Last time, we looked at how including intervertebral cartilage changes the neutral pose of a neck – or, more specifically, of the sequence of cervical vertebrae. The key finding (which is inexplicably missing from the actual paper, Taylor and Wedel 2013c) is that adding cartilage of thickness x between vertebrae whose zygapophyses are height y above the mid-height of the centra elevates the joint’s neutral posture by x/y radians.

Figure 14. Geometry of opisthocoelous intervertebral joints. Hypothetical models of the geometry of an opisthocoelous intervertebral joint compared with the actual morphology of the C5/C6 joint in Sauroposeidon OMNH 53062. A. Model in which the condyle and cotyle are concentric and the radial thickness of the intervertebral cartilage is constant. B. Model in which the condyle and cotyle have the same geometry, but the condyle is displaced posteriorly so the anteropos- terior thickness of the intervertebral cartilage is constant. C. the C5/C6 joint in Sauroposeidon in right lateral view, traced from the x-ray scout image (see Figure 12); dorsal is to the left. Except for one area in the ventral half of the cotyle, the anteroposterior separation between the C5 cotyle and C6 condyle is remarkably uniform. All of the arrows in part C are 52 mm long.

Figure 14. Geometry of opisthocoelous intervertebral joints. Hypothetical models of the geometry of an opisthocoelous intervertebral joint compared with the actual morphology of the C5/C6 joint in Sauroposeidon OMNH 53062. A. Model in which the condyle and cotyle are concentric and the radial thickness of the intervertebral cartilage is constant. B. Model in which the condyle and cotyle have the same geometry, but the condyle is displaced posteriorly so the anteroposterior thickness of the intervertebral cartilage is constant. C. the C5/C6 joint in Sauroposeidon in right lateral view, traced from the x-ray scout image (see Figure 12); dorsal is to the left. Except for one area in the ventral half of the cotyle, the anteroposterior separation between the C5 cotyle and C6 condyle is remarkably uniform. All of the arrows in part C are 52 mm long.

But how thick was the intervertebral cartilage in sauropods?

At the moment, no-one really knows. As Kent Stevens (2013) points out in his contribution to the PLOS ONE sauropod gigantism collection:

Determining the ONP of a sauropod’s cervical vertebral column given only its bones requires is necessarily speculative since the cartilage, and thus the intervertebral spacing, is unknown.

Part of the our goal in our own PLOS collection paper (Taylor and Wedel 2013c) was to take some very tentative first steps towards estimating the cartilage thickness. To do this, we used two approaches. First, we looked at CT scans of articulated vertebrae; and second, we measured the cartilage thickness in a selection of extant animals and thought about what we could extrapolate.

Since the CT scans were Matt’s domain, I’m going to pass over those for now, in the hope that he’ll blog about that part of the paper. Here, I want to look at the extant-animal survey.

Figure 18. Cartilage in the neck of a rhea. Joint between cervicals 11 (left) and 10 (right) of a rhea, sagittally bisected. Left half of neck in medial view. The thin layers of cartilage lining the C11 condyle and C10 cotyle are clearly visible.

Figure 18. Cartilage in the neck of a rhea. Joint between cervicals 11 (left) and 10 (right) of a rhea, sagittally bisected. Left half of neck in medial view. The thin layers of cartilage lining the C11 condyle and C10 cotyle are clearly visible.

The first thing to say is that our survey is inadequate in many ways. We worked with the specimens we could get hold of, in the state we had them. This means that:

  • we have a very arbitrary selection of different animals,
  • they are at different ontogenetic stages, and
  • their cartilage thickness was measured by a variety of methods.

Our goal was not at all to reach anything like a definitive answer, but just to get the question properly asked, and so hopefully to catalyse much a more detailed survey.

With that proviso out of the way, here are our main results (from Table 4 of the paper, though here I have removed the sauropod CT-scan rows since we’ll be writing about those separately).

Taxon Thickness Reference Notes
Turkey 4.56% This study Difference in measurements of intact neck and articulated sequence of cleaned, degreased and dried vertebrae.
Ostrich 6.30% Cobley et al. (2013) Difference in measurements of individual vertebrae with and without cartilage.
Rhea 2.59% This study Measurement of in situ cartilage in bisected neck.
Alligator 14.90% This study Measurement of in situ cartilage from photograph of cross section.
Horse 6.90% This study Measurement of in situ cartilage from photograph of cross section.
Camel 13.00% This study Crude measurement from condyle margin to cotyle lip of lateral-view X-ray. This is an interim measurement, which we hope to improve on when we obtain better images.
Dog 17.00% This study Measurement of intervertebral gaps in lateral-view X-ray, uncorrected for likely concavity of cotyles.
Giraffe 24.00% This study Difference in measurement of intact neck and closely articulated sequence of cleaned vertebrae. Young juvenile specimen.
Muraenosaurus 14.00% Evans (1993) Measurement of in situ cartilage in fossils.
Cryptoclidus 20.00% Evans (1993) Measurement of in situ cartilage in fossils.

We’ve expressed the measurements as a ratio between cartilage thickness and the length of the bone itself — that is, cartilage/bone. Another way to think of this is that the percentage is a correction factor which you need to add onto bone length to get whole-segment length. Note that this is not the same ratio as the proportion of total segment length that consists of cartilage: that would be (cartilage thickness + bone length) / bone length.

(We also tossed in some measurements of plesiosaur neck cartilage that Mark Evans made way back when. Get that thing properly published, Mark!)

Even this small survey throws up some interesting points.

First, there is a huge range of proportional cartilage thicknesses: almost an order of magnitude from the 2.59% of the Rhea up to the 24% of the juvenile giraffe — or, even if you discard that because of its ontogenetic stage, up to 17% for the dog. And note that the 17% for the dog is probably an under-estimate, since we were working from an X-ray that doesn’t show the concavity of the vertebral cotyles.

Figure 22. Dog neck in X-ray. Neck of a dog (dachsund), in X-ray, with the seven cervical vertebrae indicated. This photo has been used with permission from the Cuyahoga Falls Veterinary Clinic.

Figure 22. Dog neck in X-ray. Neck of a dog (dachsund), in X-ray, with the seven cervical vertebrae indicated. This photo has been used with permission from the Cuyahoga Falls Veterinary Clinic.

(Two reviewers expressed scepticism that this is the usual condition for dogs, but this X-ray is consistent with those of other dogs illustrated in the veterinary literature.)

The second thing to note is that the cartilage measurements for birds (average 4.5%) are are much lower than those of crocodilians (14.9%) or mammals (15.2%). What does this mean? Among these groups, sauropods are most closely related to birds; but birds and crocs form the extant phylogenetic bracket, so we can’t tell from phylogeny alone whether to expect them to more closely approach the avian or crocodilian condition. Furthermore, in being opisthocoelous (condyle in front, cotyle at the back) sauropod cervicals most closely resemble those of mammals in gross structure — and they have the thickest cartilage of all.

The third thing to note is that there is considerable variation within groups. Although the cartilage is proportionally thin for all three birds, it’s more than twice as thick in the ostrich as in the rhea (although some of this could be due to the different measurement methods used for these two birds). More interestingly, among mammals the cartilage is twice as thick in camels as in horses. In the horse, the condyles are deeply inserted into the cotyles of the preceding vertebrae; but in camels, they don’t reach even the lip of the cotyle. This should worry us, as horse and camel cervicals are grossly similar, and no osteological correlates have been identified that would allow us to determine from the bones alone how very different the cartilage is between these two mammals. So it seems possible that there were similarly dramatic differences in the neck-cartilage thickness of different sauropods.

Note: I said that no osteological correlates have been identified. That doesn’t mean they don’t exist. One thing I would love to see is a serious attempt to analyse cartilage thickness across a broad range of mammals, and to examine the corresponding dry bones to see whether in fact there are correlates that could be informative in this respect. One lesson that Matt and I have learned over and over again is that there’s often plenty of data in places that are out in the open, but where no-one’s thought to look.

Next time: more on searching for osteological correlates of cartilage. Then, measurements of sauropod-neck cartilage from CT scans, and likely implications for cartilage thickness in life.

References

Sauroposeidon OMNH 53062 C7-C8 left side

Sauroposeidon holotype OMNH 53062, posterior half of ?C7 and all of ?C8 in left lateral view. Scale bar is in inches.

There’s a lot more Sauroposeidon material these days than there used to be, thanks to the referral by D’Emic and Foreman (2012) of Paluxysaurus and Ostrom’s Cloverly material and the new Cloverly material to my favorite sauropod genus. I’ve seen almost all of this material firsthand, but obviously the specimen I’m most familiar with is the holotype, OMNH 53062. It was the primary thing occupying my mind from the summer of 1996 through the spring of 2000, and it has remained a frequent object of wonder ever since.

The specimen was found lying on its right side in the field, so that side is in better shape, by virtue of having been more deeply buried and thus protected from the ravages of freezing and thawing and other erosional processes. When the jackets were taken out of the ground and prepared, the not-so-well-preserved left sides were prepped first. Then permanent support jackets were made on the left sides, the vertebrae were flipped onto their left sides, the field jackets were removed from their right sides, and the vertebrae were prepped on the right. They’ve been lying in their support jackets, left side down and right side up, ever since. (For more on the taphonomy and recovery of the specimen, see this post and Wedel and Cifelli 2005 [free PDF linked below].)

Now, if I had known what I was doing, I would have photographed the crap out of the left sides before the verts were flipped. But it was my first project and I was learning on the job, and that didn’t occur to me until later.

It also didn’t occur to me that, once flipped, the left sides would be effectively out of reach forever. But the vertebrae are extremely fragile. The bigger verts have cracks running through them, and the jackets flexed noticeably when we took them for CT scanning. I am worried that if we tried to flip the bigger verts today, they might just crumble. Even the surface bone is fragile. I remember once trying to get some dust off one of the verts with a vacuum cleaner hose, and watching in horror as some of the millimeter-thin external bone just flaked off and flew away. That was in the late 1990s, when the verts were still stored in the dusty, drafty WWII-era buildings that had housed the museum collections for ages. Now they’re in what I still think of as the “new” building, which opened in 2000, in a really nice modern collection room with climate and dust control, and I’ve never seen them with any noticeable dust.

Anyway, the left sides are now obscured by their supporting jackets and will remain that way for the foreseeable future. And I don’t have a complete set of photos of the left sides of the verts. But I do have one, of the back half of ?C7 and all of ?C8, and a scan of it appears at the top of this post. It’s a scan of a physical photograph because it was taken in late 1996 or early 1997–no-one I knew had a digital camera, and if you wanted a digital version of a photograph, you shot it on a film camera, had a big print made, and scanned that on a flatbed scanner.

Here’s another version with the vertebrae outlined:

Sauroposeidon OMNH 53062 C7-C8 left side - outlined

When I and everyone else thought that Sauroposeidon was a brachiosaur, I was pretty sure that these were C7 and C8, out of a total of 13 cervicals, just like Giraffatitan. And it still might be so–a future analysis might find that the newly-expanded Sauroposeidon is a brachiosaurid after all, and even if not, Gomani (2005) posited a primitive cervical count of 13 for titanosaurs. If that’s true, then possibly 13 cervicals are primitive for all titanosauriforms, and the increases beyond that–to 17 in Euhelopus and 14-17 in more derived titanosaurs like Futalognkosaurus and Rapetosaurus–were deviations from that primitive pattern.

But.

If Sauroposeidon was a basal somphospondyl, as posited by D’Emic and Foreman (2012) and as found in the phylogenetic analysis of D’Emic (2012), then maybe it was more like Euhelopus than Giraffatitan, and maybe it had more than 13 cervicals. (Note that D’Emic [2012] found Sauroposeidon to be a basal somphospondyl but outside the Euhelopodidae, so even in his analysis, Euhelopus could have gotten its extra cervicals independently of Sauroposeidon.) That’s an interesting prospect, since the 11.5-meter neck estimate for Sauroposeidon I made back in 2000 was based on the conservative assumption of 13 cervicals. If Sauroposeidon had more cervicals, they were probably mid-cervicals (nobody adds more dinky C3s, or stubby cervico-dorsals*–that would be silly), and therefore between 1 and 1.25 meters long. So if the individual represented by OMNH 53062 had 15 cervicals, as Mike hypothetically illustrated in this post, its neck might was probably more like 14 meters long, and if it had 17 cervicals, like Euhelopus and Rapetosaurus, its neck might have topped 16 meters–as long or longer than that of Supersaurus.

Now, I’m not saying that Sauroposeidon had a 16-meter neck. The conservative estimate is still 13 cervicals adding up to 11.5 meters. But the possibility of a longer neck is tantalizing, and can’t be ruled out based on current evidence. As usual, we need more fossils.

Happily, now that Sauroposeidon is known from Oklahoma, Texas, and Wyoming, and is one of the best-represented EKNApods instead of one of the scrappiest, the chances that we’ll find more of it–and recognize it–are looking good. I will keep my fingers firmly crossed–as they have been for the last 17 years.

* Radical pedantry note: of course we have very good evidence of sauropods getting more cervical vertebrae by recruiting dorsals into the cervical series. So, for example, 13 cervicals and 12 dorsals are supposed to be primitive for neosauropods, but diplodocids have 15 and 10, respectively–the obvious inference being that the first two dorsals got cervicalized. So in this narrow meristic sense, sauropods definitely did add cervicodorsals. But my point above is about the morphology of the verts themselves–once diplodocids had those two extra cervicals at the end, the former cervicodorsals were free to become more “cervicalized” in form. So effectively–in terms of the shapes of their necks–diplodocids added mid-cervicals.

References

DEmic 2012 figure 5 titanosauriform phylogeny

D’Emic (2012: figure 5)

Now this is super-freakin’ cool, and I’ve been meaning to blog about it for a while. In Mike D’Emic’s recent titanosauriform phylogeny (D’Emic 2012), he (correctly) included Brachiosaurus and Giraffatitan as separate OTUs, and, hey, whaddayaknow, they’re not sister taxa anymore: Brachiosaurus is more closely related to a trio of Early Cretaceous North American brachiosaurids than it is to Giraffatitan.

The potential for someone to find this result was there ever since Mike broke Brachiosaurus and Giraffatitan apart, as a previously composite OTU, in his 2009 paper. It just hadn’t materialized. In fact, some authors have gone out of their way to not find this out, by keeping the old composite coding. That seems…unwise, in retrospect. Whether one agreed with Mike on the nomenclatural point of generic separation or not, not coding the two taxa as separate OTUs (especially after Mike had done that work for them) was a poor phylogenetic decision–in essence, it constrained Brachiosaurus and Giraffatitan to be sister taxa in the analysis, and outlawed any more interesting results–like the one obtained by D’Emic (2012)–before the software even started crunching trees.

So anyway, back to the coolness inherent in D’Emic’s tree. Of course, like all phylogenetic results this is just a hypothesis and it is subject to revision based on new information blah blah blah…but it is really interesting that there is now some phylogenetic support for an endemic radiation of brachiosaurids in North America (bonus goofy observation–you can’t spell ‘endemic’ without D’Emic). Or perhaps Lauriasia–I would kill to know where the British brachiosaurids (or basal titanosauriforms) fit into this story, and Lusotitan, and the apparently tiny Croatian carbonate platform brachiosaurs.

Also super-interesting that, if this tree is accurate, these endemic Early Cretaceous brachiosaurids were living alongside a giant basal somphospondyl in the form of Sauroposeidon, which came from heaven knows where. Look who it’s surrounded by–Ligabuesaurus is from Argentina, Tastavinsaurus is from Spain, and the euhelopodids are from eastern Asia. Evidently there was also a global radiation of basal somphospondyls. And why are all the Early Cretaceous North American brachiosaurids small–smaller than Brachiosaurus and Giraffatitan, anyway (at least until we find bigger individuals of the former)–while Sauroposeidon is so big? Or is that just an effect of tiny sample sizes, and one lucky strike in the form of the Sauroposeidon holotype?

So much cool stuff to think about. I don’t usually get this much enjoyment out of a tree unless it has lights and ornaments.

References

Posting palaeo papers on arXiv

September 28, 2012

Over on Facebook, where Darren posted a note about our new paper, most of the discussion has not been about its content but about where it was published. We’re not too surprised by that, even though we’d love to be talking about the science. We did choose arXiv with our eyes open, knowing that there’s no tradition of palaeontology being published there, and wanting to start a new tradition of palaeontology being routinely published there. Having now made the step for the first time, I see no reason ever to not post a paper on arXiv, as soon as it’s ready, before — or maybe even instead of — submitting it to a journal.

(Instead of? Maybe. We’ll discuss that below.)

The key issue is this: science isn’t really science until it’s out there where it can be used. We wrote the bulk of the neck-anatomy paper back in 2008 — the year that we first submitted it to a journal. In the four years since then, all the observations and deductions that it contains have been unavailable to the world. And that is stupid. The work might just as well never have been done. Now that it’s on arXiv, that’s over. I was delighted to get an email less than 24 hours after the paper was published, from an author working on a related issue, thanking us for posting the paper, saying that he will now revise his own in-prep manucript in light of its findings, and cite our paper. Which of course is the whole point: to get our science out there where it can do some damage.

Because the alternative is horrible, really. Horribly wasteful, horribly dispiriting, horribly retarding for science. For example, a couple of weeks ago in his SVPCA talk, David Norman was lamenting again that he never got around to publishing the iguanodont systematic work that was in his dissertation, I-don’t-know-how-many-years-ago. The result of that interminable delay is that others have done other, conflicting iguanodont systematic work, and Norman is now trying belatedly to undo that and bring his own perspective. A terrible an unnecessary slowing of ornithopod science, and a waste of duplicated effort. (Thankfully it’s only ornithopods.)

And of course David Norman is very far from being alone. Pretty much any palaeontologist you talk to will tell you of a handful of papers — many more in some cases — that were finished many years previously but have never seen the light of day. (I still have a couple myself, but there is no point in resurrecting them now because progress has overtaken them.) I wonder what proportion of all Ph.D work ever sees the light of day? Half? Less? It’s crazy.

Figure 8. Sauropod cervical vertebrae showing anteriorly and posteriorly directed spurs projecting from neurapophyses. 1, cervical 5 of Sauroposeidon holotype OMNH 53062 in right lateral view, photograph by MJW. 2, cervical 9 of Mamenchisaurus hochuanensis holotype CCG V 20401 in left lateral view, reversed, from photograph by MPT. 3, cervical 7 or 8 of Omeisaurus junghsiensisYoung, 1939 holotype in right lateral view, after Young (1939, figure 2). (No specimen number was assigned to this material, which has since been lost. D. W. E. Hone personal communication, 2008.)

Publish now, publish later

So, please folks: we all need to be posting our work on preprint servers as soon as we consider it finished. It doesn’t mean that the posted versions can’t subsequently be obsoleted by improved versions that have gone through peer-review and been published in conventional journals. But it does mean that the world can know about the work, and build on it, and get the benefit of it, as soon as it’s done.

You see, we have a very fundamental problem in academia: publishing fulfils two completely separate roles. Its primary role (or at least the role that should be primary) is to make work available to the community; the secondary role is to provide a means of keeping score — something that can be used when making decisions about who to appoint to jobs, when to promote, who gets grants, who gets tenure and so on. I am not going to argue that the latter shouldn’t happen at all — clearly a functioning community needs some way to infer the standing of its participants. But I do think it’s ridiculous when the bean-counting function of publication trumps the actual publication role of publication. Yet we’ve all been in a position where we have essentially complete work that could easily go on a blog, or in the PalAss newsletter, or in a minor journal, or somewhere — but we hang onto it because we want to get it into a Big Journal.

Let me say again that I do realise how unusual and privileged my own position is: that a lot of my colleagues do need to play the Publication Prestige game for career reasons (though it terrifies my how much time some colleagues waste squeezing their papers into two-and-a-half-page format in the futile hope of rolling three sixes on the Science ‘n’ Nature 3D6). Let’s admit right now that most palaeontologists do need to try to get their work into Proc B, or Paleobiology, or what have you. Fair enough. They should feel free. But the crucial point is this: that is no reason not to post pre-prints so we can all get on with actually benefitting from your work in the mean time.

Actually, I feel pretty stupid that it’s taken me this long to realise that all my work should go up on arXiv.

Figure 11. Archosaur cervical vertebrae in posterior view, Showing muscle attachment points in phylogenetic context. Blue arrows indicate epaxial muscles attaching to neural spines, red arrows indicate epaxial muscles attaching to epipophyses, and green arrows indicate hypaxial muscles attaching to cervical ribs. While hypaxial musculature anchors consistently on the cervical ribs, the principle epaxial muscle migrate from the neural spine in crocodilians to the epipophyses in non-avial theropods and modern birds, with either or both sets of muscles being significant in sauropods. 1, fifth cervical vertebra of Alligator mississippiensis, MCZ 81457, traced from 3D scans by Leon Claessens, courtesy of MCZ. Epipophyses are absent. 2, eighth cervical vertebra ofGiraffatitan brancai paralectotype HMN SII, traced from Janensch (1950, figures 43 and 46). 3, eleventh cervical vertebra of Camarasaurus supremus, reconstruction within AMNH 5761/X, “cervical series I”, modified from Osborn and Mook (1921, plate LXVII). 4, fifth cervical vertebra of the abelisaurid theropod Majungasaurus crenatissimus,UA 8678, traced from O’Connor (2007, figures 8 and 20). 5, seventh cervical vertebra of a turkey, Meleagris gallopavo, traced from photographs by MPT.

Exceptions?

So are there any special cases? Any kinds of papers that we should keep dry until they make it into actual journals? I can think of two classes that you could argue for — one of them convincingly, the other not.

First, the unconvincing one. When I discussed this with Matt (and half the fun of doing that is that usually neither of us really knows what we think about this stuff until we’re done arguing it through), he suggested to me that we couldn’t have put the Brontomerus paper on arXiv, because that would have leaked the name, creating a nomen nudum. My initial reaction was to agree with him that this is an exception. But when I thought about it a bit more, I realised there’s actually no compelling reason not to post such a paper on arXiv. So you create a nomen nudum? So what? Really: what is the negative consequence of that? I can’t think of one. OK, the name will appear on Wikipedia and mailing lists before the ICZN recognises it — but who does that hurt? No-one that I can think of. The only real argument against posting is that it could invite scooping. But is that a real threat? I doubt it. I can’t think of anyone who would be barefaced enough to scoop a taxon that had already been published on arXiv — and if they did, the whole world would know unambiguously exactly what had happened.

So what is the one real reason not to post a preprint? I think that might be a legitimate choice when publicity needs to be co-ordinated. So while nomenclatural issues should not have stopped us from arXiving the Brontomerus paper, publicity should. In preparation for that paper’s publication day, we did a lot of careful work with the UCL publicity team: writing non-specialist summaries, press-releases and FAQs, soliciting and preparing illustrations and videos, circulating materials under embargo, and so on. In general, mainsteam media are only interested in a story if it’s news, and that means you need to make sure it’s new when they first hear about it. Posting the article in advance on a publicly accessible archive would mess that up, and probably damage the work’s coverage in the press, TV and radio.

Publication venues are a continuum

It’s become apparent to us only gradually that there’s really no clear cut-off where a paper becomes “properly published”. There’s a continuum that runs from least to most formal and exclusive:

SV-POW! — arXiv — PLOS ONE — JVP — Nature

1. On SV-POW!, we write what we want and publish it when we want. We can promise you that it won’t go away, but you only have our word for it. But some of what we write here is still science, and has been cited in papers published in more formal venues — though, as far as I know, only by Matt and me so far.

2. On arXiv, there is a bit more of a barrier to clear: you have to get an existing arXiv user to endorse your membership application, and each article you submit is given a cursory check by staff to ensure that it really is a piece of scientific research rather than a diary entry, movie review or spam. Once it’s posted, the paper is guaranteed to remain at the same URL, unchanged, so long as arXiv endures (and it’s supported by Cornell). Crucially, the maths, physics and computer science communities that use arXiv uncontroversially consider this degree of filtering and permanence sufficient to constitute a published, citeable source.

3. At PLOS ONE, your paper only gets published if it’s been through peer-review — but the reviewing criteria pertain only to scientific soundness and do not attempt to evaluate likely impact or importance.

4. At JVP and other conventional journals, your paper has to make it through a two-pronged peer-review process: it has to be judged both sound scientifically (as at PLOS ONE) and also sufficiently on-topic and important to merit appearing in the journal.

5. Finally, at Nature and Science, your paper has to be sound and be judged sexy — someone has to guess that it’s going to prove important and popular.

Where along this continuum does the formal scientific record begin? We could make a case that all of it counts, provided that measures are taken to make the SV-POW! posts permanent and immutable. (This can be done submitting them to WebCite or to a service such as Nature Precedings used to provide.) But whether or not you accept that, it seems clear that arXiv and upwards is permanent, scientific and citeable.

This raises an interesting question: do we actually need to go ahead and publish our neck-anatomy paper in a more conventional venue? I’m honestly not sure at the moment, and I’d be interested to hear arguments in either direction. In terms of the progress of science, probably not: our actual work is out there, now, for the world to use as it sees fit. But from a career perspective, it’s probably still worth our while to get it into a journal, just so it can sit more neatly on our publication lists and help Matt’s tenure case more. And yet I don’t honestly expect any eventual journal-published version to be better in any meaningful way than the one on arXiv. After all, it’s already benefitted from two rounds of peer-review, three if you count the comments of my dissertation examiners. More likely, a journal will be less useful, as we have to cut length, eliminate illustrations, and so on.

So it seems to me that we have a hard choice ahead of us now. Call that paper done and more onto making more science? Or spend more time and effort on re-publishing it in exchange for prestige? I really don’t know.

For what it’s worth, it seems that standard practice in maths, physics and computer science is to republish arXiv articles in journals. But there are some scientists who routinely do not do this, instead allowing the arXiv version to stand as the only version of record. Perhaps that is a route best left to tenured greybeards rather than bright young things like Matt.

Figure 5. Simplified myology of that sauropod neck, in left lateral view, based primarily on homology with birds, modified from Wedel and Sanders (2002, figure 2). Dashed arrows indicate muscle passing medially behind bone. A, B. Muscles inserting on the epipophyses, shown in red. C, D, E. Muscles inserting on the cervical ribs, shown in green. F, G. Muscles inserting on the neural spine, shown in blue. H. Muscles inserting on the ansa costotransversaria (“cervical rib loop”), shown in brown. Specifically: A. M. longus colli dorsalis. B. M. cervicalis ascendens. C. M. flexor colli lateralis. D. M. flexor colli medialis. E. M. longus colli ventralis. In birds, this muscle originates from the processes carotici, which are absent in the vertebrae of sauropods. F. Mm. intercristales. G. Mm. interspinales. H. Mm. intertransversarii. Vertebrae modified from Gilmore (1936, plate 24).

Citing papers in arXiv

Finally, a practicality: since it’ll likely be a year or more before any journal-published version of our neck-anatomy paper comes out, people wanting to use it in their own work will need to know how to cite a paper in arXiv. Standard procedure seems to be just to use authors, year, title and arXiv ID. But in a conventional-journal citation, I like the way that the page-range gives you a sense of how long the paper is. So I think it’s worth appending page-count to the citations. And while you’re at it, you may as well throw in the figure and table counts, too, yielding the version that we’ve been using:

  • Taylor, Michael P., and Mathew J. Wedel. 2012. Why sauropods had long necks; and why giraffes have short necks. arXiv:1209.5439. 39 pages, 11 figures, 3 tables.

YPM 5449, a posterior dorsal vertebra of Sauroposeidon, from D’Emic and Foreman (2012:fig. 6A and C).

Another recent paper (part 1 is here) with big implications for my line of work: D’Emic and Foreman (2012), “The beginning of the sauropod dinosaur hiatus in North America: insights from the Lower Cretaceous Cloverly Formation of Wyoming.” In it, the authors sink Paluxysaurus into Sauroposeidon and refer a bunch of Cloverly material to Sauroposeidon as well. So in one fell swoop Sauroposeidon goes from being one of the most poorly represented Early Cretaceous North American sauropods, based on just four vertebrae from a single individual, to one of the best-known, most complete, and most widespread, based on at least seven individuals from Texas, Oklahoma, and Wyoming.

The web of connections among the different sets of material is complex, and involves the Sauroposeidon holotype OMNH 53062 from the Antlers Formation of southeastern Oklahoma, the type and referred material of Paluxysaurus from the Twin Mountains Formation of northern Texas described by Rose (2007), sauropod material from the Cloverly Formation of north-central Wyoming described and illustrated by Ostrom (1970), and UM 20800, a scap and coracoid newly excavated from one of Ostrom’s old quarries.  D’Emic and Foreman argue that (1) the Cloverly material is referable to Sauroposeidon based on the shared derived characters of a juvenile cervical, YPM 5294, and the Sauroposeidon holotype, and (2) Paluxysaurus is not distinguishable from the Cloverly material and in fact shares several autapomorphies with the Cloverly sauropod. Which means that (3) Paluxysaurus is Sauroposeidon.

But that’s not all! All the new material suggests different phylogenetic affinities for Sauroposeidon. Instead of a brachiosaurid, it is now posited to be a basal somphospondyl. That’s not super-surprising; as we noted back in 2000 (Wedel et al. 2000), if Sauroposeidon was a brachiosaurid it had evolved some features in parallel with titanosaurs, most notably the fully camellate internal structure of the cervical vertebrae. And it also makes sense because other basal somphospondyls include Erketu and Qiaowanlong, the cervicals of which are similar to Sauroposeidon in some features. D’Emic and Foreman (2012) cite a forthcoming paper by Mike D’Emic in the Journal of Systematic Paleontology that contains the cladistic analysis backing all this up, but the case based on comparative anatomy is already pretty strong.

If anyone is unconvinced by all of these referrals, please bear in mind that we haven’t heard the whole story yet, quite probably for reasons that are outside of the authors’ control.  I am inclined to be patient because I have been in that situation myself: Wedel (2003a) was intended to stand on the foundation of evidence laid down by Wedel (2003b), but because of the vagaries of publication schedules at two different journals, the interpretive paper beat the descriptive one into press by a couple of months.

Mid-cervical originally described as Paluxysaurus, now referred to Sauroposeidon, from Rose (2007:fig. 10).

Anyway, if anyone wants my opinion as “Mr. Sauroposeidon“, I think the work of D’Emic and Foreman (2012) is solid and the hypothesis that Paluxysaurus is Sauroposeidon is reasonable. So, if I think it’s reasonable now, why didn’t I synonymize the two myself? Partly because I thought there was a pretty good chance the two were not the same, based mostly on FWMSH 93B-10-8 (which I referred to as FWMSH “A” in Wedel 2003b, since I had only seen in on display without a specimen number), which I thought looked a lot more like a titanosaur cervical than a brachiosaur cervical. But of course I thought Sauroposeidon was a brachiosaur until a couple of months ago, and if it ain’t, and if brachiosaurs and basal somphospondyls have similar cervicals, that objection is considerably diminished. And partly because I’ve had other things to be getting on with, and stopping everything else to spend what would realistically be a few months looking into a possible synonymy (that I didn’t strongly suspect) wasn’t feasible in terms of time or geography. So I’m glad that D’Emic and Foreman have done that work, and I’m excited about the new things they’ve uncovered.

And I’m honored to bring you a new life restoration of Sauroposeidon by uber-talented Bob Nicholls, which we think is the first to show Sauroposeidon in its new guise as a basal somphospondyl. Click through for the mega-awesome version.

Same critter, different views. If anyone wants to GDI this baby, you now have everything you need. Many thanks to Bob for permission to post these and the following making-of images. Please visit him at Paleocreations.com to see a ton of awesome stuff, and give him some love–or at least a few thousand “likes”–on Facebook.

This is Bob’s first foray into 3D modeling, but you’d never know from the quality of his virtual sculpt. And let me tell you, that dude works fast. He sent this initial version, showing Sauroposeidon as an attenuated brachiosaur (sorta like this) on August 23, to solicit comments from Mike and me.

I wrote back and let Bob know about the new work of D’Emic and Foreman, and suggested that he could probably be the first to restore Sauroposeidon as a somphospondyl. Mike and I also voiced our opposition to the starvation-thinned neck, and Mike suggested that the forelimb was too lightly muscled and that the ‘fingers’ were probably too prominent. The very next day, this was in our inboxes:

I wrote back:

Whatever Sauroposeidon was, its neck was fairly tall and skinny in cross-section. It looks like the neck on your model sort of tapers smoothly from the front of the body to the head. I think it would be much narrower, side-to-side, along most of its length, and would have a more pronounced shoulder-step where it met the body.
The bottom view is very useful. It shows the forefeet as being about the same size as the hindfeet. AFAIK all or nearly all known sauropod tracks have much bigger hindfeet than forefeet. Certainly that is the case with Brontopodus birdi, the big Early Cretaceous sauropod tracks from Texas that were probably made by Sauroposeidon. The forefeet should be about 75-80% the width of the hindfeet, and only about half a long front-to-back. Even if you don’t quite get to those numbers, shrinking the forefeet a bit and subtly up-sizing the hindfeet would make the model more accurate.
Mike’s commentary was much shorter–and funnier:
I like how freaky it looks. It looks WRONG, but in a good way.
Bob toiled over the weekend and came back with this subtly different, subtly better version:

I had one more change to recommend:

I’m sorry I didn’t suggest this sooner, but it only just now occurred to me. With the referral of Paluxysaurus and the Cloverly material to Sauroposeidon, we now have dorsal vertebrae, and they are loooong, much more similar in proportion to the dorsals of Brachiosaurus altithorax than those of Giraffatitan brancai. So, as much as I like the compact little body on your Sauroposeidon, I think it was probably fairly long in the torso. You probably already have Mike’s Brachiosaurus paper [Taylor 2009] with the skeletal recon showing the long torso–in the absence of an updated skeletal recon for Sauroposeidon, I’d use Mike’s Figure 7 as a guide for reconstructing the general body proportions.

Bob lengthened the torso to produce the final version, which is the first one I showed above. He sent that over on August 29–the delay in getting this post up rests entirely with me.

So. It is still very weird to think of “my” dinosaur as a somphospondyl rather than a brachiosaur. I had 15 years to get used to the latter idea. But suddenly having a lot more material–essentially the whole skeleton, minus some stinkin’ skull bits–is pretty darned exciting, and the badass new life restoration doesn’t hurt, either.

Now, would it be too much to wish for some more Brontomerus?

References

This  is the fifth in a series of posts reviewing the Apatosaurus maquette from Sideshow Collectibles. Other posts in the series are:

There are really only a couple of interesting points to discuss for posture: the neck and the feet.

The neck posture is fine. Easy to say, but since I’m one of the “sauropods held their necks erect” guys, it might need some unpacking.

On one hand, animals really do use stereotyped postures, especially for the neck and head (Vidal et al. 1986, Graf et al. 1995, van der Leeuw et al. 2001). The leading hypothesis about why animals do this is that the number of joints and muscle slips involved in the craniocervical system permits an almost limitless array of possible postures, and that having a handful of stereotyped postures cuts down on the amount of neural processing required to keep everything going. That doesn’t mean that animals only use stereotyped postures, just that they do so most of the time, when there’s no need to deviate.

This might work something like the central pattern generators in your nervous system. When you’re walking down the sidewalk thinking about other things or talking with a friend, a lot of the control of your walk cycle is handled by your spinal cord, not your brain. Your brain is providing a direction and a speed, but the individual muscles are being controlled from the spinal cord. Key quote from the Wikipedia article: “As early as 1911, it was recognized, by the experiments of T. Graham Brown, that the basic pattern of stepping can be produced by the spinal cord without the need of descending commands from the cortex.”

But then you see a puddle or some dog doo and have to place your foot just so, and your brain takes over for a bit to coordinate that complex, ad hoc action. After the special circumstance is past, you go back to thinking about whatever and your spinal cord is back in charge of putting one foot in front of the other. This is the biological basis of the proverbial chicken running around with its head cut off: thanks to the spinal cord, the chicken can still run, but without a brain it doesn’t have anywhere to go (I have witnessed this, by the way–one of the numerous benefits to the future biologist of growing up on a farm).

Similarly, if the craniocervical system has a handful of regular postures–alert, feeding, drinking, locomoting, and so on–it lightens the load on the brain, which doesn’t have to figure out how to fire every muscle slip inserting on every cervical vertebra and on the skull to orient the head just so in three-dimensional space. That doesn’t mean that the brain doesn’t occasionally step in and do that, just like it takes over for the spinal cord when you place your feet carefully. But it doesn’t have to do it all the time.

van der Leeuw et al. (2001) took this a step further and showed that birds not only hold their heads and necks in stereotyped postures, they move between stereotyped postures in very predictable ways, and those movement patterns differ among clades (fig. 7 from that paper is above). There is a lot of stuff worth thinking about in that paper, and I highly recommend it, along with Vidal et al. (1986) and Graf et al. (1995), to anyone who is interested in how animals hold their heads and necks, and why.

So, on one hand, its wrong to argue that stereotyped postures are meaningless. But it’s also wrong to infer that animals only use stereotyped postures–a point we were careful to make in Taylor et al. (2009). And it’s especially wrong to infer that paleoartists only show animals doing familiar, usual things–I wrote the last post partly so I could make that point in this one.

For example, I think it would be a mistake to look at Brian Engh’s inflatable Sauroposeidon duo and infer that he accepts a raised alert neck posture for sauropods. He might or might not–the point is that the sauropods in the picture aren’t doing alert, they’re doing “I’m going to make myself maximally impressive so I can save myself the wear and tear of kicking this guy’s arse”. The only way the posture part of that painting can be inaccurate is if you think Sauroposeidon was physically incapable of raising its neck that high, even briefly (the inflatable throat sacs and vibrant colors obviously involve another level of speculation).

Similarly, the Sideshow Apatosaurus has its neck in the near-horizontal pose that is more or less standard for depictions of diplodocids (at least prior to 2009, and not without periodic dissenters). But it doesn’t come with a certificate that says that it is in an alert posture or that it couldn’t raise its neck higher–and even if it did, we would be free to ignore it. Would it have been cool to see a more erect-necked apatosaur? Sure, but that’s not a new idea, either, and there are other restorations out there that do that, and in putting this apatosaur in any one particular pose the artists were forced to exclude an almost limitless array of alternatives, and they had to do something. (Also, more practically, a more erect neck would have meant a larger box and heftier shipping charges.)

So the neck posture is fine. Cool, even, in that the slight ribbing along the neck created by the big cervical ribs (previously discussed here) gives you a sense of how the posture is achieved. Visible anatomy is fun to look at, which I suspect is one of the drivers behind shrink-wrapped dinosaur syndrome–even though it’s usually incorrect, and this maquette doesn’t suffer from it anyway.

Next item: the famous–or perhaps infamous–flipped-back forefoot. I have no idea who first introduced this in skeletal reconstructions and life restorations of sauropods, but it was certainly popularized by Greg Paul. It’s a pretty straightforward idea: elephants do this, why not sauropods?

Turns out there are good reasons to suspect that sauropods couldn’t do this–and also good reasons to think that they could. This already got some air-time in the comments thread on the previous review post, and I’m going to start here by just copying and pasting the relevant bits from that discussion, so you can see four sauropod paleobiologists politely disagreeing about it. I interspersed the images where they’re appropriate, not because there were any in the original thread.

Mike Taylor: the GSP-compliant strong flexion of the wrist always look wrong to me. Yes, I know elephants do this — see Muybridge’s sequence [above] — but as John H. keeps reminding us all, sauropods were not elephants, and one might think that in a clade optimsied for size above all else, wrist flexibility would not be retained without a very good reason.

Adam Yates: Yes I agree with Mike here, the Paulian, elephant-mimicking hyperflexion of the wrist is something that bugs me. Sauropod wrist elements are rather simple flat structures that show no special adaptation to achieve this degree of flexion. [Lourina sauropod right manus below, borrowed from here.]

Heinrich Mallison: Hm, I am not too sure what I think of wrist flexion. Sure it looks odd, but if you think it through the very reasons elephant have it is likely true in sauropods. And given the huge amount of cartilage mossing on the bones AND the missing (thus shape unknown) carpals I can well imagine that sauropods were capable of large excursions in the wrist.

 Mike: What are those reasons?

Heinrich: Mike, long humeri, very straight posture – try getting up from resting with weak flexion at the wrist. Or clearing an obstacle when walking. I can’t say too much, since this afternoon this has become a paper-to-be.

Mike: OK, Heinrich, but the Muybridge photos (and many others, including one on John H.’s homepage) show that elephants habitually flex the wrist in normal locomotion, not just when gwetting up from resting or when avoiding obstacles. Why?

The interesting thing here is that this is evidence of how flawed our (or maybe just my) intuition is: looking at an elephant skeleton, I don’t think I would ever have guessed that it would walk that way. (That said, the sauropod wrist skeleton does look much less flexible than that of the elephant.)

Matt: (why elephants flex their wrists) Possibly for simple energetics. If the limb is not to hit the ground during the swing phase, it has to be shortened relative to the stance limb. So it has to be bent. Bending the limb at the more proximal joints means lifting more weight against gravity. Flexing the wrist more might be a way to flex the elbow less.

(sauropod wrists look less flexible) Right, but from the texture of the ends of the bones we already suspect that sauropods had thicker articular cartilage caps than do mammals. And remember the Dread Olecranon of Kentrosaurus (i.e., Mallison 2010:fig. 3).

Mike: No doubt, but that doesn’t change the fact that elephant wrists have about half a dozen more discrete segments.

Matt: Most of which are very tightly bound together. The major flexion happens between the radius and ulna, on one hand, and the carpal block on the other, just as in humans. Elephants may have more mobile wrists than sauropods did–although that is far from demonstrated–but if so, it’s nothing to do with the number of bony elements. [Loxodonta skeleton below from Wikipedia, discovered here, arrow added by me.]

(Aside: check out the hump-backed profile of the Asian Elephas skeleton shown previously with the sway-backed profile of the African Loxodonta just above–even though the thoracic vertebrae have similar, gentle dorsal arches in both mounts. I remember learning about this from the wonderful How to Draw Animals, by Jack Hamm, when I was about 10. That book has loads of great mammal anatomy, and is happily still in print.)

And that’s as far as the discussion has gotten. The Dread Olecranon of Kentrosaurus is something Heinrich pointed out in the second of his excellent Plateosaurus papers (Mallison 2010: fig. 3).

Heinrich’s thoughts on articular cartilage in dinosaurs are well worth reading, so once again I’m going to quote extensively (Mallison 2010: p. 439):

Cartilaginous tissues are rarely preserved on fossils, so the thickness of cartilage caps in dinosaurs is unclear. Often, it is claimed that even large dinosaurs had only thin layers of articular cartilage, as seen in extant large mammals, because layers proportional to extant birds would have been too thick to be effectively supplied with nutrients from the synovial fluid. This argument is fallacious, because it assumes that a thick cartilage cap on a dinosaur long bone would have the same internal composition as the thin cap on a mammalian long bone. Mammals have a thin layer of hyaline cartilage only, but in birds the structure is more complex, with the hyaline cartilage underlain by thicker fibrous cartilage pervaded by numerous blood vessels (Graf et al. 1993: 114, fig. 2), so that nutrient transport is effected through blood vessels, not diffusion. This tissue can be scaled up to a thickness of several centimeters without problems.

An impressive example for the size of cartilaginous structures in dinosaurs is the olecranon process in the stegosaur Kentrosaurus aethiopicus Hennig, 1915. In the original description a left ulna (MB.R.4800.33, field number St 461) is figured (Hennig 1915: fig. 5) that shows a large proximal process. However, other ulnae of the same species lack this process, and are thus far less distinct from other dinosaurian ulnae (Fig. 3B, C). The process on MB.R.4800.33 and other parts of its surface have a surface texture that can also be found on other bones of the same individual, and may indicate some form of hyperostosis or another condition that leads to ossification of cartilaginous tissues. Fig. 3B–D compares MB.R.4800.33 and two other ulnae of K. aethiopicus from the IFGT skeletal mount. It is immediately obvious that the normally not fossilized cartilaginous process has a significant influence on the ability to hyperextend the elbow, because it forms a stop to extension. Similarly large cartilaginous structures may have been present on a plethora of bones in any number of dinosaur taxa, so that range of motion analyses like the one presented here are at best cautious approximations.

One of the crucial points to take away from all of this is that thick cartilage caps did not only expand or only limit the ranges of motions of different joints. The mistake is to think that soft tissues always do one or the other. The big olecranon in Kentrosaurus probably limited the ROM of the elbow, by banging into the humerus in extension. In contrast, thick articular cartilage at the wrist probably expanded the ROM and may have allowed the strong wrist flexion that some artists have restored for sauropods. I’m not arguing that it must have done so, just that I don’t think we can rule out the possibility that it may have. And so the flipped-back wrist in the Sideshow Apatosaurus does not bother me–but not everyone is convinced. Welcome to science!

I can’t finish without quoting a comment Mike left on Matt Bonnan’s blog a little over a year ago:

Ever since I saw Jensen’s (1987) paper about how mammals are so much better than dinosaurs because their limb-bones articulate properly, I’ve been fuming on and off about this — the notion that the clearly unfinished ends we see are what was operating in life. No.

This is a pretty fair summary of Jensen’s position. Of course, thanks to Heinrich, now we know why dinosaurs had such crap distal limb articulations: they weren’t mammals (part 1part 2part 3).

Finally, interest in articular cartilage is booming right now, as Mike blogged about here. In addition to the Dread Olecranon of Kentrosaurus, see the Dread Elbow Condyle-Thingy of Alligator from Casey Holliday’s 2001 SVP talk, and of course the culmination of that project in Holliday et al. (2010), and, for a more optimistic take on inferring the shapes of articular surfaces from bare bones, read Bonnan et al. (2010).

Next time: texture and color.

References

Preparing a talk is a time-consuming process, and there’s no question that getting the slides ready is where the bulk of that time goes.  But unless you understand exactly what it is that you’re going to talk about, even the best slides won’t rescue your talk from mediocrity, so before you fire up PowerPoint, go and read part 1 of this tutorial, on finding the narrative.  Seriously.  The slides are how you convey your message, and they’re important.  But not as important as what your message is.

Assuming you know what story you’re trying to tell, here is the overriding principle of slide design: make yourself understood.  Remember again that you have something less than twenty minutes in which to make your rich, complex research project understood to a hall full of strangers who have just sat through five or ten or fifteen other presentations.  They will be mentally tired.  Help them out.  Make every slide tell a clear story.

The slides for a conference talk are science, not art.  That doesn’t mean they have to be ugly — of course it doesn’t.  But it does mean that whenever you find yourself facing a choice between clarity and beauty, go with clarity.

That means you do not want your slides to look like this:

OK, that is not even beautiful.  But it does illustrate some horrible mistakes, and we’ll touch on all of them  in what follows.  For now, just remember that the purpose of a Results slide is to help the audience know what your results were.

So how do you make yourself understood?

1. Use the full size of the screen

Most importantly, don’t “frame” your content.  You have a specific amount of space in which to present your work.  Don’t throw any of it away.  Although the super-bad slide above may look extreme, I have seen plenty to slides that present, say, specimen photos in about the same amount of space as the graph above occupies.  So, then:

  • No picturesque borders.
  • We don’t need the talk title, or your name or address on every slide.  You can tell us once at the start of the talk and then, if you like, once more at the end.  If we truly forget who you are in the middle, we can always look at the programme.  If we forget what you’re talking about, then your talk has more profound problems.
  • That goes double for logos.  We do not need to see the following more than once (or indeed once):
    • Your institution’s crest
    • The conference logo
    • Logos of funding bodies

We don’t need any of that stuff, and all of it wastes precious real-estate.  Space that you could be using to tell your story.

Most important of all: use as much space as you can for your images.  Specimen photographs, interpretive drawings, reproduced figures from the literature, graphs, cladograms, strat sections — whatever you’re showing us, let us see it.

In my own talks, I like to make the picture fill the whole slide.  You can usually find a light area to put a dark text on, or vice versa.  I often find it’s useful to give the text a drop-shadow, so that it stands out against both light and dark background.  (You can find that option in Format -> Character… -> Font Effects if you use OpenOffice, and no doubt somewhere similar in PowerPoint.)

If the aspect ratio of an image that I want to use is not the 4:3 that projectors give you, then I will often crop it down to that aspect ratio, if some of the edges of the image are dispensable, so that the cropped version is properly shaped to fill the screen.

(On image resolution: most projectors seem to be 1024 x 768, maybe some these days are 1280 x 960.  There’s no point using images at a higher resolution than that: your audience won’t see the additional information.)

2. Legibility

Hopefully you won’t need too many words on your slides, since you’ll be talking to us about what we can see.  But what words you use, we need to see.  Specifically, this means:

  • Use big fonts.  There is absolutely no point in showing us an eighty-taxon phylogenetic tree: we just won’t be able to read the taxon names.  I tend to make my fonts really big — 32-point and up, which actually is probably bigger than you really need.  But you don’t want to be smaller than 20-point at the absolute minimum.
  • Use high contrast between the text and background.  That usually means black on white, or (if you must) white on black.  Well, OK — it doesn’t literally have to be black, but it needs to be a very dark colour (I often use very dark blue).  And it doesn’t literally have to be white, but it needs to be a very light colour.  (I occasionally use a very pale yellow “parchment”-type colour, but less often.)  Do not use grey text or a grey background.  Especially do not use grey text on a grey background, even if they are fairly different greys and the muted effect looks classy.  You’re not shooting for “classy”, you’re shooting for “legible”.  Because you remember the prime directive that you’re trying to make yourself understood.
  • If for some reason you must use a non-black, non-white text or background, don’t make it a highly saturated colour.  Some combinations, such as a red on blue, and virtually impossible to read.
  • No vertical writing (with the possible exception of short y-axis labels on graphs).  If your cladogram’s taxon names are vertical, turn your cladogram around.  Redraw it if necessary.  If the audience have their heads on one site, you’re doing it wrong.

3. Font Choice

Apart from size, what else matters about fonts?

  • Avoid elaborate fonts, such as the URW Chancery L Medium Italic that I used for my name and affiliation in the Bad Slide at the top.  They’re hard to read, and at best they draw attention away from the message to the medium.
  • Pick a single font and stick with it for consistency.  Or if you wish, one serifed font (for body text) and one sans-serif (for headings).  But you should have little enough text on your slides that it’s practically all headings.
  • Stick to standard fonts which you know will be on the computer that will be displaying your presentation.  In practice, the safest approach is it stick to Microsoft’s “core fonts for the web” — which is plenty enough choice.
  • You might want to avoid Arial, which is widely considered particularly ugly.  Other ubiquitous sans-serif fonts include Trebuchet and Verdana, which are both rather nicer than Arial (though Verdana’s glyphs are too widely spaced to my eye).
  • Do not use MS Comic Sans Serif, or no-one will take anything you say seriously.  I don’t just mean your talk, I mean ever, for the rest of your life.

Why is it important to stick to standard fonts?  Because of size, spacing and positioning.  Your computer may have the super-beautiful Font Of Awesomeness and it might make your slides looks beautiful; but when you run your PowerPoint file on the conference computer, it won’t have Font Of Awesomeness, so it will substitute whatever it thinks is closest — Arial or Times or something.  Not only will you not get the visual effect you wanted, but the glyphs will be different sizes, so that your text will run off the edge of the page, or fall right off the bottom.

(Handy household hint for users of Debian GNU/Linux and variants such as Ubuntu.  Make sure that you have the MS core fonts installed on your computer, so that OpenOffice can properly display your slides as you’re designing them, rather than substituting.  sudo apt-get install ttf-mscorefonts-installer, restart OpenOffice, and you’re good to go.)

4. How many slides?

I need to mention this issue, if only to say that there’s no right answer.  I don’t say that lightly: for most slide-design issues, there is a right answer.  (Example: should you use MS Comic Sans Serif?  Answer: no.)  But number of slides has to vary between people to fit in with presentation styles.

I tend to use a large number of slides and whiz through them very quickly — my SVPCA 2011 talk had 80 slides, and in 2010 I had 92 slides.  Lots of them are parenthetical, sometimes just a silly joke to make in passing a point that I am already making.  If you miss such a slide, it doesn’t really matter: it’s just light relief and reinforcement, not an integral part of the narrative.

.

But that many-slides-slipping-quickly-past style doesn’t suit everybody. In the eighteen minutes or so that you get to give a talk (allowing a minute for messing about getting set up and a minute for questions), getting through 80 slides in those 1080 seconds gives you an average of 13.5 seconds per slide.

Lots of people prefer to use fewer slides and talk about them for longer. You can give an excellent talk with very few slides if that approach comes naturally to you: step slowly through nine slides, talk about each one for two minutes.

Once you’ve given a few talks you’ll know which approach works best for you, and you can design accordingly. For your first talk, you’re probably best off aiming initially somewhere in the middle — thirty or so slides — and then seeing what happens when you dry-run the talk. (We’ll discuss that next time around.)

5. Miscellaneous

I’ve touched on this one already, but it’s best to use as little text as possible. That’s because you want your audience listening to your story, not reading your slides. I used to put a lot of text in my slides, because I wanted the PowerPoint file to stand alone as a sort of a record of the talk. But I don’t do that now, because a talk involves talking (clue’s in the question). I include enough text to remind myself what I want to say about each slide (sometimes just one or two words; often none at all). And I try to make sure there’s enough to let the audience know what they’re looking at if I zoom straight past it. For example:

.

I used this slide to briefly tell a typical taphonomic story of a sauropod neck.  But I didn’t need to say that I was using diagrams of the neck of Sauroposeidon taken from Wedel et al. 2000, so I just shoved that information on the slide for anyone who was interested.  That way I didn’t have to break the flow of my narrative to impart this information.

Use a consistent colour palette.  If you’ve used dark blue text on white for half of your slides, don’t switch to black on pale yellow for the other half.  It’s not a hugely important point, but it all contributes to helping the talk go down smoothly.  You’re getting rid of mental speed-bumps that could stop your audience from giving their full attention to the story you’re telling.

Where possible, avoid putting important information at the bottom — in, say, the lower 10-15% of the slide.  That’s because the lower part of the screen can sometimes be obscured by the heads of the people in the front rows.

Avoid hatching, which can look terrible on a screen, in a way that’s very hard to predict.  In the Sauroposeidon taphonomy slide above, for example, the lost bones are “greyed out” using a flat grey colour rather the close diagonal lines of the original.  I knew it would look right on the screen.

Skip the fancy slide transitions, animated flying arrows, and suchlike. It’s just distracting nonsense that no one in the audience (or anywhere else, for that matter) needs to be exposed to. It’s just gross. Also, as with fonts, you may end up giving your talk from a machine with an older version of PowerPoint that doesn’t support the turning of animated pages and the bouncing arrival of arrows and clipart, and then your presentation will either look stupid or fail to run entirely.

You might want to draw highlighting marks on your slides, e.g. circles around the relevant parts of a specimen photos.  That will save you having to mess about with the laser pointer later.  (I will have much to say about the laser pointer in part 4).  I like to show two consecutive slides: one of the unadorned photo, then one that’s identical apart from the addition of the highlight, like this:

Then as I am talking about the first slide, “in order to mount the vertebrae in something approaching a straight line, they had to leave a huge gap between consecutive centra”, I’ll step on to the next one, which highlights what I’m saying.  Slick, no?  (This is part of why I end up with such high slide counts.)

A pet hate: don’t write “monophyletic clade”.  If it’s a clade, it’s monophyletic by definition.  “Monophyletic clade” is like “round circle”, “square square” or “boring ornithopod”.

And finally …

Show us specimens.  We are vertebrate palaeontologists, and we love vertebrate fossils.  No-one goes into the field because of a deep and abiding passion for graphs or for tables of numbers.  We understand that from time to time you’ll need to show us those things in order to tell the story, but nothing makes an audience happier than big, clean photos of beautiful specimens.

Well, that’s it — how to make good slides.  Next time we’ll look at rehearsing the talk.  (It’ll be a much shorter post than this one.)

I’m pleased to announce that Darren has a new paper out (Naish and Sweetman 2011) in which he and fellow Portsmouth researcher Steve Sweetman describe a maniraptoran theropod from the Wealden Supergroup of southern England.  It’s represented only by a single cervical vertebra:

Indeterminate maniraptoran theropod BEXHM 2008.14.1, posterior cervical vertebra, in right lateral view. Sauroposeidon cervical vertebra 8 for scale.

This vertebra is described in seven and a bit pages, which means that it’s had nearly three times as much total coverage as Jobaria (Cf. Sereno et al. 1999).

Still, we can hope that Darren and Steve will return to their specimen some time and monograph it properly.

In the mean time, read all about it over on Tetrapod Zoology.

References

  • Naish, Darren, and Steven C. Sweetman.  2011.  A tiny maniraptoran dinosaur in the Lower Cretaceous Hastings Group: evidence from a new vertebrate-bearing locality in south-east England.  Cretaceous Research 32:464:471.  doi:10.1016/j.cretres.2011.03.001
  • Sereno, Paul C., Allison L. Beck, Didier. B. Dutheil, Hans C. E. Larsson, Gabrielle. H. Lyon, Bourahima Moussa, Rudyard W. Sadleir, Christian A. Sidor, David J. Varricchio, Gregory P. Wilson and Jeffrey A. Wilson.  1999.  Cretaceous Sauropods from the Sahara and the Uneven Rate of Skeletal Evolution Among Dinosaurs.  Science 282:1342-1347.

Meanwhile, elsewhere on the Internet …

On Tuesday morning, a rather nice article about our recent sauropod-necks-were-not-sexually-selected paper appeared on the BBC web-site.  At the time of writing, it’s just topped 100 comments (athough fifteen of those are by me — I wanted to respond to the questions that people were asking).

Here it is, for those who are interested (maybe more in the Q-and-A’s than in the actual article): Evolution, sex and dinosaur necks

Pimp my ‘pod 2: haids

December 13, 2010

Here’s another dual-purpose post (part 1 is here), wherein I use some of Brian Engh’s cool art to riff on a related topic (with kind permission–thanks, Brian!). Back when he was first planning his awesome Sauroposeidon life restoration, Brian sent these head studies:

(Note that Brian’s ideas were still evolving at this point, and he roofed the nasal chamber with a keratinous resonating chamber instead of the inflatable sac seen in the finished product. I think both are plausible [not likely, just plausible] and look pretty rad, although the latter is obviously a lot more metal.)

I think these are dynamite, because they show that you can avoid “shrink-wrapped dinosaur syndrome” (SWDS) and still make an anatomically detailed, realistic-looking life restoration. SWDS is what I call the common convention in paleo-art of simply draping the skeleton–and especially the skull–in Spandex and calling that a life restoration. I think it’s a popular technique because you can show off the skeleton inside the animal and thereby demonstrate that you’ve done your homework (especially to an audience that already knows the skeletons*). It gives artists an easy way to add detail to their critters; if you actually slab on realistic soft tissues and lose most of those skeletal and cranial landmarks, you have to come up with something else to make your animals look detailed and visually interesting. And by now it’s been going strong for several decades, so people expect it.

* Without harshing on anyone, I suspect that a lot of consumers of paleo-art have spent more time looking at dinosaur skeletons than looking at live animals and thinking about how much or little of their skeletal structure is visible in life, which may make them susceptible to mistaking “shows a lot of the bony structure” for “biologically realistic”. I suspect that because it was true of me for a good chunk of my life; as usual, the one ranting is ranting mostly at his former self. What cured me was dissecting animals and reading TetZoo–happily, two avenues of self-improvement that are open to everyone.

In the second image above (the one showing the innards) Brian kindly credited me for lending a little assistance. That assistance was mainly in forwarding him my full cranio-centric anti-SWDS rant, which I originally put together for a certain documentary that ended up using almost none of my ideas. I’ve been meaning to recycle it here for ages, and Brian’s new art is just the kick in the pants I needed. Without further ado:

“Sauroposeidon head suggestions no labels.jpg” [above] shows a mock-up of the skull, a traditional restoration of the head, the skull with accurate soft tissues, and an updated restoration. The traditional restoration looks like a lot of paleoart from the past two decades–it looks like someone shrink-wrapped the skull. But this is not what the heads of real animals look like at all. If you look at almost any animal, whether it is a lizard, croc,* turtle, snake, bird, cow, horse, rodent, or human, you can’t see the holes in the skull because they are filled with muscles or air sacs and smoothed over with skin. Here are the 8 specific features I fixed in the updated restoration:

* I got a little carried away here–some of the holes in croc skulls are not hard to make out, because their skin is unusually tightly bound to the very rugose skull. Most dinosaurs didn’t have that same skull texture, and there is little reason to think that their heads were similarly shrink-wrapped. Abelisaurs, maybe. Sauropods, not so much.

(1) the profile of the top of the head and start of the neck would have been smoothed out by jaw muscles bulging through holes in the top of the head (strange but true), and by neck muscles coming up onto the back of the skull.

(2) The fleshy nostril should be down on the snout at the end of the nasal troughs. The bony nostrils make that huge hump on top of the head, but they are continuous with these two grooves that run down the front of the face, and almost certainly the whole bony-nostril-plus-groove setup was covered by soft tissues and the actual air holes were down on the snout. That fleshy covering would have been propped up and not sucked down tight to the skull, so you wouldn’t be able to see the boundaries of bony nostrils from the outside. The fleshy nostril should also be fairly big; it is unlikely that a 50-ton animal with a head a yard long had nostrils the size of a horse’s.

(3) The holes in the skull should not be visible. The habit of drawing and painting dinosaurs with shrink-wrapped heads is so entrenched that smooth heads look undetailed and a little fake, but smooth heads are undoubtedly more accurate. The head wasn’t necessarily a completely smooth bullet–it probably had decorative scales and patches of color–but we can be fairly certain that the holes in the skull were not visible through the skin.

(4) The jaw joint is all the way at the back of the head, but past the tooth row the upper and lower jaws were bound together by jaw muscles.  When the jaws opened, as shown in the lower images, the muscles were covered by skin. This skin might have been outside the jaws and stretchy, as shown in the attached image “bird cheeks.jpg”, or it might have been tucked in between the jaws as shown in “croc cheeks.jpg” [below].

Another caveat in my own defense: I know that condors do not have muscular, mammal-style cheeks, so the “cheek” skin here is doing more than just covering jaw muscles (farther back on the  jaw the skin is covering jaw muscles). Remember that I was writing quick art suggestions for a less technically sophisticated audience, not a dissertation on condor heads. The take home point is that you can’t tell from looking at the condor below where the jaw muscles start or where the jaw joint is located (unless you already know something about bird skulls). Other than the  gross outline, there simply isn’t much osteology on display–and this is a naked head!

(5) The eyes are usually reconstructed as small, dull, and centered in the vertical middle of the eye socket. In fact the eyes were probably located toward the top end of the eye socket, they were probably colorful as in most reptiles and birds, and they may have been pretty big. [But not that big; see Mickey's comment below, and note that Brian got it right anyway.]

(6) The external ear hole is usually left out. It should be behind the back of the skull and in front of the hindmost jaw muscles.

(7) The profile of the back of the head follows jaw muscles, not the boundaries of the skull bones.

(8) Sauropods had true flip-top heads. The skull of Giraffatitan looks like nothing so much as an upside down toilet bowl, with the toilet seat for the lower jaw. Sauropods probably used that big gape to shove in as much plant material as possible per unit time. Crocodiles and many birds have an extensible throat pouch that allows them to bolt larger bites than you’d think, and the same was probably true of most dinosaurs, especially sauropods. There may have been a visible division between the muscular neck and this fleshy “gullet”. See “croc throat.jpg” and “bird throat.jpg” [below].

After seeing one of the preliminary designs for the documentary Sauroposeidon–which sadly ended up being a Big Gray Pachyderm in the show–I sent the following. Even though they ignored it, and even though it appears here as a rehash of an argument I’ve made several times already, I’m still proud of it. Especially the concluding advice–potential artistic collaborators take note!
I think you could safely put on a lot more color. People are used to big animals being dull, but that’s because most big animals are mammals and, except for primates, all mammals are effectively colorblind. So big mammals are a horrible guide to how colorful other big animals might be. Komodo dragons and crocs are both fairly dull, but they’re all ambush predators and they have to be dull or they don’t eat. If I get inspired I might take your Sauroposeidon into Photoshop and color it up; otherwise maybe have your artists look at tropical birds, toss back a couple of stiff drinks, and throw caution to the wind.

Pimp my ‘pod

December 10, 2010

These are happy times for me. Dinosaur rap god and burgeoning paleoartist Brian Engh, AKA The Historian Himself, has finished a new life restoration of Sauroposeidon. Here’s a smallish view, just to give you a taste; for the high resolution awesomeness, check out Brian’s post here. While you’re over there, check out his line of mini-brachiosaur sculptures–the perfect gift for the sauropod-lover in your life (the a black one is already mine).

As you might guess from the quality of the finished product, this was a project with a long gestation. Brian got in touch with me back in the summer of 2009 and we started swapping ideas on doing life restorations of sauropods. Brian incorporated some of that discussion in his blog post.

Did Sauroposeidon really look like this? Probably not. There’s no direct evidence for inflatable display structures in sauropods or in any other non-avian dinosaurs that I know of. But any life restoration of a dinosaur involves going out on a limb and positing things for which we have little or no direct evidence. So no life restoration is going to show exactly how Sauroposeidon looked. In my view, if you know you’re going to be wrong anyway, you might as well be interestingly wrong, and put in the kinds of plausible-but-not-fossilized structures that extant animals are replete with.

The larger, slightly more serious question then becomes, were big sauropods more likely to be visually flamboyant or big gray pachyderms? I think there is a case to be made for flamboyant sauropods, and I made it in the cover description for this paper (that illustration, by Brian Ford, is below). You can get the PDF for the full argument, but Brian Engh (hmm, just noticed the high correlation between Sauroposeidon life restorations and paleoartists named ‘Brian’) summarized it in eight words: “Brachiosaurs were big. Maybe too big for camouflage.”

The idea of flamboyant sauropods is a hypothesis, and for now a mostly untestable one. I could be wrong. I don’t have a lot invested in it. Flamboyant sauropods would be awesome, and there are already plenty of sauropod life restorations  from the Big Gray Pachyderm school, so I’m happy to camp out the other end of the spectrum just for the heck of it. If doing so emboldens those who are trying to kick us in the brainpans with their paleoart, that’s a win-win. I’m not trying to take any credit here–far from it–just happy that the Brians and I have gotten to make common cause.

To make a clean sweep with this post, there is one other Sauroposeidon life restoration that I’ve had the good fortune to be involved with. That one is part of the “Cretaceous Coastal Environment” mural that Karen Carr painted for the Oklahoma Museum of Natural History, an excerpt of which appears below (from this paper again, or see the full version on Karen’s website). While she was working on the mural, Karen sent me a draft illustration of Sauroposeidon for comment. My reply was basically, “Looks awesome. How about some spines?” Given the presence of dermal spines in diplodocids and armor in some titanosaurs, I don’t think it’s unreasonable to infer some kind of dermal ornamentation even in those sauropod taxa for which we have no direct evidence of it. I like Karen’s ground-level shot of the distant sauropods (that’s a squirrel-sized Gobiconodon in the foreground) because they look vast, like gods, and I think that’s how they would strike us if we could stand near them today.

Those aren’t all of the Sauroposeidon life restorations out there–Bob Nicholls has done a very sharp one, which unfortunately does not seem to be currently available on his webpage, and there are others–those are just the three I’ve had some small part in. It’s been a thrill, every time, to work with smart, talented, and hardworking people who can do something special that I can’t, which is bring the vanished world to life. When I was a kid, I didn’t want to just learn about dinosaurs, I wanted to see dinosaurs. I wanted to be a chrononaut. I ended up as a paleontologist because that’s the closest you can get to exploring in time.

So, thank you, Brian (and Brian, and Karen, and Bob, and others) for gracing Sauroposeidon with your skill. It’s phenomenal to get to see my favorite dinosaur with fresh eyes. And thanks to all the rest of you paleoartists out there, paid or unpaid, for your service as our eyes and ears in the past, for letting the rest of  us get our mental boots muddy in worlds that we often approach only clinically. Keep those dispatches coming–we can’t wait to see where you’re going to take us next.

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