Xinjiangtitan has the longest preserved neck of any lifeform to date

January 28, 2021

Xinjiangtitan when originally described, from Wu et al. (2013)

We’re way late to this party, but better late than never I guess. Wu et al. (2013) described Xinjiangtitan shanshanesis as a new mamenchisaurid from the Middle Jurassic of China. At the time of the initial description, all of the dorsal and sacral vertebrae had been uncovered, as well as a handful of the most posterior cervicals and most anterior caudals.

Xinjiangtitan revealed, from Zhang et al. (2018)

Jump a few years forward 2018, when Zhang et al. described the complete cervical series of Xinjiangtitan, based on further excavation of the holotype (they also changed some of the element identifications in the original description). It’s pretty insane: 

  • 18 cervical vertebrae, same as Mamenchisaurus youngi, and one less than M. hochuanensis, all discovered in articulation;
  • 10 of those vertebrae have centrum lengths of 1 meter or more;
  • the longest centrum, that of C12, is 123cm long;
  • the total lengths of the separate cervical vertebrae (not articulated) add up to about 15 meters;
  • even assuming that the condyles of the vertebrae were fully buried in the cotyles, the total length of articulated neck would still be 13.36 meters. 

Now, some caveating. Zhang et al. (2018) report two different lengths for most the cervicals: a maximum centrum length, which includes the anterior condyle, and a “minimum centrum length” without the anterior condyle. Reporting cervical lengths minus the condyle is fairly common–Janensch did it for what is now Giraffatitan (“ohne condylus”), McIntosh (2005) did it for the AMNH Barosaurus, Tschopp and Mateus (2017) did it for Galeamopus pabsti, and so on. In the freely available but as-yet-not-formally-published 4th chapter of my dissertation (Wedel 2007), I referred to the length without the condyle as the “functional length”, and I explicitly assumed that it was “the length that each vertebra contributes to the total neck length”. At the time I assumed that condyles were always fully buried in cotyles in life, because I didn’t know about camel necks (see Taylor and Wedel 2013b: fig. 21 and this post). 

Why am I bringing up all these minutiae? Because I’m really interested in the actual length of the neck of Xinjiangtitan in life, and that’s not so very straightforward to figure out. I’ll start with what Zhang et al. wrote, then proceed to their measurements, and then discuss their map.

At the start of the Description section, Zhang et al. (2018: p. 3) wrote:

In SSV12001, the cervical series is almost completely articulated and is exposed laterally (Figure 2). The long neck (at least 14.9 m) is well-preserved with a total of 18 cervical vertebrae. This measurement was estimated based on the maximum centrum length including the anterior condyles with the space for the cartilage assumed.

How much space is assumed for the cartilage? They don’t say, and it’s not clear, but one reading is that they just added up the total lengths of all the cervical centra and assumed that the cotyles were completely full of cartilage. Which is not so crazy as it might sound, since that’s exactly what happens in camels. But let’s see what their tables of measurements say.

Xinjiangtitan cervical vertebra measurements, from Zhang et al. (2018)

Table 1 gives the measurements of the atlas and axis, and Table 2 gives the measurements of all the remaining cervicals. Only “minimum centrum length”–without the condyle–is reported for cervicals 4 and 5, because C3-C5 were articulated as a unit, they haven’t been separated, and without CT scanning or further prep it’s going to be impossible to determine how long they were with the condyles. However, we can infer that the condyles of C4 and C5 are buried in the cotyles of C3 and C4 because (a) only the without-condyle lengths are reported, and (b) the condyles aren’t visible in the figures. File that away, it’s going to be important.

Adding up all of the max centrum lengths, including 165mm for the axis and 30mm for the atlas, per Table 1, I get a total of 14985mm, or 14.985 meters. Because Zhang et al. were so assiduous about their reporting–they really did Measure Their Damn Dinosaur–we can estimate pretty closely how much longer that total would be if it included the condyles of C4 and C5. Subtracting the min length from the max length, we find that the condyle is 70mm long in both C3 and C6, so it’s reasonable to assume the same for the vertebrae in the middle. Adding 140mm to the earlier total gets us up to 15125mm, or 15.125 meters. That’s assuming condyles end even with the rims of the cotyles, and cotyles are completely full of cartilage.

Xinjiangtitan cervicals, from Zhang et al. (2018: fig 3)

Adding up the all of the minimum centrum lengths, again including the axis and atlas, yields a total of 13360mm, or 13.36 meters. I think this smaller total is much more likely to be the actual length of the neck in life, for three reasons:

  1. As mentioned above, the condyles of C4 and C5 of this very specimen are actually buried in the cotyles of the preceding vertebrae. So we don’t need to add any space for cartilage to the summed minimum (without condyle) lengths–there certainly was cartilage between the surfaces of the condyles and cotyles, because that’s how intervertebral joints work, but there was not enough to push the condyles back outside the cotyles, unless we want to engage in some special pleading that C3-C5 were unnaturally smooshed together.
  2. Camels notwithstanding, having the condyles buried in the cotyles is pretty standard for articulated necks of big, long-necked sauropods. In the holotype specimens of Mamenchisaurus hochuanensis and Sauroposeidon, the condyles are not visible in lateral view, because they are completely buried in the cotyles of the preceding vertebrae–see the photos in this post and on this page to confirm that for yourself. In Giraffatitan, just the edges of the condyles are visible sticking out the backs of the cotyles in some of the posterior cervicals–see this post.
  3. The 13.36-meter neck is more consistent with the map of the specimen in the ground than either the 14.9-meter or 15.1-meter totals.

A little unpacking on that last point. Using the dorsal lengths from Wu et al. (2013: table 1)–and assuming that Zhang et al. are correct, and the D1 of Wu et al. is actually cervical 18, but D11 of Wu et al. is actually D10 and D11 together, so there are still 12 dorsals–I get a total length for the articulated dorsal column of 3355mm. Dividing 13360 by 3355 yields a cervical/dorsal ratio of 3.98. Using the screenshot of the map from Zhang et al. (2018: fig. 2), I measured 1505 pixels for the summed cervicals, 380 pixels for the summed dorsals, and 112 pixels for the scale bar. Assuming the scale bar is supposed to be 1 meter (and not 20 meters or 2.0 meters as it is labeled) yields a summed cervical length of 13.4 meters, a summed dorsal length of 3.39 meters, and a cervical/dorsal ratio of 3.96–all admirably close, off by no more than 4cm across 16+ meters, if the neck in the ground was articulated condyle-inside-cotyle. If we assume the map shows a 14.9-meter neck, then both the dorsal series and the scale bar are off by about 12%, which is unreasonable given the high precision of the map if the articulated neck corresponds to the summed minimum lengths.

Mounted skeleton of Omeisaurus tianfuensis: N E C C

Bonus observation #1: the holotype of Mamenchisaurus hochuanensis has a cervical/dorsal ratio of 3.52, but in Omeisaurus tianfuensis the same ratio is 4.09. So Xinjiangtitan is actually a little shorter-necked than Omeisaurus, at least compared to the length of the dorsal series.

Bonus observation #2: the 123-cm cervical of Xinjiangtitan is only the fifth-longest vertebra of anything to date:

  1. BYU 9024, possibly referable to Supersaurus or Barosaurus: 137cm
  2. Price River 2 titanosauriform: 129cm
  3. OMNH 53062, Sauroposeidon holotype: 125cm
  4. KLR1508-77-2, Ruyangosaurus giganteus referred specimen: 124cm
  5. SSV12001, Xinjiangtitan shanshanesis holotype: 123cm
  6. MPEF-PV 3400/3, Patagotitan holotype: 120cm (+?)
  7. MPM 10002, Puertasaurus holotype: 118cm

Getting pretty crowded there in the 120s, but then a big jump to BYU 9024. I’ll have more to say on that in a second.

Just to put a bow on this section, I’m pretty confident, based on all available measurements, taphonomic evidence, and the consilience between the measurements and the map, that the holotype individual of Xinjiantitan had a neck 13.36 meters (43 feet, 10 inches) long in life. 

That’s stunning.

By comparison, the second- and third-longest complete cervical series (of anything, ever, to date) belong to Mamenchisaurus hochuanensis, at 9.5 meters (Young and Zhao 1972, and confirmed by Mike in a basement in Slovenia), and Giraffatitan at 8.5 meters for MB.R.2181 (the larger XV2 specimen would have had a 9.6-meter neck).

Some other contenders, from Taylor and Wedel 2013a (fig 3)

There were things with longer necks, for sure, but none of those necks are complete (yet). Mamenchisaurus sinocanadorum is estimated to have had a neck about 12 meters long, based on the partial cervical series of the holotype. I know there are skeletal reconstructions out there with longer necks, and I will believe them as soon as the specimens they are based on are published. In the aforementioned dissertation chapter, I estimated 11.5 meters for the neck of Sauroposeidon, assuming a brachiosaurid-like cervical count of 13. Note that Mannion et al. (2013) recovered Sauroposeidon as a somphospondyl, and a cervical count of 15 or more as a synapomorphy of Somphospondyli. Adding a couple more 1.2-meter mid-cervicals would bring Sauroposeidon up to perhaps 14 meters. The longest cervicals of Patagotitan are in about the same size class, and we don’t know the cervical count in that monster, either.

BYU 9024, with the mounted (cast, composite) skeleton of Brachiosaurus altithorax and one Mike Taylor for scale

And of course, lurking out there in crazy neck-space is BYU 9024, the immense cervical originally referred to Supersaurus, but which more likely belongs to Barosaurus, and an ungodly huge one. That critter might–might–have had a 17-meter neck.

And I gotta say, in light of Xinjiangtitan, that no longer seems so unreasonable. Because Xinjiangtitan was a big sauropod but not a monster. The dorsal length of 3.3 meters and the femur length of 1.65 meters put it in roughly the same size category as the bigger individual of Jobaria (DL 3.2m, FL 1.8m) or the AMNH 5761 Camarasaurus supremus (DL 2.5m, FL 1.8m). Let’s imagine a Xinjiangtitan with a 2.4-meter femur, the size of Patagotitan or Argentinosaurus. Assuming isometric scaling, that individual would have a 2.4/1.65 = 1.45 x 13.36 = 19.4-meter neck. 

Do we really think such animals never existed?

Food for thought: the holotype individual of Xinjiangtitan was small enough to be buried as a complete skeleton. What about the individuals that were too big to bury in one shot?

Utterly unsurprising, but still nice to see: the highly pneumatic internal structure of the vertebrae of Xinjiangtitan, from Wu et al. (2013)

References

Posted by Matt Wedel
Filed in cervical, mamenchisaur, necks, Sino-pods, Things I should have posted a year ago, Xinjiangtitan
21 Comments »

What’s the deal with your wacky tail-club, Shunosaurus?

June 11, 2010

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 Omeisaurus — and 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.
Posted by Mike Taylor
Filed in caudal, fusion, mamenchisaur, Shunosaurus, Sino-pods, skeletal reconstructions, thagomizer
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Mamenchisaurus tail club, again

March 30, 2010

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.
Posted by Matt Wedel
Filed in caudal, fusion, mamenchisaur, Sino-pods, thagomizer
26 Comments »

Um, dude, there’s a thing on your neck

March 15, 2010

On the off chance that the postparapophyses of Shunosaurus weren’t enough to sate your appetite for Sino-pod rib-related weirdness, here are a couple of fused cervicals of Klamelisaurus, from the Middle Jurassic of China (from Zhao 1993:plate 1). These are weird for a couple of reasons. First, although fused caudals are pretty common in sauropods (see here), and fused dorsals turn up a lot (see discussion here), and the fusion of the atlas to the axis is not unheard of (see here and here), fusion of the middle or posterior cervicals is rare. Which makes intuitive sense–presumably fusing up your food-reaching organ is counterproductive. The only other example I know of is the pair of fused posterior cervicals in the AMNH 5761  Camarasaurus supremus (which, oddly enough, I don’t think we’ve covered yet on SV-POW!). If you know of others, please let me know.

Anyway, what’s really weird about the Klamelisaurus verts is not the fusion but the bar of bone connecting the cervical rib of the first vertebra back to one or more of the centra. I think that the weird pseudo-parapophysis-thingy is not the parapophysis of the second vert, which is hanging down just behind, but some kind of extra ossification off the postero-ventro-lateral corner of the first vert’s centrum. Admittedly, that’s a lot of interpretation to hang on one grainy photo of a specimen I’ve never seen. But I’ve seen something similar in some bird cervicals, where there is sometimes  a prong or hook of bone from that corner of the centrum sweeping down and out to brace against the longus colli ventralis tendon that comes  off the cervical rib. One of the Apatosaurus cervicals on the wall at Dinosaur National Monument has a similar pair of hooks on its posterior centrum. Irritatingly, I don’t have any digitized photos of the Apato vert, and I can’t find any photos at all that show what I’m talking about in birds. Sorry to tantalize, I learned it from Darren. When I get pix, I’ll post ’em.

In the meantime, you can amuse yourself by pondering the strangeness of the fused Klamelisaurus verts, and by watching the Dinosaur National Monument Quarry Visitor Center get demolished here.

Reference
Zhao X. 1993. A new mid-Jurassic sauropod (Klamelisaurus gobiensis gen. et sp. nov.) from Xinjiang, China. Vertebrata PalAsiatica 31(2):132-138.

Posted by Matt Wedel
Filed in cervical, fusion, Klamelisaurus, ribs, Sino-pods
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