Tuesday, January 31, 2006

Bipedal crurotarsan, harbinger of doom

Well smother me in custard and call me Michelle Thorne, a remarkable thing has happened. As revealed by Sterling Nesbitt and Mark Norell in the new issue of Proceedings of the Royal Society of London, it turns out that ‘dinosaur’ remains collected from the famous Ghost Ranch Coelophysis Quarry aren’t Coelophysis bones at all, but actually of some new bizarre theropod-mimicking crurotarsan, Effigia okeeffeae (Nesbitt & Norell 2006). Apparently facultatively bipedal, with a toothless bird-like skull sporting large orbits, dinosaur-like cervical vertebrae possessing true pneumatic foramina, and reduced gracile forelimbs and a theropod-like pelvis, Effigia is strikingly like ornithomimosaurs (ostrich dinosaurs) in several details, mostly those concerning the skull and cervical vertebrae. So it’s sort of an early ‘ostrich mimic mimic’, though of course ostrich mimics aren’t really ostrich mimics, they’re more like the originals, and it’s ostriches that are mimics of ostrich mimics, but of course now we know that ostrich mimics weren’t the originals anyway…

If Effigia is so theropod-like, how do we know that it’s a crurotarsan? Well, there are still some giveaways. The tiny hands are characteristically crocodyliform-like, the ankle is of the complex crocodile-normal type, the way the femur articulates with the pelvis is not like that of dinosaurs, and there are other crurotarsan features too. Nesbitt & Norell included Effigia, and theropods and other taxa, in a modified version of Mike Benton’s basal archosaur data set, and Effigia is consistently recovered as a suchian within a rauisuchian clade that also includes Arizonasaurus and the bizarre fin-backed Lotosaurus.

It now seems quite secure that Shuvosaurus, based on a skull described by Sankar Chatterjee (1993) as ornithomimosaurian, is a close relative of Effigia, so so much for Oli Rauhut’s contention (Rauhut 1997, 2003) that it’s actually a bizarre coelophysoid. I confess to actually liking Oli’s idea, and an interesting consequence of it is that his inclusion of Shuvosaurus within his phylogenetic analysis of Coelophysoidea ‘forced’ Dilophosaurus away from coelophysids and closer to tetanurans. As I noted when I reviewed this work (Naish 2003), given that his topology was dependent on his inclusion of Shuvosaurus, it’s especially interesting that other people later found the same topology, but without incorporating this problematical taxon. But then, different data doesn’t necessarily = different trees, and now it’s clear that it was a mistake to get so excited about Shuvosaurus as a theropod in the first place. Ah, the benefits of hindsight.

So, ‘crurotarsans did it first’, evolving gracile, vaguely ostrich-like body-plans long before theropods did. Amazing. And scary, because, while we can confidently allocate Effigia to Crurotarsi now that we have semi-complete specimens, we couldn’t have done this if we only had scraps. So this is where it becomes especially relevant for me. Dave and I spent pretty much ALL day working on our British dinosaurs article, and I’ve also spent the last several hours chasing up various details. I spent the last several days working on it, and (in between parenting) I think I’m going to be spending the next several days on it as well. In the British fossil record we have a reasonable number of bits that have been identified as coelophysoid. Now, some of them (like a partial pelvis and femur from Pant-y-ffynnon Quarry in south Wales, and the holotype of Sarcosaurus woodi, from Barrow-on-Soar) are based on remains that look securely theropod. But so many others are based on crappy fragments. Are these bits still from coelophysoids? Or might they really be from Effigia-like crurotarsans? Well, that’s the problem, and I bet loads of palaeontologists are now thinking anew about isolated Triassic elements previously assumed to belong to this group. Such is the nature of discovery.

So all I can go is go back to my bomb-site office (as seen in photo above), bury myself once more in those piles of antiquarian literature, and hope and pray that no-one else comes up with a novel reidentification of a group supposedly represented by lots of scrappy British fossils.

PS - for the latest news on Tetrapod Zoology do go here.

Refs - -

Chatterjee, S. 1993. Shuvosaurus, a new theropod. National Geographic Research & Exploration 9, 274-285.

Naish, D. 2003. [Review of] The Interrelationships and Evolution of Basal Theropod Dinosaurs. Geological Magazine 140, 729.

Nesbitt, S. J. & Norell, M. A. 2006. Extreme convergence in the body plans of an early suchian (Archosauria) and ornithomimid dinosaurs (Theropoda). Proceedings of the Royal Society of London B doi:10.1098/rspb.2005.3426

Rauhut, O. W. M. 1997. On the cranial anatomy of Shuvosaurus inexpectatus (Dinosauria: Theropoda). In Sachs, S., Rauhut, O. W. M. & Weigert, A. (eds) 1. Treffen der deutschsprachigen Palaeoherpetologen, Dusseldorf, 21.-23.02.1997; Extended Abstracts. Terra Nostra 7/97, pp. 17-21.

- . 2003. The interrelationships and evolution of basal theropod dinosaurs. Special Papers in Palaeontology 69, 1-213.

Saturday, January 28, 2006

Those Transatlantic manatees

It was on the advice of Phil Budd, chairman of the Southampton Natural History Society, that, some weeks ago, I attended a talk on sirenians (manatees and dugongs) at the National Oceanographic Centre. And, without intending offence to Phil, I was not happy: like people who have seen Battlefield Earth, I left the lecture wanting my valuable time returned to me in full. While I most certainly do not want to get rude about the speaker or his talk, he unfortunately provided a review of sirenian biology that was unoriginal, boring and thoroughly outdated and inaccurate. Example? Well, here’s the best/worse bit….

There are three extant manatee species: Trichechus inunguis of the Amazon Basin, T. manatus of the Gulf of Mexico, Caribbean and US Atlantic coast as far north as Virginia, and T. senegalensis of western Africa. So, how it is that they occur on opposite sides of the Atlantic? The speaker explained it thus: as the Americas and the Old World rifted apart in distant geological times, the ancestral manatee species got separated and, presto, a vicariance event resulted in speciation. It was at this stage that I could only look on slack-jawed in disbelief. I’m sure I don’t need to tell you how absurd it is, today, to suggest this. The North Atlantic opened something like 100 million years ago, yet manatees (well, those of the extant genus Trichechus anyway) are probably less than 10 my old (there being questionable Trichechus fossils from the Pliocene). Granted, there are sirenian workers who have, indeed, suggested that Atlantic rifting might explain manatee distribution… but, those workers were publishing their papers in the early years of the 20th century (Arldt 1907)! Dispersal is clearly the only option – that is, yes, manatees simply must have crossed the Atlantic at some stage, and a quick check of the literature on manatee evolution reveals many references to this theory.

Based on a spurious idea about North Atlantic currents, Simpson (1932) thought that manatees migrated from east to west. However, the evidence clearly shows west to east to be more likely; the fossil trichechine phylogenetically closest to Trichechus (Mio-Pliocene Ribodon) is South American, and in fact all fossil trichechines are American; T. manatus and T. senegalensis are more like each other than either is to T. inunguis; the nematode parasites of T. senegalensis seem to more specialised than the nematodes of T. manatus, and so on.

So, if manatees simply must have crossed the Atlantic to get to Africa, how did they do it? Well, they swam of course, and the really cool thing is that there are also reasons for thinking that this isn’t such a big deal: it is plausible, and in fact it’s supported by strange things that manatees have done in historical times (and I’ll return to that in a minute). Daryl Domning, world expert on sirenian evolution and history, published a paper on manatee evolution in Journal of Vertebrate Paleontology last year. In explaining the successful invasion of the African coast by American manatees, he brought in all of the arguments given above, but tied it together with data on Amazonian and Atlantic palaeocurrents. During the Pleistocene, the subtropical North Atlantic gyre was compressed, and a cold current ran along the Eurafrican coast to as far south as the Gambia. Boekschoten and Best (1988) explained how this appears to have allowed Caribbean corals and certain molluscs to have colonised the eastern Atlantic, and they also speculated that manatees also used this route. Furthermore, it turns out that an ‘appreciable fraction’ of Amazon River water gets right across the Atlantic as far as Africa, so ‘manatees taking this route might even have access to relatively fresh water for a good part of the journey, if they rode in a large lens of Amazon water’ (Domning 2005, p. 699).

And the trump card? Domning (2005) suggested that purported manatee strandings made on the coasts of the North Atlantic in historical times may really have been genuine. Animals alleged to have been manatees have been reported from the shores of Greenland (1780), Scotland (1801 and 1837) and France (1782). Though we should remain sceptical about these accounts – as Domning noted – it is not implausible that they were genuine, and Domning cites a radio-tracked Florida manatee that, in 1995, got as far as Rhode Island.

Here’s another spin on this. A long-standing mystery in the cryptozoological literature has been the purported presence of manatees on St. Helena, in the South Atlantic (not too far south: St. Helena is at the same latitude as Bolivia, Angola, or northern Madagascar). Nobody’s ever really known what these animals were – were they really manatees, or were they actually seals of some kind? The several descriptions provided sound to me like those of pinnipeds: mostly sea lions, and indeed most reviewers have concluded that this is what the animals were. After reviewing the mystery, Shuker (1995) left the case open however. While, previously, there were good reasons for doubting the idea that manatees might ever have gotten to St. Helena, our new understanding of manatee dispersal at least renders this idea a remote possibility: in other words, it probably is just about conceivable that manatees could have gotten to St. Helena after all. But I’m speculating to the extreme. To those of you that will be wondering, this explains my comments in my soon-to-appear review of Michael Newton’s Encyclopedia of Cryptozoology: A Global Guide.

At top, Will is holding a toy manatee in the bathroom sink. Best I could do without a real manatee to hand :)

Refs - -

Arldt, T. 1907. Zur Atlantisfrage. Naturwissenschaftliche Wochenschift 22, 673-679.

Boekschoten, G. J. & Best, M. B. 1988. Fossil and recent shallow water corals from the Atlantic islands off western Africa. Zoologische Mededelingen 62, 99-112.

Domning, D. P. 2005. Fossil Sirenia of the West Atlantic and Caribbean region. VII. Pleistocene Trichechus manatus Linnaeus, 1758. Journal of Vertebrate Paleontology 25, 685-701.

Simpson, G. S. 1932. Fossil Sirenia of the Floria and the evolution of the Sirenia. American Museum of Natural History Bulletin 59, 419-503.

Shuker, K. P. N. 1995. The saga of the St. Helena sirenians. Animals & Men 4, 12-16.

Friday, January 27, 2006

The Curbridge whale and Muirhead's revenge

Well, it’s nearly the end of the month. What does that mean? The deadline for a whole string of projects, not least of them being the enormous British dinosaurs review MS that Dave and I are currently bashing out. As of right now it’s 52 pp, and that’s without figures and tables. There’s also the Crato Fm turtles MS, the deadline for which is also the end of the month. Then there’s the British big cats talk, which is being given in the first week of February (more on that when it happens). Then there’s book reviews: I have to have one written on Carpenter & Tidwell’s Thunder Lizards within the next few weeks, and for your enjoyment here is a photo of me with a copy I was kindly provided by Mike P. Taylor. You’ll note that it’s clearly not a review copy, as it’s been used. Then there’s the phd thesis, but the less said about that the better. Work continues with Barbara Sanchez-Hernandez and Mike Benton on new vertebrate fossils from Galve, Spain (loads of cool stuff there, but can’t talk about it yet), new Brazilian pterosaur specimens, and Wealden sauropods. At some stage Matt Wedel and I will get around to finishing a collaborative project.

Richard Muirhead phoned last night to talk about stuff. Apparently the next issue of Animals & Men is out soon, but whether it’ll include a certain controversial article of mine remains to be seen. Steve Sweetman also phoned, and we spoke about Akidolestes cifelli and spalacotheroid biogeography, though, again, the less said about that the better at the moment. I’ve also recently been contacted by Dennis Stokes of the Botley and Curdridge Local History Society. He’s producing an article on the Curbridge (note: not Curdridge) whale: a Risso’s dolphin Grampus griseus that swam up Botley Creek in 1932, got trapped, and was then caught in a net, dragged ashore, and bludgeoned to death. Which of course is timely in view of the Northern bottle-nosed whale Hyperoodon ampullatus that just swam up the Thames.

I published on the Curbridge whale in 1997 after seeing a photo of it on a pub wall – I thought it was most likely a Risso’s dolphin (and not a narwhal as was claimed at the time) and later found out that F. C. Fraser, great cetologist of the NHM, had identified it as such in an obscure little article (Anon. 1932). Who discovered that article? …………. Muirhead.

PS - for the latest news on Tetrapod Zoology do go here.

Ref - -

Anon. 1932. Dolphin in Hampshire brook. The Fishing Gazette 20-8-1932, 217.

Wednesday, January 25, 2006

The pinnae of Megazostrodon

I do a lot of consultancy work for children’s books, and one of the things I’m asked about most often is whether certain anatomical details should or should not be included in life restorations of fossil animals. Most artists, whether they’re good and informed ones or not, are now decking out their small theropods with feathers, for example. Even so, companies that recycle old artwork still try and sneak in scaly-skinned dromaeosaurs if you let them. Yesterday I was asked if Megazostrodon (a basal mammaliaform from Lower Jurassic Lesotho) should be depicted with ‘ear flaps’ (= pinnae). I immediately said yes: after all, all the life restorations I could think of depicted them. But then I became very, very scared.

It’s generally agreed that Megazostrodon is right down at the base of Mammaliaformes, and thus, under current convention, outside of the mammaliaform crown-group Mammalia. And the thing is, that (1) while we know that mammals have pinnae, that doesn’t mean that non-mammalian mammaliaforms did, and (2) it’s well established that basal mammaliaforms like Megazostrodon differed in bony ear anatomy from mammals. Mammals have an elongated cochleal canal and a promontorium on the petrosal, features involved in improving both high-frequency hearing and the acoustic isolation of the inner ear. But several studies have shown that basal mammaliaforms were intermediate in these regards, and different from mammals (Rosowski & Graybeal 1991, Graybeal et al. 1998, Luo et al. 1995). If Megazostrodon and related forms didn’t have the same sort of dependence on high-frequency hearing as modern mammals, would they have attempted to ‘maximise’ their hearing by evolving pinnae?

Ultra-rigorous uber-scientist that I am, the first thing I went and did was look at some life restorations. In May 2001 Zhe-Xi Luo and colleagues described Hadrocodium, a new basal mammaliaform from Lower Jurassic China. The fossil was interesting enough to make the cover of the issue of Science that it was described in: the cover features a paper-clip, and a skull and life restoration of Hadrocodium (Hadrocodium was tiny you see, with an estimated weight of 2 grams). And the good news? It’s depicted as having little pinnae. In phylogenies, Hadrocodium is recovered as two or three steps up from Megazostrodon, so as a piece of circumstantial evidence this is at least suggestive. On rather more technical details, Rosowski & Graybeal (1991) thought it at least possible that Morganucodon – a close relative of Megazostrodon (according to most phylogenies, never mind McKenna & Bell) – may have ‘had ears like those of modern small mammals that are selectively sensitive to high-frequency sounds’ (p. 131). It’s hard to imagine that this might be true, and that a pinna be absent. Furthermore, while the cochleal canal is shorter, and the promontorium is smaller, in basal mammaliaforms than is the case in mammals (Luo et al. 1995), Morganucodon in more mammal-like in these features than are more basal mammaliaforms (like Sinoconodon). Forms even closer to mammals, like Haldanodon and Hadrocodium, are more mammal-like in these ear features than Morganucodon. So what we’re seeing is a gradual approach to the mammalian condition. It’s all a bit arm-wavy, but I would guess that we’d see the gradual enlargement of pinnae occurring at the same time as these changes, given that they seem to be correlated.

Do we even know whether pinnae were present in the mammalian common ancestor, as I’ve been assuming. The basal split in the mammal tree, according to current morphological phylogenies anyway, is between Australosphenida and Theriiformes, and given that both clades have extant representatives, we can make inferences about their common ancestor. Well, we all know that members of Theriiformes have pinnae, but as for australosphenidans (most of which are scrappy fossils)… Every now and again you’ll hear people saying that monotremes don’t have them, and thus they can’t be assumed to have been present, ancestrally, in mammals (incidentally, I can’t find an assertion along these lines in the literature, but there’s probably one out there somewhere). But it’s not true. While the platypus lacks a pinna, this isn’t so of echidnas. On them, Nowak (1999) wrote ‘The pinna of the external ear is well developed, but is partly concealed in the pelage’ (p. 7). So it is ok to assume pinnae in the mammalian common ancestor after all.

Back to Megazostrodon: wouldn’t these animals look pretty dumb without pinnae anyway? Of course we don’t really know whether they had fur either (despite dubious suggestions of evidence for such structures in non-mammaliaform synapsids), but it’s reasonable to think that they did given that, phylogenetically, they’re very close to the mammalian common ancestor (and, again, on the basis of parsimony that animal would have been furry), and not all that different from basal mammals.

So, next time I say ‘yes’ on the phone I’ll just assume I’m right – checking the literature is so time-consuming.

More things arose today that I’ll talk about here at some stage. Whales with trunks, the swan-necked seals, and sex determination in dinosaurs. Now back to those Wealden sauropods… For the latest news on Tetrapod Zoology do go here.

Refs - -

Graybeal, A., Rosowski, J. J., Ketten, D. R. & Crompton, A. W. 1989. Inner-ear structure in Morganucodon, an early Jurassic mammal. Zoological Journal of the Linnean Society 96, 107-117.

Luo, Z., Crompton, A. W. & Lucas, S. G. 1995. Evolutionary origins of the mammalian promontorium and cochlea. Journal of Vertebrate Paleontology 15, 113-121.

- ., Crompton, A. W. & Sun, A.-L. 2001. A new mammaliaform from the Early Jurassic and evolution of mammalian characteristics. Science 292, 1535-1540.

Nowak, R. M. 1999. Walker’s Mammals of the World (Sixth Edition), Volume 1. The Johns Hopkins University Press, Baltimore and London.

Rosowski, J. J. & Graybeal, A. 1991. What did Morganucodon hear? Zoological Journal of the Linnean Society 101, 131-168

Graeme’s Pleistocene megafrog

I didn’t talk much to people today: I spent most of it sat in front of a PC, dealing with over-due email responses and sorting through manuscripts I’m handling for my editing job. Jeff Liston phoned though, and I also caught up briefly with Dave Martill for a catch-up on the British dinosaurs project we’re working on (deadline end of this month… gack). I need not labour the point that a disturbing amount of time is passing without me working on my phd thesis. And then Graeme Elliott came to see me. He saw that I was printing out Pounds et al’s (2006) recently published Nature paper on global lissamphibian extinctions. Make no mistake, frogs and toads are in big trouble, with populations and species disappearing at a disturbing rate.

What does Graeme think about this? He thinks that there should be a giant Pleistocene frog somewhere out there in the fossil record, the size of a Labrador at least and able (theoretically, were these organisms contemporaneous) to eat puppies and small children. Skull Island should harbour relict descendants of such forms, though I doubt they would fare well among giant V. rexes, terrestrial predatory crocodyliforms and truck-sized arthropods. Are there any particularly big fossil frogs? Not really. Aubrey Smith, Marc Jones and Susan Evans have been giving conference presentations on a Cretaceous Madagascan fossil they’re referring to as a ‘hyperossified megafrog’ - I think I detect a hint of hyperbole. It’s the biggest Mesozoic frog yet reported, but even so it was probably not much bigger than, say, Ceratophrys (the extant Horned frog). I doubt if Cenozoic fossil frogs got much bigger than extant forms.

Indeed the biggest frog of all time, so far as we know, is the Goliath frog Conraua goliath (and not Rana goliath as said in some older sources, though Conraua was included in Rana until Nieden separated them in 1908) of Cameroon. Described in 1906, it’s one of six Conraua species, sometimes called the slippery frogs. I don’t have Mark Carwardine’s Guinness Book of Animal Records by my side right now, but I think they get to about 60 cm (with legs outstretched) and over 3 kg. For a frog, that’s big. Of course there’s always the unverified carn-pnay of the New Guinean highlands – a crypto-frog supposedly bigger than C. goliath.

Why aren’t there frogs the size of labradors? I don’t know if it’s been discussed in the literature, but I’ve always liked the idea that lissamphibians are constrained in size by the fact that most of them rely on cutaneous respiration. Bigger lissamphibians, having a small relative surface area, should find it more difficult to respire compared to their small relatives, and this prediction seems to be confirmed by the fact that the biggest lissamphibians (the cryptobranchid salamanders) are aquatic. Surely there’s stuff in the herpetological literature that covers this. Maybe I should check.

The picture above is taken from the University of California's amphibian pages.

Coming soon on this blog site… Why rabbits are just wrong; Birds in crevices; Transatlantic manatees; and Eagle owls take over Britain. For the latest news on Tetrapod Zoology do go here.

Ref - -

Pounds, J. A. Bustamante, M. R., Coloma, L. A., Consuegra, J. A., Fogden, M. P. L., Foster, P. N., La Marca, E., Masters, K. L., Merino-Viteri, A., Puschendorf, R., Ron, S. R., Sánchez-Azofeifa, G. A., Still, C. J. & Young, B. E. 2006. Widespread amphibian extinctions from epidemic disease driven by global warming. Nature 439, 161-167.

Tuesday, January 24, 2006

Giraffes: set for change

Giraffes, Giraffa camelopardalis. Everybody loves giraffes – how could you not. Giraffes are such fantastic and unusual mammals that all manner of questions are still being asked about their anatomy, physiology and behaviour. A mild amount of controversy exists over how many neck vertebrae they have: the old chestnut about them having the same number of cervical verts as most other mammals [7] has been challenged by Solounias (1999), who proposes that they actually have 8. Why they have long necks remains contentious – personally I’ve become a fan of the sexual selection hypothesis championed by Simmons and Scheepers (1996) – and basic questions of anatomy, such as how their circulation works (Pedley et al. 1996) and why their bones differ in density from those of other artiodactyls (van Schalkwyk et al. 2004), remain interesting areas of research.

As the only extant long-necked terrestrial tetrapods, giraffes are much employed in debates over the neck posture of sauropod dinosaurs, and recent articles by John Martin and colleagues (Martin et al. 1998), and Kent Stevens and J. M. Parrish (2005), discuss giraffes and what they might tell us about sauropod necks. Greg Paul has recently been saying a lot about giraffe necks on the dinosaur mailing list, but I haven’t yet read his comments, and I know at least two sauropod workers who have something in the pipeline on this subject. Something is happening in the world of giraffe research that will probably be unknown to dinosaur workers, and will affect the way in which giraffes are named in the literature. It’s no big deal, but it’s worth bringing to attention: it’s the species level taxonomy. Pretty soon, it’s no longer going to be ok to talk of your giraffe as being (necessarily) a Giraffa camelopardalis. Why? Because there are studies underway which indicate that more than one extant species is present.

Nine Giraffa camelopardalis subspecies are currently recognized, and while some authors have been happy to accept all of them as valid, others have wondered whether at least some of the variation is just individual. Indeed there are photos showing individuals of different supposed ‘subspecies’ standing next to each other (Dagg 1962). For the record, the subspecies are…

G. c. angolensis (Angolan Giraffe)
G. c. antiquiorum (Kordofan Giraffe)
G. c. camelopardalis (Nubian Giraffe)
G. c. giraffa (Southern/South African Giraffe)
G. c. peralta (Nigerian/West African Giraffe)
G. c. reticulata (Reticulated Giraffe)
G. c. rothschildi (Baringo/Rothschild's/Uganda Giraffe)
G. c. thornicrofti (Thornicroft's Giraffe)
G. c. tippelskirchi (Masai Giraffe)

At least some of the observed variation is real (and not just individual variation, or clinal) – but how much of it, and what does it mean for taxonomy and phylogeny?
Russell Seymour has recently been giving talks with titles like ‘How many giraffes? Temporo-spatial evolution in a "well-known" species and its implications for conservation of biodiversity’, so, reading between the lines, there is the implication that Giraffa camelopardalis is actually more than one species. Maybe one or more of the supposed subspecies is going to be elevated to species rank – or in fact restored to species rank, because at least some of the taxa were initially named as species, but later demoted when it became fashionable to lump big mammals in this way (and there’s an essay in that subject, by the way). A team involving Seymour, Rick Brenneman, David Brown, Thomas deMaar and Julian Fennessy are studying giraffe phylogeography, and their results should have bearing on this matter. Seymour has also been listed alongside Norman MacLeod and M. Bruford as looking at variation within Giraffa camelopardalis. I’ve seen Norman MacLeod listed as a coauthor on presentations regarding DAISY, an image-recognition software programme being developed at the NHM. Basically, they’ve developed software that can ‘look at’ and identify objects (including microfossils and bird bones) and, reading between the lines again, I wonder if it’s been applied to the distinctively patterned coats of giraffe subspecies? We’ll find out in due course.

So far as I know nothing has yet been published on this – please let me know if you know otherwise. But, to those who are planning to mention giraffes in any of their writings, do keep this in mind: the giraffe you are thinking of may end up being something other than Giraffa camelopardalis. At top, the photo provides damning evidence for the assertion that the neutral neck posture of giraffes is a horizontal one (that was sort of meant to be a joke). Nick Longrich looks on, with camera.

For the latest news on Tetrapod Zoology do go here.

Refs - -

Dagg, A. I. 1962. The subspeciation of the giraffe. Journal of Mammalogy 43, 550-552.

Martin, J., Martin-Rolland, V. & Frey, E. 1998. Not cranes or masts, but beams: the biomechanics of sauropod necks. Oryctos 1, 113-120.

Pedley, T. J., Brook, B. S. & Seymour, R. S. 1996. Blood pressure and flow rate in the giraffe jugular vein. Philosophical Transactions of the Royal Society of London B 351, 855-866.

Simmons, R. E. & Scheepers, L. 1996. Winning by a neck: sexual selection in the evolution of giraffe. The American Naturalist 148, 771-786.

Solounias, N. 1999. The remarkable anatomy of the giraffe’s neck. Journal of Zoology 247, 257-268.

Stevens, K. A. & Parrish, J. M. 2005. Neck posture, dentition and feeding strategies in Jurassic sauropod dinosaurs. In Tidwell, V. & Carpenter, K. (eds) Thunder-Lizards: The Sauropodomorph Dinosaurs. Indiana University Press (Bloomington & Indianapolis), pp. 212-232.

van Schalkwyk, O. L., Skinner, J. D. & Mitchell, G. 2004. A comparison of the bone density and morphology of giraffe (Giraffa camelopardalis) and buffalo (Syncerus caffer) skeletons. Journal of Zoology 264, 307-315.

Sunday, January 22, 2006

A trip to Hastings

Well, I’ve just returned from a day spent in Hastings where I spoke to members of the Hastings and District Geological Society on Wealden dinosaurs. I do enjoy visiting Hastings, and, despite the 4-hr train journeys I had to endure on the way there and back, Ken Brooks and Diana Williams, and Peter and Joyce Austen were very hospitable and I thank them for inviting, hosting and feeding me.

As it happens it’s timely that I should give a talk on Wealden dinosaurs while actually being in the Weald: timely because Dave Martill and I are finishing up the Wealden section of the British dinosaurs manuscript we’re working on (more on that another time), and also because several academic projects involving Wealden dinosaurs are presently on the go (and here I do mean dinosaurs of the Hastings Beds and Weald Clay Groups of the mainland Weald, not those of the Isle of Wight Wealden). What did I cover in the talk? Well, I promised Ken that I would provide a synopsis, and I hope the following text will serve that purpose…

Dinosaurs of the Wealden: Old and New

Dinosaurs are often thought of as animals of far-flung places, and in particular (thanks to Tyrannosaurus and Triceratops and so on) are associated with the USA. But in fact the concept of the ‘Dinosauria’ arose in England, and all of the key early discoveries were made, by English scientists, in England. The Lower Cretaceous rocks of the mainland Wealden have, historically, been among the most important British rocks in terms of early dinosaur discoveries. The stratigraphic terminology of the Wealden is complex and rarely explained clearly: the mainland Wealden consists of the Hastings Beds Group and Weald Clay Group, and both of these units are subdivided into formations (for a good up-to-date review see Radley 2004). Several distinguished Victorian collectors are particularly associated with the Wealden, including Gideon Mantell (1790-1852), Samuel Beckles (1814-1890) and George Bax Holmes (1803-1887), and many of the fossils collected by these men are still key specimens in terms of what they tell us about the respective taxa.

Some really interesting little-known tie-ins exist between Wealden dinosaurs and the world of archaeological forgery and science fiction. The 1909 acquisition of a Hastings Iguanodon specimen by the British Museum (Natural History) led to the little-known idea that William Butterfield (1872-1935), the then-curator of Hastings Museum, perpetrated the Piltdown hoax in order to make a fool of Charles Dawson (1864-1916), the discoverer of Piltdown man and extractor of the Iguanodon. Also intimated by some with the Piltdown story is Arthur Conan Doyle (1859-1930), novelist, physician, amateur detective, and ‘Crowborough kid’. Supposedly, a conspicuous number of notable parallels occur between Maple White Land of Doyle’s ‘Lost World’, and the English Wealden. Neither the cases against Butterfield nor Doyle have serious standing, and it has been easy to find gaping holes in them.

As for the dinosaurs themselves, the Wealden boasts a number of particularly interesting and significant theropods – the predatory dinosaurs. In 1983, amateur palaeontologist William Walker discovered Baryonyx walkeri in the Weald Clay of Ockley, a specimen that proved to be a ‘Rosetta stone’ for the interpretation of a hitherto enigmatic theropod group, the spinosaurids. Baryonyx specimens have since been discovered in the Hastings Beds Group and in the Wessex Formation of the Isle of Wight. Allosauroids – the group that includes Allosaurus and its close relatives – are represented by several Wealden specimens, most notably the tall-spined vertebrae from Battle known as Becklespinax. From the Wessex Formation is one of Europe’s most complete theropods: Neovenator salerii, discovered in 1978. Diverse other theropods, representing the theropod group Coelurosauria, are also present in the Wessex Formation. They include the probable oviraptorosaur Thecocoelurus (represented by just half of a single neck vertebra!) and the tyrannosaur Eotyrannus, named in 2001. New data on Eotyrannus shows that it was rather more unusual than thought when described in 2001, with unique notches at the tips of its lower jaw and distinctive lower arm bones.

Sauropods (the giant long-necked dinosaurs), armoured dinosaurs and others are also well represented in the rocks of the Wealden, but were not covered in my talk for reasons of time!

Ref - -

Radley, J. 2004. Demystifying the Wealden of the Weald (Lower Cretaceous, south-east England). OUGS Journal 25 (1), 6-16.

So there we go. The rechargeable batteries in my camera ran out as soon as I tried to take a photo of the meeting, so the photo above instead shows me at Wealden exposures at Bexhill, taken in December 2001.

Now, about those sleeping passerines….
PS - For the latest news on Tetrapod Zoology do go here.

Saturday, January 21, 2006

When eagles go bad

Welcome to the first of my blog essays – and it’s not as if I planned to write this, it’s just that the idea came to me while I was eating biscuits. One of my favourite ‘fringe’ subjects within tetrapod zoology concerns the alleged ability of eagles to attack and kill unusually large mammals, including people. Most people, and indeed most ornithologists and other zoologists, don’t take this notion too seriously, or indeed dismiss it immediately as utter nonsense. Fortean literature is replete with stories of eagles (usually European Golden eagles Aquila chrysaetos) attacking, killing and/or carrying off people, typically (but not always) young children, with the best known story of this sort being that of 5-yr-old Marie Delex from the French Alps. It’s pretty inconceivable that even the biggest eagle could carry off a human child, but as for whether they could kill one, well, read on.

Two recent items in the media have concerned this issue, and both caught my attention.

Firstly, we have news from researchers at Ohio State University on the death of the Taung child (or Taung baby, depending on your preference). This is the famous juvenile australopithecine specimen described by Dart in 1925, and thought to have been a 3 or 4 yr old. Following up on Brain’s observations of 1981 that the Taung assemblage represented an accumulation produced by a large carnivore, probably a leopard, Lee R. Berger and Ronald J. Clarke (1995) showed in Journal of Human Evolution that a large eagle was the most likely killer of the juvenile. The case was good: the assemblage consists of smallish mammals (like mole rats, spring hares and small antelopes), evidence for carnivorous mammals is absent, nick marks corresponding to those produced by eagle beaks and talons are present on some of the bones, and eggshell was also discovered at the site. The new discovery is that nick marks around the orbital margins of the Taung child demonstrate once and for all that an eagle really was the killer. Great stuff – I look forward to the paper.

What’s a little odd is that several people have started asking questions about the lifting abilities of the Taung eagle relative to the weight of the juvenile australopithecine (oh, and by the way, the eagle is [I understand] presently a theoretical one – the evidence for its presence is there, but the eagle itself has yet to be found. It has been considered by some workers that the African crowned eagle Stephanoaetus coronatus was the most likely culprit – more on that at another time). This is odd because it was discussed to death the last time there was a flurry of interest in the ‘eagle as killer’ theory. Anders Hedenström (1995) showed in Nature that, given that Stephanoaetus can carry animals weighing just over 6 kg (wow!), then it would have to have dismembered the australopithecine. Which is fine, given that the specimen is only known from its skull. However, Hedenström argued this based on an assumed mass for the Taung child of c. 10 kg, and that might have been too high.

Berger & Clarke (1996) – in an article published on the same page as Dave Martill et al.’s brief note on the possibility of finding medullary bone in non-avian theropods [more on that in another post] – countered that evisceration of the juvenile prior to its carrying was likely, given that large extant raptors commonly do this. This could mean a 30% loss in body weight of the juvenile, thus bringing it close to or within the short-range carrying abilities of Stephanoaetus. It’s also worthy of note that Berger and Clarke brought attention to cases where big living African eagles simply must have lifted animals that weighed more than 6 kg, so this perhaps wasn’t the ‘upper’ lifting limit that Hedenström thought it was.

So, to those people who have suggested that the Taung eagle killed the australopithecine there on the spot (oh, I see, coincidentally in the middle of a veritable midden pile of eagle-killed small mammals), I say check out the literature on eagle lifting abilities.

Speaking of killing the australopithecine on the spot, this introduces the next thing I wanted to talk about… can a big eagle kill a mammal that’s too big for the eagle to carry? Like it or not - and I’ve received some vitriolic emails for promoting this idea (Naish 1998, 1999) - the answer is a definite yes. In fact the ability of large eagles, specifically Golden eagles, to kill relatively enormous prey is not doubted and well established. Between 1987 and 1989 representatives of Animal Damage Control (ADC) were called in to check out mysterious domestic cattle deaths that were occurring in Socorro County New Mexico. 6 calves were killed and 13 injured, with the biggest calf attacked weighing 115 kg. The attacks were caused, unquestionably, by a pair of local Golden eagles, as verified by observed attacks and by the talon marks on calf skulls. The problem stopped when the eagles were removed (and ‘removed’ probably means ‘shot’ I guess). It seems the eagles killed by puncturing the skull base. I know this all sounds pretty incredible, ridiculous even: if you don’t believe me see Robert Phillips et al.’s 1996 paper in Wildlife Society Bulletin. You might be as surprised as I was to learn that Golden eagles are also documented as killers of Mule deer, Pronghorn and semi-domestic reindeer, and again this is all documented in the technical literature and I’m not making it up. For killing of juvenile deer, see Cooper (1969) for Red deer and Ratcliffe & Rowe (1979) for Roe deer [update: for more info on awesome eagle predation see Steve Bodio's post Blogs, eagles, synchronicity. The adjacent photo is that by-now-familiar image of an eagle kicking the crap out of a fox. For more on eagles vs foxes see below].

What was the second thing in the media that I wanted to mention? On Jan’ 17th, the BBC broadcast 'Bill Oddie's How to Watch Wildlife' (or whatever), and it included something I’ve never seen before on film. Oddie and a colleague were observing a wild Golden eagle in the Cairngorms, and the camera was on the bird too. Suddendly, it swooped down low on an adult Red deer. The deer ran down the hillside, pursued closely by the eagle, which swerved and jinked to follow and harass it. The eagle wasn't about to dig its talons into the deer - it looked as if it was trying to see if it could get it to take a nasty fall down the hill. This behaviour has been mentioned for some other raptors – Lammergeiers Gypaetus barbatus are said to do it to ibex and chamois – but I didn’t know Golden eagles did it. On Lammergeiers, Berridge (1934) wrote ‘A favourite method of dealing with [ibex and chamois] is to swoop down suddenly upon a prospective victim that may be poised somewhat insecurely upon the steep hillside, so that the startled beast loses its foot-hold, and goes tumbling to death in the ravine below’ (p. 219). The scoop is that Lammergeiers don’t just try this out on ibex and chamois, they will also try this on humans too, and I know this because it has been reliably reported by a professional biologist (I don’t have his permission to cite it as a pers. comm., but will try and get this on record).

One final thought on this subject, though to be honest it’s not that original and many people end their articles on nasty eagles with the same thought. The raptors I’ve been discussing here aren’t particularly big: Golden eagles max out at 6.6 kg, and Stephanoaetus is less than that. Given that there were, recently, extinct eagles that were substantially bigger than this – Haast’s eagle from New Zealand weighed about 13 kg (in females) for example – then eagles as a group simply must have been capable of even more amazing feats of predation. More on that another time.

By the way, the picture at the top isn't a giant killer eagle, it’s me.

UPDATE (added December 2006): for more on the now famous image of the eagle attacking the fox, visit this post at Birdchick’s site. See also her other post on the subject, where you can watch video footage of an eagle attempting to catch and kill an adult fox.

Refs - -

Berger, L. R. & Clarke, R. J. 1995. Eagle involvement in accumulation of the Taung child fauna. Journal of Human Evolution 29, 275-299.

- . & Clarke, R. J. 1996. The load of the Taung child. Nature 379, 778-779.

Berridge, W. S. 1934. All About Birds. George G. Harrap, London.

Cooper, A. B. 1969. Golden eagle killed Red deer calf. Journal of Zoology 158, 215-216.

Hedenström, A. 1995. Lifting the Taung child. Nature 378, 670.

Naish, D. 1998. Big bad eagles 2: sheep and cow on the Golden eagle menu. Mainly About Animals 36, 10-12.

- . 1999. Big bad killer eagles. Fortean Times 122, 48.

Phillips, R. L., Cummings, J. L., Notah, G. & Mullis, C. 1996. Golden eagle predation on domestic calves. Wildlife Society Bulletin 24, 468-470.

Ratcliffe, P. R. & Rowe, J. J. 1979. A Golden eagle (Aquila chrysaetos) kills an infant Roe deer (Capreolus capreolus). Journal of Zoology 189, 532-535.

Welcome to Tetrapod Zoology

Welcome to my blog site, which over the next weeks and months will include assorted thoughts and comments on various of the issues that interest me: predominantly, what's going on in the world of tetrapod zoology, and particularly the stuff I'm researching, or involved in. Of special interest to me right now are the dinosaurs of the British Wealden (of course), the intriguing tie-ins between Wealden fossil collectors, Conan Doyle's Lost World and the Piltdown fiasco, convergence between different fossorial tetrapods, manatee evolution, and British big cats (yes, really). More to come on these matters and much more in future, honest.