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