A beautiful Lego Diplodocus skeleton
June 18, 2014
Check out this beautiful Lego Diplodocus:
(Click through for the full image at full size.)
I particularly like the little touch of having of bunch of Lego Victorian gentleman scientists clustered around it, though they’re probably a bit too big for the skeleton.
This is the work of MolochBaal, and all rights are reserved. You can see five more views of this model in his Flickr gallery. I especially admire how he’s managed to get the vertebral transitions pretty smooth, the careful use of separate radius/ulna and tibia/fibula, and the use of a transparent brick in the skull to represent the antorbital fenestra.
The forefeet are wrong — their toes should not be splayed out — but you can’t blame MolochBaal for that, as he was copying the mounted CM 84/94 cast in the Madrid museum.
I need to be sleeping, not blogging, so here are just the highlights, with no touch-ups and minimal commentary.
I don’t know what these real street signs were doing sitting on the ground when I walked to the museum this morning, but it was a good omen for the conference.
Home base for this part of the conference. We head to Green River, Utah, on Friday for the Early Cretaceous half.
I had never seen this on exhibit. This is not the Brachiosaurus scapulocoracoid formerly referred to “Ultrasauros”, this is the other big scap from Dry Mesa, from the giant diplodocid Supersaurus.
Seems legit.
This is not Dinosaur Baptist Church–it is a cathedral of an entirely different order.
And that order is Sauropoda.
The sauropod bones are entombed in a matrix consisting of super-hard sandstone and non-sauropod bits.
I got about 150 photos of the Wall, but only because I ran out of time. You probably already know what I’m going to attempt with them. (If not, here’s a hint.)
Jim Kirkland (center left) literally walked us through the Morrison and Cedar Mountain Formations at this set of exposures north of the visitor center. The reddish stuff on the lower left is Morrison, and after that it’s CMF all the way up this ridge and next two behind it.
A cast of Diplodocus carnegii at the Utah Field House of Natural History State Park Museum, signalling that we’ve come to end of this tail–er, tale.
Further updates as time and opportunity allow. If you tweet about the conference, please use #MMFC14!
The case of the bandy-legged Diplodocus
March 1, 2014
Christine Argot of the MNHN, Paris, drew our attention to this wonderful old photo (from here, original caption reproduced below):
© Paleontological Museum, Moscow
In the beginning of XX century, the Severo-Dvinskaya gallery (named after prof. Amalitsky) became the gold basis of the exhibition hall of ancient life in the Geological Museum of St-Petersburg. The museum hall was completed with a cast of the Diplodicus carnegii skeleton presented by E.Carnegy fund in 1913, at the 300-th anniversary of the Romanovs dynasty.
I found a different version of what seems to be the same photo (greyscaled, lower resolution, but showing more of the surrounding area) here:
What we have here is a truly bizarre mount of Diplodocus — almost certainly one of the casts of the D. carnegii holotype CM 84 — with perfectly erect, parasagittal hind-limbs, but bizarrely everted elbows.
There are a few mysteries here.
First, where and when was this photo taken? Christine’s email described this as a “picture of a Diplodocus cast taken in St. Petersburg around 1920″, and the caption above seems to confirm that location; but then why is it copyright the Paleontological Museum, Moscow? Since the web-site in question is for a Swedish museum, it’s not forthcoming.
The second photo is from the web-site of the Borisyak Paleontological Institute in Moscow, but that site unfortunately provides no caption. The juxtaposition with two more modern Diplodocus-skeleton photos that are from its own gallery perhaps suggest that the modern mount shown in the more recent photographs is a re-pose of the old mount in the black-and white photo. If so, that might mean that the skeleton was actually in Moscow all along rather than St. Petersburg, or perhaps that it was moved from St. Petersburg to Moscow and remounted there.
Does anyone know? Has anyone out there visited the St. Petersburg museum recently and seen whether there is still a Diplodocus skeleton there? If so, is it still mounted in this bizarre way? Better yet, do you have photos?
Tornier’s sprawling, disarticulated reconstruction of Diplodocus, modified from Tornier (1909, plate II).
The second question of course is why was this posture used? This pose makes no sense for several reasons — one of which is that even if Diplodocus could attain this posture it would only serve to leave the forefeet under the torso in the same position as erect forelimbs would have them. The pose only makes any kind of sense at all if you imagine the animal lowering its torso to drink; but given that it had a flexible six-meter-long neck, that hardly seems necessary.
Of course Diplodocus does have a history of odd postures: because of the completeness of the D. carnegii holotype, it became the subject of the Sauropod Posture Wars between Tornier, Hay and Holland in the early 20th Century. Both Tornier (1909) and Hay (1910) favoured a sprawling posture like that of lizards (see images above and below), and were soundly refuted by Holland
The form and attitudes of Diplodocus. Hay (1910: plate 1)
But the Tornier and Hay postures bear no relation to that of the mounted skeleton in the photographs above: they position the forefeet far lateral to the torso, and affect the hindlimbs as well as the forelimbs. So whatever the Russian mount was doing, I don’t think it can have been intended as a representation of the Tornier/Hay hypothesis.
But it gets even weirder. Christine tells me that “I’m aware of […] the tests that Holland performed on the Russian cast to get rid of the hypothesis suggesting a potential lizard-like posture. So I think that he would have never allowed such a posture for one of the casts he mounted himself.” Now I didn’t know that Holland had executed the mounting of this cast. Assuming that’s right, it makes it even more inexplicable that he would have allowed such a posture.
Or did he?
Christine’s email finishes by asking: “What do you think? do you think that somebody could have come behind Holland to change the position? do you know any colleague or publication who could mention this peculiar cast and comment its posture?”
Can anyone help?
References
- Hay, Oliver. P. 1910. On the manner of locomotion of the dinosaurs, especially Diplodocus, with remarks on the origin of birds. Proceedings of the Washington Academy of Sciences 12(1):1-25.
- Holland, W. J. 1910. A review of some recent criticisms of the restorations of sauropod dinosaurs existing in the museums of the United States, with special reference to that of Diplodocus carnegiei in the Carnegie museum. American Naturalist 44:259-283.
- Nieuwland, Ilja. 2010. The colossal stranger. Andrew Carnegie and Diplodocus intrude European Culture, 1904–1912. Endeavour 34(2):61-68.
- Tornier, Gustav. 1909. Wie war der Diplodocus carnegii wirklich gebaut? Sitzungsbericht der Gesellschaft naturforschender Freunde zu Berlin 4:193– 209.
Measuring the elongation of vertebrae
September 20, 2013
Let’s take another look at that Giraffatitan cervical. MB.R.2180:C5, from a few days ago:
That’s a pretty elongate vertebra, right? But how elongate, exactly? How can we quantify whether it’s more or less elongate than some other vertebra?
The traditional answer is that we quantify elongation using the elongation index, or EI. This was originally defined by Upchurch (1998:47) as “the length of a vertebral centrum divided by the width across its caudal face”. Measuring from the full-resolution version of the image above, I make that 1779/529 pixels, or 3.36.
But then those doofuses Wedel et al. (2000:346) came along and said:
When discussing vertebral proportions Upchurch (1998) used the term elongation index (EI), defined as the length of the centrum divided by the width of the cotyle. Although they did not suggest a term for the proportion, Wilson & Sereno (1998) used centrum length divided by the height of the cotyle as a character in their analysis. We prefer the latter definition of this proportion, as the height of the cotyle is directly related to the range of motion of the intervertebral joint in the dorsoventral plane. For the purposes of the following discussion, we therefore redefine the EI of Upchurch (1998) as the anteroposterior length of the centrum divided by the midline height of the cotyle.
Since then, the term EI has mostly been used in this redefined sense — but I think we all agree now that it would have been better for Wedel et al to have given a new name to Wilson and Sereno’s ratio rather than apply Upchurch’s name to it.
Aaaanyway, measuring from the image again, I give that vertebra an EI (sensu Wedel et al. 2000) of 1779/334 = 5.33. Which is 58% more elongate than when using the Upchurch definition! This of course follows directly from the cotyle being 58% wider than tall (529/334 pixels).
So one of principal factors determining how elongate a vertebra seems to be is the shape of its cotyle. And that’s troublesome, because the cotyle is particularly subject to crushing — and it’s not unusual for even consecutive vertebrae from the same column to be crushed in opposite directions, giving them (apparently) wildly different EIs.
Here’s an example (though not at all an extreme one): cervicals 4 and 6 of the same specimen, MB.R.2180 (formerly HM SI), as the multi-view photo above:
Measuring from the photos as before, I make the width:height ratio of C4 683/722 pixels = 0.95, and that of C6 1190/820 pixels = 1.45. So these two vertebrae — from the same neck, and with only one other vertebrae coming in between them — differ in preserved cotyle shape by a factor of 1.53.
And by the way, this is one of the best preserved of all sauropod neck series.
Let’s take a look at the canonical well-preserved sauropod neck: the Carnegie Diplodocus, CM 84. Here are the adjacent cervicals 13 and 14, in posterior view, from Hatcher (1901: plate VI):
For C14 (on the left), I get a width:height ratio of 342/245 pixels = 1.40. For C13 (on the right), I get 264/256 pixels = 1.03. So C14 is apparently 35% broader than its immediate predecessor. I absolutely don’t buy that this represents how the vertebrae were in life.
FOR EXTRA CREDIT: what does this tell us about the reliability of computer models that purport to tell us about neck posture and flexibility, based on the preserved shapes of their constituent vertebrae?
So what’s to be done?
The first thing, as always in science, is to be explicit about what statements we’re making. Whenever we report an elongation index, we need to clearly state whether it’s EI sensu Upchurch 1998 or EI sensu Wedel et al. 2000. Since that’s so cumbersome, I’m going propose that we introduce two new abbreviations: EIH (Elongation Index Horizonal), which is Upchurch’s original measure (length over horizontal width of cotyle) and EIV (Elongation Index Vertical), which is Wilson and Sereno’s measure (length over vertical height of cotyle). If we’re careful to report EIH and EIV (or better still both) rather than an unspecified EI, then at least we can avoid comparing apples with oranges.
But I think we can do better, by combining the horizontal and vertical cotyle measurements in some way, and dividing the length by the that composite. This would give us an EIA (Elongation Index Average), which we could reasonably expect to preserve the original cotyle size, and so to give a more reliable indication of “true” elongation.
The question is, how to combine the cotyle width and height? There are two obvious candidates: either take the arithmetic mean (half the sum) or the geometric mean (the square root of the product). Note that for round cotyles, both these methods will give the same result as each other and as EIH and EIV — which is what we want.
Which mean should we use for EIA? to my mind, it depends which is best preserved when a vertebra is crushed. If a 20 cm circular cotyle is crushed vertically to 10cm, does it tend to smoosh outwards to 30 cm (so that 10+30 = the original 20+20) or to 40 cm (so that 10 x 40 = the original 20 x 20)? If the former, then we should use arithmetic mean; if the latter, then geometric mean.
Does anyone know how crushing works in practice? Which of these models most closely approximates reality? Or can we do better than either?
Update (8:48am): thanks for Emanuel Tschopp for pointing out (below) what I should have remembered: that Chure et al.’s (2010) description of Abydosaurus introduces “aEI”, which is the same as one of my proposed definitons of EIA. So we should ignore the last four paragraphs of this post and just use aEI. (Their abbreviation is better, too.)
References
- 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.
- Upchurch, Paul. 1998. The phylogenetic relationships of sauropod dinosaurs. Zoological Journal of the Linnean Society 124:43-103.
- Wedel, Mathew J., Richard L. Cifelli and R. Kent Sanders. 2000b. Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon. Acta Palaeontologica Polonica 45(4):343-388.
- Wilson, J. A. and Paul C. Sereno. 1998. Early evolution and higher-level phylogeny of sauropod dinosaurs. Society of Vertebrate Paleontology, Memoir 5:1-68.
Looking for dorsal-view images of Diplodocus cervicals
August 31, 2013
In his classic monograph, Hatcher (1901) illustrated the cervical vertebrae of the Diplodocus carnegii holotype CM 84 with beautiful drawings:
But only in lateral view.
Other plates show photos in lateral, anterior and posterior views, and these are useful even though they’re much less clear than the drawings.
But he didn’t illustrate the vertebrae at all in dorsal or ventral view — and as far as I know, no-one else has done so either. I would find these views really useful for something I’m working on. Does anyone have photos?
Help!
Reference
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.
Brachiosaurus sp. BYU 12866 c5? in left lateral view with CT slices, some corrected for distortion.
Last Tuesday Mike popped up in Gchat to ask me about sauropod neck masses. We started throwing around some numbers, derived from volumetric estimates and some off-the-cuff guessing. Rather than tell you more about it, I should just paste our conversation, minimally edited for clarity and with a few hopefully helpful links thrown in.
BYU 12613, a posterior cervical probably referable to Diplodocus, in dorsal (top), left lateral (left), and posterior (right) views. It most closely resembles C14 of D. carnegii CM 84/94 (Hatcher 1901: plate 3) despite being less than half as large, with a centrum length of 270 mm compared to 642 mm for C14 of D. carnegii. From Wedel and Taylor (in press).
* R. McNeill Alexander (1985, 1989) did estimate the mass of the neck of Diplodocus, based on the old Invicta model and assuming a specific gravity of 1.0. Which was a start, and waaay better than no estimate at all. Still, let’s pretend that Mike meant “tried based on the actual fossils and what we know now about pneumaticity”.
The stuff about putting everything off until April is in there because we have a March 31 deadline to get a couple of major manuscripts submitted for an edited thingy. And we’ve made a pact to put off all other sciencing until we get those babies in. But I want to blog about this now, so I am.
Another thing Mike and I have been talking a lot about lately is the relation between blogging and paper-writing. The mode we’ve seen most often is to blog about something and then repurpose or rewrite the blog posts as a paper. Darren paved the way on this (at least in our scientific circle–people we don’t know probably did it earlier), with “Why azhdarchids were giant storks“, which became Witton and Naish (2008). Then last year our string of posts (starting here) on neural spine bifurcation in Morrison sauropods became the guts–and most of the muscles and skin, too–of our in-press paper on the same topic.
But there’s another way, which is to blog parts of the science as you’re doing them, which is what Mike was doing with Tutorial 20–that’s a piece of one of our papers due on March 31.
Along the way, we’ve talked about John Hawks’ model of using his blog as a place to keep his notes. We could, and should, do more of that, instead of mostly keeping our science out of the public eye until it’s ready to deploy (which I will always favor for certain projects, such as anything containing formal taxonomic acts).
And I’ve been thinking that maybe it’s time for me–for us–to take a step that others have already taken, and do the obvious thing. Which is not to write a series of blog posts and then decide later to turn it into a paper (I wasn’t certain that I’d be writing a paper on neural spine bifurcation until I had written the second post in that series), but to write the paper as a series of blog posts, deliberately and from the outset, and get community feedback along the way. And I think that the sauropod neck mass project is perfect for that.
Don’t expect this to become the most common topic of our posts, or even a frequent one. We still have to get those manuscripts done by the end of March, and we have no shortage of other projects waiting in the wings. And we’ll still post on goofy stuff, and on open access, and on sauropod stuff that has nothing to do with this–probably on that stuff a lot more often than on this. But every now and then there will be a post in this series, possibly written in my discretionary blogging time, that will hopefully move the paper along incrementally.
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Alexander, R.M. 1985. Mechanics of posture and gait of some large dinosaurs. Zoological Journal of the Linnean Society, 83(1): 1-25.
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Alexander, R.M. 1989. Dynamics of Dinosaurs and Other Extinct Giants. Columbia University Press.
- Hutchinson, J.R., Bates, K.T., Molnar, J., Allen, V., and Makovicky, P.J. 2011. A computational analysis of limb and body dimensions in Tyrannosaurus rex with implications for locomotion, ontogeny, and growth. PLoS ONE 6(10): e26037. doi:10.1371/journal.pone.0026037
- Taylor, M.P. 2009. A re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropoda) and its generic separation from Giraffatitan brancai (Janensch 1914). Journal of Vertebrate Paleontology 29(3):787-806.
- Wedel, M.J., and Taylor, M.P. In press. Neural spine bifurcation in sauropod dinosaurs of the Morrison Formation: ontogenetic and phylogenetic implications. PalArch’s Journal of Vertebrate Paleontology.
- Witton, M.P., and Naish, D. 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS ONE 3(5): e2271. doi:10.1371/journal.pone.0002271
Diplodocus carnegii cervicals, from Hatcher (1901)
February 7, 2013
Here are cervical vertebrae 2-15 of Diplodocus carnegii in right lateral view, from Hatcher (1901: plate 3). Click to embiggen, and then just gaze in wonder for a while.
Wouldn’t that look smashing, printed, framed, and hanging on the wall?
I wonder if I will ever stop finding new interesting things to think about in this image. I doubt it.
(For a bit o’ fair-and-balanced, remember that this neck may not be complete, and that some of the neural spines are sculptures.)
Thanks to Mike for the scan.
Reference
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.
Caudal pneumaticity in saltasaurines. Cerda et al. (2012: fig. 1).
Earlier this month I was amazed to see the new paper by Cerda et al. (2012), “Extreme postcranial pneumaticity in sauropod dinosaurs from South America.” The title is dramatic, but the paper delivers the promised extremeness in spades. Almost every figure in the paper is a gobsmacker, starting with Figure 1, which shows pneumatic foramina and cavities in the middle and even distal caudals of Rocasaurus, Neuquensaurus, and Saltasaurus. This is most welcome. Since the 1990s there have been reports of saltasaurs with “spongy bone” in their tail vertebrae, but it hasn’t been clear until now whether that “spongy bone” meant pneumatic air cells or just normal marrow-filled trabecular bone. The answer is air cells, loads of ’em, way farther down the tail than I expected.
Caudal pneumaticity in diplodocines. Top, transverse cross-section through an anterior caudal of Tornieria, from Janensch (1947: fig. 9). Bottom, caudals of Diplodocus, from Osborn (1899: fig. 13).
Here’s why this is awesome. Lateral fossae occur in the proximal caudals of lots of neosauropods, maybe most, but only a few taxa go in for really invasive caudal pneumaticity with big internal chambers. In fact, the only other sauropod clade with such extensive pneumaticity so far down the tail are the diplodocines, including Diplodocus, Barosaurus, and Tornieria. But they do things differently, with BIG, “pleurocoel”-type foramina on the lateral surfaces of the centra, leading to BIG–but simple–camerae inside, and vertebral cross-sections that look like I-beams. In contrast, the saltasaurines have numerous small foramina on the centrum and neural arch that lead to complexes of small pneumatic camellae, giving their vertebrae honeycomb cross-sections. So caudal pneumaticity in diplodocines and saltsaurines is convergent in its presence and extent but clade-specific in its development. Pneumaticity doesn’t get much cooler than that.
Pneumatic ilia in saltasaurines. Cerda et al. (2012: fig. 3).
But it does get a little cooler. Because the stuff in the rest of the paper is even more mind-blowing. Cerda et al. (2012) go on to describe and illustrate–compellingly, with photos–pneumatic cavities in the ilia, scapulae, and coracoids of saltasaurines. And, crucially, these cavities are connected to the outside by pneumatic foramina. This is important. Chambers have been reported in the ilia of several sauropods, mostly somphospondyls but also in the diplodocoid Amazonsaurus. But it hasn’t been clear until now whether those chambers connected to the outside. No patent foramen, no pneumaticity. It seemed unlikely that these sauropods had big marrow-filled vacuities in their ilia–as far as I know, all of the non-pneumatic ilia out there in Tetrapoda are filled with trabecular bone, and big open marrow spaces only occur in the long bones of the limbs. And, as I noted in my 2009 paper, the phylogenetic distribution of iliac chambers is consistent with pneumaticity, in that the chambers are only found in those sauropods that already have sacral pneumaticity (showing that pneumatic diverticula were already loose in their rear ends). But it’s nice to have confirmation.
So, the pneumatic ilia in Rocasaurus, Neuquensaurus, and Saltasaurus are cool because they suggest that all the other big chambers in sauropod ilia were pneumatic as well. And for those of you keeping score at home, that’s another parallel acquisition in Diplodocoidea and Somphospondyli (given the apparent absence of iliac chambers in Camarasaurus and the brachiosaurids, although maybe we should bust open a few brachiosaur ilia just to be sure*).
* I kid, I kid.**
** Seriously, though, if you “drop” one and find some chambers, call me!
Pectoral pneumaticity in saltasaurines. Cerda et al. (2012: fig. 2).
But that’s not all. The possibility of pneumatic ilia has been floating around for a while now, and most of us who were aware of the iliac chambers in sauropods probably assumed that eventually someone would find the specimens that would show that they were pneumatic. At least, that was my assumption, and as far as I know no-one ever floated an alternative hypothesis to explain the chambers. But I certainly did not expect pneumaticity in the shoulder girdle. And yet there they are: chambers with associated foramina in the scap and coracoid of Saltasaurus and in the coracoid of Neuquensaurus. Wacky. And extremely important, because this is the first evidence that sauropods had clavicular air sacs like those of theropods and pterosaurs. So either all three clades evolved a shedload of air sacs independently, or the basic layout of the avian respiratory system was already present in the ancestral ornithodiran. I know where I’d put my money.
There’s loads more interesting stuff to talk about, like the fact that the ultra-pneumatic saltasaurines are among the smallest sauropods, or the way that fossae and camerae are evolutionary antecedent to camellae in the vertebrae of sauropods, so maybe we should start looking for fossae and camerae in the girdle bones of other sauropods, or further macroevolutionary parallels in the evolution of pneumaticity in pterosaurs, sauropods, and theropods. Each one of those things could be a blog post or maybe a whole dissertation. But my mind is already thoroughly blown. I’m going to go lie down for a while. Congratulations to Cerda et al. on what is probably the most important paper ever written on sauropod pneumaticity.
References
- Cerda, I.A., Salgado, L., and Powell, J.E. 2012. Extreme postcranial pneumaticity in sauropod dinosaurs from South America. Palaeontologische Zeitschrift. DOI 10.1007/s12542-012-0140-6
- Janensch, W. 1947. Pneumatizitat bei Wirbeln von Sauropoden und anderen Saurischien. Palaeontographica, Supplement 7, 3:1–25.
- Osborn, H. F. 1899. A skeleton of Diplodocus. Memoirs of the American Museum of Natural History 1:191–214.
Neural spine bifurcation in sauropods, Part 6: more reasons why Haplocanthosaurus is not a juvenile of a known diplodocid
April 15, 2012
Last time, we saw why Haplocanthosaurus couldn’t be a juvenile of Apatosaurus or Diplodocus, based on osteology alone. But there’s more:
Ontogenetic status of Haplocanthosaurus
Here is where is gets really surreal. Woodruff and Fowler (2012) blithely assume that Haplocanthosaurus is a juvenile of something, but the type specimen of the type species — H. priscus CM 572 — is an adult. As Hatcher (1903:3) explains:
The type No. 572 of the present genus consists of the two posterior cervicals, ten dorsals, five sacrals, nineteen caudals, both ilia, ischia and pubes, two chevrons, a femur and a nearly complete series of ribs, all in an excellent state of preservation and pertaining to an individual fully adult as is shown by the coössified neural spines and centra.
So far as I can see, Woodruff and Fowler are confused because the second species that Hatcher describes, H. utterbacki, is based on the subadult specimen CM 879. Where possible in the previous post, I have used illustrations of the adult H. priscus, so that the comparisons are of adult with adult. The exceptions are the two anterior cervicals and the first dorsal, which are known only from H. utterbacki. And sure enough, if you look closely at the illustrations, you can see that in these vertebrae and only these vertebrae, Hatcher had the neurocentral junction illustrated — because it wasn’t yet fused.
Haplocanthosaurus posterior, mid and anterior cervical vertebrae, C14, C9 and C4, in right lateral view. C14 of adult H. priscus (from Hatcher 1903:plate I); C9 and C4 of H. utterbacki (from plate II). Red ellipses highlight neurocentral sutures.
As it happens, the difference in ontogenetic status between these two specimens is nicely illustrated by Wedel (2009), although he was only in it for the pneumaticity:
Neurocentral fusion in Haplocanthosaurus. A, B. Posterior cervical vertebra C?12 of sub-adult H. utterbacki holotype CM 879: A, X-ray in right lateral view; B, coronal CT slice showing separate ossificaton of centrum and neural arch. C, D. Mid-dorsal vertebra D6 of adult H. priscus holotype CM 572: X-rays in (A) right lateral and (B) anterior view, showing fully fused neural arch. Wedel (2009:fig. 6)
So H. utterbacki CM 879 certainly is an immature form of something; and that something is Haplocanthosaurus, most likely H. priscus. (The characters which Hatcher used to separate the two species are not particularly convincing.)
With that out the way, we can move on to …
Phylogenetic analysis
A simple way to evaluate the parsimony or otherwise of a synonymy is to use a phylogenetic analysis. In their abstract, Woodruff and Fowler claim that “On the basis of shallow bifurcation of its cervical and dorsal neural spines, the small diplodocid Suuwassea is more parsimoniously interpreted as an immature specimen of an already recognized diplodocid taxon”. Without getting into the subject of Suuwassea again — Matt pretty much wrapped that up in part 4 — the point here is that the word “parsimony” has a particular meaning in studies of evolution: it refers to minimising the number of character-state changes. And we have tools for measuring those.
So let’s use parsimony to evaluate the hypothesis that Haplocanthosaurus is one of the previously known diplodocids. Pretending for the moment that Haplocanthosaurus really was known only from subadults, how many additional steps would we need to account for if ontogeny were to change its position to make it group with one of the diplodocids?
You don’t need to be a cladistics wizard to do this. (Which is handy, since I am not one.) Here’s the method:
- Start with an existing matrix, add constraints, re-run it, and see how the tree-length changes. Since I am familiar with it, I started with the matrix from my 2009 paper on brachiosaurs.
- Re-run the matrix to verify that you get the same result as in the published paper based on it. This gives you confidence that you’re running it right. In this case, I got a minimum tree length of 791 steps, just as in Taylor (2009).
- Add extra instructions to the run-script defining and imposing constraints. Note that you do not have to mess with the characters, taxa or codings to do this.
- Run the matrix again, with the constraint in place, and see how the tree-length changes.
- Repeat as needed with other constraints to evaluate other phylogenetric hypotheses.
(This is how we produced the part of the Brontomerus paper (Taylor et al. 2011:89) where we said “One further step is sufficient to place Brontomerus as a brachiosaurid, a basal (non−camarasauromorph) macronarian, a basal (non−diplodocid) diplodocoid or even a non−neosauropod. Three further steps are required for Brontomerus to be recovered as a saltasaurid, specifically an opisthocoelicaudiine”. And that’s why we weren’t at all dogmatic about its position.)
Anyway, going through this exercise with Haplocanthosaurus constrained in turn to be the sister taxon to Apatosaurus, Diplodocus, etc., yielded the following results:
- (no constraint) — 791 steps
- Apatosaurus — 817 (26 extra)
- Diplodocus — 825 (34 extra)
- Barosaurus — 815 (24 extra)
- Camarasaurus — 793 (2 extra)
- Brachiosaurus — 797 (6 extra)
(I threw in the other well-known Morrisson-Formation sauropods Camarasaurus and Brachiosaurus, even though Woodruff and Fowler don’t mention them, just because it was easy to do and I was interested to see what would happen. And when I say Brachiosaurus, I mean B. altithorax, not Giraffatitan.)
I hope you’re as shocked as I am to see that for Haplocanthosaurus to emerge as the sister taxon of any diplodocid needs a minimum of 24 additional steps — or an incredible 34 for it to be sister to Diplodocus. In other words, the hypothesis is grossly unparsimonious. Of course, that doesn’t in itself mean that it’s false: but it does render it an extraordinary claim, which means that it needs extraordinary evidence. And while “the simple spines of Haplocanthosaurus might bifurcate when it grows up” is extraordinary evidence, it’s not in the way that Carl Sagan meant it.
In short, running this simple exercise — it took me about a hour, mostly to remember how to do constraints in PAUP* — would have given Woodruff and Fowler pause for thought before dragging Haplocanthosaurus into their paper.
Oh, and it’s ironic that placing Haplo as sister to Brachiosaurus requires only a quarter as many steps as the closest diplodocid, and as sister to Camarasaurus requires only two steps. If you really want to synonymise Haplocanthosaurus, Camarasaurus is the place to start. (But don’t get excited, it’s not Camarasaurus either. It’s Haplocanthosaurus.)
[By the way, anyone who’d like to replicate this experiment for themselves is welcome: all the files are available on my web-site. You only really need the .nex file, which you can feed to PAUP*, but I threw in the log-file, the generated tree files and the summary file, too. Extra Credit: run this same exercise to evaluate the parsimony of Suuwassea as a subadult of one of these other genera. Report back here when you’re done to earn SV-POW! points.]
Conclusion
It’s a truism that we stand on the shoulders of giants. In the case of sauropod studies, those giants are people like J. B. Hatcher, Charles Gilmore, Osborn and Mook and — bringing it up to date — John McIntosh, Paul Upchurch, Jeff Wilson and Jerry Harris. When Hatcher described Haplocanthosaurus as a new genus rather than a subadult Diplodocus, he wasn’t naive. He recognised the effects of ontogeny, and he was aware that one of his two specimens was adult and the other subadult. He was also probably more familiar with Diplodocus osteology than anyone else has ever been before or since, having written the definitive monograph on that animal just two years previously (Hatcher 1901).
By the same token, people like Upchurch and Wilson have done us all a huge favour by making the hard yards in sauropod phylogenetics. If we’re going to go challenging the standard consensus phylogeny, it’s just good sense to go back to their work (or the more recent work of others, such as Whitlock 2011), re-run the analyses with our pet hypotheses encoded as constraints, and see what they tell us.
So in the end, my point is this: let’s not waste our giants. Let’s take the time to get up on their shoulders and survey the landscape from up there, rather than staying down at ground level and seeing how high we can jump from a standing start.
The rest of the series
Links to all of the posts in this series:
- Part 1: what we knew a month ago
- Part 2: why serial position matters
- Part 3: the evidence from ontogenetic series
- Part 4: is Suuwassea a juvenile of a known diplodocid?
- Part 5: is Haplocanthosaurus a juvenile of a known diplodocid?
- Part 6: more reasons why Haplocanthosaurus is not a juvenile of a known diplodocid
and the post that started it all:
References
- Hatcher, J.B. 1901. Diplodocus (Marsh): its osteology, taxonomy, and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1:1-63.
- Hatcher, J.B. 1903. 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.
- Taylor, M.P. 2009. A re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropoda) and its generic separation from Giraffatitan brancai (Janensch 1914). Journal of Vertebrate Paleontology 29(3):787-806.
- Taylor, M.P., Wedel, M.J. and Cifelli, R.L. 2011. A new sauropod dinosaur from the Lower Cretaceous Cedar Mountain Formation, Utah, USA. Acta Palaeontologica Polonica 56(1):75-98. doi:10.4202/app.2010.0073
- Wedel, M.J. 2009. Evidence for bird-like air sacs in saurischian dinosaurs. Journal of Experimental Zoology 311A:611-628.
- Whitlock, J.A. 2011. A phylogenetic analysis of Diplodocoidea (Saurischia: Sauropoda). Zoological Journal of the Linnean Society 161(4):872-915. doi: 10.1111/j.1096-3642.2010.00665.x
- Woodruff, D.C, and Fowler, D.W. 2012. Ontogenetic influence on neural spine bifurcation in Diplodocoidea (Dinosauria: Sauropoda): a critical phylogenetic character. Journal of Morphology, online ahead of print.
Neural spine bifurcation in sauropods, Part 5: is Haplocanthosaurus a juvenile of a known diplodocid?
April 14, 2012
Introduction
Last time around, Matt walked through a lot of the detailed cervical morphology of Suuwassea and known diplodocids to show that, contra the suggestion of Woodruff and Fowler (2012), Suuwassea is distinct and can’t be explained away as an ontogenomorph of a previously known genus.
Although Suuwassea is singled out for special treatment in this paper, other genera do not escape unscathed. From the Conclusions section on page 9:
Just as particularly large diplodocid specimens (e.g., Seismosaurus; Gillette, 1991) have been more recently recognized as large and potentially older individuals of already recognized taxa (Diplodocus; Lucas et al., 2006; Lovelace et al., 2007), taxa defined on small specimens (such as Suuwassea, but also potentially Barosaurus, Haplocanthosaurus, and ‘‘Brontodiplodocus’’), might represent immature forms of Diplodocus or Apatosaurus.
I have to admit I more or less fell out of my chair when I saw the suggestion that poor old Haplocanthosaurus might be Diplodocus or Apatosaurus. I think this idea comes from a misstatement in the very first sentence of the abstract:
Within Diplodocoidea (Dinosauria: Sauropoda), phylogenetic position of the three subclades Rebbachisauridae, Dicraeosauridae, and Diplodocidae is strongly influenced by a relatively small number of characters.
As a statement of fact, this is simply the opposite of the truth: in all the major phylogenetic analyses, the arrangement of subclades with Diplodocoidea is the most stable part of the tree, supported by more characters than all the other clades.
For example, in the analysis of Upchurch et al. (2004) in The Dinosauria II, fig. 13.18 shows that the nodes with the highest bootstrap percentages are Diplodocinae (96%), Dicraeosauridae (95%) and Diplodocidae (93%).
Or consider the analysis of Wilson (2002). While it’s getting on a bit, it still scores highly by being the most explicit published sauropod analysis, with comprehensive lists of apomorphies. Table 12 lists the decay indexes for the 24 nodes in the strict consensus tree. Apart from the three very basal nodes separating sauropods from their outgroups, the two highest-scoring clades are Diplodocidae and Diplodocinae (DI=7), followed by four clades all with DI=5 of which two are Dicraeosauridae and Flagellicaudata (which Wilson just called “Dicraeosauridae + Diplodocidae” as it had not yet been named). (It’s well worth reading Wilson’s Appendix 3 to see the synapomorphies supporting these nodes in the MPTs: he lists 14 separating Diplodocimorpha from the node it shares with Haplocanthosaurus, 18 separating Flagellicaudata from the node it shares with Rebbachisauridae, 16 separating Diplodocidae from the node it shares with Dicareosauridae, and seven separating Diplodocinae from the node it shares with Apatosaurus).*
* Why are the lists of apomorphies longer than the decay indexes? Because they list the apomorphies as they occur in the specific topology of the consensus tree. Nodes within that tree can be made to collapse without wiping out all the apomorphies by rejuggling other parts of the tree to move character-state transitions around. So although (for example) 26 characters separate Flagellicaudata from Rebbachisauridae (18 + 8 synapomorphies respectively) you can rejuggle the whole tree to break the monophyly of Flagellicaudata while making the entire tree only five steps longer.
Anyway, for whatever reason, Woodruff and Fowler felt that the stability of the diplodocoid clades was in question, and this presumably influenced their hypothesis that Haplocanthosaurus could be easily moved down into one of the diplodocid genera.
Next time we’ll be considering the implications for the tree. But today, let’s take a moment to do this the old-fashioned way, by looking at …
Osteology
Pelvis
Hatcher (1903), ever helpful, included a comparative plate in his monograph which should help us to evaluate the idea that Haplo is a known diplodocid:
Pelves of diplodocids and Haplocanthosaurus. 1. Pelvis of Brontosaurus excelsus (No. 568); 2. Pelvis of Diplodocus carnegii (No. 94); 3. Pelvis of Haplocanthosaurus priscus (No. 572). All seen from left side. 1, 2, 3, 4, 5 indicate neural spines of respective sacral vertebra. Presumably to scale. Direct from Hatcher (1903:plate IV).
Based on this, the pelvis of Haplocanthosaurus differs from those of the diplodocids in having a proportionally lower ilium, in the absence of the laterally facing rugosity on the posterodorsal margin of the ilium, in the very small distal expansion of the pubis and in the almost non-existent distal expansion of the ischium. These are all characters of the limb-girdle elements, which do not change greatly through ontogeny in sauropods.
But the evidence from the sacral vertebrae is just as significant: the neural spines in the sacral area are less than half as tall as in the diplodocids — and this in an animal whose dorsal neural spines are conspicuously tall. The spines are also more anteroposteriorly elongate and plate-like. What’s more, sacral spines 1, 2 and 3 have fused into a single plate in Haplocanthosaurus, while the spine of S1 remains well separated from 2 and 3 in the diplodocids. So the ontogenetic hypothesis would have to say that the spine of S1 unfuses through ontogeny. Which is not something I’ve heard of happening in any sauropod, or indeed any animal.
So the pelvis and sacrum seem distinct. But Woodruff and Fowler’s (2012) notion of ontogenetic synonymy is built on the idea that the differences in the cervical and dorsal vertebrae are ontogenetic. So let’s take a look at them.
Cervical vertebrae
Posterior, mid and anterior cervical vertebrae, in right lateral view, of (top to bottom), Haplocanthosaurus, Apatosaurus louisae CM 3018 (from Gilmore 1936:plate XXIV, reversed for ease of comparison) and Diplodocus carnegii CM 84 (from Hatcher 1901:plate III), scaled to roughly the same size. For the diplodocids, we illustrate C13, C9 and C4. For Haplocanthosaurus, we illustrate C14 of H. priscus (from Hatcher 1903:plate I) and C9 and C4 of H. utterbacki (from plate II).
It should be immediately apparent that the Haplocanthosaurus cervicals have less extensive pneumatic features than those of the diplodocids, but that is one feature which we know does vary ontogenetically. There are other differences: for example, the cervical ribs in Haplocanthosaurus are level with the bottom centrum rather than hanging below. Still, if you kind of squint a bit, you could probably persuade yourself that the Haplocanthus vertebrae look like possible juveniles of Diplodocus.
Unless you look at them from behind:
Posterior cervical vertebrae C15 and C14, in posterior view, of (top to bottom), Haplocanthosaurus priscus CM 572 (from Hatcher 1903:plate I), Apatosaurus louisae CM 3018 (from Gilmore 1936:plate XXIV) and Diplodocus carnegii CM 84 (from Hatcher 1901:plate III), scaled to the same centrum-to-neural-spine height.
(Unfortunately, these are the only Haplocanthosaurus cervical vertebrae that Hatcher had illustrated in posterior view, so we can’t compare more anterior ones.)
From this perspective, we can immediately significant differences:
- First, that unsplit spine. Yes, we know that Woodruff and Fowler (2012) have argued that it could be ontogenetic, but these are vertebrae from the most deeply bifurcated region of a diplodocid neck, in a decent sized animal, and there is nothing that so much as hints at bifurcation.
- That whacking great ligament scar running right down the back (and also the front, not pictured) of the neural spine. There is nothing like this in any diplodocid — neither on the metapophyses nor running though the trough. And remember, scars like these tend to become more prominent through ontogeny.
- The neural arch (i.e. the region between the postzygapophyses and the centrum) is taller in Haplocanthosaurus — much taller in the case of C15.
- The plates running out to the diapophyses are less dorsoventrally expanded in Haplocanthosaurus.
- The centrum is smaller as a proportion of total height — especially, much smaller than in Diplodocus.
- The parapophyses extend directly laterally rather than ventrolaterally (hence the position of the cervical ribs level with the bottom of the centrum).
So it doesn’t look good for the juvenile-diplodocid hypothesis. But let’s take a look at the …
Dorsal vertebrae
Posterior, mid and anterior dorsal vertebrae, in right lateral view, of (top to bottom), Haplocanthosaurus, Apatosaurus louisae CM 3018 (from Gilmore 1936:plate XXV, reversed for ease of comparison) and Diplodocus carnegii CM 84 (from Hatcher 1901:plate VII), scaled to roughly the same size. For the diplodocids, we illustrate D9, D5 and D2. For Haplocanthosaurus, which has four more dorsals, we illustrate D13 and D7 of H. priscus (from Hatcher 1903:plate I) and D2 of H. utterbacki (from plate II).
Here we see that Haplocanthosaurus has dorsolaterally inclined diapophyses (which we’ll see more clearly in a minute), a prominent spinodiapohyseal lamina in posterior dorsals, and no infraparapophyseal lamination. Also, the dorsal vertebrae have reached their full height by the middle of the series (in fact the last nine dorsals are startlingly similar in proportions), whereas in diplodocids, total height continues to increase posteriorly.
Now let’s see those vertebrae in posterior view:
Posterior, mid and anterior dorsal vertebrae, in posterior view, of (top to bottom), Haplocanthosaurus priscus CM 572 (From Hatcher 1903:plate I), Apatosaurus louisae CM 3018 (from Gilmore 1936:plate XXV) and Diplodocus carnegii CM 84 (from Hatcher 1901:plate VII), scaled to the same height of the mid dorsal. For the diplodocids, we illustrate D9, D5 and D1. For Haplocanthosaurus, which has four more dorsals, we illustrate D13, D6 and D1.
Here is where it all falls apart. The Haplocanthosaurus dorsals differ from those of the diplodocids in almost every respect:
- Of course we have the non-bifid spine in again, in the anterior dorsal, but let’s not keep flogging that dead horse.
- In the mid and posterior dorsals, the neurapophysis is rounded in posterior view rather than square.
- In the posterior dorsal, the neural spine has laterally directed triangular processes near the top.
- All three Haplocanthosaurus neural spines have broad, rugose ligament scars, whereas those of the diplodocids have narrow postspinal laminae.
- The neural spines (measured from the diapophyses upwards) are much shorter than in the diplodocids; but
- The neural arches (measured from the centrum up to the diapophyses) are much taller.
- The diapophyses have distinct club-like rugosities at their tips.
- the diapophyses of the mid and posterior dorsals are inclined strongly upwards
- The hyposphenes of mid and posterior dorsals have very long centropostzygapophyseal laminae curving up in a gentle arch.
- The centra are smaller than those of Apatosaurus, and much smaller than those of Diplodocus.
(By the way, it’s interesting how very different the D5s of Apatosaurus and Diplodocus are. Since both are from uncontroversially adult specimens, bifurcation was evidently very different between these genera.)
So based on the vertebrae alone, the case of Haplocanthosaurus as an immature form of Diplodocus or Apatosaurus is blown right out of the water. And this is without even looking at the appendicular material — for example, the scapula and coracoid illustrated by Hatcher (1903:figs 17-19), which are so completely different from those of diplodocids.
But there’s more. Tune in next time for the rest.
The rest of the series
Links to all of the posts in this series:
- Part 1: what we knew a month ago
- Part 2: why serial position matters
- Part 3: the evidence from ontogenetic series
- Part 4: is Suuwassea a juvenile of a known diplodocid?
- Part 5: is Haplocanthosaurus a juvenile of a known diplodocid?
- Part 6: more reasons why Haplocanthosaurus is not a juvenile of a known diplodocid
and the post that started it all:
References
- Gillette, D.D. 1991. Seismosaurus halli, gen. et sp. nov., a new sauropod dinosaur from the Morrison Formation (Upper Jurassic/Lower Cretaceous) of New Mexico, USA. Journal of Vertebrate Paleontology 11(4):417-433.
- Gilmore, C.W. 1936. Osteology of Apatosaurus with special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum 11:175-300.
- Hatcher, J.B. 1901. Diplodocus (Marsh): its osteology, taxonomy, and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1:1-63.
- Hatcher, J.B. 1903. 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.
- Lovelace, D.M., Hartman, S.A., Wahl, W.R. 2008. Morphology of a specimen of Supersaurus (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of diplodocid phylogeny. Arquivos do Museu Nacional, Rio de Janeiro 65(4):527-544.
- Lucas, S.G., Spielmann, J.A., Rinehart, L.F., Heckert, A.B., Herne, M.C., Hunt, A.P., Foster, J.R., Sullivan, R.M. 2006, Taxonomic status of Seismosaurus hallorum, a Late Jurassic sauropod dinosaur from New Mexico. New Mexico Museum of Natural History and Science Bulletin 36:149-162.
- Upchurch, P. Barrett, P.M., Dodson, P. 2004. Sauropoda. pp. 259-322 in D.B. Weishampel, P. Dodson and H. Osmólska (eds.), The Dinosauria, 2nd edition. University of California Press, Berkeley and Los Angeles. 861 pp.
- Wilson, J.A. 2002. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136:217-276.
- Woodruff, D.C, and Fowler, D.W. 2012. Ontogenetic influence on neural spine bifurcation in Diplodocoidea (Dinosauria: Sauropoda): a critical phylogenetic character. Journal of Morphology, online ahead of print.
Special bonus illustrations
I composited the cervical and dorsal series above into the following compound illustrations. As always, click through for full resolution.
Lateral view:
Posterior, mid and anterior dorsal vertebrae and cervical vertebrae, in right lateral view, of (top to bottom), Haplocanthosaurus, Apatosaurus louisae CM 3018 (from Gilmore 1936:plates XXIV and XXV, reversed for ease of comparison) and Diplodocus carnegii CM 84 (from Hatcher 1901:plates III and VII), scaled to roughly the same size. For the diplodocids, we illustrate D9, D5, D2, C13, C9 and C4. For Haplocanthosaurus, which has four more dorsals, we illustrate D13, D7 and C14 of H. priscus (from Hatcher 1903:plate I) and D2, C9 and C4 of H. utterbacki (from plate II).
Posterior view:
Posterior, mid and anterior dorsal vertebrae and posterior cervical vertebrae C15 and C14, in posterior view, of (top to bottom), Haplocanthosaurus priscus CM 572 (From Hatcher 1903:plate I), Apatosaurus louisae CM 3018 (from Gilmore 1936:plates XXIV and XXV) and Diplodocus carnegii CM 84 (from Hatcher 1901:plates III and VII), scaled to the same height of the mid dorsal. For the diplodocids, we illustrate D9, D5 and D1. For Haplocanthosaurus, which has four more dorsals, we illustrate D13, D6 and D1.
Sauropod Vertebra Picture of the Week 
