You! Shall not! Pass!

August 22, 2020

OK, technically this is MB.R.3822, a dorsal vertebra of Giraffatitan brancai formerly known as HMN Ar1, in posterior view, rendered from a 3D scan provided by Heinrich Mallison.

But you can’t tell me that when you look at that you don’t see Gandalf shouting at a balrog.

Long before Matt and others were CT-scanning sauropod vertebrae to understand their internal structure, Werner Janensch was doing it the old-fashioned way. I’ve been going through old photos that I took at the Museum für Naturkunde Berlin back in 2005, and I stumbled across this dorsal centrum:

Dorsal vertebra centum of ?Giraffatitan in ventral view, with anterior to top.

You can see a transverse crack running across it, and sure enough the front and back are actually broken apart. Here there are:

The same dorsal vertebral centrum of ?Giraffatitan, bisected transversely in two halves. Left: anterior half in posterior view; right: posterior half in anterior view. I had to balance the anterior half on my shoe to keep it oriented corrrectly for the photo.

This does a beautiful job of showing the large lateral foramina penetrating into the body of the centrum and ramifying further into the bone, leaving only a thin midline septum.

But students of the classics will recognise this bone immediately as the one that Janensch (1947:abb. 2) illustrated the posterior half of in his big pneumaticity paper:

It’s a very strange feeling, when browsing in a collection, to come across a vertebra that you know from the literature. As I’ve remarked to Matt, it’s a bit like running into, say, Cameron Diaz in the corner shop.

Reference

  • Janensch, W. 1947. Pneumatizitat bei Wirbeln von Sauropoden
    und anderen Saurischien. Palaeontographica, supplement
    7:1-25.

Daniel Vidal et al.’s new paper in Scientific Reports (Vidal et al. 2020) has been out for a couple of days now. Dealing as it does with sauropod neck posture, it’s obviously of interest to me, and to Matt. (See our earlier relevant papers Taylor et al. 2009, Taylor and Wedel 2013 and Taylor 2014.)

Overview

To brutally over-summarise Vidal et al.’s paper, it comes down to this: they digitized the beautifully preserved and nearly complete skeleton of Spinophorosaurus, and digitally articulated the scans of the bones to make a virtual skeletal mount. In doing this, they were careful to consider the neutral pose of consecutive vertebrae in isolation, looking at only one pair at a time, so as to avoid any unconscious biases as to how the articulated column “should” look.

Then they took the resulting pose, objectively arrived at — shown above in their figure 1 — and looked to see what it told them. And as you can well see, it showed a dramatically different pose from that of the original reconstruction.

Original skeletal reconstruction of Spinophorosaurus nigerensis (Remes et al. 2009:figure 5, reversed for ease of comparison). Dimensions are based on GCP-CV-4229/NMB-1699-R, elements that are not represented are shaded. Scale bar = 1 m.

In particular, they found that as the sacrum is distinctly “wedged” (i.e. its anteroposterior length is greater ventrally than it is dorsally, giving it a functionally trapezoidal shape, shown in their figure 1A), so that the column of the torso is inclined 20 degrees dorsally relative to that of the tail. They also found lesser but still significant wedging in the last two dorsal vertebrae (figure 1B) and apparently some slight wedging in the first dorsal (figure 1C) and last cervical (figure 1D).

The upshot of all this is that their new reconstruction of Spinophorosaurus has a strongly inclined dorsal column, and consequently an strongly inclined cervical column in neutral pose.

Vidal et al. also note that all eusauropods have wedged sacra to a greater or lesser extent, and conclude that to varying degrees all eusauropods had a more inclined torso and neck than we have been used to reconstructing them with.

Response

I have to be careful about this paper, because its results flatter my preconceptions. I have always been a raised-neck advocate, and there is a temptation to leap onto any paper that reaches the same conclusion and see it as corroboration of my position.

The first thing to say is that the core observation is absolutely right, — and it’s one of those things that once it’s pointed out it’s so obvious that you wonder why you never made anything of it yourself. Yes, it’s true that sauropod sacra are wedged. It’s often difficult to see in lateral view because the ilia are usually fused to the sacral ribs, but when you see them in three dimensions it’s obvious. Occasionally you find a sacrum without its ilium, and then the wedging can hardly be missed … yet somehow, we’ve all been missing its implications for a century and a half.

Sacrum of Diplodocus AMNH 516 in left lateral and (for our purposes irrelevant) ventral views. (Osborn 1904 figure 3)

Of course this means that, other thing being equal, the tail and torso will not be parallel with each other, but will project in such a way that the angle between them, measured dorsally, is less than 180 degrees. And to be fair, Greg Paul has long been illustrating diplodocids with an upward kink to the tail, and some other palaeoartists have picked up on this — notably Scott Hartman with his very uncomfortable-looking Mamenchisaurus.

But I do have three important caveats that mean I can’t just take the conclusions of the Vidal et al. paper at face value.

1. Intervertebral cartilage

I know that we have rather banged on about this (Taylor and Wedel 2013, Taylor 2014) but it remains true that bones alone can tell us almost nothing about how vertebrae articulated. Unless we incorporate intervertebral cartilage into our models, they can only mislead us. To their credit, Vidal et al. are aware of this — though you wouldn’t know it from the actual paper, whose single mention of cartilage is in respect of a hypothesised cartilaginous suprascapula. But buried away the supplementary information is this rather despairing paragraph:

Cartilaginous Neutral Pose (CNP): the term was coined by Taylor for “the pose found when intervertebral cartilage [that separates the centra of adjacent vertebrae] is included”. Since the amount of inter-vertebral space cannot be certainly known for most fossil vertebrate taxa, true CNP will likely remain unknown for most taxa or always based on estimates.

Now this is true, so far as it goes: it’s usually impossible to know how much cartilage there was, and what shape it took, as only very unusual preservational conditions give us this information. But I don’t think that lets us out from the duty of recognising how crucial that cartilage is. It’s not enough just to say “It’s too hard to measure” and assume it didn’t exist. We need to be saying “Here are the results if we assume zero-thickness cartilage, here’s what we get if we assume cartilage thickness equal to 5% centrum length, and here’s what we get if we assume 10%”.

I really don’t think it’s good enough in 2020 to say “We know there was some intervertebral cartilage, but since we don’t know exactly how much we’re going to assume there was none at all”.

The thing about incorporating cartilage into articulating models is that we would, quite possibly, get crazy results. I refer you to the disturbing figure 4 in my 2014 paper:

Figure 4. Effect of adding cartilage to the neutral pose of the neck of Diplodocus carnegii CM 84. Images of vertebra from Hatcher (1901:plate III). At the bottom, the vertebrae are composed in a horizontal posture. Superimposed, the same vertebrae are shown inclined by the additional extension angles indicated in Table 2.

I imagine that taking cartilage into account for the Spinophorosaurus reconstruction might have given rise to equally crazy “neutral” postures. I can see why Vidal et al. might have been reluctant to open that can of worms; but the thing is, it’s a can that really needs opening.

2. Sacrum orientation

As Vidal et al.’s figure 1A clearly shows, the sacrum of Spinophorosaurus is indeed wedge-shaped, with the anterior articular surface of the first sacral forming an angle of 20 degrees relative to the posterior articular surface of the last:

But I don’t see why it follows that “the coalesced sacrum is situated so that the posterior face of the last sacral centrum is sub-vertical. This makes the presacral series to slope dorsally and the tail to be subhorizontal (Figs. 1 and 4S)”. Vidal et al. justify this with the claim by saying:

Since a subhorizontal tail has been known to be present in the majority of known sauropods[27, 28, 29], the [osteologically induced curvature] of the tail of Spinophorosaurus is therefore compatible with this condition.

But those three numbered references are to Gilmore 1932, Coombs 1975 and Bakker 1968 — three venerable papers, all over fifty years old, dating from a period long before the current understanding of sauropod posture. What’s more, each of those three was about disproving the previously widespread assumption of tail-dragging in sauropods, but the wedged sacrum of Spinophorosaurus if anything suggests the opposite posture.

So my question is, given that the dorsal and caudal portions of the vertebral column are at some specific angle to each other, how do we decide which (if either) is horizontal, and which is inclined?

Three interpretations of the wedged sacrum of Spinophorosaurus, in right lateral view. In all three, the green line represents the trajectory of the dorsal column in the torso, and the red line that of the caudal column. At the top, the tail is horizontal (as favoured by Vidal et al. 2020) resulting in an inclined torso; at the bottom, the torso is horizontal, resulting in a dorsally inclined tail; in the middle, an intermediate posture shows both the torso and the tail slightly inclined.

I am not convinced that the evidence presented by Vidal et al. persuasively favours any of these possibilities over the others. (They restore the forequarters of Spinophorosaurus with a very vertical and ventrally positioned scapula in order to enable the forefeet to reach the ground; this may be correct or it may not, but it’s by no means certain — especially as the humeri are cross-scaled from a referred specimen and the radius, ulna and manus completely unknown.)

3. Distortion

Finally, we should mention the problem of distortion. This is not really a criticism of the paper, just a warning that sacra as preserved should not be taken as gospel. I have no statistics or even systematic observations to back up this assertion, but the impression I have, from having looked closely at quite a lot of sauropod vertebra, is the sacra are perhaps more prone to distortion than most vertebrae. So, for example, the very extreme almost 30-degree wedging that Vidal et al. observed in the sacrum of the Brachiosaurus altithorax holotype FMNH PR 25107 should perhaps not be taken at face value.

Now what?

Vidal el al. are obviously onto something. Sauropod sacra are screwy, and I’m glad they have drawn attention in a systematic way to something that had only been alluded to in passing previously, and often in a way that made it seems as though the wedging they describe was unique to a few special specimens. So it’s good that this paper is out there.

But we really do need to see it as only a beginning. Some of the things I want to see:

  • Taking cartilage into account. If this results in silly postures, we need to understand why that is the case, not just pretend the problem doesn’t exist.
  • Comparison of sauropod sacra with those of other animals — most important, extant animals whose actual posture we can observe. This might be able to tell us whether wedging really has the implications for posture that we’re assuming.
  • Better justification of the claim that the torso rather than the tail was inclined.
  • An emerging consensus on sauropod shoulder articulation, since this also bears on torso orientation. (I don’t really have a position on this, but I think Matt does.)
  • The digital Spinophorosaurus model used in this study. (The paper says “The digital fossils used to build the virtual skeleton are deposited and accessioned at the Museo Paleontológico de Elche” but there is no link, I can’t easily find them on the website and they really should be published alongside the paper.)

Anyway, this is a good beginning. Onward and upward!

References

  • Bakker, Robert T. 1968. The Superiority of Dinosaurs. Discovery 3:11–22.
  • Coombs, Walter P. 1975. Sauropod habits and habitats. Palaeogeography, Palaeoclimatology, Palaeoecology 17:1-33.
  • Gilmore, Charles W. 1932. On a newly mounted skeleton of Diplodocus in the United States National Museum. Proceedings of the United States National Museum 81:1-21.
  • Hatcher, John Bell. 1901. Diplodocus (Marsh): its osteology, taxonomy, and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1:1-63.
  • Osborn, Henry F. 1904. Manus, sacrum and caudals of Sauropoda. Bulletin of the American Museum of Natural History 20:181-190.
  • Taylor, Michael P. 2014. Quantifying the effect of intervertebral cartilage on neutral posture in the necks of sauropod dinosaurs. PeerJ 2:e712. doi:10.7717/peerj.712
  • Taylor, Michael P., and Mathew J. Wedel. 2013c. The effect of intervertebral cartilage on neutral posture and range of motion in the necks of sauropod dinosaurs. PLOS ONE 8(10):e78214. 17 pages. doi:10.1371/journal.pone.0078214
  • Taylor, Michael P., Mathew J. Wedel and Darren Naish. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54(2):213-230.
  • Vidal, Daniel, P Mocho, A. Aberasturi, J. L. Sanz and F. Ortega. 2020. High browsing skeletal adaptations in Spinophorosaurus reveal an evolutionary innovation in sauropod dinosaurs. Scientific Reports 10(6638). Indispensible supplementary information at https://static-content.springer.com/esm/art%3A10.1038%2Fs41598-020-63439-0/MediaObjects/41598_2020_63439_MOESM1_ESM.pdf
    doi:10.1038/s41598-020-63439-0

 

I swear I’m not making this up: I was recently contacted by one of our patrons, who said he’d like to support us at the SV-POW! Patreon at $10/month. We didn’t have that tier at the time, only $1/mo. and $5/mo. So to accommodate him, and any others who theoretically might like to support us at that level, we created a $10 tier. There’s a new reward to go with this tier: in addition to being acknowledged in any papers that get written as a result of a trip that you help to fund, at $10/month you’ll also get an 8×10 art print once a year, either one of my skull drawings or a photograph, signed or unsigned. Here’s the link.

Our support is up to $57/mo. That might not sound like much, but $7/mo. is $84/yr., which is what we wanted when Mike launched the Patreon so we could get rid of ads on the site. The other $50/mo. is $600/yr., which is roughly the cost of a trans-Atlantic plane ticket. So that’s already one Matt-and-Mike get-together a year to do research and write papers, in addition to any others we were going to do anyway.

What would we do with more support? More research, and more writing. I get small grants now and then, and I get a yearly travel budget from my department, but grant-writing takes time away from research and paper-writing, and the departmental travel money doesn’t cover all the things I’d like to do. For example, I skipped SVPCA in 2018 so I could visit the Carnegie last spring. That’s a tough choice, a whole conference worth of ideas and conversations that I missed out on. And Mike is basically self-funded. We’re pretty good at converting travel money into new ideas and new data, and we’re going to start doing writing retreats where we hole up someplace cheap, far from museums, field sites, and other distractions, and just write. So if you like the stuff we do, please consider supporting us–we promise not to waste your donation.

Many thanks to everyone who supports our work, and to everyone else for sitting through this post. In the spirit of giving you more than you asked for, up top is the cervicodorsal transition in Giraffatitan brancai, MB.R.2181, in my favorite, inconvenient portrait orientation. And here’s a version with the centrum lengths and posterior widths given in cm. From Janensch (1950: figs. 49 and 50).

Reference

Janensch, Werner. 1950. Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica (Suppl. 7) 3: 27-93.

If you’re thinking that it’s about time to look at some sauropod vertebrae from the Salt Wash member of the Morrison Formation, well, you’re gol-durned right, pardner. Let’s ride.

Here’s a vertebra sticking out of the rock. For once it’s not in cross-section. We’re simply looking at the posterior surface of a dorsal vertebra and bits of its associated ribs. Let’s stand it up correctly:

And, well, heck, Alex, I’d like to go ahead and solve the puzzle:

Figure on the right from Wedel and Taylor (2013a), and composed in turn from plates in Hatcher (1901, Diplodocus), Hatcher (1903, Haplocanthosaurus), and Gilmore (1936, Apatosaurus).

UPDATE: I had the discovery sequence wrong–this is one of the bones that was first found by photographer Guy Tal, who then put ReBecca Hunt-Foster onto the area. ReBecca has since gone on to become Monument Paleontologist at Dinosaur National Monument, but at the time she was working as a BLM paleontologist out of the Moab office. ReBecca then brought out some more of us out to take a look, and that was the genesis of my work with her and John in the Salt Wash.

John Foster and Cary Woodruff were both there when I saw this vertebra for the first time. I think we set a new record for a consensus among paleontologists in concluding that this vertebra belongs to Haplocanthosaurus. The super-tall, cathedral-esque laminae arching over the neural canal and the up-tilted transverse processes are absolutely diagnostic, and not present in any other Morrison sauropods. Haplocanthosaurus is one of the rarer sauropods in the Morrison, so it’s nice to have one in our Salt Wash fauna. Not least because of all the other awesome sauropods out there, it’s this weird little duck that my destiny seems to have become intertwingled with (exhibits A, B, C, D, E, and counting).

Speaking of: did you remember that the Western Science Center exhibit on the Snowmass Haplocanthosaurus is still up for a couple more months? Have you seen it? Go see it!

Life restoration of Haplocanthosaurus by Brian Engh, for the Western Science Center exhibit.

So, hey, rock and roll, we have Haplocanthosaurus, and that is legitimately exciting. Between that and Camarasaurus (covered here) we have the primitive-and-unspecialized end of the Morrison sauropods sewn up. Anything bigger or more exotic? Why, yes, in fact. Stay tuned.

This is another “Road to Jurassic Reimagined, Part 2″ post. You know the drill: Part 1 is here, Part 2 will be going up here in the near future, Part 3 will be along sometime after that.

References

Nature’s CT machine

January 28, 2020

Because I’ve worked a lot on the anatomy and evolution of air-filled bones in sauropod dinosaurs, I’ve spent most of my career looking at images like this:

CT sections through a cervical vertebra of an apatosaurine (Apatosaurus or Brontosaurus), OMNH 1094. Wedel (2003b: fig. 6). Scale bar is 10cm.

…and thinking about images like this:

Physical sections through pneumatic vertebrae of Giraffatitan. Janensch (1950: figs. 71-73).

Turns out, that’s pretty good practice for fossil prospecting in the Salt Wash member of the Morrison Formation, where we frequently find things like this:

That’s a bit hard to read, so let’s pull it out from the background:

This is almost certainly a pneumatic vertebra of a sauropod, sectioned more-or-less randomly by the forces of erosion to expose a complicated honeycomb of internal struts and chambers. The chambers are full of sandstone now, but in life they were full of air. I say “almost certainly” because there is small chance that it could belong to a very large theropod, but it looks more sauropod-y to me (for reasons I may expand upon in the comments if anyone is curious).

I’m not 100% certain what section this is. At first I was tempted to read it as a transversely-sectioned dorsal, something like the Allosaurus dorsal shown in this post (link) but from a small, possibly juvenile sauropod. But the semi-radial, spoke-like arrangement of the internal struts going to the round section at the bottom looks very much like the inside of the condyle of a sauropod cervical or cervico-dorsal–compare to fig. 71 from Janensch (1950), shown above. And of course there is no reason to suspect that the plane of this cut is neatly in any of the cardinal anatomical directions. It is most likely an oblique cut that isn’t purely transverse or sagittal or anything else, but some combination of the above. It’s also not alone–there are bits and bobs of bone to the side and above in the same chunk of sandstone, which might be parts of this vertebra or of neighboring bones. Assuming it is a sauropod, my guess is Diplodocus or Brachiosaurus, because it looks even more complex than the sectioned cervicals and dorsals I’ve seen of Haplocanthosaurus, Camarasaurus, or the apatosaurines.

Sometimes we can do a little better. This is one of my favorite finds from the Salt Wash. This boulder, now in two parts, fell down out of a big overhanging sandstone cliff. When the boulder hit, it broke into two halves, and the downhill half rolled over 180 degrees, bringing both cut faces into view in this photo. And there in the boulder is what looks like two vertebrae, but is in fact the neatly separated halves of a single vertebra. I know I refer to erosion and breakage as “Nature’s CT machine”, but this time that’s really on the nose. Let’s take a closer look:

Here’s what I see:

It’s a proportionally long vertebra with a round ball at one end and a hemispherical socket at the other end: a cervical vertebra of a sauropod. Part of the cervical rib is preserved on the upper side, which I suspect is the left side. The parapophysis on the opposite side is angled a bit out of the rock, toward the camera. Parapophyses of sauropod cervicals tend to be angled downward, and if we’re looking at the bottom of this vertebra, then the rib on the upper side is the left. The right cervical rib was cut off when the boulder broke. All we have on this side are the wide parapophysis and the slender strut of the diapophysis aiming out of the rock toward the missing rib, which must still be embedded in the other half of the boulder–and in fact you can see a bit of it peeking out in the counterpart in the wide shot, above.

Can we get a taxonomic ID? I think so, based on the following clues:

  • The cervical ribs are set waaay out to either side of the centrum, by about one centrum diameter. Such wide-set cervical ribs occur in Camarasaurus and the apatosaurines, Apatosaurus and Brontosaurus, but not typically in Diplodocus, Brachiosaurus, or other Morrison sauropods.
  • The cervical rib we can see the most of is pretty slender, like those of Camarasaurus, in contrast to the massive, blocky cervical ribs of the apatosaurines (for example).
  • We can see at least bits of both the left and right cervical ribs in the two slabs–along with a section right through the centrum. So the cervical ribs were set wide from the centrum but not displaced deeply below it, as in Camarasaurus, and again in contrast to the apatosaurines, in which the cervical ribs are typically displaced far below (ventral to) the centrum (see this).
  • This one is a little more loosey-goosey, but the exposed internal structure looks “about right” for Camarasaurus. There is a mix of large and small chambers, but not many small ones, and nothing approaching the coarse, regular honeycomb we’d expect in Apatosaurus, Brontosaurus, or Diplodocus, let alone the fine irregular honeycomb we’d expect in Barosaurus or Brachiosaurus (although I will show you a vert like that in an upcoming post). On the other hand, the internal structure is too complex for Haplocanthosaurus (compare to the top image here).
  • As long as Camarasaurus is on the table, I’ll note that the overall proportions are good for a mid-cervical of Cam as well. That’s not worth much, since vertebral proportions vary along the column and almost every Morrison sauropod has cervicals with this general proportion somewhere in the neck, but it doesn’t hurt.

So the balance of the evidence points toward Camarasaurus. In one character or another, every other known Morrison sauropod is disqualified.

When it’s too dark to hunt for sauropods, you can look at other things.

Now, Camarasaurus is not only the most common sauropod in the Morrison, it’s also the most common dinosaur of any kind in the formation. So this isn’t a mind-blowing discovery. Still, it’s nice to be able to get down to a genus-level ID based on a single vertebra fortuitously sectioned by Mother Nature. In upcoming posts, I’ll show some of the more exciting critters that we’ve been able to ID out of the Salt Wash, ‘we’ here including Brian Engh, John Foster, ReBecca Hunt-Foster, Jessie Atterholt, and Thuat Tran. Brian will also be showing many of these same fossils in the next installment of Jurassic Reimagined. Catch Part 1 here (link), and stay tuned to Brian’s paleoart channel (here) for more in the very near future.

References

 

I had an interesting opportunity when I was in Utah and Colorado a couple of weeks ago. At Dinosaur Journey in Fruita, Colorado, I went looking for a cast of the Potter Creek Brachiosaurus humerus. I found it — more on that another time — and I also found a cast of BYU 4503, the holotype dorsal vertebra of Dystylosaurus (now almost universally regarded as Supersaurus [but then…]), lurking with it in a corner of the collections room.

Dystylosaurus cast, posterior view.

Somehow I had overlooked the Dystylosaurus cast on all of my previous visits to DJ, which is a shame, because the cast is easy to pick up, flip over, and manipulate. Very much unlike the actual fossil, which combines the charming attributes, shared with many other sauropod vertebrae, of weighing hundreds of pounds but still being awfully fragile.

Dystylosaurus cast, anterior view.

So, hey ya, I had a chance to photograph and measure both sides of the vertebra. You’re not supposed to take measurements from casts, but I figured what the heck, no-one was going to lock me up for it, and I could compare the measurements from the cast to the measurements of the real thing when I visited BYU later in the trip. And that’s exactly what I did. It was easy to make sure I took the second set of measurements the same way I had done the first set, because I took them just a few days apart.

The real deal at BYU.

Here’s what I got. For each measurement, the actual value measured from the real fossil at BYU comes first, followed by the same measurement from the cast at Dinosaur Journey, followed by the difference as a percentage of the first (true) measurement.

  • Total Height (as preserved): 1050mm / 1022mm / -2.6%
  • Max Width (as preserved): 905mm / 889mm / -1.8%
  • Anterior Centrum Height: 400mm / 394mm / -1.5%
  • Anterior Centrum Width: 470mm / 454mm / -3.4%
  • Posterior Centrum Height: 365mm / 352mm / -3.5%
  • Posterior Centrum Width: 480mm / 473mm / -1.5%

They’re not the same! On average, the measurements of the cast are 2.4% smaller than the same measurements taken from the actual bone. (Incidentally, you may be wondering how I measured the posterior centrum faces of the BYU vertebra without flipping it. I used a couple of wooden blocks as orthogonators and measured between them, and I did it at several points to make sure they were truly parallel. In essence, I made giant redneck calipers, a method that Mike and I have had to employ many times when measuring huge, weirdly-shaped fossils. Remind me to show you John Foster’s giant caliper setup sometime.)

Dinosaur Journey cast in right lateral view, big doofus for scale.

Anyway, the discrepancy in the measurements should not be surprising. It is a known phenomenon that when an object is molded and cast, there is a little bit of shrinkage. You can see it bedevil Adam Savage in his quest for the ultimate Maltese Falcon replica in this charming video:

So, on one hand, no outright disasters here; all of the cast measurements are within a few percent of the real measurements, so if all you had was a cast, you could get a pretty good sense of the size of the real thing. But precision counts, even among giant sauropods. In a world where the largest vertebra of Argentinosaurus is only 1cm bigger in diameter than the largest vertebra of Patagotitan, differences like I got with Dystylosaurus would be enough to scramble the order of giant vertebrae. So if you’re ever stuck measuring something from a cast, be forthright and say as much, so that no-one mistakes the cast measurements for the real thing.

Here are some more measurements from BYU 4503, the real thing, for you completists. Note that the vertebra is sheared a bit from right postero-ventral to left antero-dorsal, so figuring out how to take the centrum length is not straightforward. I ended up doing it twice, once orthogonal to the posterior centrum face, and once following the slant of the centrum, both at the mid-height of the centrum, as shown in the little diagram from my notebook (above).

  • Centrum Length, left side, orthogonal: 295mm
  • Centrum Length, left side, on the slant: 310mm
  • Centrum Length, right side, orthogonal: 280mm
  • Centrum Length, right side, on the slant: 305mm
  • Max Width across prezygs: 305mm
  • Min gap between prezygs: 19mm
  • Max Width across parapophyses: 620mm
  • Max antero-posterior length of prezyg articular surfaces: 55mm
  • Max antero-posterior depth of hypantrum: 95mm
  • Max antero-posterior depth of fossa between spino-prezyg laminae (SPRLs): 80mm
  • Neural spine cavity, max antero-posterior extent: 40mm
  • Neural spine cavity, max medio-lateral extent: 70mm

Finally, a huge thanks to Julia McHugh at Dinosaur Journey and Brooks Britt and Rod Scheetz at BYU for letting me come play with their huge toys er, hugely important scientific specimens. Rod was particularly helpful, shifting giant things about with a forklift, helping me measure bones that are longer than I am tall, and boxing up loan specimens for me. Mike and I have had really good luck with pro-science curators and collections managers, but the folks at DJ and BYU have always been standouts, and I can’t thank them enough.

Back into the Corner of Shame, artificially tiny Dystylosaurus!

This awesome photo was taken in the SVPCA 2019 exhibit area by Dean Lomax (L). On the right, Jessie Atterholt, me, and Mike are checking out some Isle of Wight rebbachisaurid vertebrae prepped by Mick Green, who is juuuust visible behind Dean. Jessie’s holding a biggish (as rebbachisaurids go) dorsal or caudal centrum and partial arch, me a lovely little cervical, and Mike an astonishingly delicate and beautiful dorsal. You can see behind us more tables full of awesome fossils, and there were more still across the way, behind Dean and Mick. I was going to throw this photo into the last post to illustrate the exhibit area, but by the time the caption had hit three lines long, I realized it needed a post of its own.

Photo courtesy of Dean, and used with permission. Mark your calendars: on Sunday, Oct. 13, Dean will be speaking at TEDx Doncaster, with a talk titled, “My unorthodox path to success: how my passion for the past shaped my future”. You can follow the rest of Dean’s gradual conquest of the paleosphere through his website, http://www.deanrlomax.co.uk/.

My talk (Taylor and Wedel 2019) from this year’s SVPCA is up!

The talks were not recorded live (at least, if they were, it’s a closely guarded secret). But while it was fresh in my mind, I did a screencast of my own, and posted it on YouTube (CC By). I had to learn how to do this for my 1PVC presentation on vertebral orientation, and it’s surprisingly straightforward on a Mac, so I’ve struck while the iron is hot.

For the conference, I spoke very quickly and omitted some details to squeeze the talk into a 20-minute slot. In this version, I go a bit slower and make some effort to ensure it’s intelligible to an intelligent layman. That’s why it runs closer to half an hour. I hope you’ll find it worth your time.

References

We’re just back from an excellent SVPCA on the Isle of Wight. We’ll write more about it, but this time I just want to draw attention to a neat find. During a bit of down time, Matt and Vicki were wandering around West Cowes (the town where the scientific sessions were held), when they stumbled across a place called That Shop. Intrigued by all the Lego figures in the window, they went in, and Matt found a small section of fossils. Including … an Iguanodon pelvis, supposedly certified as such by the Dinosaur Isle museum.

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Here it is: I imagine that whoever classified it read this elongate concave surface as part of the acetabulum. Matt’s hypothesis is that they mistook it for a sacral vertebra and that became “pelvis” via over-simplification.

It’s about 18 cm in a straight line across the widest part, or 20 cm around the curve.

Here is an actual documentary record of Matt’s moment of discovery:

Yep, you got it! It’s a sauropod vertebra! (Matt would never have spent good money on a stinkin’ appendicular element of a stinkin’ ornithopod.)

Specifically, it’s the bottom half of the front part of the centrum of a dorsal vertebra:

Eucamerotus” dorsal vertebra NHMUK PV R88 in right lateral and anterior views. Non-faded portions show the location of the Wedel Specimen. Modified from Hulke (1880: plate IV).

In these photos, we’re looking down into it more or less directly dorsal view, with anterior to the left. Click through the photos, and — once you know what you’re looking at — you can clearly see the pneumatic spaces: nice patches of finished bone lining the camellae, with trabecular bone in between.

Clearly there’s nowhere near enough of this to say what it is with any certainty. But our best guess is that it seems compatible with a titanosauriform identity, quite possibly in same space as the various Wealden sauropod dorsals that have been assigned to Ornithopsis or Eucamerotus.

References

  • Hulke, J. W.  1880.  Supplementary Note on the Vertebræ of Ornithopsis, Seeley, = Eucamerotous, Hulke. Quarterly Journal of the Geological Society 36:31–35.  doi:10.1144/GSL.JGS.1880.036.01-04.06