October 31, 2011
Back when Darren and I did the Xenoposeidon description, we were young and foolish, and only illustrated the holotype vertebra NHM R2095 in four aspects: left and right lateral, anterior and posterior. No dorsal or ventral views.
Also, because the figure was intended for Palaeontology, which prints only in greyscale, I stupidly prepared the figure in greyscale, rather than preparing it in colour and then flattening it down at the last moment. (Happily I’d learned that lesson by the time we did our neck-posture paper: although it was destined for Acta Palaeontologia Polonica, which also prints in greyscale, and though the PDF uses greyscale figures, the online full-resolution figures are in colour.)
As if that wasn’t dumb enough, I also composited the four featured views such that the two lateral views were adjacent, and above the anterior and posterior views — so it wasn’t easy to match up features on the sides and front/back between the views. Since then, I have landed on a better way of presenting multi-view figures, as in my much-admire’d turkey cervical and pig skull images.
So, putting it all together, here is how we should have illustrated illustrated Xenoposeidon back in 2007 (click through for high resolution):
(Top row: dorsal view, with anterior facing left; middle row, from left to right: anterior, left lateral, posterior, right lateral; bottom row, ventral view, with anterior facing left. As always with images of NHM-owned material, this is copyright the NHM.)
Of course, if we’d published in PLoS ONE, then this high-resolution (4775 x 4095), full colour image could have been the published one rather than an afterthought on a blog somewhere. But we didn’t: back then, we weren’t so aware of the opportunities available to us now that we live in the Shiny Digital Future.
In other news, the boys and I all registered Xbox Live accounts a few days ago. I chose the name “Xenoposeidon”, only to find to my amazement that someone else had already registered it. But “Brontomerus” was free, so I used that instead.
September 3, 2009
UPDATE (from Matt): I also bring good news … and bad news.
The good news is that the entire dinosaur issue of Anatomical Record is open access after all. So this post is mainly of historical interest now, and you should get on over to the page for this issue and download all the free dinosaurian goodness.
The bad news is that the representatives from Wiley never told anyone any of this when inquiries were made two weeks ago–if they had, this particular teacup could have stayed storm-free–and that they apparently still want institutions to pay $575 for a single Open Access issue of the journal. Whether those moves are predatory or just clueless, they are not earning Wiley any friends.
I bring good news … and bad news.
Good news! Tom Holtz reported in a message to the Dinosaur Mailing List that there is new issue of The Anatomical Record out that is concerned entirely with dinosaurs! The online table of contents shows that there’s lots of good stuff.
Bad news! It’s not open access.
Good news! You can buy access to the articles.
Bad news! The price of the articles is NOT STATED. That’s right, folks: you have to register with Wiley InterScience before they will EVEN TELL YOU THE PRICE! Way to go, Wiley! THAT’s the way to make sure important research is widely disseminated!
Good news! B tH wrote to ask the publisher for a price, and got a reply, which he shared in another Dinosaur Mailing List message:
Bad news! This is the reply (which I can’t format better, thanks to totally unnecessary limitations in WordPress):
Date: Mon, 31 Aug 2009 12:48:21 -0700 (PDT)
From: B tH <email@example.com>
Subject: re: special all-dino issue
I wrote to ask them how much ordering this singl issue was – they wanted to know if I was ordering for an institution or myself. This is the price they quoted me to buy and read it at night with a flashlight under the blankey – and I am totally serious:
That’s right, five HUNDRED and seventy-five buckeroos. I assured them they were quite mad, and have to face the fact I won’t get to see it. Waaah.
Good news! B tH realised that Wiley had quoted him the institutional rate and wrote to clarify. The exchange is documented in yet another Dinosaur Mailing List message.
Bad news! This is the exchange:
Sent: Monday, August 31, 2009 6:07 PM
Subject: RE: wanting to purchase an issue of the magazine [pfCase:1078353,
Um, I think you’ve made an error.
Five-Hundred and Seventy-Five dollars for an issue of a magazine? ??
The Anatomical Record, Volume 292, Issue 9
Thank you for your email.
As we do not have Individual rates for this title, hence the Institutional single issue rate was quoted instead.
Please provide us with a billing and shipping address if you require a proforma invoice for this order and I will happy to assist you.
Customer Services Advisor
Journal Customer Services for John Wiley & Sons
Good news! The revolution is coming, and things like this can only bring it on. And Wiley’s InterScience department are a bunch of mindless jerks who will be first up against the wall when the revolution comes.
Yes, Wiley’s behaviour here is totally absurd and absolutely unethical. No, Wiley didn’t themselves write the articles that they want to charge FIVE HUNDRED AND SEVENTY-FIVE FREAKIN’ DOLLARS for. Neither did they pay the authors to do so. Do you know how it comes to be that Wiley are the owners of these articles, and thus in a position to extort for access? Happily, the reason is right here in the Instructions to Authors:
Upon acceptance of an article for publication, the author will be asked to sign a Copyright Transfer Agreement transferring rights to the publisher, who reserves copyright.
Yes, it’s as simple as that. Like all of us do most times we submit a manuscript, the authors just signed away the ownership of their work. Just like that. Work that was funded, if at all, by public funds, just handed over to a grossly exploitative for-profit commercial enterprise that — quite clearly, from the exchanges above — has no interest whatsoever in the advancement or dissemination of science.
Folks, we have got to stop doing this. I can (just) stomach handing copyright of my work over to professional societies such as the Society of Vertebrate Paleontology (required for the Journal of Vertebrate Paleontology) or the Palaeontological Association (required for Palaeontology) [although frankly there is absolutely no good reason for these journals to make that requirement]. But I will NOT give my work to these parasitic commercial publishers, and I strongly urge you not to, either. We should all of us be supporting open-access journals where possible; and failing that, at least those published by non-profit organisations. I am not going to be propping up Elsevier, Wiley and the rest with any of my stuff.
Deep in our heart, we all — Wiley included — know that non-open academic publishing is dead, even if the corpse is still blundering around trying to eat our brains. This sort of extortion (I mean the FIVE HUNDRED AND SEVENTY-FIVE FREAKIN’ DOLLARS kind) is death throes. It’s probably going to get messier before the stakes are finally driven through the hearts of the bloodsuckers. But take heart: morning is coming, and they will all turn to dust.
And finally …
More Good news! I give you NHM 46869, the holotype of Chondrosteosaurus gigas Owen 1876, a badly eroded cervical centrum from some kind of sauropod, in right lateral view:
This is the mate of NHM 46870, a specimen that we have already given way too much coverage, and which has sometimes been considered the cotype along with 46869. Unlike its mate, it has not been sliced down the middle, and is — for what it’s worth — “complete” (i.e. not actually complete at all).
- Owen, Richard. 1876. Monograph of the fossil Reptilia of the Wealden and Purbeck formations. Supplement 7. Crocodilia (Poikilopleuron), Dinosauria (Chondrosteosaurus), Palaeontographical Society of London [Monographs], 29:15-93.
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.
Cetiosaurus, Pelorosaurus, Streptospondylus or maybe Iguanodon(?!) in bizarre Fused Chevrons scandal!
March 9, 2009
We have sometimes neglected tails on SV-POW!, in favour of the more obviously charismatic charms of presacral vertebrae, but every now and then you come across a caudal vertebra so bizarre that it just cries out to be blogged.
One such is this specimen, which may or may not be BMNH R 2144:
The reason I’m not sure whether this is BMNH R2144 is that I noticed this at the very last minute while visiting the NHM collections to see a different specimen, and just had time to take a couple of quick photos before kicking-out time. The label on the side of the vertebra has the unexplained number 2144 written on it, so I am guessing this is the specimen number, but I wouldn’t stake my life on it.
(By the way, both these photographs are copyright the NHM.)
The interesting thing about this vertebra is of course that that the chevrons are co-ossified with the centrum — an extremely rare condition in sauropods, in fact unique as far as I know. As we’ve shown here and here, among other places, the chevrons are usually separate bones from the vertebrae.
This vertebra caught my eye not only because it’s, well, weird, but also because I’d seen it a couple of times in published figures. It’s in Mantell’s (1850) description of Pelorosaurus, where it appears as figure 11 in plate XXIII, and is considered to belong to Pelorosaurus; and also in Owen (1859: plate V: figs. 3-4). Owen seems pretty confused about the identity of this element, and in this paper alone assigns it to Streptospondylus (p. 22), Iguanodon(!) (p. 25) and implicitly Cetiosaurus (p. 34). So what is it? Well, its provenance is vague in the extreme, so given that it’s not associated with any more diagnostic material, about the best we can say with any honesty is that it’s Sauropoda incertae sedis.
Let’s take a look at those old figures:
If you’re like me, your first thought was that Owen’s figures are simply mirror images of Mantell’s. I checked this out by Photoshopping the two sets of figures, flipping them horizontally, scaling and rotating as necessary, and found to my mild surprise that Owen’s figures are in fact redrawn, despite the startling resemblance they bear to Mantell’s. As it happens, the same is true with the Owen 1859 plate that is the humerus of Pelorosaurus figured by Mantell 1850, and in that case Owen’s figure is rather better than Mantell’s, so let’s give a bit of credit to Owen here. Most embarrassing for Mantell (not that he cares, having been dead for 157 years) is that Owen’s flipped images seem to be correct (at least, as best I can judge from the photographs I took) — looks like Mantell or his illustrator badgered this up.
So what is going on with these co-ossified chevrons? As is so often the case, we just don’t know. Some possibilities: this might be a pathology of an individual, caused either by injury or infection; it might be a natural ontogenetic character in very old individuals; or it might by a taxonomically significant character of a taxon we’ve not yet found — or one that we have found, but don’t yet recognise as being the same thing. It’s perfectly possible that this is a chevron of Xenoposeidon, for example, but until someone finds a nice complete specimen we’ll never know.
Not much is known about skeleton fusion in sauropods, and most of what’s in the literature is anecdote. That is set to change, I am pleased to say, as Matt is putting together a paper with his colleague Elizabeth Rega that will survey and interpret the various fusions known in sauropod vertebrae. I’m looking forward to seeing what they have to say about this vertebra.
- Brusatte, Stephen L., Roger B. J. Benson, and Stephen Hutt. 2008. The osteology of Neovenator salerii (Dinosauria: Theropoda) from the Wealden Group (Barremian) of the Isle of Wight. Monograph of the Palaeontographical Society 162 (631): 1-166.
- Calvo, Jorge O., Juan D. Porfiri, Claudio Veralli, Fernando Novas and Federico Poblete. 2004. Phylogenetic status of Megaraptor namunhuaiquii Novas based on a new specimen from Neuquen, Patagonia, Argentina. Ameghiniana 41 (4): 565-575.
- Mantell, Gideon Algernon. 1850. On the Pelorosaurus: an undescribed gigantic terrestrial reptile, whose remains are associated with those of the Iguanodon and other saurians in the strata of Tilgate Forest, in Sussex. Philosophical Transactions of the Royal Society of London 140: 379-390.
- Owen, R. 1859a. Monograph on the fossil Reptilia of the Wealden and Purbeck formations. Supplement no. II (pages 20-44 and plates V-XII): Crocodilia (Streptospondylus, &c.) [Wealden]. Palaeontographical Society, London.
Thanks to Mickey Mortimer for pointing out that this kind of centrum-chevron fusion is known in the theropod Megaraptor. Here is the relevant figure from Calvo et al.’s (2004) revision of that genus:
The strange thing is this comment in the text (p. 569): “Two articulated caudal vertebrae are preserved (figure 5), slightly laterally compressed. Their centra and the neural arches are firmly co-ossified, as well as their respective haemal arches [i.e. chevrons]. This fusion, not infrequent among dinosaurs, may be pathological.” Not infrequent? Is this going on all over the place and I’ve just never noticed it? Anyone have any more examples?
Here is that pair of fused Neovenator caudals with a co-ossified chevron, which Darren mentions in the comments below.
February 17, 2009
It’s been a while since we looked at everybody’s favourite partial dorsal vertebra, and there may be those who feel we’ve said all that can be said about it, but there is one feature of Xenoposeidon that we’ve never really highlighted here and which is well worth a look.
For anyone who’s not up to speed, a super-brief resumé: Xeno is an indeterminate neosauropod which Darren and I named in 2007 on the basis of a single element, a superbly preserved partial dorsal vertebra loaded with distinctive features that make it very clearly distinct from any other named taxon. For anyone who wants more background, the original paper is freely available, as is a page summarising the story for the media, some unnofficial supplementary information, and a whole week’s worth of SV-POW! posts.
Here is the canoncial Xenoposeidon photo: the specimen in left lateral view. (Don’t worry, this old chestnut is not your Picture of the Week — it’s just setting the scene.)
Up near the top of the preserved part of the vertebra, where the neural arch is broken off, there is a distinctive “V”-shaped pair of laminae, which we identified as accessory infraparapophyseal and infrapostzygapophyseal laminae. The more posterior of the two (on the right as we look at at it here) has a very distinctive wrinkled texture, and that’s what I want to show you today:
Now I’ve heard different things said of those wrinkles: I’ve never seen them on any other specimen of anything before, but then I’ve not seen a whole lot of material. Other people have told me that this kind of thing is pretty common, though I don’t recall anyone ever having told me a specific other specimen that has it. What is completely clear is that no-one seems to know what it is or what it means. It’s very hard to see how this could be the result of any kind of post-mortem distortion, so this must be what the bone was like when the animal was alive. What are the possibilities?
- I wondered whether it could be some kind of pneumatic feature, perhaps the trace left by a diverticulum or set of diverticula; but IIRC Matt doesn’t think that’s likely.
- Could it be the result of some sort of infection? Maybe neontologists, or for that matter doctors, see this kind of thing all the time but we poor palaeontologists are ignorant.
- Er … what else? Seriously, I am out of ideas here.
So, comments are open. Enlighten me. What is the cause of this distinctive texture?
Oh, and finally — for some reason, I don’t think I’ve ever mentioned that I uploaded most of the Xenoposeidon news spots onto Youtube a while back. So if anyone wants to hear me talking about my favourite subject, and arguing with the Channel 4 News guy, or indeed just wants to see how mainstream media can get a science story completely right when we trouble to give them good information, get over to http://www.youtube.com/user/Mirk101
November 15, 2008
Happy Xenoposeidon day! Today, November 15, 2008, is the one-year anniversary of the publication of Xenoposeidon Taylor and Naish 2007.
By happy coincidence, I’ve just been sent a courtesy copy of Kids Only, a new guide-book for the Natural History Museum … and there is Xenoposeidon on page 5, exemplifying dinosaur diversity. Rock!
It’s good to see our baby out there educating people!
For much more of Xeno, see Xenoposeidon week.