My Oct. 13 National Fossil Day public lecture, “Lost Giants of the Jurassic”, for the Museums of Western Colorado – Dinosaur Journey is now up on their YouTube channel. First 48 minutes are talk, last 36 minutes are Q&A with audience, moderated by Dr. Julia McHugh. New stuff from the 2021 field season — about which I’ll have more to say in the future — starts at about the 37-minute mark. Hit the 44-minute mark (and this and this) to find out what to do with all of the unwanted bird necks that will be floating around at the upcoming holidays.

Finally, big thanks to Brian Engh for finding our brachiosaur and for letting me use so much of his art, to John Foster, Kaelen Kay, Tom Howells, Jessie Atterholt, Thierra Nalley, and Colton Snyder for such a fun field season this year, and to Julia McHugh for giving me the opportunity to yap about one of my favorite dinosaurs!

 

The last time we saw the sauropod femur that Paige Wiren discovered sticking out of a riverbank, it had been moved into the prep lab at the Moab Museum, with the idea that it would eventually go on exhibit as a touch specimen for the public to enjoy and be inspired by. That has come to pass.

I was in Moab last month with Drs. Jessie Atterholt and Thierra Nalley and we stopped in the Moab Museum to digitize some vertebrae from SUSA 515, an unusual specimen of Camarasaurus that I’ve blogged about before, and will definitely blog about again. While we were there, we got to see and touch the Wiren femur. The museum folks told us that femur has been the first dinosaur bone that a lot of schoolkids and tourists have seen up close, or gotten to touch. As a former dinosaur-obsessed kid who never stopped being excited about touching real dinosaur bones–and as one of the lucky folks that got to rescue this particular fossil from erosion or poaching–that pleases me deeply. 

So, obviously, you should go see this thing. And the rest of the museum–as you can see from the photos above, the whole place has been renovated, and there are lots of interesting fossils from central and eastern Utah on display, not to mention loads of historical artifacts, all nicely presented in a clean, open, well-lit space that invites exploration. Go have fun!

Last time, we looked at the difference between cost, value and price, and applied those concepts to simple markets like the one for chairs, and the complex market that is scholarly publication. We finished with the observation that the price our community pays for the publication of a paper (about $3,333 on average) is about 3–7 times as much as its costs to publish ($500-$1000)?

How is this possible? One part of the answer is that the value of a published paper to the commnity is higher still: were it not so, no-one would be paying. But that can’t be the whole reason.

In an efficient market, competing providers of a good will each try to undercut each other until the prices they charge approach the cost. If, for example, Elsevier and Springer-Nature were competing in a healthy free market, they would each be charging prices around one third of what they are charging now, for fear of being outcompeted by their lower-priced competitor. (Half of those price-cuts would be absorbed just by decreasing the huge profit margins; the rest would have to come from streamlining business processes, in particular things like the costs of maintaining paywalls and the means of passing through them.)

So why doesn’t the Invisible Hand operate on scholarly publishers? Because they are not really in competition. Subscriptions are not substitutable goods because each published article is unique. If I need to read an article in an Elsevier journal then it’s no good my buying a lower-priced Springer-Nature subscription instead: it won’t give me access to the article I need.

(This is one of the reasons why the APC-based model — despite its very real drawbacks — is better than the subscription model: because the editorial-and-publication services offered by Elsevier and Springer-Nature are substitutable. If one offers the service for $3000 and the other for $2000, I can go to the better-value provider. And if some other publisher offers it for $1000 or $500, I can go there instead.)

The last few years have seen huge and welcome strides towards establishing open access as the dominant mode of publication for scholarly works, and currently output is split more or less 50/50 between paywalled and open. We can expect OA to dominate increasingly in future years. In many respects, the battle for OA is won: we’ve not got to VE Day yet, but the D-Day Landings have been accomplished.

Yet big-publisher APCs still sit in the $3000–$5000 range instead of converging on $500-$1000. Why?

Björn Brembs has been writing for years about the fact that every market has a luxury segment: you can buy a perfectly functional wristwatch for $10, yet people spend thousands on high-end watches. He’s long been concerned that if scholarly publishing goes APC-only, then people will be queuing up to pay the €9,500 APC for Nature in what would become a straightforward pay-for-prestige deal. And he’s right: given the outstandingly stupid way we evaluate reseachers for jobs, promotion and tenure, lots of people will pay a 10x markup for the “I was published in Nature” badge even though Nature papers are an objectively bad way to communicate research.

But it feels like something stranger is happening here. It’s almost as though the whole darned market is a luxury segment. The average APC funded by the Wellcome Trust in 2018/19 was £2,410 — currently about $3,300. Which is almost exactly the average article cost of $3,333 that we calculated earlier. What’s happening is that the big publishers have landed on APCs at rates that preserve the previous level of income. That is understandable on their part, but what I want to know is why are we still paying them? Why are all Wellcome’s grantees not walking away from Elsevier and Springer-Nature, and publishing in much cheaper alternatives?

Why, in other words, are market forces not operating here?

I can think of three reasons why researchers prefer to spend $3000 instead of $1000:

  1. It could be that they are genuinely getting a three-times-better service from the big publishers. I mention this purely for completeness, as no evidence supports the hypothesis. There seems to be absolutely no correlation between price and quality of service.
  2. Researchers are coasting on sheer inertia, continuing to submit to the journals they used to submit to back in the bad old days of subscriptions. I am not entirely without sympathy for this: there is comfort in familiarity, and convenience in knowing a journal’s flavour, expectations and editorial board. But are those things worth a 200% markup?
  3. Researchers are buying prestige — or at least what they perceive as prestige. (In reality, I am not convinced that papers in non-exceptional Elsevier or Springer-Nature journals are at all thought of as more prestigous than those in cheaper but better born-OA journals. But for this to happen, it only needs people to think the old journals are more prestigious, it doesn’t need them to be right.)

But underlying all these reasons to go to a more expensive publishers is one very important reason not to bother going to a cheaper publisher: researchers are spending other people’s money. No wonder they don’t care about the extra few thousand pounds.

How can funders fix this, and get APCs down to levels that approximate publishing cost? I see at least three possibilities.

First, they could stop paying APCs for their grantees. Instead, they could add a fixed sum onto all grants they make — $1,500, say — and leave it up to the researchers whether to spend more on a legacy publisher (supplementing the $1,500 from other sources of their own) or to spend less on a cheaper born-OA publisher and redistribute the excess elsewhere.

Second, funders could simply publish the papes themselves. To be fair several big funders are doing this now, so we have Wellcome Open Research, Gates Open Research, etc. But doesn’t it seem a bit silly to silo research according to what body awarded the grant that funded it? And what about authors who don’t have a grant from one of these bodies, or indeed any grant at all?

That’s why I think the third solution is best. I would like to see funders stop paying APCs and stop building their own publishing solutions, and instead collaborate to build and maintain a global publishing solution that all researchers could use irrespective of grant-recipient status. I have much to say on what such a solution should look like, but that is for another time.

We have a tendency to be sloppy about language in everyday usage, so that words like “cost”, “value” and “price” are used more or less interchangeably. But economists will tell you that the words have distinct meanings, and picking them apart is crucial to understand economic transaction. Suppose I am a carpenter and I make chairs:

  • The cost of the chair is what it costs me to make it: raw materials, overheads, my own time, etc.
  • The value of the chair is what it’s worth to you: how much it adds to your lifestyle.
  • The price of the chair is how much you actually pay me for it.

In a functioning market, the value is more than the cost. Say it costs me £60 to make the chair, and it’s worth £100 to you. Then there is a £40 range in which the price could fall and we would both come out of the deal ahead. If you buy the chair for £75, then I have made £15 more than what it cost me to make, so I am happy; and you got it for £25 less than it was worth to you, so you’re happy, too.

(If the value is less than the cost, then there is no happy outcome. The best I can do is dump the product on the market at below cost, in the hope of making back at least some of my outlay.)

So far, so good.

Now let’s think about scientific publications.

There is a growing consensus that the cost of converting a scientific manuscript into a published paper — peer-reviewed, typeset, made machine-readable, references extracted, archived, indexed, sustainably hosted — is on the order of $500-$1000.

The value of a published paper to the world is incredibly hard to estimate, but let’s for now just say that it’s high. (We’ll see evidence of this in a moment.)

The price of a published paper is easier to calculate. According to the 2018 edition of the STM Report (which seems to be the most recent one available), “The annual revenues generated from English-language STM journal publishing are estimated at about $10 billion in 2017 […] collectively publishing over 3 million articles a year” (p5). So, bundling together subscription revenues, APCs, offsets deals and what have you, the average revenue accruing from a paper is $10,000,000,000/3,000,000 = $10,000/3 = $3,333.

(Given that these prices are paid, we can be confident that the value is at least as much, i.e. somewhere north of $3,333 — which is why I was happy earlier to characterise the value as “high”.)

Why is it possible for the price of a paper to be 3–7 times as high as its cost? One part of the answer is that the value is higher still. Were it not so, no-one would be paying. But that can’t be the whole reason.

Tune in next time to find out the exciting reason why the price of scholarly publishing is so much higher than the cost!

I have the honor of giving the National Fossil Day Virtual Lecture for The Museums of Western Colorado – Dinosaur Journey, next Wednesday, October 13, from 7:00 to 8:00 PM, Mountain Daylight Time. The title of my talk is “Lost Giants of the Jurassic” but it’s mostly going to be about Brachiosaurus. And since I have a whole hour to fill, I’m gonna kitchen-sink this sucker and put in all the good stuff, even more than last time. The talk is virtual (via Zoom) and free, and you can register at this link.

The photo up top is from this July. That’s John Foster (standing) and me (crouching) with the complete right humerus of Brachiosaurus that we got out of the ground in 2019; that story is here. The humerus is in the prep lab at the Utah Field House of Natural History State Park Museum in Vernal, and if you go there, you can peer through the tall glass windows between the museum’s central atrium and the prep lab and see it for yourself.

If you’ve forgotten what a humerus like that looks like in context, here’s the mounted Brachiosaurus skeleton at the North American Museum of Ancient Life with my research student, Kaelen Kay, for scale. Kaelen is 5’8″ (173cm) and as you can see, she can just get her hand on the animal’s elbow. The humerus–in this case, a cast of the right humerus from the Brachiosaurus altithorax holotype–is the next bone up the line. Kaelen came out with us this summer and helped dig up some more of our brachiosaur–more on that story in the near future.

Want more Brachiosaurus? Tune in next week. Here’s that registration link again. I hope to see you there!

Two and a half years ago, I posted a glorious hemisected hen, taken (with permission) from a poster by Roberts et al. 2016, and supplied by Ray Wilhite, best known in this parish for his work on sauropod appendicular material.

At the end of that post, I blithely promised “More from this poster in a subsequent post!”, and then — predictably — forgot all about it. My apologies. Here is the fulfilment of that promise, in glorious colour:

Segmented 3D model (from CT scans) showing lungs and air-sacs of a domestic hen, in left lateral view. Key (roughly left-to-right): cyan: trachea; yellow: interclavical air-sac; orange: lung; green: cranial thoracic air-sac; white: caudal thoracic air-sac; blue: abdominal air-sac; pink: connections from lung to posterior thoracic and abdominal air-sacs. From Roberts et al. 2016.

There’s lots to love here, not least the sheer extent of the respiratory system — it almost seems there is no space in the hen’s torso for any actual soft tissue. But the big thing for me is how tiny a part of the respiratory system the lung contributes. It’s almost an afterthought: it’s a fool’s game judging 3d volumes from a single perspective, but here it seems that the lung makes up at most 20% of the system.

And yet it’s the only part of the system that has parenchymal tissue — the only place where gas exchange takes place. The air-sacs are not doing anything: they just sit there, moving air through the lung as they expand and contract but otherwise inert. Isn’t that strange? Doesn’t it seem wasteful? Why not respire though the entire air-sac system?

And of course this raises questions about how the system worked in sauropods. Long-time followers of this blog, or indeed of Matt’s research output, will know that there is very good evidence that sauropods had an air-sac system similar to that of birds, but since the air-sacs themselves do not fossilise we can’t know the details of the soft-tissue anatomy — only what we can infer from fossilised vertebrae. So I can’t help speculating about whether the greater metabolic demands of sauropods compelled them to evolve more extensive gas-exchange in their respiratory systems.

[“Greater metabolic demands”? Yes, because metabolic throughput scales roughly with body mass to the 3/4 power (Kleiber 1932) but air gets into an animal though a gas-exchange surface whose area, if isometric, goes with the square of linear dimension, i.e. body mass to the 2/3 power. So metabolic demand relative to gas-exchange area goes with body mass to the power 3/4 / 2/3 = 3*3/4*2 = 9/8. All numbers very subject to debate.]

Long, long ago (2004), in an email, I asked Matt this same question. His response, in part:

Blue whales, of up to 209 tons, get by just fine with the horribly inefficient mammalian design, so why couldn’t 100 ton sauropods get by with the avian one?

Which is a good point. But as I responded at the time:

Maybe the real mystery here is what the heck are whales doing that we’re not? And the answer would seem to be “swimming in water, which is an order of magnitude less energetically demanding than walking on land”. Hmm.

(And yes, it really does seem to be true that swimming is about an order of magnitude less energetic than running: see Schmidt-Nielsen 1972:figure 4.)

And there, my record of our discussion fizzles out. If we discussed further, history does not record what was said. And I feel this is still worthy of some exploration. In short, whales are big blubbery cheats, and nothing they say or do can be taken at face value.


Bonus content! Here is the whole poster!

Roberts et al. 2016.

References

  • Kleiber, M. 1932. Body size and metabolism. Hilgardia 6:315–353.
  • Roberts, John, Ray Wilhite, Gregory Almond, Wallace D Berry, Tami Kelly, Terry Slaten, Laurie McCall and Drury R. Reavill. 2016. Gross and histologic diagnosis of retrograde yolk inhalation in poultry. The American Association of Avian Pathologists, San Antonio, Texas. doi:10.13140/RG.2.2.28204.26246
  • Schmidt-Nielsen, Knut. 1972. Locomotion: energy cost of swimming, flying, and running. Science 177(4045):222-228. doi:10.1126/science.177.4045.222

On Thursday, I took the family to the Cotswolds Wildlife Park, a rather lovely zoo just over an hour away from us in Burford, Oxfordshire. Somehow I’d never even heard of this place until we passed a sign for it on the A417 a few weeks ago. Lots of great stuff there, but I wanted to focus on this:

As you can see, the clump of big trees in the giraffe enclosure has had all its foliage methodically stripped off, right up to the point where the tallest giraffe can reach, giving it a striking mushroom shape.

In mammals — certainly the most-studied vertebrates — regional differentiation of the vertebral column is distinct and easy to spot. But things aren’t so simple with sauropods. We all know that the neck of any tetrapod is made up of cervical vertebrae, and that the trunk is made up of dorsal vertebrae (subdivided into thoracic and lumbar vertebrae in the case of mammals). But how do we tell whether a given verebra is a posterior cervical or an anterior dorsal?

Here two vertabrae: a dorsal vertebra (D3) and a cervical vertebra (C13) from CM 84, the holotype of Diplodocus carnegii, modified from Hatcher (1901: plates III and VII):

It’s easy to tell these apart, even when as here we have only lateral-view images: the dorsal vertebra is tall, its centrum is short, its neural spine is anteroposteriorly compressed and its parapophysis is up on the dorsal half of the centrum; but the cervical vertebra is relatively low, its centrum is elongated, its neural spine is roughly triangular and its parapophysis hangs down well below the centrum (and has a cervical rib fused to it and the diapophysis).

But things get trickier in the shoulder region because, in sauropods at least, the transition through the last few cervicals to the first few dorsals is gradual — the vertebrae become shorter, taller and broader — and tends to have no very obvious break point. In this respect, they differ from mammals, in which the regional differentiation of the spinal column is more abrupt. (Although even here, things may not be as simple as generally assumed: for example, Gunji and Endo (2016) argued that the 1st thoracic vertebra of the giraffe behaves functionally like an 8th cervical.)

So here are those two vertebrae in context: the sequence D3 D2 D1 C15 C14 C13 in CM 84, the holotype of Diplodocus carnegii, modified from Hatcher (1901: plates III and VII):

Given that the leftmost is obviously a dorsal and the rightmost obviously a cervical, where would you place the break-point?

The most usual definition seems to be that the first dorsal vertebra is the first one that has a free rib, i.e. one not fused to the vertebra: in the illustration above, you can see that the three cervicals on the right all have their cervical ribs fused to their diapophyses and parapophyses, and the three dorsals on the left do not. This definition of the cervical/dorsal distinction seems to be widely assumed, but it is rarely explicitly asserted. (Does anyone know of a paper that lays it out for sauropods, or for dinosaurs more generally?)

But wait!

Hatcher (1903:8) — the same dude — in his Haplocanthosaurus monograph, writes:

The First Dorsal (Plate I., Fig. 1). […] That the vertebra now under consideration was a dorsal is conclusively shown not by the presence of tubercular and capitular rib facets showing that it supported on either side a free rib, for there are in our collections of sauropods, skeletons of other dinosaurs fully adult but, with the posterior cervical, bearing free cervical ribs articulating by both tubercular and capitular facets as do the ribs of the dorsal region. The character in this vertebra distinguishing it as a dorsal is the broadly expanded external border of the anterior branch of the horizontal lamina [i.e. what we would now call the centroprezygapophyseal lamina]. This element has been this modified in this and the succeeding dorsal, no doubt, as is known to be the case in Diplodocus to give greater surface for the attachment of the powerful muscles necessary for the support of the scapula.

Hatcher’s illustrations show this feature, though they don’t make it particularly obvious: here are the last two cervicals and the first dorsal, modified from Hatcher (1903:plate I), with the facet in question highlighted in pink: right lateral view at the top, then anterior, and finally posterior view at the bottom. (The facet is only visible in lateral and anterior views):

Taken at face value, Hatcher’s words here seem to imply that he considers the torso to begin where the scapula first lies alongside the vertebral column. Yet if you go back to the Diplodocus transition earlier in this post, a similar scapular facet is not apparent in the vertebra that he designated D1, and seems to be present only in D2.

Is this scapular-orientation based definition a widespread usage? Can anyone point me to other papers that use it?

Wilson (2002:226) mentions a genetic definition of the cervical/dorsal distinction

Vertebral segment identity may be controlled by a single Hox gene. The cervicodorsal transition in many tetrapods, for instance, appears to be defined by the expression boundary of the Hoxc-6 gene.

But this of course is no use in the case of extinct animals such as sauropods.

So what’s going on here? In 1964, United States Supreme Court Justice Potter Stewart, in describing his threshold test for obscenity, famously said “I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description, and perhaps I could never succeed in intelligibly doing so. But I know it when I see it.” Is that all we have for the definition of what makes a vertebra cervicals as opposed to dorsal? We know it when we see it?

Help me out, folks! What should the test for cervical-vs-dorsal be?

References

  • Gunji, Mego, and Hideki Endo. 2016. Functional cervicothoracic boundary modified by anatomical shifts in the neck of giraffes. Royal Society Open Science 3:150604. doi:10.1098/rsos.150604
  • Hatcher, Jonathan B. 1901. Diplodocus (Marsh): its osteology, taxonomy and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1:1-63 and plates I-XIII.
  • Hatcher, J. B. 1903b. Osteology of Haplocanthosaurus with description of a new species, and remarks on the probable habits of the Sauropoda and the age and origin of the Atlantosaurus beds; additional remarks on Diplodocus. Memoirs of the Carnegie Museum 2:1-75 and plates I-VI.
  • Wilson, Jeffrey A. 2002. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136:217-276.

Various Internet rumours have suggested that the Archbishop is a super-giant sauropod one third larger than the mounted Giraffatitan specimen MB.R.2181 (formerly HMN SII). This is incorrect.

Figure E. Skeletal inventory of NHMUK PV R5937, “The Archbishop”, showing which bones were excavated by Migeod’ expedition. Based on a skeletal reconstruction of Giraffatitan brancai kindly provided by Scott Hartman: note that this image does not illustrate the shapes or proportions of the Archbishop material. Bones prepared and available for study are shown in white; those still in jackets awaiting preparation in light grey; those excavated by Migeod but apparently lost or destroyed in dark grey.

Migeod’s assessment of the size of the animal was based on the vertebrae: “The [neck] vertebrae found give a 20-foot [6.10 m] length […] The length of the back including the sacral region was about 15 feet [4.57 m]. The eight or nine caudal vertebrae cover about 6 feet [1.83 m]” (Migeod 1931a:90). This gives the total preserved length of the skeleton as 41 feet (12.50 m). By comparison, Janensch (1950b:102) gives lengths of portions of the mounted skeleton of MB.R.2181 as 8.78m (neck), 3.92m (torso) and 1.07m (sacrum) for a torso-plus-sacrum length of 4.99m. On this basis, the preserved neck of NHMUK PV R5937 is only 69% as long as that of MB.R.2181, but since the first four vertebrae were missing and omitted from Migeod’s measurement, this factor cannot be taken at face value. More informative is the torso-plus-sacrum length, which in NHMUK PV R5937 is 92% the length of MB.R.2181.

This is consonant with measurements of individual elements, which compare as follows:

Table 4. Comparative measurements of Archbishop and Giraffatitan elements

ElementMeasurement (cm)ArchbishopGiraffatitanRatio
Torso plus sacrumtotal length4574990.916
C10 (mC4)centrum length991000.990
C11 (mC3)centrum length104100[1]1.040
D4 (mD3)centrum length27360.750
Longest riblength over curve2352630.894
Left scapulocoracoidlength over curve221238[2]0.929
Right humeruslength1462130.685
Right humeruswidth51590.864
Right iliumlength98123[3]0.797
Right iliumheight7996[4]0.823
Femurlength122196[5]0.622
Average0.846

Archbishop measurements taken from Migeod (1931a) and converted from imperial; Giraffatitan measurements are for MB.R.2181 except where noted, and are taken from Janensch (1950a:44) and Janensch (1961).
Notes.
[1] Janensch (1950a) did not report a total centrum length for C11, as its condyle had not been removed from the cotyle of C10; but since the length of its centrum omitting the condyle was, at 87 cm, identical to that of C10, it is reasonable to estimate its total length as also equal to that of C10.
[2] Janensch (1961:181) did not include measurements for the right scapula of MB.R.2181, which is incorporated into the mounted skeleton, but does give the proximodistal length of its right coracoid as 45 cm. Using the 193 cm length given for the similarly sized scapula Sa 9, we can deduce a reasonable total estimate of 238 cm for the scapulocoracoid.
[3] Estimated by Janensch (1950b:99) based on cross-scaling from the fibula and ilium of Find J from the Upper Saurian Marl.
[4] This is the measurement provided by Janensch (1961:199) for the ilium Ma 2, which is incorporated into the mounted skeleton, and which Janensch (1950b:99) considered to match MB.R.2181 very precisely.
[5] Based on a restoration of the midshaft which Janench (1950b:99) calcuated based on other finds.

Individual lines of this table should each be treated with caution: Migeod’s measurements may have been unreliable, and in any case are underspecified: for example, we do not know whether, when he gave a vertebra’s length, he included overhanging prezygapophyses or the condyle. Similarly, we know that Migeod (1931:96) wrote that a rib “was as much as 92.5 inches long”, but we do not know for certain that, like Janensch, he measured the length over the curve rather than the straight-line distance between the ends. And when Migeod says that the ilium “measured 38.5 by 31 inches” we do not know that the height was measured “at the public process”, as Janensch (1961:199) specified.

With those caveats in place, nevertheless, a picture emerges of a sauropod somewhat smaller than MB.R.2181, though by no means negligible. On average, the measurements come out about 15% smaller than those of Giraffatitan.

But this average conceals a great deal of variation. The cervical vertebrae are comparable in length to those of MB.R.2181 (The total of 203 cm for C10 and C11 in the Archbishop, only 1.5% longer than 200 cm for MB.R.2181, is a difference well within the margin of measurement error). The Archbishop’s scapulocoracoid may have been 93% as long as in MB.R.2181. But the limb bones are signficantly shorter (87% for the humerus and a scarcely credible 62% for the femur), and the humeri at least bseem to be have been proportionally more robust in the Archbishop: only 2.86 times as long as wide, whereas the ratio is 3.61 in MB.R.2181. If Migeod’s measurements can be trusted, we have here an animal whose neck is as long as that of Giraffatitan, but whose limbs are noticably shorter. These proportions corroborate the hypothesis that the Archbishop is not a specimen of Giraffatitan.

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.
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