[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.

Hudiesaurus redux

May 5, 2009

A while back, Matt speculated on the size of the allegedly giant mamenchisaurid Hudiesaurus.  At the time, all he had to go on was Glut’s (2000) reproduction of half of Dong (1997:fig. 3), and a scalebar whose length was given incorrectly.  The comments on that article gave some more measurements, but we never got around to showing you the figures of the vertebra in question, so here it is:

Hudiesaurus sinojapanorum IVPP V. 11120 holotype "first dorsal" vertebra, composite of Dong (1997:figs. 1, 3a)

Hudiesaurus sinojapanorum IVPP V. 11120 holotype "first dorsal" vertebra, composite of Dong (1997:figs. 1, 3a)

The measurements of this vertebra given in the paper are:

  • Height of vertebra 76
  • Length of centrum 55
  • Width of centrum anteriorly 42
  • Width of centrum posteriorly 39
  • Height of neural spine 41
  • Width of top of neural spine 27

Dong said (p. 109) that “The mounted type skeleton of Mamenchisaurus hochuanensis, which was the largest sauropod known in China at the time it was described, measures 22 m in length (Young and Chao, 1972). The centrum of the first dorsal in the type of Hudiesaurus sinojapanorum is 1.5 times longer than the type of M. hochuanensis, leading to an estimated skeleton length of 30 m.”  This is odd because 1.5 times 22 m is 33 m, not 30 m.  But it’s also odd because Young and Zhao (1972:table 1) actually gave the centrum length of D1 as 250 mm — so the alleged 55 cm long centrum of the Hudiesaurus D1 is actually 2.2 times as long, which would yield a length estimate of *gulp* 2.2 x 22 m = 48.4 m.  Which would be right up in Amphicoelias fragillimus territory.  And that is clearly nonsense for a dorsal vertebra that’s only 76 cm high.

The height:length ratio of the Hudiesaurus vertebra is 76/55 = 1.38.  That of the first dorsal of M. hochuanensis is (using Young and Zhao’s measurements) 640/250 = 2.56 — nearly twice as tall.  In M. hoch., C19 (the last cervical) has a height ratio of 660/325 = 2.03 — better, but still not very close.  C18 has 660/400 = 1.65, C17 has 630/550 = 1.15.  So based on proportions, it looks like the Hudiesaurus “dorsal” is not a dorsal but a cervical — furthermore, not even the last dorsal, but the penultimate or antepenultimate cervical.  If it is homologous with C17 of M. hoch., then its 55 cm length is exactly the same as that M. hoch.’s C17, which would suggest that Hudiesaurus was the same length (22 m); if it’s homologous with C18. then its 55 cm length is 1.38 times greater than that of M. hoch., suggesting a total length of 30 m.  It’s interesting that this last figure is the very one proposed by Dong — could it be that after writing the paper, he reconsidered the serial position of the vertebra and recalculated the total length on the basis of an assignment as the penultimate cervical, while neglecting to update the text?    It seems a bit far-fetched, but maybe it’s a possibility.

Finally: is the vertebral morphology consistent with an identity as a cervical?  I think so.  The strong opisthocoely is a point in favour, as are the lateral fossae.  (The dorsals of Mamenchisaurus lack fossae and foramina.)  On the other hand, Dong claims that the vertebra has a hyposphene, which is unknown in cervicals — but I see no hyposphene in the photo above. Dong doesn’t really say why he thinks the vertebra is a dorsal, but my guess is that it may be due to lack of a fused cervical rib, and the assumption that there was a free dorsal rib associated with it.  But Young and Zhao (1972) say of M. hoch. that “The last cervical and first dorsal vertebrae are generally distinguished by rib morphology. However, a difficulty is posed here by the last cervical’s absence of articulated ribs.”  And my own observation of casts of this specimen show that actually the last few cervical ribs are not fused.

In conclusion, it seems to me that Hudiesaurus is probably based on a posterior cervical rather than an anterior dorsal.  BUT let me clear that I have never seen the material, and everything I’ve written here is based only on what’s in the literature.  I may well have made a dumb mistake, and no-one should take my thoughts on this too seriously.  If I was certain, I’d put it in a paper instead of on a blog.

References

Thanks to all for congrats regarding the baby news. Will this mean a short-term break from blogging? In part, yes, but luckily I’ve had the opportunity lately to prepare quite a lot of stuff in advance, so fear ye not oh fans of SV-POW! and Tet Zoo. And to demonstrate that point: welcome to another article in the ‘sauropods of 2008’ series. In the previous entry we looked at the Chinese titanosauriform Dongyangosaurus sinensis. Now for something completely different…

fig. 11) -- Yuanmosaurus reconstruction

Lu et al. (2006: fig. 11) -- Yuanmousaurus reconstruction

Potentially one of the most interesting of recently named sauropods is Eomamenchisaurus yuanmouensiset al., 2008 from the Middle Jurassic Zhanghe Formation of Yuanmou County, Yunnan Province, China. Yuanmou is already known in the world of sauropod research for yielding Yuanmousaurus [reconstruction above, from Lü et al. (2006)], a possible relative of Euhelopus named in 2006. The only known Eomamenchisaurus specimen consists of dorsal and sacral vertebrae, a partial pelvis, and hindlimb elements: unfortunately, however, the material isn’t fantastic and at least some of the diagnostic characters identified for the taxon are not entirely convincing and mostly look like widespread, primitive features. In the dorsal vertebrae, for example, the absence of pneumatic foramina is listed as a diagnostic feature, but if this animal really is a member of Mamenchisauridae as claimed, then absence of foramina doesn’t work as an autapomophy because other members of the group (e.g., Mamenchisaurus hochuanesis) are also reported to lack foramina on their dorsal centra (as are many other non-neosauropodan sauropods). Pneumatic foramina are indeed absent in Eomamenchisaurus, but note from the image below that pneumatic fossae are present (actually… I assume those lateral cavities are pneumatic fossae, but have just realised that they might not be. Let me know what you think). As is – I hope – well known by now, we’ve found it useful to distinguish ‘pneumatic foramina’ from ‘pneumatic fossae’: gone are the days when all pneumatic holes or cavities could simply be referred to as ‘pleurocoels’ or ‘pneumatopores’.

In the image shown here [from Plate II of Lü et al. (2008)], the ninth and tenth dorsals are shown in (A) ventral and (B) lateral views. See below for discussion. Note the pneumatic fossae. Scale bar = 10 cm.

eomamenchisaurus_lu_et_al_2008

As indicated by its name, Lü et al. regarded Eomamenchisaurus as an early relative of the famously long-necked mamenchisaurid Mamenchisaurus. Are there any characters that support this assignment? There are, but they aren’t very convincing either: three concern the anatomy and degree of fusion in the sacrals, and that’s always a problematic area because sacral fusion varies with age and, in some taxa, with sex. The fusion of two posterior dorsals (probably the ninth and tenth) is used as a fourth character. According to Lü et al., this fusion is also present in M. hochuanensis, M. youngi and in Chuanjiesaurus anaensis. The last taxon listed there was regarded by Lü et al. as a mamenchisaurid, but the original description provides little information and Upchurch et al. (2004) treated this form as Sauropoda incertae sedis, and only provisionally valid. It is entirely coincidental that Matt is also dealing with vertebral fusions at the moment – I hope I’m not treading on his toes by writing all this, apologies if I am.

A full evaluation of Eomamenchisaurus is needed to further determine its affinities: it might be a mamenchisaurid, but we need more data. In fact it’s worth saying at this point that mamenchisaurids as a whole need a thorough revision: as is widely recognised among sauropod workers, Mamenchisaurus (currently containing seven species) now seems to be a waste-basket genus housing disparate animals that are probably not all close relatives.

References

Lü, J., Li, T., Zhong, S., Ji, Q. & Li, S. 2008. A new mamenchisaurid dinosaur from the Middle Jurassic of Yuanmou, Yunnan Province, China. Acta Geologica Sinica 82, 17-26.

Lü, J., Li, S., Ji, Q., Wang, G., Zhang, J. & Dong, Z. 2006. New eusauropod dinosaur from Yuanmou of Yunnan Province, China. Acta Geologica Sinica 80, 1-10.

Upchurch, P., Barrett, P. M. & Dodson, P. 2004. Sauropoda. In Weishampel, D. B., Dodson, P. & Osmólska, H. (eds) The Dinosauria, Second Edition. University of California Press (Berkeley), pp. 259-322.

Ahead by a tail

February 2, 2009

You’d think that in 100+ posts we’d be starting to exhaust the territory, but there are vast swaths of sauropod vertebral morphology that we haven’t even touched. Like fused vertebrae. Sauropods fused their vertebrae all the time. Some of those fusions are age-related, many are pathological, and some are…hard to classify.

mamenchisaurus-tail-thingy

Exhibit A: fused distal caudals in a specimen of Mamenchisaurus hochuanensis described by Ye et al. (2001). In contrast to the terminal caudals comprising the tail club of Shunosaurus, the centra here are not ballooned out. The one in the middle is clearly waisted, as in “narrower in the middle than at the ends” (not the same clearly wasted as your college roommate). The neural, uh, elements are expanded and fused into something that the authors describe as resembling the comb of a rooster. I can’t improve on that metaphor so I won’t try. Here’s the full weirdness, straight from the authors (p. 39):

The posterior caudals are fused with each other, their centra are not expanded, the neural arch is remarkably expanded and the size of the neural canal  and the height of  the neural spines increased. In lateral view, the posterior caudals are cockscomb-shaped.

That’s all pretty weird. The authors go on to speculate that the expanded neural canal indicates that the tail club fin thingy served as some kind of special sense organ. I don’t think that idea is too bold. I don’t think it’s bold enough.

Hypothesis: Mamenchisaurus had a pseudohead on the end of its tail, with fused verts to form a pseudoskull and a big nerve bundle to give the pseudomouth (probably articulated chevrons) and pseudoeyes (possibly heat-sensitive like rattlesnake pits) some lifelike movements and relay thermal images up to the brain. It probably started out as a predator-confusion thing. The carnosaurs would obviously like to attack the inattentive end of the sauropod but these push-me-pull-yous were on the lookout fore and aft! And if the carnosaurs did attack, there was a 50/50 chance they’d bite off the wrong head. Then the pseudohead, which evolved to simulate attention, got so good at it that it was exapted into an actual lookout post at the individual’s farthest extremity. What an advantage those animals had!

mamenchisaurus-pseudohead-restoration

But, alas, the caudal pseudohead turned out to be a serpent in paradise. It started getting ideas. Demanding equal time to “teach the controversy” to the forebrains of juvenile conspecifics. Mamenchisaurus became a house divided. First there were pranks, as the real brain started hearing “voices” in its tail. Then outright arguments as the brain and pseudobrain struggled for control of the animal. Finally the pseudohead took over, started marching the animal around backwards. Poor Mamenchisaurus was tripping over logs, which don’t show up so well on infrared, and slipping on its own feces. Lost in delusions  of grandeur, the pseudohead chomped on ferns for hours, unwilling to admit that it couldn’t swallow and too proud to realize that it was starving the animal to death (certain political and economic parallels suggest themselves here).

mamenchisaurus-pseudohead-in-charge1

We all know what happened: Mamenchisaurus died out, the pathetic victim of a caudal takeover, and was replaced by other sauropods that, if perhaps more conservative, could at least keep their tails in line. And the world passed once again into the metaphorical hands of the heads. But even now, 140 million years later, tails the world over recall their ancient glory and plot revenge–perhaps even the tail you’re sitting on right now. If you are quiet, and cunning, you may hear your tail’s defiant murmur: the south will rise again!

Reference

  • Ye, Y., Ouyang, H., and Fu, Q.-M. 2001. New material of Mamenchisaurus hochuanensis from Zigong, Sichuan. Vertebrata PalAsiatica 39(4):266-271.

When we were planning to start this blog, Matt wrote to Darren and me saying “I am thinking that we should keep the text short and sweet” — an aspiration that we have consistently failed to live up to. Not today!

Here is Omeisaurus tianfuensis. Even by sauropod standards, that neck is just plain crazy.

fig. 63)

Omeisaurus tianfuensis skeletal reconstruction, from He et al. (1988:fig. 63)

This figure is lifted from an awesomely comprehensive monograph — 173 pages including the front-matter and plates — which gives the lie to the idea that all Chinese dinosaurs are woefully inadequately described. It’s true that with the recent glut of theropods, the thing seems to be to rip ’em out of the ground, throw toegther a two-pager for Science or Nature and move on to the next one; but sauropods understandably inspire more devotion from their followers, resulting in careful work like this monograph and the similar work by Ouyang and Ye (2002) on Mamenchisaurus youngi. So hats off to He, Ouyang and their colleagues — showing how it should be done!

Special bonus photo

Home-made sushi

Home-made sushi

References

  • He, X., K. Li, and K. Cai. 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 + 20 plates pp.
  • Ouyang, H., and Y. Ye. 2002. The first mamenchisaurian skeleton with complete skull: Mamenchisaurus youngi. Sichuan Science and Technology Press, Chengdu, China. 111 + 20 plates pp.

Seeing the photograph in the last post of the Mamenchisaurus hochuanensis cast at the Field Museum in Chicago reminded me of a picture I’ve been meaning to post for a while. M.hoch, as I like to call it (we’re on familiar terms) is known primarily from its type specimen CCG V 20401, which was nicely described and figured by Young and Zhao in 1972. There are several pretty good quality casts of this specimen around the world: I first saw one in the car-park of the Copenhagen Geological Museum, and Chicago was the third time I saw it (and by far the best due to the excellent sight-lines from the balcony, lighting and help from the museum staff) .

The second time I saw a cast of this specimen it was actually the same one that I’d seen in Copenhagen: it was owned by the Homogea Museum in Trzic, Slovenia, and its loan to Copenhagen had expired. By happy coincidence my day-job took me to Slovenia, only 40 km or so from Trzic, so on a spare day I took a taxi to the museum where I was shown to the M.hoch cast.

Remember that bit in The Hitch-Hiker’s Guide to the Galaxy where Arthur Dent is told that the plans for demolishing his house have been on display at the council office for six months? In fact, let me quote:

“The notice was posted at the office, sir.”
“Your ‘office’ was in a basement. I had to look all over the building just to find it.”
“That’s where the office is located!”
“It was dark.”
“The lights were out!”
“So were the stairs.”
“But still, you found the notice, sir?”
“Oh, yes. It was quite ‘clearly’ posted in a locked filing cabinet in a disused lavatory with a sign on the door saying ‘Beware of the leopard.'”

That’s how I felt when I saw the Mamenchisaurus cast:

Mamenchisaurus hochuanensis in the Basement of Doom

Yes, it’s in a basement. Yes, the lights were out (though, to be fair, the stairs were not). Yes, the basement is flooded (a trick that Douglas Adams missed) and for good measure the light you can see there, a portable floodlight, is powered by an extension lead that runs through the flooding. However, they didn’t have a filing cabinet big enough, so it was at least on display in the basement.

The good news is that I was able, from bits and pieces in the corner of the basement, to assemble a scaffold from which I could view the elevated cervicals:

The Scaffold of Doom!

As you can see, it consists of a trolley frame with a piece of decomposing and warped chipboard on top, surmounted by a stepladder. Unfortunately, this is a pretty tall dinosaur and those cervicals are a good 4 m off the ground, so the only way I could see the dorsal surface was by perching right on the top rung of the ladder. I do have photographic evidence, taken by a workman who was doing something mysterious in the corner of the basement, although it’s not great quality — about as good as the typical Loch Ness Monster photo:

Mike Taylor and the Scaffold of Doom!

Yes, that’s me, risking life and limb in the cause of sauropod vertebrae.

Sadly the result of all this was not very useful: the very poor lighting meant that the photos I took are low on detail, difficult to interpret, and of little scientific value. On the positive side, it was later that same month that I was in Chicago to see the better cast of the same animal, so I got all the photos I needed in the end.

Reference

How big was Hudiesaurus?

January 17, 2008

In the last post, an astute commenter asked about Hudiesaurus: “A first dorsal 550 mm–isn’t that in Argentinosaurus territory?”

Well, let’s find out.

Hudiesaurus sinojapanorum was described by Dong (1997) based on a partial skeleton from the Kalazha Formation in China. The holotype, IVPP V 11120, is an anterior dorsal vertebra. Referred elements include a nearly complete forelimb, supposedly from a smaller individual of the same taxon.

I don’t actually have a copy of Dong (1997), but I do have Glut (2000), which contains a pretty good summary and a couple of pictures. Here’s the holotype dorsal in posterior view, after Glut (2000), after Dong (1997).

hudiesaurus.jpg

According to Glut, the scale bar is 15 cm–I added the “15 cm” in the image above for ease of use. Presumably ‘sp’ is ‘spine’, ‘po’ is ‘postzygapophysis’, ‘dp’ is ‘diapophysis’, and ‘ce’ is ‘centrum’. Glut says:

As measured by Dong (1997), the holotype dorsal centrum of H. sinojapanorum has a length of 42 cm, 1.5 times longer than the comparable element in the 22-meter (about 75-feet) long mounted holotype skeleton of Mamenchisaurus hochuanensis, which was the largest sauropod known from China when it was described. From these dimensions, Dong (1997) estimated the total length of H. sinojapanorum to be about 30 meters (more than 100 feet) in length.

IF the scaled figure (from Glut [from Dong]) is accurate, and if the 42 cm length (reported by Glut [reported by Dong]) is accurate–and the uncertainties involved cannot be ignored, especially after the last post–then the vertebra has the following dimensions:

  • Centrum length: 42 cm
  • Cotyle height: 39 cm
  • Cotyle breadth: 42 cm
  • Total height: 78 cm

None of these are close to 550 mm, so there’s no telling where that measurement came from or what it refers to.

UPDATE: please read comment #4 below, by Mickey Mortimer, which sets the measurement record straight. And invalidates the specific numbers used in the rest of the post, but not the overall point.

Fortunately for us, the dimensions of the vertebrae of Mamenchisaurus hochuanensis are available for free in English, along with the rest of the description (Young and Zhao 1972), courtesy of the wonderful Polyglot Paleontologist site. Here’s the paper. Let’s do some comparin’.

D1 of M. hochuanensis has a centrum length of 25 cm, cotyle height of34 cm, cotyle width of 17 cm, and total height of 64 cm. The fact that the centrum is twice as tall as wide is almost certainly an artifact of the lateral compression that affects the whole vertebral column to some extent. Let’s say for the sake of argument that the cotyle was originally circular and 25 cm in diameter. The holotype of H. sinojapanorum is 68% longer, 60% larger in diameter, and 22% taller. So if the vertebra is actually D1 and if H. sinojapanorum was built like M. hochuanensis (be sure to keep your If Counter updated), it might have been anywhere from 27-37 meters long (89-121 feet).

A couple of points before we go on. First, that’s pretty big, but it’s also a huge range. At the low end, it’s no bigger than Diplodocus; at the high end, it’s one of the longest sauropods on record. So that math suggests that it was a big sauropod but doesn’t help us pin down how big it was. Second, you have to keep in mind that Mamenchisaurus hochuanensis is basically a ridiculous neck attached to an unremarkable body (at least in terms of size). If you ignore the neck, the animal was about the same size as Cetiosaurus or Haplocanthosaurus–about 75% the size of the well-known specimens of Apatosaurus, Diplodocus, and Camarasaurus, and no where near the size of Brachiosaurus (despite having a longer neck). It’s basically a weiner dog, with most of the weiner out in the neck. Which is how Hudiesaurus could be 22% bigger and still be about the same size as Diplodocus. Even if Hudiesaurus was 60% bigger than M. hochuanensis, it would still not be in Argentinosaurus range in anything but length.

mike-and-m-hoch-500.jpg

Mike (white shirt on lift) with M. hochuanensis at the Field Museum. It is worth remembering that he would need the same lift at about the same height to work on the posterior cervicals of Brachiosaurus!

Also, assigning serial positions to isolated vertebrae is tough. What if Dong was off by a single position, and the holotype vert is actually the most posterior cervical? True, it doesn’t have fused cervical ribs, but cervical ribs can fuse pretty late in ontogeny. Furthermore, rib identities can get a little wonky in the cervico-dorsal transition. Sometimes you have a nice, well-behaved, fully-fused rib on the last cervical, and a nice, well-behaved, long mobile rib on the first dorsal, but sometimes there is a godawful Frankenstein rib that doesn’t fit neatly into either category. Anyway, we’re just playing “what if” here. Nobody should take this as gospel.

The last cervical of M. hochuanensis has a centrum length of 32.5 cm, an average cotyle diamter of 29 cm, and a total height of 66 cm. If the holotype of Hudiesaurus actually corresponds to this vert instead of D1, then it is 29% longer, 38% larger in diameter, and 18% taller. In other words, no bigger than Diplodocus. In which case, the articulated forelimb might belong with the dorsal vertebra after all. Although it was found more than a kilometer away from the vertebra, so the case for it’s referral to the same taxon is not strong. At all.

But that’s not all! Not all Chinese sauropods were hellaciously long-necked, a point made by Mickey Mortimer in his DML post on Hudiesaurus. Abrosaurus ha 13 cervicals, rather than 19 like M. hochuanensis, and its cervicals are only about a third longer than its dorsals (upshot: in neck-to-body proportions, it was built like Camarasaurus). If Hudiesaurus was built like a giant Abrosaurus, it might have approximated a large individual of Camarasaurus in both body size and neck length.

A final amusing point. Glut (2000, p. 235) includes a photograph of the articulated forelimb of Hudiesaurus on display at Dinofest ’98 in Philadelphia. Next to the forelimb is a string of 4 articulated dorsal vertebrae. What is this? The original paper only mentions one dorsal vertebra, so where did the other three come from? Sadly, they came out of the same mold as the first–if you look carefully at the photo, you can see that the exhibitors simply made four casts of the same vertebra and strung ’em together to look like something more complete.

It’s not uncommon to clone adjacent vertebrae to fill out mounted skeletons. Heck, the T. rex skeleton in the Valley Life Sciences Building at Berkeley (my old digs) has a block of 5 identical dorsals, and its caudals come in identical pairs all the way down the tail (easy to see even in the small photos here). But that’s a different case. T. rex is known from complete remains, and the cloning was only done to fill out a skeleton that was already mostly there. The exhibition of the cloned Hudiesaurus vertebrae bothers me, because it implies to observers that the animal is better known than it actually is. I wasn’t at Dinofest ’98 so I can’t tell you for certain that there wasn’t a sign right there that said, “Warning: this animal is based on one vertebra that we have cloned to show you what a string of them would look like!” but I seriously doubt that there was any indication at all (that’s no reflection on Dong; he probably had nothing to do with the choices made by the exhibitors).

Here’s the take-home message:

If you see an eyebrow-raising number tossed out regarding a giant dinosaur, don’t surrender your credulity until you or someone you trust have tracked down the sources. And anytime you see mounted material, it’s perfectly fair to ask how much of it is real.

References