May 29, 2013
We jumped the gun a bit in asking How fat was Camarasaurus? a couple of years ago, or indeed How fat was Brontosaurus? last year. As always, we should have started with extant taxa, to get a sense of how to relate bones to live animals — as we did with neck posture.
So here we go. I give you a herd of Indian elephants, Elephas maximus (from here):
You will notice, from this conveniently-close-to-anterior view, that their torsos bulge out sideways, much further than the limbs.
The rib-cage is tiny. It doesn’t even extend as far laterally as the position of the limb bones.
(And lest you think this is an oddity, do go and look at any mounted elephant skeleton of your choice, Indian or African. They’re all like this.)
What’s going on here?
Is Oxford’s elephant skeleton mounted incorrectly? More to the point, are all museums mounting their elephants incorrectly? Do elephants’ ribs project much more laterally in life?
Do elephants have a lot of body mass superficial to the rib-cage? If so, what is that mass? It’s hard to imagine they need a huge amount of muscle mass there, and it can’t be guts. Photos like this one, from the RVC’s televised elephant dissection on Inside Nature’s Giants, suggest the ribs are very close to the body surface:
I’m really not sure how to account for the discrepancy.
Were sauropods similarly much fatter than their mounted skeletons suggest? Either because we’re mounting their skeletons wrongly with the ribs too vertical, or because they had a lot of superficial body mass?
Consider this mounted Camarasaurus skeleton in the Dinosaur Hall at the Arizona Museum of Natural History (photo by N. Neenan Photography, CC-BY-SA):
Compare the breadth of its ribcage with that of the elephant above, and then think about how much body bulk should be added.
This should encourage palaeoartists involved in the All Yesterdays movement to dramatically bulk up at least some of their sauropod restorations.
It should also make us think twice about our mass estimates.
March 15, 2013
Today sees the publication of my big paper with Mike on neural spine bifurcation, which has been in the works since last April. It’s a free download here, and as usual we put the hi-res figures and other supporting info on a sidebar page.
Navel-gazing about the publication process
This paper is a departure for us, for several reasons.
For one thing, it’s a beast: a little over 13,000 words, not counting tables, figure captions, and the bibliography. I was all geared up to talk about how it’s my longest paper after the second Sauroposeidon paper (Wedel et al. 2000), but that’s not true. It’s my longest paper, period (13192 vs 12526 words), and the one with the most figures (25 vs 22).
It’s the first time we’ve written the paper in the open, on the blog, and then repackaged it for submission to a journal. I have several things to say about that. First, it was more work than I expected. It turns out that I definitely do have at least two “voices” as a writer, and the informal voice I used for the initial run of blog posts (linked here) was not going to cut it for formal publication. So although there is very little new material in the paper that was not in the blog posts, a lot of the prose is new because I had to rewrite almost the whole thing.
I have mixed feelings about this. On one hand, last May kinda sucked, because just about every minute that wasn’t spent eclipse chasing was spent rewriting the paper. On the other hand, as Mike has repeatedly pointed out to me, it was a pretty fast way to generate a big paper quickly, even with the rewriting. It was just over two months from the first post in the destined-to-become-a-paper series on April 5, to submission on June 14 (not June 24 as it says on the last page of the PDF), and if you leave out the 10 days in late May that I was galavanting around Arizona, the actual time spent working on the paper was a bit under two months. It would be nice to be that productive all the time (it helped that we were basically mining everything from previously published work; truly novel work usually needs more time to get up and going).
You may fairly wonder why, if almost all the content was already available on the blog, we went to the trouble of publishing it in a journal. Especially in light of sentiments like this. For my part, it’s down to two things. First, to paraphrase C.S. Lewis, what I wrote in that post was a yell, not a thought. I never intended to stop publishing in journals, I was just frustrated that traditional journals do so many stupid things that actually hurt science, like rejecting papers because of anticipated sexiness or for other BS reasons, not publishing peer reviews, etc. Happily, now there are better options.
Second, although in a sane world the quality of an argument or hypothesis would matter more than its mode of distribution, that’s not the world we live in. We’re happy enough to cite blog posts, etc. (they’re better than pers. comms., at least), but not everyone is, and the minimum bound of What Counts is controlled by people at the other end of the Overton window. So, bottom line, people are at least theoretically free to ignore stuff that is only published on blogs or other informal venues (DML, forums, etc.). If you want to force someone to engage with your ideas, you have to publish them in journals (for now). So we did.
Finally, ever since Darren’s azhdarchids-were-storks post got turned into a paper, it has bothered me that there is an icon for “Blogging on Peer-Reviewed Research” (from ResearchBlogging.org), but not one (that I know of) for “Blogging Into Peer-Reviewed Research”. If you have some graphic design chops and 10 minutes to kill, you could do the world a favor by creating one.
Hey, you! Want a project?
One of the few things in the paper that is not in any of the blog posts is the table summarizing the skeletal fusions in a bunch of famous sauropod specimens, to show how little consistency there is:
(Yes, we know that table legends typically go above, not below; this is just how they roll at PJVP.)
I want this to not get overlooked just because it’s in a long paper on neural spine bifurcation; as far as I’m concerned, it’s the most important part of the paper. I didn’t know that these potential ontogenetic indicators were all mutually contradictory across taxa before I started this project. Not only is the order of skeletal fusions inconsistent among taxa, but it might also be inconsistent among individuals or populations, or at least that’s what the variation among the different specimens of Apatosaurus suggests.
This problem cries out for more attention. As we say at the end of the paper:
To some extent the field of sauropod paleobiology suffers from ‘monograph tunnel vision’, in which our knowledge of most taxa is derived from a handful of specimens described decades ago (e.g. Diplodocus carnegii CM 84/94). Recent work by McIntosh (2005), Upchurch et al. (2005), and Harris (2006a, b, c, 2007) is a welcome antidote to this malady, but several of the taxa discussed herein are represented by many more specimens that have not been adequately described or assessed. A comprehensive program to document skeletal fusions and body size in all known specimens of, say, Camarasaurus, or Diplodocus, could be undertaken for relatively little cost (other than travel expenses, and even these could be offset through collaboration) and would add immeasurably to our knowledge of sauropod ontogeny.
So if you’re looking for a project on sauropod paleobiology and you can get around to a bunch of museums*, here’s work that needs doing. Also, you’ll probably make lots of other publishable observations along the way.
* The more the better, but for Morrison taxa I would say minimally: Yale, AMNH, Carnegie, Cleveland Museum of Natural History, Field Museum, Dinosaur National Monument, BYU, University of Utah, and University of Wyoming, plus Smithsonian, University of Kansas, OMNH, Denver Museum, Wyoming Dinosaur Center, and a few others if you can swing it. Oh, and Diplodocus hayi down in Houston. Check John Foster’s and Jack McIntosh’s publications for lists of specimens–there are a LOT more out there than most people are familiar with.
- Wedel, M.J., R.L. Cifelli and R.K. Sanders. 2000. Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon. Acta Palaeontologica Polonica 45(4): 343-388.
- Wedel, M.J., and Taylor, M.P. 2013. Neural spine bifurcation in sauropod dinosaurs of the Morrison Formation: ontogenetic and phylogenetic implications. Palarch’s Journal of Vertebrate Palaeontology 10(1): 1-34.
March 3, 2013
If you’re just joining us, this post is a follow-up to this one, in which I considered the possible size and identity of the Recapture Creek femur fragment, which “Dinosaur Jim” Jensen (1987: page 604) said was “the largest bone I have ever seen”.
True to his word, Brooks Britt at BYU got back to me with measurements of the Recapture Creek femur fragment in practically no time at all:
Length 1035 mm, width 665 mm. However, you cannot trust the measurements because Jensen put a lot of plaster on the proximal half of the bone.
Now, taking plaster off a bone is not going to make it any larger. So the plastered-up specimen is the best case scenario for the RC femur to represent a gigapod. And I know the stated width of 665 mm is the max width of the proximal end, because I sent Brooks a diagram showing the measurements I was requesting. The length is a little less than anticipated, and doesn’t quite jibe with the max proximal width–I suspect a little might have broken off from the distal end where the preservation looks not-so-hot.
Based on those measurements, it looks like Jensen got the scale bar in Figure 8 in his 1987 paper approximately right–if anything, the scale bar is a little undersized, but only by 5% or so, which is actually pretty good as these things go (scale bars without measurements are still dag-nasty evil, though). By overlapping Jensen’s photo with the femur of the Brachiosaurus altithorax holotype (FMNH P25107) to estimate the size of the element when complete, I get a total length of 2.2 meters–exactly the same size as the Brachiosaurus holotype. If the Recapture Creek femur is from a Camarasaurus, which I don’t think we can rule out, it was 2 meters long when complete, or 11% longer and 37% more massive than the big C. supremus AMNH 5761–about 35 tonnes or maybe 40 on the outside. So it’s a big bone to be sure, but it doesn’t extend the known size range of Morrison sauropods.
So, as before, caveat estimator when working from scaled illustrations of single partial bones of possibly immense sauropods.
Now, here’s a weird thing. Let’s assume for the sake of this discussion that the Recapture Creek femur is from a brachiosaur. That gives us three individual Late Jurassic brachiosaurids–the Recapture Creek animal, the Brachiosaurus altithorax holotype, and the mounted Giraffatitan brancai–that are almost exactly the same size in limb bone dimensions (although B.a. had a longer torso). But we know that brachiosaurids got bigger, as evidenced by the XV2 specimen of Giraffatitan, and based on the lack of scapulocoracoid fusion in both FMNH P25107 and the mounted Giraffatitan. So why do we keep finding these (and smaller) subadults, and so few that were XV2-sized? I know that there gets to be a preservation bias against immense animals (it’s hard to bury a 50-tonne animal all in one go), but I would not think the 13% linear difference between these subadults and XV2-class adults would be enough to matter. Your thoughts?
February 28, 2013
From Jensen (1987, page 604):
“In 1985 I found the proximal third of an extremely large sauropod femur (Figs. 8A, 12A) in a uranium miner’s front yard in southern Utah. The head of this femur is 1.67 m (5’6″) in circumference and was collected from the Recapture Creek Member of the the Morrison Formation in Utah near the Arizona border. It is the largest bone I have ever seen.”
Jensen included not one but two figures of this immense shard of excellence. Here they are:
The specimen was heavily reconstructed, as you can see from the big wodge of unusually smooth and light-colored material in the photo. So we can’t put much stock in that part of the specimen.
Unfortunately, the only measurement of the specimen that Jensen gives in the paper is that circumference; there are no straight-line linear measurements, and the figures both have the dreaded scale bars. Why dreaded? Check this out:
As you can see, when the scale bars are set to the same size, the bones are way off (the scale bar in the drawing is 50 cm). This is not an uncommon problem. I make the Fig 8 version 30% bigger in max mediolateral width of the entire proximal end, and still 17% bigger in minimum diameter across the femoral head, as measured from the slight notch on the dorsal surface (on the right in this view).
Can we figure out which is more accurate based on the internal evidence of the paper? For starters, the Fig 12 version is a drawing (1), that does not match the outline from the photo (2), and the hand-drawn scale bar (3) does not actually coincide with any landmarks (4), and that’s plenty of reasons for me not to trust it.
What about that circumference Jensen mentioned? Unfortunately, he didn’t say exactly where he took it, just that the head of the femur had a circumference of 1.67 meters. Is that for the entire proximal end, or for the anatomical head that fits in the acetabulum, er wot? I’m afraid the one measurement given in the paper is no help in determining which of the figures is more accurately scaled.
The obvious thing to do would be to see if this bone is in the BYU collections, and just measure the damn thing. More on that at the end of the post.
In the meantime, Jensen said that the shape of the Recapture Creek femur was most similar to the femur of Alamosaurus, or to that of Brachiosaurus among Morrison taxa, and he referred it to Brachiosauridae. So how does this thing–in either version–compare with the complete femur of FMNH P25107, the holotype of Brachiosaurus altithorax?
The first thing to notice is that the drawn outline from Figure 12 is a much better match for the Brachiosaurus altithorax femur–enough so that I wonder if Jensen drew it from the Recapture Creek specimen, or just traced the B.a. proximal femur and scaled it accordingly (or maybe not accordingly, since the scale bars don’t match).
But let’s get down to business: how long would the complete femur have been?
Using the scale bar in the photograph from Figure 8 (on the left in above image), I get a total femur length of 2.36 meters. Which is long, but only 7.7% longer than the 2.19-meter femur of FMNH P25107, and therefore only 25% more massive. So, 35 tonnes to Mike’s 28-tonne B.a., or maybe 45 tonnes to a more liberal 36-tonne B.a. Big, yeah, but not world-shattering.
Using the scale bar in the drawing from Figure 12 (on the right in the above image)–which, remember, is 50 cm, not 1 meter–I get a total femur length of about 1.9 meters, which is considerably smaller than the B.a. holotype. That is very much at odds with Jensen’s description of it as “the largest bone I have ever seen”, and given that we have many reasons for not trusting the scale bar in the drawing, it is tempting to just throw it out as erroneous.
So it would seem that unless Jensen got both scale bars too big, the Recapture Creek brachiosaur was at most only a shade bigger than the holotype specimen of Brachiosaurus altithorax.
But wait–is the Recapture Creek brachiosaur a brachiosaur at all? Jensen didn’t list any characters that pushed him toward a brachiosaurid ID, and I don’t know of any proximal femur characters preserved in the specimen that would separate Brachiosaurus from, say, Camarasaurus. And in fact a camarasaur ID has a lot to recommend it, in that Camarasaurus femora have very offset heads (the ball- or cylinder-like articular surface at the top end sticks out a big more to engage with the hip socket–see Figure 12 up near the top of the post), moreso than in many other Morrison sauropods, and that would make them better matches for the Recapture Creek femur photo. Here’s what the comparo looks like:
I make that a 2.07-meter femur using the photo on the left, and a 1.66-meter femur using the drawing on the right. The one decent femur in the AMNH 5761 Camarasaurus supremus collection is 1.8 meters long, so these results are surprisingly similar to those for the B. althithorax comparison–the drawing gives a femur length shorter than the largest known specimens, and the photo gives a length only slightly longer. A camarasaur with a 2.07 meter femur would be 15% larger than the AMNH C. supremus in linear terms, and assuming isometric scaling, 1.5 times as massive–maybe 38 tonnes to AMNH 5761′s estimated 25. A big sauropod to be sure, but not as big as the largest apatosaurs, and not nearly as big as the largest titanosaurs.
I have always been surprised that the Recapture Creek femur frag has attracted so little attention, given that “Dinosaur Jim” himself called it the biggest bone he had ever seen. But it appears that the lack of attention is justified–whether it was a brachiosaur or a camarasaur, and using the most liberal estimates the scale bars allow, it simply wasn’t that big.
Update about half an hour later: Okay, maybe I was a little harsh here. IF the photo scale bar is right, the Recapture Creek femur might still represent the largest and most massive macronarian from the Morrison Formation (Edit: only if it’s a brachiosaur and not a camarasaur; see this comment), which is something. I suppose I was particularly underwhelmed because I was expecting something up in OMNH 1670-to-Argentinosaurus territory, and so far, this ain’t it. I’ll be interested to see what the actual measurements say (read on).
The Moral of This Story
So, if it wasn’t that big after all, and if no-one has made a stink about it being big before now, why go to all this trouble? Well, mostly just to satisfy my own curiosity. If there was a truly gigantic brachiosaur from the Morrison, it would be relevant to my interests, and it was past time I crunched the numbers to find out.
But along the way something occurred to me: this should be a cautionary tale for anyone who gets all wound up about the possible max size of Amphicoelias fragillimus. As with A. fragillimus, for the Recapture Creek critter we have part of one bone, and at least for this exercise I was working only from published illustrations with scale bars. And as with A. fragillimus, the choice of a reference taxon is not obvious, and the size estimates are all over the place, and some of them just aren’t that big.
It always amuses me when A. fragillimus comes up and people (well, trolls) accuse us of being big ole’ wet blankets that just don’t want to believe in 200-tonne sauropods. It amuses me because it’s wrong on so many levels. Believe me, when we have our sauropod fanboy hats on, we most definitely do want to believe in 200-tonne sauropods. That would rock. But when we put our scientist hats on, wanting and belief go right out the window. We have to take a cold, hard look at the data, and especially at its limitations.
Oh, the other moral is to go buy a tape measure, and use it. Sheesh!
As I said above, the obvious thing to do would be to just track down the bone and measure it. It does still exist, it’s in the BYU collections, and Brooks Britt has kindly offered to send along some measurements when he gets time. So we should have some real answers before long (and here they are). But I wanted to work through this example without them, to illustrate how much uncertainty creeps in when trying to estimate the size of a big sauropod from published images of a single partial bone.
November 29, 2012
It’s been a while since I posted here. I haven’t gone off SV-POW! or anything, just going through one of my periodic doldrums (read: super-busy with Other Stuff). I’m writing now to draw your attention to two books that I’m pretty darned excited about.
The first is All Yesterdays: Unique and Speculative Views of Dinosaurs and Other Prehistoric Animals, by John Conway, Memo Kosemen, and Darren Naish, with skeletal diagrams by Scott Hartman (lulu, Amazon). This is sort of an SV-POW! love-fest, in that Darren is One Of Us, John and Scott let us use their art a lot–even the goofy stuff–and get a shout-out now and then, and I’ve been awed by the work of Memo–a.k.a. Nemo Ramjet–for longer than SV-POW! has existed (he also created Brontosapiens!). But wait–there’s more! One of the first people to review the book is Emily Willoughby, who was also as far as we know the first person after Paco Gasco to illustrate Brontomerus–that image is still Bronto‘s flagship portrait on Wikipedia.
But enough navel-gazing. The book is based around the mind-blowing presentations “All Yesterdays” and “All Todays” at SVPCA 2011 and 2012, both delivered by John Conway. True story: “All Yesterdays” was the intro to the icebreaker/mixer thing at Lyme Regis, so right after the talk people jumped up to grab pints and socialize. Sometime in the next few minutes, John was separately approached by three different paleontologists who thought that “All Yesterdays” should be a book, and wanted to help write it. Those three hopefuls were Darren, Mike, and me. I’m extremely happy that Darren is the one on the book. Mike and I can wrangle sauropods and we’re both “All [Some]days” fanboys, but the book really needed someone approaching tetrapod omniscience, and that’s obviously Darren.
Whoops, that was actually just another paragraph of navel-gazing. Anywho, I knew after this year’s SVPCA that there would be a book, but I had no idea it would be out so soon. I can’t tell you much about the book itself, for two reasons. First, my dead-tree copy is still en route from lulu.com. Second, I wouldn’t tell you much about the book if I could, because you should see it for yourself. It’s firmly in the tradition of speculative zoology but also has a serious point to make about the memes that drive a lot of paleoart. That’s all you need to know–get the book and prepare to be surprised, amused, amazed, and moved to wonder.
The other new book I’m all het up about is Zombie Tits, Astronaut Fish, and Other Weird Animals, by Becky Crew (Amazon, New South Books). My mutual admiration pact with Bec goes back to 2009. She blogged about one of my posts, I blogged about how indescribably wonderful her blog was, she published something I wrote–my first paying gig as a writer, I think. Now she’s blogging at SciAm, which is great, because although she’s smart, irreverent, and freakin’ hilarious, she’s also mortal, and we need to get as much of that good stuff out of her head and into general circulation as possible while she’s still around. (She’s not sick or anything, she’s just going to die sometime in the next century, and if you read her blog I think you’ll agree that that’s too damn soon.) Zombie Tits does not seem to be available stateside yet, but I will keep a weather eye on things and post an update when that changes.
I’ll probably review both books here in due time, if by “review” one means “alternately drool over and hyperbolically gush about with no attempt at objectivity whatsoever”. And I do mean precisely that.
It’s been a while since we’ve served you up a sauropod, so, finally and fittingly, here’s John Conway’s playful Camarasaurus taking a mud bath. Or maybe just trying to hide its hideousness; as the authors of All Yesterdays note, “Camarasaurus [...] is considered by some experts to be among the ugliest of all sauropods”.
July 18, 2012
This is the sacrum of Camarasaurus supremus AMNH 5761. Top row: dorsal view, with anterior to left. Middle row, from left to right: anterior, left lateral and posterior views. Bottom row: ventral view, with anterior to left. Modified from Ostrom and Mook (1921:figs. 43-44).
It’s instructive to compare with the “Apatosaurus” minimus sacrum. Direct comparison is somewhat hindered for two reasons: first, the ilia are fused to that sacrum but not to this; and second, different views are available, so I put the composites together differently. We can’t do anything about the ilia. But to facilitate comparison, here is a reworked version of the “Apatosaurus” minimus illustration with the right-lateral view discarded, a ventral-view silhouette added, and the composition mirroring that of Osborn and Mook’s Camarasaurus:
One thing is for sure: whatever else “Apatosaurus“ minimus might be, it ain’t Camarasaurus.
July 14, 2012
More goodness from Osborn and Mook’s (1921) gargantuan Camarasaurus monograph, again prepared largely for comparison with “Apatosaurus” minimus. Last time, I showed you one of O&M’s pubis illustrations. Now an ischium:
This shows the left ischium AMNH 576o’/Is.4. Left column: proximal aspect. Middle column, from top to bottom: medial, lateral, posterior (no dorsal view was provided). Right column: distal. Heavily modified from Osborn and Mook (1921: fig. 101) — cleaned up, lettering and lines removed, recomposed in a more informative layout, views rescaled to better match each other, and tweaked for colour.
As usual, click through for full resolution (only 989 x 978 this time).
It’s interesting to compare this with the similarly composed illustration of the “Apatosaurus” minimus ischium from last week.
July 13, 2012
(First of all, for anyone who’s not familiar with the plural of “pubis”, it’s spelled “pubes” but pronounced “pyoo-bees”. Stop sniggering at the back.)
As Matt and I struggle to figure out the partial pubis that is one of the elements of the “Apatosaurus” minimus specimen AMNH 675, one of the most helpful references is Osborn and Mook’s (1921) epic monograph on Camarasaurus. It’s not that 675 particularly resembles Cam — it doesn’t. It’s just that Osborn and Mook is very lavishly illustrated, so that it is (as far as I know) the only published paper in the history of sauropod studies to have shown a sauropod pubis in more than one aspect.
Here is one of the two pubes that they illustrated in the six cardinal aspects:
This shows the left pubis AMNH 5761/Pb.2. Top row: proximal aspect, with anterior to left. Middle row, from left to right: anterior, lateral, posterior, medial. Bottom row: distal, with anterior to left. Heavily modified from Osborn and Mook (1921: fig. 102) — cleaned up, lettering and lines removed, recomposed in a more informative layout, views rescaled to better match each other, and tweaked for colour.
As usual, click through for full resolution (only 1159 x 940 this time).
As you can see, the pubis is a very strangely shaped bone, twisted and with odd rugosities everywhere. If you’re very lucky, we’ll discuss these in more detail later. For now, the take-home message is that sauropod pubes are very weird and confusing, and the simple lateral view that’s typically all you ever see is terribly misleading.
May 1, 2012
Probably everyone who reads SV-POW! already knows that the manus, or forefoot, or sauropods was very distinctive. The metacarpal bones, rather than being splayed out horizontally as in the forefeet of most animals, were arranged more or less vertically in a horseshoe shape, hence the characteristic shape of sauropod manus prints.
This was first recognised by Osborn (1904), a paper which contains the greatest single sentence in any scientific paper:
My previous figures and descriptions of the manus are all incorrect.
Here is the rather beautiful illustration from that paper (fig. 1):
It depicts the right manus, in anterior view, of AMNH 965, “Morosaurus” sp. As described by Osborn and Mook (1921:376-377), that genus was subsequently synonymised with Camarasaurus by Mook (1914), following the earlier suggestion of Osborn (1898), and this synonymy is universally accepted — for now, at least.
If anything, trackway evidence suggests that this illustration shows the metacarpals insufficiently vertical, resulting in the manus being too splayed out.
I have nothing more to say about that; just wanted to post the illustration because it’s beautiful and out of copyright (so feel free to use it however you want!)
- Mook, Charles C. 1914. Notes on Camarasaurus Cope. Annals of the New York Academy of Science 24:19-22.
- Osborn, Henry F. 1898. Additional characters of the great herbivorous dinosaur Camarasaurus. Bulletin of the American Museum of Natural History 10: 219-233.
- Osborn, Henry F. 1904. Manus, sacrum and caudals of Sauropoda. Bulletin of the American Museum of Natural History 20:181-190.
- Osborn, Henry Fairfield, and Charles C. Mook. 1921. Camarasaurus, Amphicoelias and other sauropods of Cope. Memoirs of the American Museum of Natural History, n.s. 3:247-387, and plates LX-LXXXV.
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.
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:
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 …
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.]
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:
- 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.