Although I’m on record of being no fan of the tabloids, there’s no doubt that they are hugely influential.  So it has to be good news to find that in the last few hours, both Nature and Science have publicly come out against the Research Works Act.

The Nature Publishing Group (with publishes Nature), writing jointly with Digital Science, published this statement:

Nature Publishing Group (NPG) and Digital Science note the concern amongst the scientific and library communities about the Research Works Act (H.R. 3699), currently under consideration by the U.S. federal government, and wish to clarify our position.

NPG and Digital Science do not support the Research Works Act.

And within the last couple of hours, the American Association for the Advancement of Science (which publishes Science), has followed suit with its own statement:

The nonprofit American Association for the Advancement of Science (AAAS), the world’s largest general scientific society and publisher of the journal Science, today reaffirmed its support for the current public access policy of the U.S. National Institutes of Health (NIH).

Contrary to recent news reports, AAAS does not endorse the Research Works Act, which would prevent the NIH from requiring its grantees to make biomedical research findings freely available via the National Library of Medicine’s Web site.

This is excellent and very welcome news.  I have written to the NPG and AAAS to express my thanks for their statements.

I hope and expect to see other publishers following their example: this page on the Harvard cyber-law site is maintaining a list of AAP-member publishers who have done so.

Line drawing and photograph of the axis and third cervical vertebra of Chuanjiesaurus anaensis (LCD9701-I). Bar = 10 cm. From Sekiya 2011:fig. 6. Note the absurdly elongated postzygapophysis.

And remember — it’s not too late for you to make a difference to the RWA’s success or failure.  See the Alliance for Taxpayer Action’s page, Call to action: Oppose H.R. 3699, a bill to block public access to publicly funded research.

In our recent paper on how the long necks of sauropods did not evolve primarily due to sexual selection (Taylor et al. 2011), one of the ideas we discussed is that sexual dimorphism between the necks of male and female sauropods would be an indicator of sexual selection.  And, rather despairingly, we wrote (page 4):

As Senter himself recognized, available samples of sauropod taxa are unfortunately not large enough to demonstrate bimodal distribution of morphological features within any sauropod species.

But I wonder if we realise just how true this is, and how blind we are flying?  How very far short we are of being able to do any kind of statistical analysis on sauropod necks.

How many complete necks of a given sauropod would we need in order to demonstrate a bimodal distribution of, say, length?  (That is, to show that the necks mostly fall into two separate buckets, a short-necked group and a long-necked group of which one is presumably male and the other female.)  I don’t know enough about stats, but this article at least suggests that you’d need thirty or so before you could be confident that you were seeing something statistically significant.

And how many sauropod species do we have thirty complete necks for?

Correct: none.

All right, then how many do we have ten complete necks for?

Five complete necks?

OK, how about just two necks?

ONE neck?

The answer is: not many species.  Off the top of my head, I think complete necks are known for Camarasaurus lentus (Gilmore 1925, one specimen), Mamenchisaurus hochuanensis (Young and Zhao 1972, one specimen), Shunosaurus lii (e.g. Zhang et al. 1984; probably multiple specimens but the paper is in Chinese so I don’t know for sure) Mamenchisaurus youngi (Ouyang and Ye 2002, one specimen, I think), and Spinophorosaurus nigerensis (Remes et al. 2009, one specimen).

No doubt I have missed some, but the point is that the total number of sauropods for which even one complete neck is known is a tiny, tiny proportion of all the sauropods that have been named.  I have listed five species here, and of those only one is known from more than a single complete neck.  And those multiple specimens have not been described (have they?)  So while in theory it might be possible to determine whether there is a bimodal distribution in the length of Shunosaurus lii necks, the data doesn’t exist to do this work.  (If there really are enough complete necks then someone ought to get out to China and measure those babies.)

So anyway.  We have very, very few complete sauropod necks.

Diplodocus carnegii

“But Mike!”, I hear you cry; “What about Diplodocus carnegii?  We’ve all seen its skeleton in a half-dozen different museums!”

Oh yes.  Here is its “complete” neck, from Hatcher (1901:plate 8):

Let’s, for now, ignore the fact that the scapula seems to articulate with the base of the neck rather than the torso.  We can all see that there are fifteen cervical vertebrae, right?

Right?

Well, let’s see what Uncle J. Bell had to say (Hatcher 1901:4):

[Diplodocus carnegii holotype CM 84] has been entirely freed from the matrix and is found to consist of the right femur and pelvis complete except for the left ilium, which is for the most part wanting, right scapula and coracoid, two sternals, eighteen ribs and forty-one vertebrae divided as follows: fourteen cervicals including the axis, eleven dorsals, four sacrals, and twelve caudals.  These vertebrae are for the most part fairly complete, though unfortunately the sacrals and anterior cervicals are more or less injured.  This series of forty-one vertebrae are believed to pertain to one individual and to form an unbroken series from the axis to the twelfth caudal, although as was shown in a previous paper, there is some evidence that there are perhaps one or more interruptions in the series and that one or more vertebrae are missing.  On the other hand, as will appear later, it is not entirely impossible that at least one vertebra of this supposed series pertains to a second individual belonging perhaps to a distinct genus.

Oh and there’s this, from page 10:

Unfortunately no diagram of the quarry was made, at the time of exhuming the remains, showing the relative position of each of the several vertebrae and other bones as they lay in the rock.  [Plate 1 is a map of the quarry as remembered by W. H. Reed.]

Hey!  That’s not what it said in the brochure!  So, as it turns out, our conclusion is: Diplodocus carnegii had fifteen cervicals, or more, or maybe less.

Giraffatitan brancai

“Well, then, Mike, how about that awesome mounted Giraffatitan skeleton in the Berlin museum?”

Well, the presacral vertebrae of that mount are not real bone, nor even casts, but they are very good sculptures based on real bones.  However, the real bones that they’re based on are those of two specimens — the lectotype SI and paralectotype SII.  The former includes cervicals 2-7, and we can be confident about that because C2 in sauropods is very distinctive, having a completely different anterior articular surface from all the other cervicals; and the latter includes cervicals 3-13 (although many of them are damaged).

But but but.  SI and SII were smushed up and mixed in together, with little articulation.  Any reconstruction — or even assignment of individual vertebrae to one specimen or the other — has to be considered provisional.  Take a look at this quarry map, from Heinrich (1999:fig. 16):

Yeesh, what a mess.  I’ve previously suggested (Taylor 2009:800-801) that the distinctively high-spined dorsal vertebra usually considered the fourth of SII may not actually belong to that specimen, or even that taxon — that it may belong to a more Archbishop-like animal (which may be what SI is).  Janensch (1950:33) says that things are not so bad for the cervical vertebrae, but still not good:

The vertebrae from the 3rd to 15th presacrals [of SII] lay in articulation in a consolidated lime sandstone lens; of them, the 3rd to 5th vertebrae are tolerably complete, the remaining 10 vertebrae were articulated with one another, with one interruption that arose when the 8th presacral vertebra rotated out of the series and was displaced.

So might there have been other displaced cervicals, before and/or after the “8th”, that were not recovered?  And can we be confident that the anteriormost cervical of SII really is C3?  Why?  Because of the overlap with vertebrae of SI?  But we’re not even certain that SI is the same species as SII.  Maybe the anteriormost preserved cervical is really C4?  Maybe some of the “SII” cervicals really belong to SI?

So all in all, our conclusion is: Giraffatitan brancai had thirteen cervicals, or more, or maybe less.

What does it all mean?

Only this: we don’t know as much as we think we do.  We don’t know how many cervical vertebrae Diplodocus and Giraffatitan had, even.  We don’t have complete necks for either of these sauropods, nor for almost any others.  Even those we do have are in some cases badly crushed (e.g. Mamenchisaurus hochuanensis, which I must post about properly some time).  To summarise: we are woefully short of sauropod necks.

We need to get out of the habit of blithely asserting, “oh, Diplodocus had 15 cervicals and Giraffatitan only 13″.  Because we really don’t know this.  We think it’s true: these numbers are certainly the best guesses for the taxa in question.  But they are, in the end, only guesses.

References

Why did sauropods have such long necks?

Mamenchisaus hochuanensis skeletal reconstruction (Young and Zhao 1972:fig. 4), based on the holotype

It’s the single most obvious and important question about sauropods, so it’s a bit surprising to think that we’ve never really addressed this question directly.

Maybe sauropod necks are so obvious and familiar that we just take them for granted, and move straight on to questions of how they were able to grow so long and remain workable.

Well, let’s fix that.  Let’s think about why they had such long necks.  What were they for?  What were sauropods doing with their necks that was valuable enough to justify all that investment?

Back in the good old days, everyone assumed that sauropod necks were all about high browsing.  If you have a 9.5m neck, then of course you will use it to browse high up in trees — it’s intuitively obvious.  But of course “intuitively obvious” is not the same thing as “true”.

Then John Martin (1987) proposed that the long necks were used for low browsing — not raised above shoulder level, but swept back and forth to allow food to be gathered across a wide area without all that tedious mucking about with locomotion.  This interpretation was of course endorsed by Stevens and Parrish (1999) in their DinoMorph work.

There has been plenty written about habitual sauropod posture — including by us (Taylor et al. 2009).  But actually the high-browsing and low-browsing explanations of sauropod neck elongation have much in common.  Most crucially, they both relate to enlarging the feeding envelope; more broadly they are both explanations that rely on the neck having a survival benefit.  But Senter (2006) proposed a completely different explanation — that sauropod necks were sexual signals, selected not for survival advantage but for reproductive success.  The idea is that female sauropods, being very shallow, would go for the males with the biggest protuberances.

Are there other candidate explanations that I’ve missed?

Or is it between high browsing, low browsing and sexual selection?

Comments are open!

References

[This is a guest post by frequent commenter Heinrich Mallison.  Heinrich is maybe best known to SV-POW! readers for his work on digital modelling of sauropodomorphs, though that may change now that his paper on sauropod rearing mechanics is out.  Read on …]

Maybe this post should have been titled “How sauropods breathed, ate, and farted”. Or maybe not. But breathing, eating and fermenting the food will play an important role.

Last week held a special pleasure for me. I spent it in New York, digitizing sauropods bones in the American Museum of Natural History’s Big Bone Room. Treasure trove that this room is, the museum still held something even better: the opening of a new special exhibit titled The World’s Largest Dinosaurs. While all such exhibits are of general interest to me, this one is special. Mark Norell, famous palaeontologist and curator at the AMNH, had a co-curator for this exhibit, Martin Sander of Bonn University, who is the head and speaker of the German Research Foundation Research Unit FOR 533 “Sauropod Biology”. As a member of FOR 533, and having received funding for both my PhD work and my first post-doc project, I am obviously somewhat biased, so please take this into account when you read this report.

The exhibition does not show a large amount of sauropods material. Not that it wouldn’t make for a nice exhibit, as the AMNH’s Hall of Saurischian Dinosaurs doesn’t really have that many sauropods (one Apatosaurus mount, to be exact, with a mashed up Barosaurus vertebral column half-hidden away and a wonderful but obviously depressed “prosauropod”, my old friend Plateosaurus, thrown in to make up a bit for the many, many stinkin’ theropod specimens). But instead of showcasing some of the usually hidden-away bones of the AMNH collection (and believe me, there is some wonderful stuff there), it rather focuses on those parts of the animal that are usually missing: the soft tissues. “How did sauropods get so big?”, or, reversing the question: “Why did and does no other group of terrestrial vertebrates reach such gigantic body sizes?” These were the questions our research group has been busily investigating for the last six years, and the answers to these question are what the exhibit now tries to communicate to the public. And it does so quite successfully!

The centerpiece of the AMNH exhibit: the belly of Mama Mamenchisaurus.

The centrepiece is a full-sized, fleshed out model of a sauropod (Mamenchisaurus hochuanensis), but on one side the skin and superficial musculature has been cut away. The visitor can see the neck vertebrae, the trachea, the carotid artery, and the ribcage. And the ribcage is also a projection area, on which a video is played that shows the internal organs and how they work.

With a voice-over that explains the actions in simple terms, the principle of the avian-style unidirectional lung and the air sacs is explained (albeit with a small error, as lung physiologist and FOR 533 member Steve Perry was quick to point out – the AMNH has promised to fix things), as well as the basic principles of sauropod reproduction (high number of offspring). Many things are not said or shown here, which is a good thing as it allows for the normal short attention span of the average museum visitor for one piece of exhibit. Instead, interesting stuff like how much fodder a sauropod needed per day (or even per hour), a comparison of a sauropod’s and an elephant’s heart, and of a giraffe’s and a sauropod’s neck vertebra (wow, how light the sauropod one is!) are explored at small science stations spread around the room. I won’t go into a detailed description here, you can find that elsewhere on the web. The AMNH did a blogger’s preview a while ago, and invited the press for a press conference and walk-through of the exhibit with the chance to interview the scientists present on Wednesday, so much info has already been plastered all over the web. Instead, I’ll just show you some pics and talk a bit about the concept of the exhibition, and how various issues were handled that can make or break a show.

One thing is how to catch the attention of visitors and direct it to the content of the exhibit. You don’t want people just going “aw, sh*t! That is one HUGE bone/animal!” and wandering off into the next room. If you want to educate them (and that, may I remind you, is the central purpose of a museum exhibit), you need to get them interested in stuff. Get them to read texts, look at stuff (not just let their eyes wander across it for a few seconds), try to get their brains going. The sauropod exhibit manages this by, first of all, being behind a closed door you can’t see through. Usually, the AMNH halls are accessible either through an open doorway, or in a few cases through glass doors. Secondly, the exhibit, especially the rather confined area you enter first, is dark. Very dark. Again a marked contrast to the AMNH’s usually well-lit halls. Just a few plants greet the visitor, and it takes a second to adjust to the dark – enough time to look around a bit and notice the neck and head of Argentinosaurus (fleshed out model) above.

My esteemed colleague Vivian Allen from Royal Veterinary College London going "Aw, sh*t! That is one HUGE sauropod!"

Next, the visitor is channeled along, with only a very few specimens to catch his attention. Well done, because these few pieces (sauropod leg, Komodo dragon skeleton, human skeleton, etc.) focus on getting the main message across (sauropods = way larger than everything else), aided by the largest animals (or their silhouettes) or various groups painted on the wall. Only once the message has been driven home, as I could detect from the comments I overheard, are the visitors released into the main area that contains the sauropod model and the various detail exhibits around it.

The next thing is giving people time to check things out. If you herd them too much, they will get driven along by the masses. That’s why the larger, opener area around the sauropod model and the smaller bits around it works so well: people can sit down to see the projected videos on the sauropod belly, or they can drift around from one specimen or science station to the next.

The stations are not just glass cabinets with some bones in them. Instead, at many of them you can DO things. One allows you to measure either an adult or baby sauropod femur or your own, and then calculate how heavy a sauropod of that size was. At another you can pump a sauropod’s and an elephant’s lung. One I liked very much simply had an unpainted sauropod model, and two sets each (adult and children height) of oculars. One showed a colorful “show-off” version, the other a “camouflage” one. “Which one is true? We don’t know!” is how I’d paraphrase the text that goes with it. One that innocently hides in the corner is among the most impressive: a 5 ½ ft cube (1.7 m, for the civilized) made from Plexiglas filled with sauropod food. A serving sufficient for one day! On it, also, the various plant groups available in the Mesozoic were rated for various factors, getting an easily understood rating in stars. That’s another big thing: make things easily understandable, visualize them!

Yummy! 100% Recommended Daily Value for your average sauropod.

With all these things well done, there remains only one more thing: make things fun for kids! And the AMNH did just that by adding a kids’ dinosaur dig. OK, it is one of those cheesy things where you use brushes and stuff to brush sand off fossils (cast), but it was done well enough that kids lined up like there was no tomorrow.

Overall, the exhibit gets two big thumbs up from me. If you make it to NY while it is on, or to any of its future stations, go see it! However, as FOR 533 member Steve Perry was quick to point out: if you’re in it only for the size, you’ll be disappointed! Aside from a few isolated bones, not much of the largest dinosaurs (Argentinosaurus and Amphicoelias) is to be seen in bone. It is the biological details that matter!  But don’t get me started about the tail musculature, especially the caudofemoralis, of the big model.

And then, there is the other thing about it that is closely tied to shameless self-promotion: the AMNH did not produce a catalogue or anything similar. Instead, the latest book from the “Life of the Past” series (Editor: James Farlow) of Indiana University Press was presented at the press conference. The lucky reporters all even got a free copy! The title is Biology of the Sauropod Dinosaurs: Understanding the Life of Giants, edited by N. Klein, K. Remes, C. T. Gee and P. M. Sander. And by now, I am sure, you have figured out who the authors are … It is intended to be a summary of the research findings of the first (and part of the second) funding period of FOR 533, and yours truly has two chapters in it. The first doesn’t really give much new information; most is already contained in my two papers here and here. The second, however, presents novel research that didn’t make it into the AMNH exhibit. But hey, why spoil the surprise – go and buy our book!) Overall, it is quite a technical book, so laypeople beware, but we did try to make the research as accessible as possible while retaining a high standard. For the even more technically minded there is the summary of our research group’s work (which cost the DFG ~€6.000.000) to be found in Sander et al. 2010. However, reading that paper is not half as much fun as the book, or the exhibit.

References

A month ago, I posted an article containing all the examples known to me of that sadly neglected palaeo-art theme, Sauropods Stomping Theropods: Mark Hallet’s Jobaria squishing Afrovenator, Luis Rey’s Astrodon biting/carrying a raptor, Mark Witton’s Camarasaurus grinding juvenile theropods to dust, and of course Francisco Gascó’s and Emily Willoughby’s Brontomerus pieces, both of them showing Bronto giving Utahraptor a good kicking.

I closed that article with a question and a challenge: had I missed any existing pieces on this theme?  And would anyone go out and make a new one?

Well, there were a few interesting responses in the comments and by email, so I thought I’d report back.

First, I am delighted that David Maas was provoked by the earlier article to produce a speedpaint entitled Sauropod Stomp, whose progress he described on his own site (version 1, version 2, version 3), and which I reproduce here:

I love the boldness of this, and the “Hey!  Quit it!” expression on the theropod’s face.

Also partly provoked by the earlier post — it’s an old project, but only brought to completion in response to our challenge — is Brian Engh’s new Shunosaurus whacking the head of a theropod with its tail club.  (We’ve previously discussed Shunosaurus tail clubs here and here.)  Brian also chronicled the evolution of his image on his own blog (version 1 [scroll down], version 2, version 3), and here is the result:

There are a few more Shunosaurus pieces out there, of which my favourite is Mark Hallett’s Direct Hit:

This image was used in Czerkas & Czerkas’s book Dinosaurs: A Global View.  The original painting is for sale on Mark’s site (as other pieces, including the classic Long March).

Todd Marshall also has a Shunosaurus, but I don’t know anything about its history as the only non-tiny version of this image I’ve found is in Wikidino:

(I think Todd Marshall’s pencil drawings are absolutely sensational, as for example in this Spinosaurus, but for me the colour versions of his work seem to lose something in comparison.)

There’s also a Shunosaurus-whacking-Gasosaurus piece that’s cropped up in various places, but I won’t reproduce it here because I am keen to avoid violating his copyright.

And now for something completely different: Brad McFeeters’s unintentionally carnivorous Omeisaurus, about to find a Scansoriopteryx in its salad.  This was done for ArtEvolved’s sauropod challenge.

Har har.

As we now start to head towards the sillier end of the spectrum, there is this, which Jonathan Kane says is by Emily Willoughby (though I’ve not not been able to find it on her DeviantArt site):

And of course this never-to-be-forgotten classic by our own Darren Naish (previously featured here):

Finally, I urge you to watch this video, which has given me many hours of uncomplicated joy.

In a comment on an earlier article, What’s the deal with your wacky postparapophyses, Shunosaurus?, brian engh asked:

What’s the deal with most Shunosaur “life restorations” showing spikes on the tail club? I can’t find a picture anywhere of a skeleton with any indication of spikes, and yet almost every fleshed-out illustration of Shunosaurs has spikes on it’s tail. Anybody know what that’s about?

It seems we’ve never actually featured the famous Shunosaurus tail-club here before — an amazing oversight, and one that I’m going to remedy right now, thanks to Dong et al. (1989).  This short paper is written in Chinese, so I can’t tell you anything beyond what’s in the figures, captions and English-language abstract.

First up, though, here is his illustration of the famed tail-club:

I can’t help noticing, though, that although the fused clump of enlarged distal caudal vertebrae constitutes a nice club, it’s noticably devoid of spikes.  So it remains a mystery why so many restorations show a spiked club.  Anyone out know why?

Dong et al. (1989) also obligingly includes a figure of the tail-club of Omeisaurus:

And also a photographic plate showing both clubs (though, as is so often the case, the scan has lost a lot of details):

Now, the big question is: why do Shunosaurus and Omeisaurusand Mamenchisaurus, for that matter — have tail-clubs when they are not closely related, according to modern phylogenies such as those of Wilson (2002) and Upchurch et al. (2004)?  [To be precise, Wilson (2002:fig. 13) had Omeisaurus and Mamenchisaurus clading together, but that clade well separated from Shunosaurus; and Upchurch et al. (2004:fig. 13.18) had all three separate, though with the former two as consecutive branches on the paraphyletic sequence leading to Neosauropoda.]

One possibility is just sheer coincidence: but it’s asking a lot to believe that of the 150 or so known sauropods, the only three for which tail-clubs are known just happened to live more or less at the same time and in the same place.

Another option is some oddity in the environment that strongly encouraged the evolution of tail clubs.  Yes, this is wildly hand-wavy, but you can sort of imagine that maybe all the local theropods thought it was cool to hunt sauropods by biting their tails, and the clubs evolved in response to that.  Or something.  There’s a similar, but even more mystifying, situtation in the late Early Cretaceous Sahara, where the theropod Spinosaurus, the ornithopod Ouranosaurus and arguably even the sauropod Rebbachisaurus all evolved sails.  Why then?  When there?  No-one knows and no-one’s even advanced a hypothesis so far as I know.

Getting back to Jurassic Chinese sauropod tail-clubs, though, there is a third option: could it possibly be that Shunosaurus, Omeisaurus and Mamenchisaurus all form a clade together after all, as proposed back in the day by Upchurch (1998:fig. 19)?  Upchurch’s pioneering (1995, 1998) analyses both recovered a monophyletic “Euhelopodidae” — a clade of Chinese sauropods that included the three genera above plus the early Cretaceous Euhelopus, also from China.  The existence of this clade was one of the two major points of disagreement between Upchurch’s and Wilson’s phylogenies (the other being the position of the nemegtosaurids, Nemegtosaurus and Quaesitosaurus, which Upchurch placed basally within Diplodocoidea but Wilson recovered as titanosaurs).

Upchurch himself has abandoned the idea of the monophyletic Euhelopodidae, as seen in that 2004 analysis and also in Wilson’s and his joint (2009) reassessment of Euhelopus: everyone now agrees that Euhelopus is a basal somphospondyl, i.e. close to Titanosauria, which is a looong way from the basal position that the other Chinese sauropods hold within Sauropoda.)  And so the name Euhelopodidae is no longer used.  But could it be that Upchurch was half-right, and that when Euhelopus is removed that the group that was named after it, a clade remains?

[If so, then that clade is called Mamenchisauridae: as noted by Taylor and Naish (2007), this name was coined by Young and Zhao (1972) and so has priority over the Omeisauridae of Wilson (2002), as Wilson himself now recognises.  Mamenchisauridae was phylogenetically defined (or, as they have it, “diagnosed”) by Naish and Martill (2007:498) as “all those sauropods closer to Mamenchisaurus constructus Young, 1954 than to Saltasaurus loricatus Bonaparte”.]

As already noted, Omeisaurus and Mamenchisaurus are close together in the recent analyses of both Upchurch and Wilson, so the question becomes: how many additional steps are required to recover Shunosaurus as a member of their clade rather than in its usual more basal position (in the the case of Upchurch’s analysis, to move Omeisaurus up a node)?  And to this, I do not know the answer — to the best of my knowledge, it’s never been tested (or if it has, the result has never been published).  I’d test it myself, but I need to stop working on this post and watch Inca Mummy Girl soonest.  If , say, 20 additional steps are needed, then forget it.  But if we only need, say, three steps, then maybe someone should look at this more closely.  Back in 2004, when he was Young And Stupid, Matt Wedel wrote to me, in a private email which I now quote without permission because I am pretty sure he’s not going to sue me:

Now that I’ve defended the status quo [of using unweighted characters in cladistic analysis], there are some things I’d be happy to bend the rules for.  If an Omeisaurus pops up with a tail club, then Wilson and Sereno be damned, Omeisaurus and Shunosaurus belong in the same clade. […] So my final word is unweighted characters, please, except for sauropod tail clubs.

Food for thought.

Finally, I leave you with the skeletal reconstruction of Omeisaurus from Dong et al. (1989:fig 3).  Long-time readers will notice a more than passing resemblance to the reconstruction from He et al. (1988:fig. 63), which you can see in Omeisaurus is Just Plain Wrong.

It looks very much as though Dong et al. produced their reconstruction by flipping that of He et al. horizontally and pasting on a tail-club.  Well, we can’t hold that against them — I’d have done the same.

References

  • Dong Zhiming, Peng Guangzhao and Huang Daxi. 1988. The Discovery of the bony tail club of sauropods. Vertebrata PalAsiatica 27(3):219-224.
  • He Xinlu, Li Kui and Cai Kaiji. 1988. The Middle Jurassic dinosaur fauna from Dashanpu, Zigong, Sichuan, vol. IV: sauropod dinosaurs (2): Omeisaurus tianfuensis. Sichuan Publishing House of Science and Technology, Chengdu, China. 143 pp. + 20 plates.
  • Naish, Darren, and David M. Martill. 2007. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia. Journal of the Geological Society, London, 164: 493-510. (Bicentennial Review issue.)
  • Taylor, Michael P. and Darren Naish. 2007. An unusual new neosauropod dinosaur from the Lower Cretaceous Hastings Beds Group of East Sussex, England. Palaeontology 50 (6): 1547-1564. doi: 10.1111/j.1475-4983.2007.00728.x
  • Upchurch, Paul. 1995. The evolutionary history of sauropod dinosaurs. Philosophical Transactions of the Royal Society of London Series B, 349: 365-390.
  • Upchurch, Paul. 1998. The phylogenetic relationships of sauropod dinosaurs. Zoological Journal of the Linnean Society 124: 43-103.
  • Upchurch, Paul, Paul M. Barrett and Peter Dodson. 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, Jeffrey A. 2002. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136: 217-276.
  • Wilson, Jeffrey A. and Paul Upchurch. 2009. Redescription and reassessment of the phylogenetic affinities of Euhelopus zdanskyi (Dinosauria – Sauropoda) from the Early Cretaceous of China. Journal of Systematic Palaeontology 7: 199-239. doi:10.1017/S1477201908002691
  • Young, Chung-Chien, 1954. On a new sauropod from Yiping, Szechuan, China. Acta Palaeontologica Sinica II(4):355-369.
  • Young, Chung-Chien, and X. Zhao. 1972. [Chinese title. Paper is a description of the type material of Mamenchisaurus hochuanensis]. Institute of Vertebrate Paleontology and Paleoanthropology Monograph Series I, 8:1-30. English translation by W. Downs.

In color, this time, with multiple views, thanks to Xing et al. (2009). They also did a finite element analysis of the tail club and concluded that it was a fairly pathetic weapon. Xing et al. closed by supporting the contention of Ye et al. (2001) that the tail club was a sensory organ. As they stated at the end of the abstract:

The tail club of Mamenchisaurus hochuanensis probably also had limitations as a defense weapon and was more possibly a sensory organ to improve nerve conduction velocity to enhance the capacity for sensory perception of its surroundings.

One thing Xing et al. (2009) cite in support of this is the expanded neural canal inside the club, which they compare to the sacral enlargement in stegosaurs and to the glycogen bodies of birds. They rule out a glycogen body on the grounds that the sacral enlargement in stegosaurs is much bigger than the brain volume, whereas the neural canal enlargement in the M. hochuanensis tail club is much smaller (if you don’t follow that logic, don’t worry, neither do I).

I’m not sure what to make of this thing. On one hand, it would be nice to have more than one club available to rule out the possibility that it’s just a weird paleopathology. On the other hand, it looks oddly regular to be pathological, and the definitive clubs in Shunosaurus and Omeisaurus are at least weak support for this being a genuine feature, although the clubs of the former taxa look very different.

Furthermore, I don’t understand how the authors can rule out the presence of a glycogen body based on the size of the neural expansion alone–especially since the functions of glycogen bodies in extant taxa are very poorly understood (as you may remember from this dustup). Nor can I fathom how a titchy little nerve bundle–if such existed–down at the end of the tail could do much to improve nerve conduction velocity up the rest of the tail. Either my understanding of neuroscience is completely shot, or this hypothesis…lacks support. I am open to being enlightened either way.

Finally, I am disappointed that the authors didn’t pursue the cutting-edge pseudohead hypothesis that has figured prominently here and elsewhere in the blogosphere. There’s a Nobel lurking in there, I just know it.

References

  • Xing, L, Ye, Y., Shu, C., Peng, G., and You, H. 2009. Structure, orientation, and finite element analysis of the tail club of Mamenchisaurus hochuanensis. Acta Geologica Sinica 83(6):1031-1040.
  • Ye, Y., Ouyang, H., and Fu, Q.-M. 2001. New material of Mamenchisaurus hochuanensis from Zigong, Sichuan. Vertebrata PalAsiatica 39(4):266-271.