Back in 2010, SVPCA was held in Cambridge. (It was the year that I gave the “why giraffes have short necks” talk [abstract, slides].)
While we were there, I took a lot of photos in the excellent Cambridge University Museum of Zoology, which was just across the courtyard from the lecture theatre where the scientific sessions were held.
In light of the recent discussion here on how many cervical vertebrae giraffes have (spoiler: seven), I thought it would be good to air the sloth photos, since the two genera of sloths constitute 66% of all the mammals have that a cervical count other than seven. (The third is the manatee Trichechus, with six cervicals.)
Three-toed sloth, Bradypus tridactylus. This specimen has nine cervicals vertabrae, but apparently the count can vary between eight and ten in different individuals.
Three-toed sloth, Bradypus tridactylus, full skeleton.
Two-toed sloth, Choloepus didactylus. Six cervical vertebrae.
Two-toed sloth, Choloepus didactylus, full skeleton.
Camel necks: condyles don’t reach the cotyles
April 2, 2013
Long, long ago — back in 2010! — Gordon Dzemski of the University of Flensburg, Germany, sent me a copy of a miniposter that he had prepared, and invited me to share it on SV-POW!. Somehow, it fell through the cracks, and I never did so. Time to fix that!
First, the highlight: a X-ray of a camel neck:
The great thing about this is that the condyles and cotyles are so thickly coated in cartilage that the condyles don’t even reach, let alone nestle inside, the cotyles. Amazing.
Now in contrast, the condyles of horse cervicals do nestle in their corresponding cotyles – very neatly. And the distressing thing is that, to the best of our knowledge, there are no osteological correlates that would allow us to distinguish these conditions. That is, nothing about the naked bones of the camel and horse that would let us infer this huge difference in their cartilage.
Unless anyone knows different?
(Of course, here at SV-POW!, we have previous with camels: the Cambridge camel, all the camels, the Oxford camel, the Paris camel)
Anyway, here is the whole of the poster that Gordon prepared:
And here is his own commentary on it:
Hi Mike,
for your nice Blog and the never ending story of articulated or disarticulated camels, giraffes, goos or ostrichs necks I have made a nice overview of some x-ray pictures of my work.
I think we can postulate some basic principles:
1) There is in every mammal an invertebral disc space between the neck vertebrae.
2) Every mounted skeleton of an animal with a free space between the cotyle-condyle joint system is in articulated postion (but without an invertebral disc).
3) The joint capulse with the specific system components of invertebral discs, cartilage, ligaments and tendons are capable of great dorsoventral and lateral flexion and is capable of high pressure or great tensile force to reach/generate the postures of the living animal neck . And yes, the space beween the camels vertebrae can be 30 or more mm.
4) For prehistoric animals we can assume an average invertebral disc space of 5% of the neck length. I think it is the best guess so far.Please use the picture and this email freely for your Blog if it is in your opinion.
I am inclined to think that the 5% estimate for extinct animals may be a little on the high side (for reasons that will become apparent in due course) but all the evidence is that it’s in the right ballpark.
This has implications.
So, this happened today
March 28, 2013
Titanosaurs have stupid cervicals
March 21, 2013
As I noted in a comment on the previous post, titanosaurs have stupid cervicals.
As evidence, here is as gallery of titanosaur cervicals featured previously on SV-POW!.
1. From Whassup with your segmented lamina, Uberabatitan ribeiroi?, an anterior cervical of that very animal, from Salgado and Carvalho (2008: fig. 5). As well as the titular segmented lamina, note the ridiculous ventral positioning of the cervical rib. It’s like it’s trying to be Apatosaurus, but it just doesn’t have the chops.
2. From Mystery of the missing Malawisaurus vertebra, this alleged vertebra of that taxon from Jacobs et al. (1993:fig. 1), which completely fails to resemble all the other cervicals subsequently described from Malawisaurus (see the earlier post for details). Note the crazy sail-like neural spine and super-fat parapophyseal stump.
3. From Futalognkosaurus was one big-ass sauropod, this completely insane posterior cervical vertebra of Futalognkosaurus in right anterolateral view, with Juan Porfiri (175 cm) for scale. It’s super-tall — much taller than it is wide, and seemingly taller than it is long.
4. From Ch-ch-ch-changes, cervical 11 of Rapetosaurus, from Curry Rogers (2009:fig. 5). Notice how tiny the centrum is compared with the tall superstructure, and how the neural spine has such a distinct peak. Weird.
5. From Talking about sauropods on The Twenty-First Floor, cervical 9 of the same Rapetosaurus individual, from Curry Rogers (2009:fig. 9). The neural spine is a completely different shape from that of C11, but that is presumably mostly due to damage. One of the interesting things here is the apparent lack of pneumatic foramina in the centrum. They’re there somewhere: Curry Rogers (2009:1054) writes “In cervical vertebrae 9, 11, and 12, the centrum bears an elongate shallow pneumatic fossa with two anterior pneumatic foramina surrounded by sharp, lip-like boundaries.” But they are hard to make out!
The meta-oddity here is that the cervicals of the four titanosaur genera pictures here are all so different from each other. What does this mean?
Probably only that Titanosauria is a huge, disparate, long-lived clade that encompasses far more morphological variation than (say) Diplodocidae. It’s a truism that we don’t, even now, really have a handle on titanosaur phylogeny — every new study that comes out seems to recover a dramatically different topology — so our perception of the clade is really as a big undifferentiated blob. In contrast, the division of Diplodocoidea into Rebbachisaurids, Dicraeosaurids and Diplodocids (plus some odds and ends) is nicely established and easy to think about.
So. Lots of work to be done on titanosaurs.
References
- Curry Rogers, K. 2009. The postcranial osteology of Rapetosaurus krausei (Sauropoda: Titanosauria) from the Late Cretaceous of Madagascar. Journal of Vertebrate Paleontology 29(4):1046-1086.
- Jacobs, L.L., Winkler, D.A., and Downs, W.R., and Gomani, E.M. 1993. New material of an Early Cretaceous titanosaurid sauropod dinosaur from Malawi. Palaeontology 36:523-534.
- Salgado, L. & Carvalho, I. S. 2008. Uberabatitan riberoi, a new titanosaur from the Marília Formation (Bauru Group, Upper Cretaceous), Minas Gerais, Brazil. Palaeontology 51:881-901.
Neural spine paper: new file available
March 16, 2013
Figure 7. BYU 12613, a posterior cervical of Diplodocus or Kaatedocus in dorsal (top), left lateral (left), and posterior (right) views. It compares most favourably with C14 of D. carnegii CM 84/94 (Hatcher, 1901: plate 3) despite being only 42% as large, with a centrum length of 270 mm compared to 642 mm for C14 of D. carnegii.
The original version of the PDF of our new paper (Wedel and Taylor 2013) had a couple of obvious errors: Kaatedocus was misspelled in the caption to Figure 7 (as Kaatedocu), and the submission date was given as June 24, 2012, not the correct date of June 14. Both of these errors were introduced during the editorial handling, so I politely asked if they could be fixed, and thanks to the kind offices of the folks at PalArch, now they have been. However, to avoid confusion (or perhaps propagate it, depending on your feelings), the corrected PDF has a different filename. The original version will continue to be available at:
and the corrected version (with an extra ’1′ on the end of the filename) is at:
Two things:
- I will go around changing the links here and elsewhere (FigShare, etc.) to the new version, but I probably won’t have time today, as I have an all-afternoon community outreach at the local public library to help organize.
- I realize that some people, including possibly my coauthor, will hate this because now we have created some uncertainty about which is the version of record. So we’re not going to ask for any more changes, no matter how egregious the errors we find (and we are certain to find a few more, that’s just the nature of the beast); as far as I’m concerned, the second corrected version is the final version. Also, the changes made are tiny and don’t affect the science at all, so it’s not like we’ve moved any important goalposts here.
If you have strong feelings about this either way, feel free to sound off in the comments.
Our neural spine bifurcation paper is out
March 15, 2013
Figure 4. Cervical vertebrae of Camarasaurus supremus AMNH 5761 cervical series 1 in anterior view, showing different degrees of bifurcation of the neural spine. Modified from Osborn & Mook (1921: plate 67).
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).
Figure 18. Middle cervical vertebrae of Barosaurus AMNH 6341 (top) and Supersaurus BYU 9024 (bottom) in left lateral view, scaled to the same centrum length. The actual centrum lengths are 850 mm and 1380 mm, respectively. BYU 9024 is the longest single vertebra of any known animal.
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.
References
- 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.
Giraffes’ necks are lamentable
March 13, 2013
At the top: our old friend BYU 9024 — the cervical vertebra that’s part of the Supersaurus vivianae holotype. At the bottom, C2 (the longest cervical) of Giraffa camelopardalis angolensis FMNH 34426.
The Supersaurus vertebra is 138 cm long. We don’t know which cervical it is, but there’s no reason to think it’s the longest. The giraffe vertebra is 31 cm long. Not only is the Supersaurus vertebra four times as long as that of the giraffe, it’s one of more than twice as many cervicals as the giraffe has.
Did we cheat by using an unusually small giraffe? Not really. When we articulated all seven cervicals as best we could, the sequence measured 171 cm, which is a fairly healthy 71% of the 2.4 m neck of the world-record giraffe. It’s not a monster, but it’s a decent-sized adult.
Bottom line, giraffes are just lame.
Tutorial 21: how to measure the length of a centrum
March 11, 2013
For a paper that I and Matt are preparing, we needed to measure the centrum length of a bunch of turkey cervicals. That turns out to be harder than you’d think, because of the curious negative curvature of the articular surfaces.
Above is a C7 from a turkey: anterior view on the left; dorsal, left lateral and ventral views in the middle row; and posterior on the right. As you can see from the anterior, dorsal and ventral views, the anterior articular surface[1] is convex dorsoventrally but concave transversely; and as you can see from the lateral view, the posterior face is concave dorsoventrally and convex transversely.
This means you can’t just put calipers around the vertebra. If you approach the vertebra from the top or bottom, then the upper or lower lip of the posterior articular surface will protrude past the centre of the saddle, and give you too long a length. If you approach from the side, the same will happen with the left and right lips of the anterior articular surface.
What are we trying to measure anyway?
But this raises the question of what it is we’re trying to measure. I said “we needed to measure the centrum length of a bunch of turkey cervicals”, but what exactly is centrum length? Why shouldn’t the upper and lower lips of the posterior articular surface count towards it?
What does centrum length mean?
The problem doesn’t only arise with bird cervicals. The same issue arises in measuring more sensible and elegant vertebrae, such as our old friend HMN SII:C8, or MB.R.2181:C8 as we must now learn to call it.
Although the back of the vertebra is nice and simple here — it’s obvious what line we’re measuring to at the back — we have three choices of where the “front” of the vertebra is, and a case can be made for any of them as being “the length of the vertebra”.
The longest measurement (here marked “T” for “total length”) goes to the front of the prezygapophyseal rami. The next one (“C” for “centrum length”) goes to the anteriormost point of the condyle. The distinction is important: as noted recently, the longest vertebra in the world belongs to Sauroposeidon if we use total length, but to Supersaurus if we use centrum length.
But in life, most of the condyle would be buried in the cotyle of the preceding vertebra. So should it count towards the length of the vertebra? If you consider a string of articulated vertebrae, the buried condyles don’t contribute to the overall length of the neck. So Matt and I call the length from the posterior margin of the condyle to the posterior margin of the cotyle the functional length (marked “F” above), which I believe is a new term.
Another way to think of the functional length is the distance from a given point on a vertebra (in this case the posterior margin of the cotyle) to the same point on the adjacent vertebra:
For our current project, Matt and I are interested in how the lengths of individual vertebrae contribute to total neck length, so for our purposes, functional length is definitely what we want.
By the way, Janensch is the only author I know of to have even recognised the importance of functional length. The measurement tables on pages 39 and 44 have columns for “Gesamtlänge des Wirbels ab Vorderende per Präzygapophyse”, “Gesamtlänge der Wirbel-Körpers in 1/2 Höhe” and “Länge der Wirbel-körpers ohne Condylus in 1/2 Höhe” — that is, ”Total length of the vertebra from the anterior end of the prezygapophysis”, “Total length of the centrum measured at mid-height” and “Length of the centrum minus condyle at mid-height”. This is typical of his careful and methodical approach. Kudos!
Hey! I thought this was about turkeys
And so it is. Here is the functional length measurement for a turkey cervical:
It’s the shortest anteroposterior distance between the two articular surfaces.
Measuring functional length
Matt and I chatted about this at some length, and I am ashamed to say that we thought through all sorts of complicated solution involving subtracting measurements from known scaffold length and suchlike.
It took us a stupidly long to to arrive at the very obvious solution, which is just to modify the calipers to have a “tooth” that can protrude into the concavity of the anterior articulation between its left and right lips. Easily done with a flat-ended screw and a blob of wood glue:
With the measurements of all the vertebrae in my series, I can now fairly confidently expect that the sum of the individual lengths will come out at about the length of the complete neck.
You know, unless intervertebral cartilage turns out to be important or something.
References
- Janensch, Werner. 1950. Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica (Suppl. 7) 3:27-93.
Footnotes
1. Matt and I are so used to opisthocoelous sauropod presacrals that when we’re talking about vertebrae — any vertebrae — we tend to say “condyle” and “cotyle” for the anterior and posterior articular surfaces, no matter what their morphology. When talking about crocodile cervicals or titanosaur caudals, we’re even likely to say ridiculous things like “the condyle is concave and the cotyle is convex”. Nonsense, of course: condyle means “A rounded prominence at the end of a bone, most often for articulation with another bone.” What we should say is “the condyle is at the back and the cotyle is in front”.
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
Terrifying hypothetical cervical vertebrae of the Morrison Formation
February 13, 2013
In our PeerJ neck-anatomy paper, we speculated on how long individual cervical vertebrae might have grown. Here is the relevant section:
Mere isometric scaling would of course suffice for larger animals to have longer necks, but Parrish (2006, p. 213) found a stronger result: that neck length is positively allometric with respect to body size in sauropods, varying with torso length to the power 1.35. This suggests that the necks of super-giant sauropods may have been even longer than imagined: Carpenter (2006, p. 133) estimated the neck length of the apocryphal giant Amphicoelias fragillimus Cope, 1878 as 16.75 m, 2.21 times the length of 7.5 m used for Diplodocus, but if Parrish’s allometric curve pertained then the true value would have been 2.21^1.35 = 2.92 times as long as the neck of Diplodocus, or 21.9 m; and the longest single vertebra would have been 187 cm long.
Now this speculation is shot through with uncertainty. As we’ve discussed before, at length, all estimates of Amphicoelias fragillimus length and mass are wildly speculative; and Parrish’s allometry result was extrapolated from an unconvincingly small data set. But still, these numbers are probably the best we can do with what we have.
In Diplodocus carnegii, C14 is the longest individual vertebra at 642 mm long (Hatcher 1901, p. 38). The Amphicoelias:Diplodocus size ratio of 2.21 from Carpenter and the neck allometry constant of 1.35 from Parrish suggest that the corresponding vertebra in the big boy would have been 2.92 times as long as that 642 mm, hence the 187 cm that we reported.
So what does a 187-cm long cervical vertebra look like? Scaling up from the Diplodocus carnegii C14 in Hatcher (1901: plate III) and using my good self as a scalebar, here it is:
I find that just a little bit frightening. In more ways than one.
References
- Carpenter, Kenneth. 2006 Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus (Cope, 1878). New Mexico Museum of Natural History and Science Bulletin 36:131.
- Cope, Edward D. 1878. Geology and paleontology: a new species of Amphicoelias. The American Naturalist 12:563.
- 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.
- Parrish, J. Michael. 2006. The origins of high browsing and the effects of phylogeny and scaling on neck length in sauropodomorphs. pp 201-224 in: Amniote paleobiology, University of Chicago Press, Chicago.
