Update

This is an actual page from the late, lamented Weekly World News, from December 14, 1999. I always thought it was pretty darned funny that they had the alien remains discovered in the “belly” of an animal known only from neck vertebrae. Now, subjecting a tabloid story to technical scrutiny really is like dancing about architecture, but…it just tickles me. As does the entire story. I haven’t been able to get hold of Dr. Posvby to confirm his findings, but it’s been over a decade and he still hasn’t published, so I’m not holding my breath.

Incidentally, the WWN archives are available on Google Books: go here to read about Bat Boy siring a 3-headed alien Elvis baby on a female Sasquatch. Or something to that effect.

In an email, Vladimir Socha drew my attention to the fact that Tom Holtz’s dinosaur encyclopaedia estimates the maximum height of Sauroposeidon as 20 meters plus, and asked whether that was really possible.  Here’s what Tom actually wrote: “Sauroposeidon was one of the largest of all dinosaurs.  At perhaps 98 to 107 feet (30 to 32.5 meters) long and weighing 70 to 80 tons […] Sauroposeidon would have been the tallest of all dinosaurs. […] If it could crane its neck up, it might have been able to hold its head 66 to 69 feet (20 to 21 meters) high or more” (Holtz and Rey 2007:207).  Vladimir was understandably skeptical.  But can it be true?

Wedel and Cifelli (2005: fig. 15) shows Matt’s best skeletal reconstruction of Sauroposeidon, with Boring Old Brachiosaurus and a human for scale:

Sauroposeidon with Boring Old Brachiosaurus and human for scale and 20 m height indicated. Lightly modified from Wedel and Cifelli (2005: fig. 15)

Sauroposeidon with Boring Old Brachiosaurus and human for scale and 20 m height indicated. Lightly modified from Wedel and Cifelli (2005: fig. 15)

Amazingly, those dummies didn’t include an actual scalebar; but apparently the human figure is 1.8 m tall, so by measuring pixels and cross-scaling, I determined that in this image, Sauroposeidon is a mere 13.43 m tall.  I took the liberty of adding in a marker for the 20 m height proposed by Holtz, and as things stand you’d have to say that it doesn’t look probable.

But let’s see what we can do.  We’ll begin with the classic brachiosaur skeleton of Paul (1988), which shows the well represented species Brachioaurus brancai:

Brachiosaurus brancai skeletal reconstruction in left lateral view. From Paul (1988:fig. 1)

Brachiosaurus brancai skeletal reconstruction in left lateral view. From Paul (1988:fig. 1)

(Some other time, we should take a moment to discuss the differences between this and the Wedel brachiosaur reconstruction; but it will not be this day.)

This reconstruction is in a nice erect-necked posture which, in light of our own recent paper, is probably not too extreme.  Since all the neural arches and processes are missing from the only known posterior cervicals of this species, we don’t know how much flexibility they allowed, and so in light of how the rest of the animal is built (high shoulders and all) it seems reasonable to allow a lot of extension at the base of the neck.  So let’s assume that the pose offered by Paul is correct.  By measuring my scan of that figure, and I see that the 2.13 m humerus is 306 pixels long.  The entire reconstruction, from tip of cranial crest down to forefoot, is 1999 pixels tall, which is 1999/306 = 6.53 times as long as the humerus, which scales to 6.53*2.13 = 13.91 m — a little taller than Sauroposeidon (not Brachiosaurus) in Matt’s reconstruction, which seems about right if we imgine Matt’s Brachiosaurus raising its neck into a Paul-compliant posture.

Now Paul’s reconstruction is based on the Berlin mounted skeleton HMN S II.  Cervical 8 is very well preserved in that animal, and has a centrum length of 98 cm (Janensch 1950a:44).  By contrast, the centrum of C8 of Sauroposeidon OMNH 53062 (the only known specimen) is 125 cm long (Wedel et al. 2000a: 110). So if Sauroposeidon is merely an elongated Brachiosaurus brancai, then it’s 125/98 = 1.28 times as long and tall, which would be 17.74 m.

But wait: it seems that Sauroposeidon is to Brachiosaurus brancai as Barosaurus is to Diplodocus — similar overall but more elongate.  And it turns out that Barosaurus has at least 16, maybe 17 cervicals (McIntosh 2005:45) compared with Diplodocus‘s 15.  So maybe Sauroposeidon also added cervicals from the brachiosaur base-state — in fact, that would hardly be surprising given that Brachiosaurus brancai has so few cervicals for a long-neck: 13, compared with 15 in most diplodocids, 16 or 17 in Barosaurus, and 19 in Mamenchisaurus.  If you reconstruct Sauroposeidon with two more C8-like cervicals in the middle of the neck, that adds 2*125 = 250 cm, which would give us a total height of 17.74+2.5 = 20.24 m.

So I don’t think Tom Holtz’s estimate is completely unrealistic, even for the one Sauroposeidon specimen we have now — and remember that the chances of that individual being the biggest that species got are vanishingly small.

On the other hand, maybe Sauropodseidon‘s neck was the only part of it that was elongated in comparison to Brachiosaurus brancai — maybe its forelimbs were no longer than those of its cousin, so that only the neck elongation contributed to greater height.  And maybe it had no additional cervicals, so its neck was “only” 1.28 times as long as that of Brachiosaurus brancai — 1.28*8.5 = 10.88 m, which is 2.38 m longer; so the total height would be 13.91+2.38 = 16.29 m (assuming the additional neck length was vertical).  And maybe the neck couldn’t get very close to vertical, so that the true height was lower still.

All of this just goes to show the perils of reconstructing an animal based only on a sequence of four cervicals.  (Reconstructing on the basis of a single partial mid-to-posterior dorsal, on the other hand, is a much more exact science.)

Finally: Matt’s reconstruction of Sauroposeidon is really rather conservative, and looks very much like a scaled-up vanilla brachiosaur.  Just to see how it looks, I’ve made a reconstruction of the putative (and very possible) elongated, attenuated version of Sauroposeidon, showing the legs and cervicals 28% longer than in B. brancai, and with two additional cervicals.  I made this by subjecting Greg Paul’s 1988 brachiosaur to all sorts of horrible and half-arsed distortions, so apologies to Greg.  But remember, folks: this is just as likely correct as Matt’s version!

A different view of Sauroposeidon, based on elongation of the cervicals and legs of Brachiosaurus brancai and the insertion of two additional cervicals. Heavily and carelessly modified from Paul (1988: fig. 1)

A different view of Sauroposeidon, based on elongation of the cervicals and legs of Brachiosaurus brancai and the insertion of two additional cervicals. Heavily and carelessly modified from Paul (1988: fig. 1)

References

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Internal structure of a cervical vertebra of Sauroposeidon, OMNH 53062. A, parts of two vertebrae from the middle of the neck. The field crew that dug up the bones cut though one of them to divide the specimen into manageable pieces. B, cross section of C6 at the level of the break, traced from a CT image and photographs of the broken end. The left side of the specimen was facing up in the field and the bone on that side is badly weathered. Over most of the broken surface the internal structure is covered by plaster or too damaged to trace, but it is cleanly exposed on the upper right side (outlined). C, the internal structure of that part of the vertebra, traced from a photograph. The arrows indicate the thickness of the bone at several points, as measured with a pair of digital calipers. The camellae are filled with sandstone.

Image and caption recycled from fig. 14 here. Hat tip to Mike from Ottawa for the wonderful title.

Addendum (from Mike)

What Matt’s failed to mention is that this section of prezygapophyseal ramus is one of the elements for which he calculated the Air-Space Proportion (ASP) in his chapter in “The Sauropods”. As shown in his table 7.2, this calculation yielded 0.89.  Just think about that for a moment.  89% of the bone was air.  Yikes.

It’s interesting that this was the only prezygpapophyseal ramus in the survey, and that it had a way higher value that any of the other elements considered, which topped out at 0.77, i.e., more than twice as much bone as this specimen.  So maybe all prezyg rami are ridiculously pneumatic? So far (as far as I know) no-one’s measured the ASP of another ramus, so the answer remains, for now, ridiculously unknown to our planet.

Special bonus weirdness

Basal sauropodomorph wizard Adam Yates has posted an entry on his blog showing more sauropod vertebrae/ceratopsian frill convergence, as follow-up to our own recent post. Too weird.

Since my last post was rather heavier on the sushi than on the sauropod vertebrae, I offer this special bonus post. One of the frustrating things about the otherwise marvelous Sauroposeidon monograph (Wedel et al. 2000b) is that the figures are so small. Sadly this is also true of all the other publications that illustrate its remains, and so the published literature has no nice, detailed images.

No longer!  I’ve scored a rare paper copy of Matt’s undergraduate thesis (Wedel 1997) which contained basically all the material that eventually became that monograph, and which in addition has much larger versions of the figures.  So without further ado, I give you figure 5 of that paper:

Sauroposeidon cervical vertebrae. A, C5-C8; B, C6

Part A is similar to Wedel et al. (2000b:fig 6), and part B to Wedel et al. (2000b:fig. 7A), but this older version is rather nicer, and from a waaay better scan than is available for Wedel et al. (2000b).

And that’s all I have to say about that.

References.

This figure is stolen from Wedel et al. (2000:fig. 5). A shows the first 11 cervical vertebrae* of Sauroposeidon in articulation. B shows how the holotype specimen, OMNH 53062, must have disarticulated, and C shows it as it was found. Shaded vertebrae and bits of vertebrae were not found. The thickness of the cervical ribs is greatly exaggerated for clarity.

*We assume that Sauroposeidon had 13 cervicals like Brachiosaurus. It is not beyond the bounds of possibility that it had more, but it is unlikely that it had fewer. Sauroposeidon seems to be all about crazy neck elongation, and it doesn’t make sense to make some vertebrae longer while losing others.

Some facts:

  • In life, the long cervical ribs formed overlapping bundles, just like the long neck tendons of birds, and that is how the preserved cervical ribs are arrayed–in vertically stacked bundles.
  • Each cervical rib is about 4 cm in diameter where it attaches to its vertebra, and tapers to a point about 3 meters away. The last meter or so of each rib goes from being the diameter of a pencil to the diameter of a mechanical pencil lead. They just sort of peter out into nothingness.
  • The fact that even the pencil-lead-sized wisps of the cervical ribs are still in articulation suggests pretty strongly that the neck was buried with the muscles intact.
  • If the neck had simply been broken transversely (like a guillotine cut), the two most anterior vertebrae in the preserved block of four should have the cervical ribs of even more anterior vertebrae beneath them, and the cervical ribs from the two most posterior vertebrae would not stick out the back of the preserved block.
  • The facts that the cervical ribs from the missing anterior vertebrae are also missing, and that the cervical ribs from the preserved vertebrae trail behind the articulated block, suggest that the neck was pulled apart lengthwise, as shown in B.
  • None of the vertebrae have any teeth marks or any sign of mechanical damage, other than the missing neural spine from the third preserved vertebra. The front third of the first preserved vertebra was eroded away before the vertebrae were discovered in the field.
  • Assuming that Sauroposeidon was built like Brachiosaurus, it must have had a body mass somewhere between 40 and 60 tons. Even if it was built more like Mamenchisaurushellacious neck tacked on fairly dinky body–it was still probably a 20-ton critter.
  • After 14 years of subsequent erosion and fieldwork, no other sauropod bones have been discovered at the site.

Some questions:

  • How did the neck get separated from the body? The body was presumably too big to move, and the neck is too well preserved to have been moved very far.
  • What pulled the neck apart?
  • How did the neck come apart without disturbing those little pencil-lead cervical rib ends?

I don’t know the answers to those questions, by the way. And I’m open to suggestions.

Here’s my best guess. I think the body stayed put, and the neck floated away. Not far–a few hundred feet would be enough to put the body outside the outcrop area at the holotype site, but not so far that the neck would be all beat up. I think it floated rather than being dragged (by an Acrocanthosaurus, for example) because the vertebrae are all in such good shape and none of them have any tooth marks. I think it floated in calm water because the preservation is so good. I think the neck muscles rotted enough to let the force of the current rip part of the neck away from the base, just like you can pull a cooked chicken neck apart lengthwise without messing up the articulations among the vertebrae in the chunk that breaks free.

All of that will suffice to get the neck separated from the body. What really bugs me is the separation of the anterior part of the neck from the preserved block of vertebrae. It is tempting to think that the anterior part never came off, and that those vertebrae simply eroded away before they were found, like the front third of the most anterior preserved vert. But that can’t be; if those vertebrae were in articulation and just eroded away, we should still have their cervical ribs below the first two preserved verts.

Who knows, maybe the scenario I outlined above is good enough to explain both breaks. For some reason it is just easier to image most of the neck coming off the carcass than to imagine one part of the neck coming off the other part of the neck. But maybe the anteriormost vertebrae were ripped off and floated away first, and then the preserved block came free and floated off on its own later. (The head probably exploded, as these things were wont to do.)

It is worth noting that there are probably only a handful of people alive who have any first-hand experience with how multi-ton animal carcasses are dispersed, and zero people alive who have ever seen a dead sauropod rot. So, like too much in paleontology, what seems plausible or reasonable to me may not line up with objective reality.

BTW, this post fulfills a promise I made in a comment thread here. If we promise a post, we deliver. (We just don’t specify a due date.)

Comments, suggestions, hypotheses, rants, and crank fringe theories welcome.

References:

Here’s a pretty cool image: Plate 7 from Lull (1919), showing the partial skeleton of Barosaurus YPM 429 (above), compared to the much more complete skeleton of Diplodocus CM84/94 (below).

I’ve been pretty familiar with that Barosaurus skeleton diagram since I was about 9 years old, because it’s in Donald Glut’s New Dinosaur Dictionary, which I’ve written about here before. In particular, I like that Lull was scrupulous about drawing in the lateral pneumatic cavities in the caudal vertebrae. It’s pretty common in Diplodocus for the tail to be pneumatized out to somewhere between caudal 15 and 19, and the same is true in Barosaurus. I’m not just relying on the figure–Lull was also good about saying explicitly what was going on with the pneumatization in the centrum of each vertebra.

I returned to this image as an adult doing research on sauropod pneumaticity, and I read big swaths of Lull (1919), but never the bit about the sacrum. Why would I? The sacrum of YPM 429 is pretty scrappy, and I was mostly interested in the big honkin’ cervicals, and in learning how to distinguish bones of Barosaurus and Diplodocus. I always assumed that the sacrum of Barosaurus was pneumatized right the way through.

Only, er, it ain’t. As I just discovered.

Lull (1919: p. 22):

See that second sentence? “The central fragment is extremely massive, with no adaptation for lightening the weight appreciable in the portion preserved.” That’s old-timey talk for, “the chunk of centrum has no pneumatic openings or cavities”. Which is kind of a big deal, because:

…a gap of one or more apneumatic vertebrae with pneumatic vertebrae on either side constitutes a pneumatic hiatus. Why that’s a big deal is explained in this post.

If I had read this in the early 2000s, I would have flipped out. I did flip out when I discovered what seemed to be a pneumatic hiatus at the base of the tail in Haplocanthosaurus. Just that possibility sent me scurrying off to the Carnegie Museum to investigate, and precipitated both a dissertation chapter, later published as Wedel (2009), and an enduring fascination with Haplocanthosaurus. If I’d been reading Lull instead of Hatcher, my air sac paper would have been about Barosaurus, probably, and I wouldn’t have known enough about Haplo to get interested in the other specimens, which would have been a real shame.

A pneumatic hiatus in Barosaurus would have been big news in 2009. In 2021, it’s still nice, but not groundbreaking. The groundbreaking pneumatic hiatuses in Barosaurus were described in two different juvenile skeletons by Melstrom et al. (2016) and Hanik et al. (2017). Those were both mid-thoracic hiatuses, which probably separated the pneumatization domains of the cervical air sacs anteriorly and the abdominal air sacs posteriorly. A mid-sacral hiatus in YPM 429 is probably within the domain of the abdominal air sac, just like the hiatus in sacral 5 of CM 879 that I described in my 2009 paper. It’s still exciting, in that it shows that there were abdominal air sacs, and they were separate from the lungs and cervical air sacs, but this example in YPM 429 is now third in line in terms of priority, just within this one genus. Which is why I’m telling the world with a blog post, instead of hopping on a plane (or, er, planning a very long road trip) to New Haven. I’ll check on YPM 429 the next time I’m out there, but the specifics will keep for now.

References

  • Hanik, Gina M., Matthew C. Lamanna and John A. Whitlock. 2017. A juvenile specimen of Barosaurus Marsh, 1890 (Sauropoda: Diplodocidae) from the Upper Jurassic Morrison Formation of Dinosaur National Monument, Utah, USA. Annals of Carnegie Museum 84(3):253–263.
  • Lull, R.S. 1919. The sauropod dinosaur Barosaurus Marsh. Memoirs of the Connecticut Academy of Arts and Sciences 6:1-42.
  • Melstrom, Keegan M., Michael D. D’Emic, Daniel Chure and Jeffrey A. Wilson. 2016. A juvenile sauropod dinosaur from the Late Jurassic of Utah, USA, presents further evidence of an avian style air-sac system. Journal of Vertebrate Paleontology 36(4):e1111898. doi:10.1080/02724634.2016.1111898
  • Wedel, M.J. 2009. Evidence for bird-like air sacs in saurischian dinosaurs. Journal of Experimental Zoology 311A:611-628.

A. Recovered skeletal elements of Haplocanthosaurus specimen MWC 8028. B. Caudal vertebra 3 in right lateral view. C. The same vertebra in posterior view. Lines show the location of sections for D and E. D. Midsagittal CT slice. The arrow indicates the ventral expansion of the neural canal into the centrum. E. Horizontal CT slice at the level of the neural arch pedicles, with anterior toward the top. Arrows indicate the lateral expansions of the neural canal into the pedicles. B-E are shown at the same scale. Wedel et al. (2021: fig. 1).

New paper out today:

Wedel, Mathew; Atterholt, Jessie; Dooley, Jr., Alton C.; Farooq, Saad; Macalino, Jeff; Nalley, Thierra K.; Wisser, Gary; and Yasmer, John. 2021. Expanded neural canals in the caudal vertebrae of a specimen of Haplocanthosaurus. Academia Letters, Article 911, 10pp. DOI: 10.20935/AL911 (link)

The paper is new, but the findings aren’t, particularly. They’re essentially identical to what we reported in our 1st Paleo Virtual Conference slide deck and preprint, and in the “Tiny Titan” exhibit at the Western Science Center, just finally out in a peer-reviewed journal, with better figures. The paper is open access and free to the world, and it’s short, about 1600 words, so this recap will be short, too.

A. Photograph of a 3D-printed model of the first three caudal vertebrae of Haplocanthosaurus specimen MWC 8028, including endocasts of the neural canal (yellow) and intervertebral joints (blue), in right lateral view, and with the neural canal horizontal. B. Diagram of the same vertebrae in midsagittal section, emphasizing the volumes of the neural canal (yellow) and intervertebral joint spaces (blue). Anterior is to the right. Wedel et al. (2021: fig. 2).

John Foster and I described Museum of Western Colorado (MWC) specimen 8028, a partial skeleton of Haplocanthosaurus from Snowmass, Colorado, in late 2014. One weird thing about that specimen (although not the only weird thing) is that the neural canals of the tail vertebrae are bizarrely expanded. In most vertebrae of most critters, the neural canal is a cylindrical tunnel, but in these vertebrae the neural canals are more like spherical vacuities.

John and I didn’t know what to make of that back in 2014. But a few years later I started working with Jessie Atterholt on bird anatomy, which led me to do a little project on the whole freaking zoo of weird stuff that birds and other dinosaurs do with their neural canals, which led to the 1PVC presentation, which led to this. 

Caudal vertebra 3 of Haplocanthosaurus specimen MWC 8028 in left posterolateral (A), posterior (B), and right posterolateral (C) views, with close-ups (D and E). In A and B, a paintbrush is inserted into one of the lateral recesses, showing that the neural canal is wider internally than at either end. Wedel et al. (2021: fig. 3).

Of course there will be more posts and more yapping, as signaled by the ‘Part 1’ in the post title. Although I am extremely satisfied with the streamlined, 1600-word missile of information and reasoning that just dropped, there are parts that I want to unpack, that haven’t been unpacked before. But the paper launched at midnight-thirty, Pacific Daylight Time, I’m up way too late finishing this first post, and I reckon the rest will keep for a few hours at least.

Anatomical features of the neural canal in birds and other dinosaurs. A. MWC 9698, a mid caudal vertebra of Apatosaurus in posterodorsal view. Arrows highlight probable vascular foramina in the ventral floor of the neural canal. B. LACM 97479, a dorsal vertebra of Rhea americana in left anterolateral view. Arrows highlight pneumatic foramina inside the neural canal. C. A hemisected partial synsacrum of a chicken, Gallus domesticus, obtained from a grocery store. Anterior is to the right. The bracket shows the extent of the dorsal recess for the glycogen body, which only spans four vertebrae. Arrows highlight the transverse grooves in the roof of the neural canal for the lumbosacral organ. D. Sagittal (left) and transverse (right) CT slices through the sacrum of a juvenile ostrich, Struthio camelus. The bracket shows the extent of the lumbosacral expansion of the spinal cord. Indentations in the roof of the neural canal house the lumbosacral organ. In contrast to the chicken, the ostrich has a small glycogen body that does not leave a distinct osteological trace. Yellow arrows show the longitudinal troughs in the ventral floor of the neural canal that house the ventral eminences of the spinal cord. Wedel et al. (2021: fig. 4).

I have a ton of people to thank. John Foster, obviously, for initiating the line of research that led here. Julia McHugh for access to the MWC collections, and for being an excellent sounding board regarding the Morrison Formation, sauropod dinosaurs, and crafting ambitious but tractable research projects. Anne Weil for helping me be methodical in thinking through the logic of the paper, and Mike Taylor for helping me get it polished. Niels Bonde, Steven Jasinski, and David Martill for constructive reviews, which were published alongside the paper. We couldn’t take all of their suggestions because of space limitations, but figures 3 and 4 were born because they asked for them, and that’s not a small thing. Vicki and London Wedel for putting up with me at various points in this project, especially in the last few days as I’ve been going bonkers correcting page proofs. And finally, because I’m the one writing this blog post, my coauthors: Jessie Atterholt, Alton Dooley, Saad Farooq, Jeff Macalino, Thierra Nalley, Gary Wisser, and John Yasmer, for their contributions and for their patience during the unusually long gestation of this very short paper.

More to say about all that in the future. For now, yay, new paper. Have fun with it. Here’s the link again.

References

Back in 2017, I showed the world 83.33% of my collection of sauropod-themed mugs. Time passes, and I have lost some of them and gained some more. The tally now stands at eight, and here they are:

My missing Brontomerus mug never did turn up. In the mean time, I have also lost or maybe broken the Sauroposeidon mug, the old black-and-white Archbishop mug, and the single-view Xenoposeidon mug. The dissertation mug still survives, but has faded into total illegibility, so I don’t count it any more.

On the more positive side, the sexual selection mug — second from the right in the old photo, and bottom left in the new one — survives, in fact the only one to have done so. All the others are new acquisitions. Let’s take a look:

Back row, left to right:

  1. The new, improved Archbishop dorsals A and B mug. Unlike the original, this is in glorious colour, and rearranges the elements to show anterior view on the front, and left and right lateral on the sides.
  2. The new, improved Xenoposeidon mug. It’s laid out the same way with the anterior view on the front and left and right lateral views on the sides.
  3. One that Fiona made for my birthday, showing one of the publicity photos from the original Xenoposeidon description: the one of which a newspaper columnist wrote “I wish my husband looked at me the way he looks at this bone”.
  4. A mug made by Mark Witton, which I saw at TetZooCon 2019 and made him an offer for. It shows his own Diplodocus artwork, an update of an earlier piece that he did for Matt, Darren and me to publicise our 2009 paper on sauropod neck posture. (Details here.)

Front row, left to right:

  1. The sole survivor, showing the introductory here’s-what-sauropod-necks-are-like illustration from our 2011 paper on why those necks were not sexually selected.
  2. The sauropod neck gallery used as Figure 3 in my and Matt’s 2013 PeerJ paper “why giraffes have short necks”.
  3. One of the world’s few caudal pneumaticity mugs, using all the illustrations from Matt’s and my 2013 paper, and inspired by the freakily consistent colour palette of those illustrations.
  4. This one needs a bit of explaining. See below.

For reasons that no-one — least of all he — understands, my youngest son bought a pair of Dawn French mugs as a birthday or Christmas present for Fiona. (No-one in our family is particularly a fan, it was one of those random things.) Since then, he has given her five or six more identical mugs.

Because I do not like these, I insist that they hang on one mug tree, and the sauropod mugs on another. It was to break down this mug apartheid that our eldest made for us this final mug, which shows both Dawn French and a reconstruction of the Xenoposeidon vertebra (from my 2018 paper). Where does it live? Usually, it sits on the shelf between the two mug trees.

So this is how things stand. (I drink a lot of tea, so these mugs all see plenty of action.) I really should make myself a new Brontomerus mug, and perhaps a pneumatic variation one.

 

FIGURE 7.1. Pneumatic features in dorsal vertebrae of Barapasaurus (A–D), Camarasaurus (E–G), Diplodocus (H–J), and Saltasaurus (K–N). Anterior is to the left; different elements are not to scale. A, A posterior dorsal vertebra of Barapasaurus. The opening of the neural cavity is under the transverse process. B, A midsagittal section through a middorsal vertebra of Barapasaurus showing the neural cavity above the neural canal. C, A transverse section through the posterior dorsal shown in A (position 1). In this vertebra, the neural cavities on either side are separated by a narrow median septum and do not communicate with the neural canal. The centrum bears large, shallow fossae. D, A transverse section through the middorsal shown in B. The neural cavity opens to either side beneath the transverse processes. No bony structures separate the neural cavity from the neural canal. The fossae on the centrum are smaller and deeper than in the previous example. (A–D redrawn from Jain et al. 1979:pl. 101, 102.) E, An anterior dorsal vertebra of Camarasaurus. F, A transverse section through the centrum (E, position 1) showing the large camerae that occupy most of the volume of the centrum. G, a horizontal section (E, position 2). (E–G redrawn from Ostrom and McIntosh 1966:pl. 24.) H, A posterior dorsal vertebra of Diplodocus. (Modified from Gilmore 1932:fig. 2.) I, Transverse sections through the neural spines of other Diplodocus dorsals (similar to H, position 1). The neural spine has no body or central corpus of bone for most of its length. Instead it is composed of intersecting bony laminae. This form of construction is typical for the presacral neural spines of most sauropods outside the clade Somphospondyli. (Modified from Osborn 1899:fig. 4.) J, A horizontal section through a generalized Diplodocus dorsal (similar to H, position 2). This diagram is based on several broken elements and is not intended to represent a specific specimen. The large camerae in the midcentrum connect to several smaller chambers at either end. K, A transverse section through the top of the neural spine of an anterior dorsal vertebra of Saltasaurus (L, position 1). Compare the internal pneumatic chambers in the neural spine of Saltasaurus with the external fossae in the neural spine of Diplodocus shown in J. L, An anterior dorsal vertebra of Saltasaurus. M, A transverse section through the centrum (L, position 2). N, A horizontal section (L, position 3). In most members of the clade Somphospondyli the neural spines and centra are filled with small camellae. (K–N modified from Powell 1992:fig. 16.) [Figure from Wedel 2005.]

Here’s figure 1 from my 2005 book chapter. I tried to cram as much pneumatic sauropod vertebra morphology into one figure as I could. All of the diagrams are traced from pre-existing published images except the horizontal section of the Diplodocus dorsal in J, which is a sort of generalized cross-section that I based on broken centra of camerate vertebrae from several taxa (like the ones shown in this post). One thing that strikes me about this figure, and about most of the CT and other cross-sections that I’ve published or used over the years (example), is that they’re more or less bilaterally symmetrical. 

We’ve talked about asymmetrical vertebrae before, actually going back to the very first post in Xenoposeidon week, when this blog was only a month and a half old. But not as much as I thought. Given how much space asymmetry takes up in my brain, it’s actually weird how little we’ve discussed it.

The fourth sacral centrum of Haplocanthosaurus CM 879, in left and right lateral view (on the left and right, respectively). Note the distinct fossa under the sacral rib attachment on the right, which is absent on the left.

Also, virtually all of our previous coverage of asymmetry has focused on external pneumatic features, like the asymmetric fossae in this sacral of Haplocanthosaurus (featured here), in the tails of Giraffatitan and Apatosaurus (from Wedel and Taylor 2013b), and in the ever-popular holotype of Xenoposeidon. This is true not just on the blog but also in our most recent paper (Taylor and Wedel 2021), which grew out of this post.

Given that cross-sectional asymmetry has barely gotten a look in before now, here are three specimens that show it, presented in ascending levels of weirdness.

First up, a dorsal centrum of Haplocanthosaurus, CM 572. This tracing appeared in Text-fig 8 in my solo prosauropod paper (Wedel 2007), and the CT scout it was traced from is in Fig 6 in my saurischian air-sac paper (Wedel 2009). The section shown here is about 13cm tall dorsoventrally. The pneumatic fossa on the left is comparatively small, shallow, and lacks very distinct overhanging lips of bone. The fossa on the right is about twice as big, it has a more distinct bar of bone forming a ventral lip, and it is separated from the neural canal by a much thinner plate of bone. The fossa on the left is more similar to the condition in dorsal vertebrae of Barapasaurus or juvenile Apatosaurus, where as the one on the right shows a somewhat more extensive and derived degree of pneumatization. The median septum isn’t quite on the midline of the centrum, but it’s pretty stout, which seems to be a consistent feature in presacral vertebrae of Haplocanthosaurus.

 

Getting weirder. Here’s a section through the mid-centrum of C6 of CM 555, which is probably Brontosaurus parvus. That specific vert has gotten a lot of SV-POW! love over the years: it appears in several posts (like this one, this one, and this one), and in Fig 19 in our neural spine bifurcation paper (Wedel and Taylor 2013a). The section shown here is about 10cm tall, dorsoventrally. In cross-section, it has the classic I-beam configuration for camerate sauropod vertebrae, only the median septum is doing something odd — rather than attaching the midline of the bony floor of the centrum, it’s angled over to the side, to attach to what would normally be the ventral lip of the camera. I suspect that it got this way because the diverticulum on the right either got to the vertebra a little ahead of the one on the left, or just pneumatized the bone faster, because the median septum isn’t just bent, even the vertical bit is displaced to the left of the midline. I also suspect that this condition was able to be maintained because the median septa weren’t that mechanically important in a lot of these vertebrae. We use “I-beam” as a convenient shorthand to describe the shape, but in a metal I-beam the upright is as thick or thicker than the cross bits. In contrast, camerate centra of sauropod vertebrae could be more accurately described as a cylinders or boxes of bone with some holes in the sides. I think the extremely thin median septum is just a sort of developmental leftover from the process of pneumatization.

EDIT 3 days later: John Whitlock reminded me in the comments of Zurriaguz and Alvarez (2014), who looked at asymmetry in the lateral pneumatic foramina in cervical and dorsal vertebrae of titanosaurs, and found that consistent asymmetry along the cervical column was not unusual. They also explicitly hypothesized that the asymmetry was caused by diverticula on one side reaching the vertebrae earlier than diverticula on other other side. I believe they were the first to advance that idea in print (although I should probably take my own advice and scour the historical literature for any earlier instances), and needless to say, I think they’re absolutely correct.

Both of the previous images were traced from CTs, but the next one is traced from a photo of a specimen, OMNH 1882, that was broken transversely through the posterior centrum. To be honest, I’m not entirely certain what critter this vertebra is from. It is too long and the internal structure is too complex for it to be Camarasaurus. I think an apatosaurine identity is unlikely, too, given the proportional length of the surviving chunk of centrum, and the internal structure, which looks very different from CM 555 or any other apatosaur I’ve peered inside. Diplodocus and Brachiosaurus are also known from the Morrison quarries at Black Mesa, in the Oklahoma panhandle, which is where this specimen is from. Of those two, the swoopy ventral margin of the posterior centrum looks more Diplodocus-y than Brachiosaurus-y to me, and the specimen lacks the thick slab of bone that forms the ventral centrum in presacrals of Brachiosaurus and Giraffatitan (see Schwarz and Fritsch 2006: fig. 4, and this post). So on balance I think probably Diplodocus, but I could easily be wrong.

Incidentally, the photo is from 2003, before I knew much about how to properly photograph specimens. I really need to have another look at this specimen, for a lot of reasons.

Whatever taxon the vertebra is from, the internal structure is a wild scene. The median septum is off midline and bent, this time at the top rather than the bottom, the thick ventral rim of the lateral pneumatic foramen is hollow on the right but not on the left, and there are wacky chambers around the neural canal and one in the ventral floor of the centrum. 

I should point out that no-one has ever CT-scanned this specimen, and single slices can be misleading. Maybe the ventral rim of the lateral foramen is hollow just a little anterior or posterior to this slice. Possibly the median septum is more normally configured elsewhere in the centrum. But at least at the break point, this thing is crazy. 

What’s it all mean? Maybe the asymmetry isn’t noise, maybe it’s signal. We know that when bone and pneumatic epithelium get to play together, they tend to make weird stuff. Sometimes that weirdness gets constrained by functional demands, other times not so much. I think it’s very seductive to imagine sauropod vertebrae as these mechanically-optimized, perfect structures, but we have other evidence that that’s not always true (for example). Maybe as long as the articular surfaces, zygapophyses, epipophyses, neural spine tips, and cervical ribs — the mechanically-important bits — ended up in the right places, and the major laminae did a ‘good enough’ job of transmitting forces, the rest of each vertebra could just sorta do whatever. Maybe most of them end up looking more or less the same because of shared development, not because it was so very important that all the holes and flanges were in precisely the same places. That might explain why we occasionally get some really odd verts, like C11 of the Diplodocus carnegii holotype.

That’s all pretty hand-wavy and I haven’t yet thought of a way to test it, but someone probably will sooner or later. In the meantime, I think it’s valuable to just keep documenting the weirdness as we find it.

References

Figure 3. BIBE 45854, articulated series of nine mid and posterior cervical vertebrae of a large, osteologically mature Alamosaurus sanjuanensis. Series is estimated to represent the sixth to fourteenth cervical vertebrae. A, composite photo-mosaic of the cervical series in right lateral view; identification of each vertebra indicated by C6 to C14, respectively. B, line drawing based on the photo-mosaic in A. C, line drawing in B with labels shown and vertebral fossae indicated by solid grey fill; cross-hatching represents broken bone surfaces and reconstructive material. Abbreviations: C, cervical vertebra; cdf, centrodiapophyseal fossa; clf, centrum lateral fossa; pocdf, postzygapophyseal centrodiapophyseal fossa; prcdf, prezygapophyseal centrodiapophyseal fossa; prcdf1, dorsal prezygapophyseal centrodiapophyseal fossa; prcdf2, ventral prezygapophyseal centrodiapophyseal fossa; sdf, spinodiapophyseal fossa; spof, spinopostzygapophyseal fossa; sprf, spinoprezygapophyseal fossa. (Tykoski and Fiorillo 2016)

Have you been reading Justin Tweet’s series, “Your Friends the Titanosaurs“, at his awesomely-named blog, Equatorial Minnesota? If not, get on it. He’s been running the series since June, 2018, so this notice is only somewhat grotesquely overdue. The latest installment, on Alamosaurus from Texas and Mexico, is phenomenal. I have never seen another summary or review that pulled together so much of the relevant literature and explained it all so well. Seriously, that blog post deserves to be a review paper; it could be submitted pretty much as-is, although it would be even better with his two other Alamosaurus posts integrated (this one, and this one). It’s great work, is what I’m saying, and it needs to be acknowledged.

In particular, I was struck by the note by Anonymous in 1941 on the discovery of a cervical vertebra 1.2 meters long. I’d never heard of that ref, and I’ve never seen that vert, but at 120cm it would be in the top 7 longest cervical vertebrae on the planet (see the latest version of the list in this post), narrowly beating out the 118-cm cervical of Puertasaurus. In fairness, the preserved cervical of Puertasaurus is probably a posterior one, and more anterior cervicals might have been longer. Then again, in the big Alamosaurus neck the longest verts are pretty darned posterior, so…we need more Puertasaurus.

EDIT a few hours later: Thanks to the kind offices of Justin Tweet, I’ve now seen Anonymous (1941), and the exact wording is, “A single vertebra, or neck joint bone, is three feet across, only two inches less than four feet long, and in its present fossilized state weighs 600 pounds.” ‘Two inches less than four feet long’ is 46 inches or a hair under 117cm, which puts the supposed giant cervical just behind Puertasaurus after all, but still firmly in the top 10. And depending on how one interprets the passage in Anonymous (1941), it might not have been any bigger than BIBE 45854–see this comment for details.

Big cervical showdown. From the top left: BYU 9024, originally referred to Supersaurus but more likely representing a giant Barosaurus (137cm); the single available cervical of Puertasaurus (118cm); a world-record giraffe neck (2.4m); Alamosaurus referred cervical series BIBE 45854, longest centra are ~81cm; Sauroposeidon holotype OMNH 53062, longest centrum is 125cm. This image makes it very clear that whatever Sauroposeidon was doing, it was a way different thing from Alamosaurus.

Crucially, the longest vertebrae in the BIBE 45854 series are about 80 or 81 cm long, which means that a 1.2-meter cervical would be half again as large. That is a pretty staggering thought, and that individual of Alamosaurus–assuming it was the same taxon as BIBE 45854, and not some other, longer-necked critter–would definitely be a contender for the largest sauropod of all time.

Illustrations here are of the big Alamosaurus cervical series from Big Bend, which was comprehensively described by Ron Tykoski and Tony Fiorillo in 2016, and which we have covered in these previous posts:

References

  • Anonymous. 1941. Find dinosaur neck bone nearly four feet long. The Science News-Letter 39(1):6–7.
  • Tykoski, R.S. and Fiorillo, A.R. 2016. An articulated cervical series of Alamosaurus sanjuanensis Gilmore, 1922 (Dinosauria, Sauropoda) from Texas: new perspective on the relationships of North America’s last giant sauropod. Journal of Systematic Palaeontology 15(5):339-364.