July 26, 2009
One of these things ought to be familiar, but the other one may not be (they are shown to scale here). The first commenter to correctly identify them both wins 100 SV-POW!bucks (TM), which aren’t worth diddly in the real world* but can be exchanged for worship, admiration, and bragging rights on teh intert00bz.
The contest will run until someone gets the right answer or the week is out. All will be revealed next week. Mike and Darren are forbidden to compete, not because it would be unfair but because I don’t like them very much.
This isn’t an impossible task, by the way. The info is out there. The only question is whether you are lonely geeky awesome enough to solve the mystery.
* That’s just a guess. It’s possible that at SVP you might find someone who would you buy you a beer in exchange for some SV-POW!bucks (TM), or just because you have more than them.
Update: answer posted here.
July 21, 2009
I hesitate to inflict these images on SV-POW! readers, but I have to post them somewhere if only so I can point my family to them; and who knows, maybe some of the rest of you will enjoy the amusing hat.
Last Friday (17th July), I drove down to Portsmouth, with my wife Fiona, to graduate — the consummation of my Ph.D programme. I’d expected to be issued with a sober black robe and one of those hats with a flat square on top, but I was unprepared for just how silly the kit would turn out to be:
In fact, I looked less like a palaeontologist and more like a member of the Spanish Inquisition. Which, I’m sure I need not point out, was the last thing I’d expected.
My supervisor Dave Martill was there for the ceremony, also dressed up as a silly person; and Darren came along in civvies to say hello before the show, and to meet up afterwards at the reception at the Department:
Also present and graduating was Portsmouth pterosaur maven Mark Witton, but I don’t have a picture of him in regalia, as he turned up too late to have his photo taken — wise man.
As I sat through the very, very long ceremony — if you’ve never listened through a list of 600 names being read out and watched 600 people walk up on stage and shake hands with the pro vice chancellor, you don’t know the meaning of the word “party” — I became bored enough to read the programme cover to cover, and so I discovered that photography during the ceremony is strictly forbidden. Fiona, however, did not realise this, and so I am able to show you this actual photograph of me caught in the act of graduating:
We doctoral graduands got special treatment: not only did we shake hands with the pro vice chancellor — as though this were not thrill enough — but we also had the titles of our dissertations read out. As mine sounds rather vague (“Aspects of the history, anatomy, taxonomy and palaeobiology of sauropod dinosaurs”) I was left wishing that I’d stuck with my original title.
After the ceremony it was back to the department for nibbles and also to — finally! — pick up the printed-and-bound copies of my dissertation, which until then I’d not seen in the flesh. Apart from the two mandatory copies (for the University and Department libraries), I had four printed — one each for me, Dave, Darren and Matt. Those of you not fortunate enough to have received one of the printed copies can assuage your lust for my dissertation by buying it in mug form:
I’m not quite sure what made me think this would be a cool thing to do, but anyway I did it, and this is now my first-choice mug as I make my way through the numerous cups of tea that, as an Englishman, I am obliged to drink each day. (And yes, you really can buy one of your very own.)
You may wish to know that, at the time of writing, the top five search terms that are bringing people to SV-POW! are: rabbit, flamingo, basement, svpow, and twinkie.
July 20, 2009
Weren’t we just discussing the problem of keeping up with all the good stuff on da intert00bz? The other day Rebecca Hunt-Foster, a.k.a. Dinochick, posted a “mystery photo” that is right up our alley here at SV-POW!, but, lazy sods that we are, we missed it until just now. Here’s the pic:
I flipped it 90 degrees so that you can see more clearly what is going on. This is a cut and polished section of a pneumatic sauropod vertebra–the bottom half of the mid-centrum of a dorsal vertebra, to be precise. Cervicals usually have concave ventral surfaces, and sacrals are usually either wider and flatter or narrower and V-shaped in cross sections, so I am pretty confident that this slice is from a dorsal. Compare to the classic anchor cross-section in this Camarasaurus dorsal:
(You may remember this image from Xenoposeidon week–almost two years ago now!)
As usual, bone is black, air is white, and everything else is gray. And the ASP is:
461080 white pixels/(461080 white + 133049 black pixels) = 0.78
So, we know what this is, and we know the ASP of this bit of it, and we can even figure out the in vivo density of this bit. The density of cortical bone ranges from about 1.8 g/cm^3 for some birds to about 2.0 for most mammals. For the sake of this example–and so I can hurry back to writing my lecture about the arse–let’s call it 1.9. The density is then the fraction of bone multiplied by the density of bone, full stop. If it was an apneumatic bone, we’d have to add the fraction of marrow multiplied by the density of marrow, but the density of air is negligible so we can skip that step here. The answer is 0.22 x 1.9 = 0.42 g/cm^3, which is pretty darned light. Keep in mind, though, that some slices of Sauroposeidon (and ‘Angloposeidon’, as it turns out) have ASPs of 0.89, and thus had an in vivo density half that of the above slice (0.11 x 1.9 = 0.21 g/cm^3).
What’s that in real money? Well, your femora are roughly 60% bone and 40% marrow, with a density of ((0.6 x 2.0)+(0.4 x 0.93)) = 1.6 g/cm^3, four times as dense as the bit of vertebra shown above, and eight times as dense as some slices of Sauroposeidon and ‘Angloposeidon’. If that doesn’t make you self-conscious about your heavy thighs, I don’t know what will.
Yes, that was a lame joke, and yes, I’m going out on it.
Hat tip to Dinochick.
P.S. It’s the 40th anniversary of the first moon landing today. Hoist a brew for Neil and Buzz, wouldja?
July 18, 2009
By now you’ll recognize this as NHM 46870, a minor celebrity in the world of pneumatic sauropod vertebrae. Darren has covered the history of the specimen before, and in the last post he showed photographs of both this chunk and its other half. He also briefly discussed the Air Space Proportion (ASP) of the specimen, and I’ll expand on that now.
People have mentioned the weight-saving properties of sauropod vertebrae from the very earliest discoveries of sauropods. But as far as I know, no one tried to quantify just how light they might have been until 2003.
That fall I was starting my third year of PhD work at Berkeley, and I was trying to think of everything that could possibly be investigated about pneumaticity in sauropod vertebrae. I came up with a list of four things:
- external traces of pneumaticity (foramina, fossae, tracks, laminae)
- form and complexity of internal spaces (camerae, camellae, branching patterns)
- ratio of bone to air space within a pneumatic element
- distribution of postcranial skeletal pneumaticity (PSP) in the body
That list of four things formed the outline for my first dissertation chapter (Wedel 2005), and for my dissertation itself. In fact, all of my papers that have anything to do with pneumaticity can be classified into one or more of those four bins:
- external traces: Wedel (2005, 2007)
- internal complexity: Wedel et al. (2000a, 2000b), Wedel (2003b)
- bone/air ratio: Wedel (2005)
- distribution in the body: Wedel (2003a, 2006, 2009)
That list is not exhaustive. It’s every aspect of PSP that I was able to think of back in 2003, but there are lots more. For example, I’ve only ever dealt with the internal complexity of sauropod vertebrae in a qualitative fashion, but the interconnections among either chambers or bony septa could be quantified, as Andy Farke has done for the frontal sinuses of hartebeests (Farke 2007). External traces on vertebrae and the distribution of PSP in the body can also be quantified, and were shortly after I drew up the list–see Naish et al. (2004) for a simple, straightforward approach to quantifying the extent of external pneumatic fossae, and O’Connor (2004, 2009) for a quantitative approach to the extent of pneumaticity in the postcranial skeletons of birds. There are undoubtedly still more parameters waiting to be thought of and measured. All of these papers are first steps, at least as applied to pneumaticity, and our work here is really just beginning.
Also, it took me an embarrassingly long time to “discover” ASPs. I’d had CT slices of sauropod vertebrae since January, 1998, and it took me almost six years to realize that I could use them to quantify the amount of air inside the bones. I later discovered that Currey and Alexander (1985) and Casinos and Cubo (2000) had done related but not identical work on quantifying the wall thickness of tubular bones, and I was able to translate their results into ASPs (and MSPs for marrow-filled bones).
The procedure is pretty simple, as Mike has shown here before. Open up the image of interest in Photoshop (or GIMP if you’re all open-sourcey, like we are), make the bone one color, the air space a second color, and the background a third color. Count pixels, plug ‘em into a simple formula, and you’ve got the ASP. I always colored the bone black, the air space white, and the background gray, so
ASP = (white pixels)/(black + white pixels)
For the image above, that’s 460442/657417 = 0.70.
Two quick technical points. First, most images are not just black, white, and one value of gray. Because of anti-aliasing, each black/white boundary is microscopically blurred by a fuzz of pixels of intermediate value. I could have used some kind of leveling threshold thing to bin those intermediate pixels into the bone/air/background columns, but I wanted to keep the process as fast and non-subjective as possible, so I didn’t. My spreadsheet has columns for black, white, gray, and everything else. The everything else typically runs 1-3%, which is not enough to make a difference at the coarse level of analysis I’m currently stuck with.
Second, I prefer transverse sections to longitudinal, because most of the internal chambers are longitudinally oriented. That means that longitudinal sections, whether sagittal or horizontal, are likely to cut through a chamber wall on its long axis, which makes the walls look unnaturally thick. For example, in the image above the median septum looks 5-10 times thicker than the outer walls of the bone, which would be a first–usually the outer walls are thicker than the internal septa, as you can see here. I don’t think the median septum really is that thick; I strongly suspect that a very thin plate of bone just happened to lie in the plane of the cut. It takes some work to get used to thinking about how a 2D slice can misrepresent 3D reality. When I first started CT scanning I was blown away by how thick the bone is below the pre- and postzygapophyses. I was thinking, “Wow, those centrozygapophyseal laminae must have been way more mechanically important than anyone thinks!” It took me a LONG time to figure out that if you take a transverse slice through a vertical plate of bone, it is going to look solid all the way up, even if that plate of bone is very thin.
Even apart from those considerations, there is still a list of caveats here as long as your arm. You may not get to choose your slice. That’s almost always true of broken or historically sectioned material, like NHM 46870. It’s even true in some cases for CT scans, because some areas don’t turn out very clearly, because of mineral inclusions, beam-hardening artifacts, or just poor preservation.
The slice you get, chosen or not, may not be representative of the ASP of the vertebra it’s from. Even if it is, other elements in the same animal may have different ASPs. Then there’s variation: intraspecific, ontogenetic, etc. So you have to treat the results with caution.
Still, there are some regularities in the data. From my own work, the mean of all ASP measurements for all sauropods is about 0.60. That was true when I had only crunched my first six images, late on the evening of October 9, 2003. It was true of the 22 measurements I had for Wedel (2005), and now that I have over a hundred measurements, it’s still true. More data is not shifting that number at all. And Woodward (2005) and Schwartz and Fritsch (2006) got very similar numbers, using different specimens.
This is cool for several reasons. It’s always nice when results are replicated–it decreases the likelihood that they’re a fluke, and in this case it suggests that although the limitations listed above are certainly real, they are not deal-killers for answering broad questions (we are at this point seeing the forest more clearly than the trees, though).
More importantly, the mean 0.60 ASP for all sauropod vertebrae is very similar to the numbers that you get from the data of Currey and Alexander (1985) and Cubo and Casinos (2000): 0.64 and 0.59, respectively. So sauropod vertebrae were about as lightly built as the pneumatic long bones of birds, on average.
Naturally, there are some deviations from average. Although I didn’t have enough data to show it in 2005, brachiosaurids tend to have higher ASPs than non-brachiosaurids. And Early Cretaceous brachiosaurids from the US and England are especially pneumatic–the mean for all of them, including Sauroposeidon, ‘Angloposeidon’, some shards of excellence from the Isle of Wight, and assorted odds and ends, is something like 0.75-0.80, higher even than Brachiosaurus. So there’s probably a combined phylogenetic/functional story in there about the highly pneumatic, hyper-long-necked brachiosaurids of the Early Cretaceous of Laurasia. Another paper waiting to be written.
Here’s another shard of excellence, referred to Chondrosteosaurus, NHM R96. As Mike had discussed here before, there’s no good reason to believe that it actually is Chondrosteosaurus, and the internal structure looks considerably more subdivided than in NHM 46870. This is an anterior view, and normally you’d be seeing a nice hemispherical condyle, but all of the cortical bone is gone and the internal structure is revealed. The little black traces are bone and the brownish stuff is rock matrix filling the pneumatic cavities.
A few years ago, Mike asked me to look at that photo and guess the ASP, and then run the numbers and see how close I got. I guessed about 78%, then did the calculation, and lo and behold, the answer was 78%. So I’m pretty good at guessing ASPs.
Except I’m not, because as any of you armed with photo software can tell, that picture has 24520 black pixels and 128152 white ones, so the ASP is actually 128152/(128152+24520) = 0.84. The moral of the story is check your homework, kids! Especially if you seem to be an unnaturally good estimator.
ASP-ESP aside, I think ASP is cool and has some interesting potential at the intersection of phylogeny and biomechanics. But the method is severely limited by sample size, which is severely limited by how much of a pain in the butt preparing the images is. In most cases you can’t just play with levels or curves to get a black and white image that faithfully represents the morphology, or use the magic wand, or any of the other myriad shortcuts that modern imaging programs offer. Believe me, I’ve tried. Hard. But inevitably you get some matrix with the bone, or some bone with the matrix, and you end up spending an impossible amount of time fixing those problems (note that this is not a problem if you use perfect bones from extant animals, which is sadly not an option for sauropod workers). So almost all of my ASP images were traced by hand, which is really time-consuming. I could pile up a lot more data if I just sat around for a few weeks processing images, but every time I’ve gotten a few free weeks there has been something more important demanding my attention, and that may always be the case. Fortunately I’m not the only one doing this stuff now, and hopefully in the next few years we’ll get beyond these first few tottering steps.
Side Note: Does NHM 46870 represent a juvenile, or a dwarf?
This came up amongst the SV-POW!sketeers and we decided it should be addressed here. Darren noted that the vert at top is pretty darned small, ~23 cm for the preserved part and probably only a foot and a half long when it was complete, which is big for an animal but small for a sauropod and dinky for a brachiosaurid (if that’s what it is). Mike made the counter-observation that the internal structure is pretty complex, citing Wedel (2003b:fig. 12) and surrounding text, and suggested that it might be an adult of a small or even dwarfed taxon. And I responded:
I’m not at all certain that it is dwarfed. It matters a lot whether the complex internal structure is polycamerate or camellate. I was agnostic for a long time about how different those two conditions are, but there is an important difference that is relevant in this case: the two internal structures develop differently. Polycamerate verts really do get progressively more complex through development, as illustrated–there are at least two great series that show this, that I need to publish one of these days. But I think camellate vertebrae may be natively complex right from the get-go; i.e., instead of a big simple diverticulum pushing in from the side and making a big camera first, a bunch of smaller diverticula may remodel the small marrow spaces into small air spaces with no prior big cavities. At least, that’s how birds seem to do it. This needs more testing from sauropods–a good ontogenetic sequence from Brachiosaurus would be clutch here–but it’s my working hypothesis. In which case NHM 46870 may be a juvenile of a camellate taxon, rather than an adult of a polycamerate taxon.
The whole camerate-vs-camellate problem deserves a post of its own, and this post is already too long, so we’ll save that for another day.
- Cubo, J., and Casinos, A. 2000. Incidence and mechanical significance of pneumatization in the long bones of birds. Zoological Journal of the Linnean Society 130: 499–510.
- Currey, J. D., and Alexander, R. McN. 1985. The thickness of the walls of tubular bones. Journal of Zoology 206:453–468.
- Farke, A. A. 2007. Morphology, constraints, and scaling of frontal sinuses in the hartebeest, Alcelaphus buselaphus (Mammalia: Artiodactlya, Bovidae). Journal of Morphology 268:243-253.
- 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.
- O’Connor, P.M. 2004. Pulmonary pneumaticity in the postcranial skeleton of extant Aves: a case study examining Anseriformes. Journal of Morphology 261:141-161.
- O’Connor, P. M. 2009. Evolution of archosaurian body plans: Skeletal adaptations of an air-sac-based breathing apparatus in birds and other archosaurs. Journal of Experimental Zoology DOI: 10.1002/jez.548
- Schwarz D, Fritsch G. 2006. Pneumatic structures in the cervical vertebrae of the Late Jurassic Tendaguru sauropods Brachiosaurus brancai and Dicraeosaurus. Eclogae Geologicae Helvetiae 99:65–78.
- Woodward, H. 2005. Bone histology of the titanosaurid sauropod Alamosaurus sanjuanensis from the Javelina Formation, Texas. Journal of Vertebrate Paleontology 25 (Supplement to No. 3):132A.
July 12, 2009
It’s no secret – at least, not if you’re a regular SV-POW! reader – that the Lower Cretaceous Wealden Supergroup of southern England includes more than its fair share of enigmatic sauropod remains (see Mystery sauropod dorsals of the Wealden part 1, part 2, part 3). Poor taxonomic decisions, a dearth of adequate descriptive literature, and (perhaps) the vague concept that sauropod diversity in the Lower Cretaceous of Europe must be low have combined to prevent adequate appraisal. Recent comments on Wealden sauropods have been provided by Naish et al. (2004), Naish & Martill (2007), Taylor & Naish (2007) and Mannion (2008).
One of the most interesting Wealden sauropods – and I mean ‘interesting’ in an entirely subjective, historiographical sense – is Chondrosteosaurus gigas. This taxon has a rather confusing history that I don’t want to repeat here. The type series consists of two cervical vertebrae: BMNH R46869 and BMNH R46870 (and it is BMNH R46870, despite the occasional use in the literature of ‘46780’). We’ve looked at BMNH R46869 before. This time round I want to briefly talk about BMNH R46870. Anyone familiar with the literature on Wealden sauropods will know that this specimen was sectioned and polished. However, to date, only half of BMNH R46870 has been published (Owen 1876, plate V; Naish & Martill 2001, text-fig. 8.4), on both occasions as a mirror-image of the actual specimen. Previously unreported is that both halves of the specimen were polished, and both are in the Natural History Museum’s collection today. And here they are, shown together for the first time ever. I screwed up on the lighting, so sorry for the poor image quality [images © Natural History Museum, London].
A little bit of science has been done on this specimen. Chondrosteosaurus has had a mildly controversial history: it’s been suggested at times to be a camarasaur, but its camellate interior show that it’s a titanosauriform. Because the exact ratio of bone to air can be measured, the specimen lends itself particularly well to an Air Space Proportion analysis of the sort invented by Matt. Indeed, Matt did some ASP work on the figured half of BMNH R46870 in his thesis, finding an ASP of 0.70 (Wedel, Phd thesis, 2007). The average ASP of sampled neosauropod vertebrae is 0.61, and an ASP of 0.70 for the mid-centrum (as opposed to the condyle or cotyle) is most similar to the values present in camarasaurs and brachiosaurs. Mid-centrum ASP values of titanosaurs seem to be lower (Wedel, Phd thesis, 2007).
Anyway, more on Wealden sauropods – hopefully, a lot more – in the future.
- Mannion, P. 2008. A rebbachisaurid sauropod from the Lower Cretaceous of the Isle of Wight, England. Cretaceous Research 30, 521-526.
- Naish, D. & Martill, D. M. 2001. Saurischian dinosaurs 1: Sauropods. In Martill, D. M. & Naish, D. (eds) Dinosaurs of the Isle of Wight. The Palaeontological Association (London), pp. 185-241.
- Naish, D. & Martill, D. M. 2007. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia. Journal of the Geological Society, London, 164, 493-510.
- 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.
- Owen, R. 1876. Monograph on the fossil Reptilia of the Wealden and Purbeck Formations. Supplement 7. Crocodilia (Poikilopleuron). Dinosauria (Chondrosteosaurus). Palaeontographical Society Monographs, 30, 1-7.
- Taylor, M. P. & Naish, D. 2007. An unusual new neosauropod dinosaur from the Lower Cretaceous Hastings Beds Group of East Sussex, England. Palaeontology 50, 1547-1564.
For those of you who care about such things, the new issue 66(2) of the Bulletin of Zoological Nomenclature contains two comments on our petition to the ICZN to fix Cetiosaurus oxoniensis as the type species of the historically important genus Cetiosaurus (Upchurch et al. 2009) — both of them supporting the proposal (Barrett 2009 and Galton 2009).
Paul Barrett wrote (in part):
Cetiosaurus was the first sauropod dinosaur to be scientifically described (Owen, 1841) and one of the earliest dinosaurs to be recognised: the taxon is clearly of historical importance and stabilising its taxonomy would represent an important contribution to dinosaur studies.
Cetiosaurus is not only a historically important taxon, but also one that has been used to specify other groups within Dinosauria, including Cetiosauridae. In addition, Ornithischia, one of the major dinosaur sub-groups, has been defined as all dinosaurs that are more closely related to Iguanodon than they are to Cetiosaurus (Norman et al., 2004).
(I’d completely missed that use of Cetiosaurus as an external specifier for Ornithischia, which I suppose just goes to show that I should pay more attention to the ornithischian literature.)
Pete Galton wrote (in part):
It should be noted that the “Monograph of the genus Cetiosaurus” by Owen (1875) is based almost entirely on the Bletchington Station material of C. oxoniensis (Owen even used Phillips’ figures!). Also, as noted by Galton & Knoll (2006), the family CETIOSAURIDAE Lydekker, 1888 is based on C. oxoniensis Phillips, 1871 because Lydekker (1888, p. 137) indicated it as being the type species of Cetiosaurus Owen.
More good arguments there for the conservation of prevalent usage by formally recognising C. oxoniensis.
Anyone else who has strong feelings on this subject, either way, should get them in writing to the Executive Secretary, ICZN., c/o Natural History Museum, Cromwell Road, London SW7 5BD, U.K. (e-mail: email@example.com).
- Barrett, Paul B. 2009. Comment on the proposed conservation of usage of Cetiosaurus Owen, designation of Cetiosaurus oxoniensis Phillips, 1871 as the type species [comment 1 of 2]. Bulletin of Zoological Nomenclature 66(2): 187-188.
- Galton, Peter M. 2009. Comment on the proposed conservation of usage of Cetiosaurus Owen, designation of Cetiosaurus oxoniensis Phillips, 1871 as the type species [comment 2 of 2]. Bulletin of Zoological Nomenclature 66(2): 187-188.
- Galton, Peter M., and Fabien Knoll. 2006. A saurischian dinosaur braincase from the Middle Jurassic (Bathonian) near Oxford, England: from the theropod Megalosaurus or the sauropod Cetiosaurus? Geological Magazine 143: 905921.
- Lydekker, Richard. 1888. Catalogue of the fossil Reptilia and Amphibia in the British Museum (Natural History), Cromwell Road, S.W. Part 1. Containing the orders Ornithosauria, Crocodylia, Dinosauria, Squamata, Rhynchocephalia, and Proterosauria. British Museum (Natural History), London.
- Norman, David B., Lawrence M. Witmer, and David B. Weishampel. 2004. Basal Ornithischia. pp. 325334 in David B. Weishampel, Peter Dodson and Halszka Osmólska (eds.), The Dinosauria, Second edition. University of California Press, Berkeley and Los Angeles. 861 pp.
- Owen, Richard. 1841. A description of a portion of the skeleton of Cetiosaurus, a gigantic extinct saurian occurring in the Oolitic Formation of different parts of England. Proceedings of the Geological Society of London 3: 457-462.
- Owen, Richard. 1875. Monograph of the Mesozoic Reptilia, part 2: Monograph on the genus Cetiosaurus. Palaeontolographical Society Monograph 29: 2743 and plate X.
- Phillips, John. 1871. Geology of Oxford and the Valley of the Thames. Clarendon Press, Oxford.
- Upchurch, Paul and John Martin. 2002. The Rutland Cetiosaurus: the anatomy and relationships of a Middle Jurassic British sauropod dinosaur. Palaeontology, 45(6): 1049-1074.
- Upchurch, Paul, John Martin, and Michael P. Taylor. 2009. Case 3472: Cetiosaurus Owen, 1841 (Dinosauria, Sauropoda): proposed conservation of usage by designation of Cetiosaurus oxoniensis Phillips, 1871 as the type species. Bulletin of Zoological Nomenclature 66(1): 51-55.
July 3, 2009
Big news today: Australia’s dinosaur fauna just got a little less depauperate. Hocknull et al. (2009) described three new saurischian dinosaurs in PLoS ONE, and two of them are sauropods! I’m just going to hit the highlights in this post. For all 51 pages of awesome, you can download the full paper for free.
Here are the new critters (Hocknull et al. 2009:fig. 40; oddly, the size of the scale bar is not given in the figure caption, but I assume it’s one meter). From top to bottom they are:
- Australovenator wintonensis, an allosauroid possibly close to Carcharodontosauridae;
- Wintonotitan wattsi, a basal titanosauriform;
- Diamantinasaurus matildae, a lithostrotian titanosaur.
The new taxa are from the late Early Cretaceous Winton Formation of eastern Australia. All three are represented by incomplete but diagnostic remains, and some of the material is really beautiful.
Here’s one of my favorite bits: the complete reconstructed manus of Diamantinasaurus (Hocknull et al. 2009:fig. 7). Sauropod forefeet were uniquely weird; for the full scoop read this. Note the thumb claw; if it’s legit–and the authors make a pretty good case that it is–then it’s unusual for a titanosaur, most of which are thought to lack hand claws and even manual phalanges.
Sadly no vertebrae were recovered with Diamantinasaurus, and those of Wintonotitan are not as pretty as the appendicular material. Still, they’re shards of excellence and they do carry some informative characters. Here are some dorsals and proximal caudals from Wintonotitan (Hocknull et al. 2009:fig. 13). You can see the partial rim of a pneumatic cavity on the dorsal in the upper left corner. According to the paper the sacrum was also pneumatic, which is to be expected in a titanosauriform.
There’s loads more to say about these critters and their implications for the evolution and biogeography of their respective clades, but tomorrow’s the 4th of July and I’ve got a barbeque to organize. Catch you on the flip side.
Hocknull SA, White MA, Tischler TR, Cook AG, Calleja ND, et al. (2009) New Mid-Cretaceous (Latest Albian) Dinosaurs from Winton, Queensland, Australia. PLoS ONE 4(7): e6190. doi:10.1371/journal.pone.0006190