upper Jurassic humerus should be referred to a genus based on Cretaceous vertebrae.

Then there’s Bothriospondylus suffossus, based on vertebrae. Often regarded as a brachiosaurid, its remains are not diagnostic, nor is there any reason to think that they belong to a brachiosaurid, nor even to a macronarian (Macronaria is the sauropod clade that includes brachiosaurids and titanosaurs). Because Bothriospondylus was named early in the scientific discovery of sauropods (in 1875), it quickly became a sort of ‘waste-basket’ taxon to which sauropod remains from all over the world were referred. Thus, various Cretaceous sauropod remains from England, as well as remains from the Middle Jurassic of Madagascar and the Upper Jurassic of France, have been identified (erroneously) as Bothriospondylus. Incidentally, the specific name of the type species of this genus is conventionally spelt incorrectly, with it usually being written ‘suffosus’. On naming the species in 1875, Richard Owen used both double f and double s, but most authors seem to have missed this for some reason.

Kimmeridge Clay theropods

Only a few theropods (predatory dinosaurs) have been reported from the Kimmeridge Clay, and two of them are particularly interesting. The first is interesting because it’s both reasonably well represented (its remains include vertebrae from all parts of the column, pelvic and hind-limb elements), and something new. It’s some kind of peculiar, gracile tetanuran, and is due to be studied as part of a larger project on Jurassic theropods.

The second specimen is considerably less impressive, consisting only of two phalanges from the foot. Discovered at Fleet in Dorset, they are presently part of a private collection. What makes them particularly interesting is the fact that they’ve been identified as belong to an ornithomimid (Brokenshire & Clarke 1993): a theropod clade (often known as ostrich dinosaurs) otherwise restricted to the Cretaceous. If the identification is correct, the history of this group would be extended considerably. However, an identification this precise, given that the material consists only of worn, isolated toe bones, is problematic and there is little reason to think that it is correct. The bones do superficially resemble the toe bones of ornithomimids, but they superficially resemble the toe bones of many other theropods as well. Consequently they are better identified as Theropoda indet. (Martill et al. 2006).

That’ll do for now. Of course there are also the ornithischians: anachronistic ornithopods and pliosaur chew-toys. More on them in the near future. Remember to keep checking for new Christmas cards. Seasons greetings to all - I don’t think I’ll get the chance to do any blogging between now and the new year.

A pdf of Martill et al. (2006) is available should anyone want it (email me: eotyrannus at gmail dot com).

For the latest news on Tetrapod Zoology do go here.

Refs - -

Brokenshire, A. J. and Clarke, J. B. 1993. Important recently collected dinosaurian remains from the Lower Kimmeridge Clay at Weymouth. Proceedings of the Dorset Natural History and Archaeological Society 115, 177-178.

Dodson, P. 1996. The Horned Dinosaurs. Princeton University Press, Princeton, NJ.

Martill, D. M., Naish, D. & Earland, S. 2006. Dinosaurs in marine strata: evidence from the British Jurassic, including a review of the allochthonous vertebrate assemblage from the marine Kimmeridge Clay Formation (Upper Jurassic) of Great Britain. In Colectivo Arqueológico-Paleontológico Salense (ed) Actas de las III Jornadas sobre Dinosaurios y su Entorno. Salas de los Infantes (Burgos, España), pp. 47-83.

Upchurch, P., Barrett, P. M. & Dodson, P. 2004. Sauropoda. In Weishampel, D. B., Dodson, P. & Osmólska, H. (eds) The Dinosauria, Second Edition. University of California Press (Berkeley), pp. 259-322.

- . & Martin, J. 2003. The anatomy and taxonomy of Cetiosaurus (Saurischia, Sauropoda) from the Middle Jurassic of England. Journal of Vertebrate Paleontology 23, 208-231.

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Monday, December 18, 2006

Matt Wedel: officially, a bastard

I really should stop talking to other people qualified in vertebrate palaeontology. It’s so bloody depressing. “I’m working on this”, “I’m writing about that”, “Oh, and did I mention the award I won?”. Yes, I am very pleased to congratulate my good friend Matt Wedel – whom you may or may not know better as Dr Vector, or as ‘that pneumaticity guy’ (shown here posing with an enormous bone*) – for winning the 2006 International Award on Paleontology. The award stems from his excellent 2005 paper ‘Postcranial skeletal pneumaticity in sauropods and its implications for mass estimates’: required reading here at Tetrapod Zoology Towers (free pdf available here). Well done Matt. Bastard.

* Oh alright, it’s an apatosaurine vertebra.

Kimmeridge Clay dinosaurs post to follow soon, once other assorted crap is out of the way. For the latest news on Tetrapod Zoology do go here.

Saturday, December 16, 2006

Christmas cards

Some say that the people involved in palaeontology are all a bit mad. Of course, I don't know whether this is true or not, but - on a completely unrelated note - here are some of the Christmas e-cards that are winging their way around cyberspace right now. Because I can't get the pictures into the exact configuration I have in mind (despite copious mucking around with the html) I'm having to shrink them right down, so please click to enlarge (do we ever really need to say this?).

My card is the big one at the top (and, yes, that IS a hellboy reference). I just showed it to Toni (my wife). "Oh", she said. The enigmatic one featuring the vertebra is from sauropod worker Mike P. Taylor; the festive dromaeosaur is from (... who else) Luis Rey; the hat-wearing Mantellisaurus is from Simon Clabby (Mantellisaurus is the iguanodont dinosaur formerly known as Iguanodon atherfieldensis. It was finally given its own genus by Greg Paul this year: I am fairly confident that this is its first appearance on a Christmas card). The vertebra on Mike's card is a particularly interesting one and has been sort of alluded to in a previous post (see Lots of sauropods). Rest assured I will have a lot more to say about it in the near future.

The image at left is from Mark Witton. An earlier version was first seen here on Mark's flickr site - he didn't send me a copy (sob, the rejection: maybe this is because I still owe him comments on a pterosaur manuscript we're supposedly collaborating on), so I initially nicked... err, borrowed it. I needn't have worried, as I later received a personally emailed version: it's different from the older version, and is the version shown here. Anyway, it features everyone's favourite pterosaur: that ridiculous antlered nyctosaur described by Chris Bennett (2003). Note the fact that Mark depicts the posterior prong of the crest as far longer than is normally shown. Why? Because this is apparently correct, that's why. I'm going to be blogging about nyctosaurs soon, by the way, as I've recently done reading the Muzquizopteryx paper.

Next we have a most worthy contribution from he of dead fishes fame, my huge pal Graeme Elliott. It's a very nicely done composite of student still life, cutting-edge computer wizardly, outstanding humour, and giant robot dinosaurs. The odd creature at far right (it's wearing lots of denim) is owl specialist Richard Hing. Again, I borrowed the image from Graeme's flickr site (go here)... in fact, Graeme has produced a second Christmas image featuring what might be a cryptid, the elusive black dog of Bickwell (go here). I found it hilarious. Anyway, I'll add further cards to this post as and when they arrive.

Kimmeridge Clay dinosaurs coming next (update: I lied), though the possibility remains that a certain mysterious Bornean mammal might get covered instead... For the latest news on Tetrapod Zoology do go here.

Ref - -

Bennett, S. C. 2003. New crested specimens of the Late Cretaceous pterosaur Nyctosaurus. Paläontologische Zeitschrift 77, 61-75.

Tuesday, December 12, 2006

The most inconvenient seal

These are exciting times, if you’re into uber-nerdy zoological discoveries. At long long last, New Zealand’s Miocene fossil mammals have finally been published. Not only do these fossils show that terrestrial mammals were formerly present on New Zealand, they are remarkable in apparently belonging to an animal that must have diverged during the Cretaceous. If you’re wondering: yes, this is the fossil that inspired my previous posts on late-surviving non-mammalian synapsids (here and here). And also on Mesozoic mammals we have the amazing new gliding mammal Volaticotherium [image at left] from the controversial Daohugou beds of Inner Mongolia. Other neat recent discoveries – from the Cretaceous – include the new Mongolian dromaeosaur Tsaagan mangas and the (allegedly) flightless enantiornithean Elsornis keni. I’ll blog about all of these things, time permitting (famous last words).

On the subject of fossils, a major personal event occurred today, and it involves SVP (the Society of Vertebrate Paleontology). To whom it concerns: thank you, sincerely. Anyway, moving on: what about those goddam seals?

One of the most asked about questions I’ve encountered in tetrapod zoology concerns the mysterious seals of Siberia’s Lake Baikal. Everyone knows that an endemic, particularly small species of land-locked freshwater seal lives there, but nobody really knows how it got there. Less well known is that it isn’t the only lake-dwelling seal in the world: there are populations of Ringed seals Phoca hispida in Lake Saimaa (P. h. saimensis) and Lake Ladoga (P. h. ladogensis) in Fennoscandia, there is the Caspian seal P. caspica, and there are freshwater populations of the Common or Harbour seal P. vitulina in the Lacs des Loups Marins of northern Quebec, and in Alaska’s Lake Iliamna (Smith et al. 1996). Furthermore, Ringed seals became isolated in the Baltic Sea about 12,500 years ago when the connection with the North Sea closed due to glaciation, and effectively found themselves in a giant enclosed inland lake. I was planning to discuss these other forms, but have run out of space and time.

First named by Johann Friedrich Gmelin (1748-1804) in 1788*, the Baikal seal (also known as the Nerpa) was mentioned in print as early as 1763. Much exploited by local people for its meat and pelt, it was seriously reduced in numbers during the 1930s, and during the 1970s 2-3000 pups were being harvested each year for their skins. Bonner (1994) later gave higher numbers of 5-6000, implying that harvest numbers have increased within recent decades. A survey performed in 2000 revealed the presence of about 85,000 seals in total, and their numbers are reported to be falling as increasing numbers of pups are being killed.

* Incidentally, Gmelin thought that Baikal seals were just a form of Common seal, and not a distinct species.

Outbreaks of canine distemper virus resulted in the deaths of about 5000 Baikal seals during 1987-88, and it is inferred that the seals were infected by domestic dogs at some stage (Kennedy et al. 2000). Exactly how this happened is not clear, though canine distemper has also caused die-offs in Antarctic Crabeater seals Lobodon carcinophagus and other pinnipeds. This problem has afflicted Asia’s other land-locked seal, the Caspian seal. Between April and May 2000, over 10,000 Caspian seals are estimated to have died along the coast of Kazakhstan, with high death rates also reported from the coasts of Azerbaijan and Turkmenistan. Necropsies demonstrated that canine distemper virus was also the primary cause of death for all of the dead Caspian seals.

Despite its early discovery, the Baikal seal remained all but unknown to western scientists until the 20th century, and only in 1909 did specimens first arrive in Britain. These were collected by Charles Hose who was using the Trans-Siberian railway to get to Sarawak (which is where, in 1895, he discovered the cetacean that later became known as Fraser’s dolphin Lagenodelphis hosei). During a two-day stop at Lake Baikal, Hose managed to get local fishermen to catch three of the seals for him, alive, and he then resumed the train journey with the seals stuck in the luggage racks of his train compartment. Two of the seals died and Hose performed dissections on them while still in the carriage, ‘flinging the more perishable parts out of the train window, to the consternation of fellow passengers’ (King 1983, p. 92). The third seal died while on a ship bound for Shanghai. This little-known information was published in Hose’s autobiographical work of 1927, amusingly titled Fifty Years of Romance and Research or a Jungle-Wallah at Large. I’ve never seen this book, but the information is repeated in Judith King’s excellent Seals of the World. The first live Baikal seals weren’t seen in Britain until 1959 when Moscow Zoo sent a pair to London Zoo.

Baikal seals are morphologically interesting for a number of reasons. Firstly, they are one of the smallest seals, reaching just 1.4 m and 80-90 kg at most (Ringed seals are smaller, as are members of some lake-dwelling Common seal populations). Secondly, for their size they have among the biggest eyes of any pinniped, with the eyeballs being so big that they almost contact one another along the skull midline. Thirdly, the huge eyes appear to have forced other skull structures to become compressed or reduced: the frontal sinuses are strongly compressed and located further ventrally than is normal for seals; the nasal cavity has been forced into an unusually low position; and the brain has been displaced backwards. The jaw muscles, the ear region and the bones around the jaw joint are also modified relative to the condition in other seals, mostly in being smaller and weaker (Endo et al. 1998a, b, 1999). The foreflippers and their claws are larger and stronger in Baikal seals than is usual for seals, and the foreclaws are distinctive in being triangular in cross-section and in having a marked dorsal ridge at their distal end. It is inferred that these forelimb structures make Baikal seals better at making and maintaining breathing holes and grasping prey than other seals (Thomas et al. 1982).

Baikal seals are thermophobic and pagophilic (that is, they avoid heat and like ice and snow), and their pups have white silky natal fur and are born on the ice that covers the lake between February and April. In these respects, Baikal seals are like the cold-adapted Ringed seal, Harp seal P. groenlandica and Ribbon seal P. fasciata, and as we’ll see this has implications for Baikal seal origins and history. Despite their small size, they are surprisingly long-lived, with males living to 52 and females to 56 (incidentally, Caspian seals are also long-lived, surviving to age 50). Average longevity for seals is about 20 years. Further remarkable is that female Baikal seals continue to reproduce while in their fourth decade.

The great mystery, of course, concerns how the seals got into Lake Baikal: ultimately, we don’t yet know the proper answer, but that hasn’t stopped people from speculating. In fact it’s been said that more articles have been published on the biogeography of Lake Baikal’s seals than on the biogeography of all other pinnipeds combined. Even without the seals, Lake Baikal is a pretty remarkable lake, and would be better termed an inland sea. It’s 636 km long, nearly 80 km wide at its widest point, its average depth is 700 m and its maximum depth is 1.6 km. It is home to assorted endemic molluscs, crustaceans and nearly 60 fish species, and at least some of these animals are clearly of Arctic origin.

To date, two competing hypotheses have been proposed to explain the origins of the Baikal seals. Hypothesis 1 will be termed here the ‘Paratethyan hypothesis’, while hypothesis 2 will be termed the ‘Arctic origins hypothesis’.

The Paratethyan hypothesis

The Paratethyan hypothesis accepts the conclusion, supported by some details of morphology, that Baikal seals, Ringed seals and Caspian seals all form a clade (the genus or subgenus Pusa*). Diverse phocine seals – some apparently resembling the extant Pusa** seals – are known to have inhabited Paratethys during the Miocene (Paratethys was a brackish inland sea that covered much of south-east Europe and south-west Asia during the Miocene) and, according to the Paratethyan hypothesis, it is phocines from this region that managed to invade the Caspian Sea, later getting as far east as Lake Baikal. During the Pliocene, Paratethys was linked to the Arctic Ocean via a seaway just west of the Urals, apparently, and accordingly it has been proposed that the Ringed seal of the Arctic Ocean descends from a phocine that migrated north from the Paratethys (Ray 1976, Grigorescu 1977) [adjacent image shows a Ringed seal].

* Whether the Pusa seals really share a single ancestor, however, has been contested and a recent DNA study found no support for the monophyly of Pusa: instead, the Baikal seal formed a clade, albeit weakly supported, with the Grey seal Halichoerus grypus (Palo & Väinölä 2006).

** Pusa pontica, from the Upper Miocene of Ukraine, has been referred to Pusa, but this is probably not correct.

Needless to say, there are problems with this hypothesis. Firstly, while it appears that the Caspian Sea is a relict of Paratethys (as is the Aral Sea), Lake Baikal appears way too far in the north-east for this to work, and where are all the connecting rivers and lakes that would be required in order to get seals from Paratethys all the way over to the Siberian interior? There are big lakes found between the Aral Sea and Lake Baikal, such as Lake Balkash, but they aren’t connected to the Paratethyan remnants, nor were they in the past. Secondly, the Paratethyan hypothesis requires that the phocines ancestral to Baikal seals and Ringed seals were animals of enclosed basins, relatively low latitudes and warm temperatures, and this is problematic given that Baikal and Ringed seals are thermophobic and pagophilic, with thickly-furred pups kept in snow dens. Furthermore, excepting the unusual inland populations, all phocines are oceanic, and not denizens of enclosed basins.

The Arctic origins hypothesis

The competing hypothesis posits that neither Baikal seals nor Ringed seals have descended from Paratethyan phocines that migrated south to north, but that all the pagopholic Pusa seals are of Arctic ancestry, and that seals got into Lake Baikal from the north. The fact that Baikal seals are thermophobic and pagopholic provides support for this model, as does the fact that many Baikal animals are apparently Arctic in origin.

Further support for the Arctic origins hypothesis comes from the fact that large ice-dammed lakes occupied central Siberia about 300,000 years ago. These apparently had connections with the Arctic Ocean and, via the Enisei-Angara river system, with Lake Baikal. Temporary downstream connections with the Caspian Sea also existed. This hypothesis better explains the ecology and life history of Baikal (and Caspian) seals, and is also superior to the Paratethyan hypothesis in that there are (and were) plausible dispersal routes that allowed the seals to get into the inland lakes. Worth noting is that Baikal seals occur in the rivers that flow north out of Lake Baikal even today. Particularly notable is a case where a seal was observed at the Irkutsk Dam on the Angara River, 400 km away from the lake (Thomas et al. 1982).

All in all, the Arctic origins hypothesis better fits the data and is the favoured hypothesis of recent authors (Deméré et al. 2003, Palo & Väinölä 2006). However, this isn’t the end of the debate. The degree of genetic divergence found amongst living phocines suggests – based on molecular clock inferences (which are always controversial and problematic) – that Baikal seals and other phocines diverged around 4 million years ago, during the late Pliocene. Why is this interesting? Because a divergence that occurred at this time doesn’t match with either the Paratethyan or the Arctic origin hypothesis.

According to the former model, the ancestors of Baikal seals must have diverged from other phocines some time during the Miocene, and according to the latter model, Baikal seals evolved from a more northerly ancestor during the Pleistocene. In other words, if the genetic data is accurate, then the evolution of Baikal seals pre-dates the key event that is supposed to explain their distribution: the development of immense Siberian lakes connected both to the Arctic Ocean and to Lake Baikal. Palo & Väinölä (2006) therefore concluded that ‘the actual geographical conditions that would have facilitated the continental invasions in these times still remain undocumented and enigmatic’ (p. 70).

Huh. And there the story ends. For a previous seal-themed post see Swan-necked seals.

Coming soon: obscure dinosaurs of the Kimmeridge Clay. For the latest news on Tetrapod Zoology do go here.

Refs - -

Bonner, N. 1994. Seals and Sea Lions of the World. Blandford, London.

Deméré, T. A., Berta, A. & Adam, P. J. 2003. Pinnipedimorph evolutionary biogeography. Bulletin of the American Museum of Natural History 279, 32-76.

Endo, H., Sasaki, H., Hayashi, Y., Petrov, E. A., Amano, M. & Miyazaki, N. 1998a. Functional relationship between muscles of mastication and the skull with enlarged orbit in the Baikal seal (Phoca sibirica). Journal of Veterinary Medical Sciences 60, 699-704.

- ., Sasaki, H., Hayashi, Y., Petrov, E. A., Amano, M. & Miyazaki, N. 1998b. Macroscopic observations of the facial muscles in the Baikal seal (Phoca sibirica). Marine Mammal Science 14, 778-788.

- ., Sasaki, H., Hayashi, Y., Petrov, E. A., Amano, M., Suzuki, N. & Miyazaki, N. 1999. CT examination of the head of the Baikal seal (Phoca sibirica). Journal of Anatomy 194, 119-126.

Grigorescu, D. 1977. Paratethyan seals. Systematic Zoology 25, 407-419.

Kennedy, S., Kuiken, T., Jepson, P. D., Deaville, R., Forsyth, M., Barrett, T., van de Bildt, M. W. G., Osterhaus, A. D. M. E., Eybatov, T., Duck, C., Kydyrmanov, A., Mitrofanov, I. & Wilson, S. 2000. Mass die-off of Caspian seals caused by canine distempter virus. Emerging Infectious Diseases 6, 637-639.

King, J. E. 1983. Seals of the World. British Museum (Natural History), London.

Palo, J. U. & Väinölä, R. 2006. The enigma of the landlocked Baikal and Caspian seals addressed through phylogeny of phocine mitochondrial sequences. Biological Journal of the Linnean Society 88, 61-72.

Ray, C. E. 1976. Geography of phocid evolution. Systematic Zoology 25, 391-406

Smith, R. J., Hobson, K. A., Koopman, H. N. & Lavigen, D. M. 1996. Distinguishing between populations of fresh- and salt-water harbour seals (Phoca vitulina) using stable-isotope ratios and fatty acid profiles. Canadian Journal of Fisheries and Aquatic Science 53, 272-279.

Thomas, J., Pastukhov, V. & Petrov, E. 1982. Phoca sibirica. Mammalian Species 188, 1-6.

Sunday, December 10, 2006

History writ large at Electric Politics

As mentioned in the agama post, I recently did a podcast interview, and it’s now available online. Strangely perhaps, it wasn’t done for a website that specialises in zoology, nor even in science, but for George Kenney’s excellent Electric Politics site. Covering all manner of issues related to the world of American and/or global politics, Electric Politics might seem an odd venue for a podcast interview with a palaeontologist, but perhaps this is an indication of – dare I say it – how popular Tetrapod Zoology has become. Jon Downes insists on calling me the ‘people’s palaeontologist’*, and presumably that’s a reference to the same thing [the adjacent image shows me, after a heavy rain-storm, at a dig site. I dont normally dress like that, honest].

* Inspired itself by a soundbite once used by Tony Blair.

As is the case with a lot of people, I’m never really happy when I listen back on myself talking in interviews – I always wish that I’d said things differently, or explained them better – but overall it’s pretty good and George was great fun to talk to. We spoke about the evolution of domestic dogs, about brain size and intelligence, about speculations on smart dinosaurs and the future evolution of humans, and also on cryptozoology, sasquatch and dinosaur extinction. There are a few parts of the interview where I become confused and lose my train of thought, and there’s a hilarious segment where I totally lose the plot in trying to explain the history of domestic horses. Cringe.

For the record, the deal with horses in North America is that, while members of the genus Equus were numerous and important there in the Pleistocene, they later became extinct (to quote R. Dale Guthrie (2003): ‘equid species dominated North American late Pleistocene faunas in terms of abundance, geographical distribution, and species variety, yet none survived into the Holocene epoch’ (p. 169)). Meanwhile, Asian steppe horses were domesticated about 6000 years ago (probably in or around Ukraine and Kazakhstan [nod to Steve Bodio]), apparently from several different groups of wild horses (Bennett & Hoffmann 1999, Pennisi 2001, Vilà et al. 2001), and not until the 16th century did Spanish conquistadors reintroduce horses to the Americas. The descendants of these animals, the feral American horses known as mustangs, were being killed for pet food as recently as the 1960s and, despite the 1971 Free Roaming Wild Horse and Burro Act, remain persecuted today. About 42,000 currently live wild in North America. The fact that the wild horses closest to the ancestry of domestic horses, such as the tarpan E. ferus and takhi E. przewalskii, are extinct or highly endangered is an interesting point and probably not a coincidence [the horses in the adjacent image are New Forest ponies].

Anyway, you can listen to and/or download the interview – History writ largehere. It’s a long interview, at 85 minutes or so. Many thanks to George for the invitation, and for the opportunity to do this.

On another subject, thanks to those who have made recent donations to the blog: it’s really appreciated, and helps immensely. I’ve been trying to figure out a way to get enough funding to become a full-time blog writer, but sadly I don’t think that’s an option.

Coming soon: that inconvenient seal, obscure dinosaurs of the Kimmeridge Clay, more on pterosaurs, temnospondyls, and more cryptic intermediates in agamas. For the latest news on Tetrapod Zoology do go here.

Refs - -

Bennett, D. & Hoffmann, R. S. 1999. Equus caballus. Mammalian Species 628, 1-14.

Guthrie, R. D. 2003. Rapid body size decline in Alaskan Pleistocene horses before extinction. Nature 426, 169-171.

Pennisi, E. 2001. Horses domesticated multiple times. Science 291, 412.

Vilà, C., Leonard, J. A., Götherstrom, A., Marklud, S., Sandberg, K., Lidén, K., Wayne, R. K. & Ellegren, H. 2001. Widespread origins of domestic horse linages. Science 291, 474-477.

Saturday, December 02, 2006

Harduns and toad-heads; a tale of arenicoly and over-looked convergence

So, life goes on. Overall, I feel that the sasquatch post – the most popular article yet posted to this blog (attracting c. 3000 hits on one day) – got a fair hearing, though I continue to be unhappy with people who consider themselves sceptics but are, in fact, ‘rejectionists’ (and I’m not necessarily referring to anyone who posted comments to this blog). While research plans have generally fallen by the wayside due to other commitments, various projects involving pterosaurs, sauropods and other Cretaceous tetrapods are still on-going. Mark Witton (yes yes, Buckingham Palace, blah blah blah) and I are now collaborating on a project about azhdarchid ecology, and the big British dinosaurs manuscript is STILL trundling through the system (ah, the wonder that is co-authors). The other day I attended the Hampshire Wildlife Trust bat and badger social evening and got to listen to recordings of screaming rabbits, all in the name of an evening’s entertainment. Then there was the podcast interview: more on that in a few days [adjacent image of Laudakia - see below - from].

And given that I’ve hardly mentioned it so far, feel free to nip over to Biology & Palaeontology Qs & As: a blog site where people can ask a team of experts any question about, well, biology or palaeontology. The august team of experts include P. Z. Myers, Steve Jones, Carl Zimmer and a host of others. It’s run by my good friend Dave Hone: sorry for not mentioning it before Dave.

Moving on… today I am covering one of the subjects that I’ve been planning to cover for months and months and months: agamas, or agamids (previously promised in At last, Dr Naish, ‘Angloposeidon’, the unreported story, part I, Did ichthyosaurs fly? and Macropredation in lions). As usual, I’ve had to restrict my coverage to one specific area of the agamid world, and I hope to write more about this fascinating group in future.

Agamids are iguanian lizards found across Africa, southern Asia and Australasia, and they’re fascinating for a host of reasons. For one they include some of the most fantastically ornamented of all lizards, with numerous species sporting sail-like frills, spiky crests, horns, knobs and other structures. They are often territorial and sexually dimorphic; they include the gliding Draco species, the herbivorous mastigures (Uromastyx), and the often bizarre Australasian dragons. Adjacent image shows the nifty threat display used by some toad-headed agamas, on which there is more below...

Studies generally agree that there are three major agamid clades: the Australo-papuan clade (Amphibolurinae), the southern Asian clade (Draconinae), and the African-west Asian clade (Agaminae). Several agamids, including butterfly agamas, mastigures and water dragons, don’t fit into these groups and sit on their own. The antiquity of the divergences within Agamidae has proved controversial, with some authors arguing that the major clades diverged as a consequence of Gondwanan vicariance (Macey et al. 2000). If this is true then these groups are more than 100 million years old, but this is highly unlikely and probably wrong (Hugall & Lee 2004). Agamids are close relatives of the bizarrely specialised chameleons: more on that later. Agamids and chameleons share what are known as acrodont teeth: a morphology in which the teeth are fused to the jaw bones, and are therefore not replaced during the animal’s life (however, socketed teeth – which are replaced continuously – are usually found at the front of an agama’s jaws).

The herpetofauna’s lament

There are over 400 living agamid species, and this brings me on to pet peeve # 407. Should you wish to learn about – say – all the species of any given group of birds, you have it easy. Entire volumes devoted to bird families exist, and detailed species-by-species accounts of all extant bird species can be found in the outstanding, multi-volume Handbook to the Birds of the World, produced by Lynx Edicions. For mammals you have the awesome two-volume Walker’s Mammals of the World as your first stop, as well as McDonald’s Encyclopedia of Mammals. Lynx Edicions are also working on a species-by-species, multi-volume set that goes through all the world’s extant mammals.

But what really bugs me is that there are no such sources for living reptile or amphibian species. Well, there are for crocodilians and testudines, and also for a few charismatic groups such as chameleons and monitor lizards. But it is otherwise pretty much impossible to get hold of species-level reviews of amphibian and reptile species. Why is this? It drives me nuts. The only way to even come close to getting some understanding of species-level diversity within non-avian, non-mammalian tetrapods seems to be to obtain ALL of the primary literature, and/or to visit the collections of ALL relevant repositories. Both aims are of course impossible.

I rely on field guides a lot, but because they are heavily biased in terms of area coverage (e.g., there are tens of field guides on the reptiles of southern Africa, but hardly any on much of western Africa) there are still whole suites of species that, at best, only ever get listed or mentioned, let alone illustrated or described. So even today, people interested in herpetology are afflicted with the most basic of problems: a lack of the right kind of literature. Having mentioned lizards and books, I am forced to make an honorary mention of Pianka & Vitt’s Lizards: Windows to the Evolution of Diversity. Awesome, and one of my favourite books on any subject.

Moody’s splintering of Agama

Here in Europe – or, as I like to call it, the European Field Guide Region (EFGR) – there is usually stated to be just one agamid, the Hardun, Starred agama or Sling-tailed agama Laudakia stellio [image at left: from]. This isn’t correct, however, as we have three species of toad-headed agamas (Phrynocephalus) in the EFGR, as well as two additional Laudakia species. All of these lizards belong to the agamid clade Agaminae, and it’s a few members of this group that I’m going to look at here.

The Sling-tailed agama is a large, robust lizard (c. 300 mm long) with an armour-plated look, and it’s wide ranging, occurring across eastern Europe, northern Africa, north-east Arabia and Asia. It can change colour, from light brown to almost black, and is an excellent climber on both trees and rocky surfaces. Multiple (20) species of Laudakia have been named, but it is has proved almost impossible to reliably differentiate many of them on the basis of either morphology or range.

Those field guides that I mentioned always use the name Agama stellio for L. stellio. This is because, while the name Laudakia isn’t new (having been coined by Gray in 1845), it later became sunk into synonymy with Agama and only became resurrected following S. Moody’s 1980 doctoral study on agamid relationships. This is one of those annoying studies that gets cited all the time, but has yet to be published. Moody argued that the genus Agama was, as perceived for most of the 20th century, actually a polyphyletic assemblage of quite distinct, disparate agamines which deserved separation as Agama Daudin, 1802 sensu stricto, Xenagama Boulenger, 1895, Pseudotrapelus Fitzinger, 1843, Trapelus Cuvier, 1817 and Stellio Laurenti, 1768. Moody’s concept of Stellio proved to be an artificial assemblage of distinct Eurasian and African species, and in any case this generic name isn’t available for agamines (it was first used for a monitor lizard). So the Eurasian forms were then labelled with Gray’s Laudakia, while Fitzinger’s name of 1843, Acanthocercus, became attached to the African forms. There is also the confusing suggestion that Placoderma Blyth, 1854 should be used for some members of Laudakia (Henle 1995): confusing because placoderms are a group of ancient fossil fishes.

Basing their phylogeny on that of various previous studies, Stuart-Fox & Owens (2003) depicted Laudakia as the sister-taxon to a Phrynocephalus-Bufoniceps clade (the latter are the toad-headed agamines, more below: adjacent image shows P. melanurus, image from the Siberian Zoological Museum site). Macey et al. (2006) found Laudakia to be paraphyletic as toad-heads were nested within it. And of the Laudakia species, L. stellio was the one closest to the toad-heads. Right now, the monophyly of Laukadia remains controversial, and the idea that L. stellio might be particularly close to toad-heads is particularly interesting. I would dearly love to know if it exhibits any morphological characters that make it closer to toad-heads than to other members of Laudakia. In other words, is it a sort of cryptic intermediate?

Toad-heads old and new

Toad-headed agamas, or toad-heads (Phrynocephalus Kaup, 1825), are a mostly desert-dwelling Asian group of agamines, occurring as far east as Mongolia, as far south as southern Arabia and Pakistan, and as far west as Turkey. The adjacent image (from reptiles.passion) answers the question: why are they called toad-heads? There are more than 40 species, but species boundaries and often unsure and several taxa have been only briefly characterised. An important component of Asian desert fauna, some toad-head species occur below sea level while others inhabit high plateaus, and many are specialised for highly arid, cold environments. As is seen in other squamate groups that have invaded cool, elevated places, toad-heads have evolved viviparity: this is present in just six Chinese species.

The Rajasthan toad-head Bufoniceps laungwalaensis, originally described in 1978 as a new species of Phrynocephalus, was awarded its own genus by Arnold (1992) [adjacent image from here]. Unlike the Phrynocephalus species, Bufoniceps has a short tail that is not held raised or curled and it still possesses an external ear opening (abeit a very small one). It’s small, with a total length of only c. 100 mm (snout to vent length is c. 60 mm). A diurnal, fast-moving denizen of sand dunes, it feeds on ants, beetles and other insects, and buries itself in soft sand when not active or when pursued. This doesn’t work against humans as an obvious trace in the sand is made. Bufoniceps and Phrynocephalus share a large number of characters, including a notably short snout, a strongly reduced ear opening, a short retroarticular process (= a muscle attachment site projecting from the rear edge of the lower jaw), and fringes of pointed scales on their digits. However, Bufoniceps lacks a suite of derived characters present in Phrynocephalus, and as such has been regarded as a primitive sister-taxon to the latter (Arnold 1992, 1999a, b).

In contrast to Laudakia, most Trapelus species, and various other agamines, toad-heads are strictly terrestrial and do not climb. But because there are toad-heads that live both on soft, wind-blown sand, and on stony or gravely ground, herpetologists have disagreed as to which habitat is the ancestral one for the group. If Bufoniceps is the sister-taxon to Phrynocephalus, then its sand-dune habitat suggests that arenicoly (= ‘sand loving’) is primitive for toad-heads, and that saxicoly (= ‘stone loving’) evolved later on. This is further supported by the fact that fringed toes evolved early in the group, as did a countersunk lower jaw, valvular nostrils, fringes of elongate scales along the eyelids, and a reduced external ear (Arnold 1999a). All of these features are associated with an entry into sandy habitats, as they help protect the animal from sand grains.

As with so many phylogenetic hypotheses that seem reasonable based on morphological data, the idea that Bufoniceps really is a sort of proto-Phrynocephalus has recently been challenged on the basis of genetic information, however. By sampling mitochondrial data from Xenagama [pictured at left: image from], Bufoniceps and other agamines, Macey et al. (2006) found Bufoniceps to be the sister-taxon to Trapelus, and a close relationship with Phrynocephalus was rejected. If this is correct then the characters shared by Phrynocephalus and Bufoniceps are convergences to arenicoly, and pretty remarkable convergences at that.

Agamines are a really interesting group in terms of adaptation: we have scansorial, arenicolous and saxicolous species, the evolution of viviparity, and morphological transitions such as external ear loss. However, if the new genetic studies cited here are correct, then they are even more interesting in demonstrating an outstanding and previously overlooked example of convergent evolution, and in perhaps exhibiting a few ‘cryptic intermediates’. And there’s more to say on the latter: watch this space. For the latest news on Tetrapod Zoology do go here.

Refs - -

Arnold, E. N. 1992. The Rajasthan toad-headed lizard, Phrynocephalus laungwalaensis (Reptilia: Agamidae), represents a new genus. Journal of Herpetology 26, 467-472.

- . 1999a. Phylogenetic relationships of Toad-headed lizards (Phrynocephalus, Agamidae) based on morphology. Bulletin of British Museum of Natural History (Zoology) 65, 1-13.

- . 1999b. Modes of ear reduction in iguanian lizards (Reptilia, Iguania); different paths to similar ends. Bulletin of British Museum of Natural History (Zoology) 65, 165-171.

Henle, K. 1995. A brief review of the origin and use of ‘Stellio’ in herpetology and a comment on the nomenclature and taxonomy of agamids of the genus Agama (sensu lato). Herpetozoa 8, 3-9.

Hugall, A. F. & Lee, M. S. Y. 2004. Molecular claims of Gondwanan age for Australian agamid lizards are untenable. Molecular Biology and Evolution 21, 2102-2110.

Macey, J. R., Schulte, J. A., Fong, J. J., Das, I. & Papenfuss, T. J. 2006. The complete mitochondrial genome of an agamid lizard from the Afro-Asian subfamily agaminae [sic] and the phylogenetic position of Bufoniceps and Xenagama. Molecular Phylogenetics and Evolution 39, 881-886.

- ., Schulte, J. A., Larson, A., Ananjeva, N. B., Wang, Y., Pethiyagoda, R., Rastegar-Pouyani, N. & Papenfuss, T. J. 2000. Evaluating trans-Tethys migration: an example using acrodont lizard phylogenetics. Systematic Biology 49, 233-256.

Stuart-Fox, D. & Owens, I. P. F. 2003. Species richness in agamid lizards: chance, body size, sexual selection or ecology? Journal of Evolutionary Biology 16, 659-669.