Today is a good day for sauropod science. Since we’re not getting this up until the afternoon, you’ve probably already seen that Emanuel Tschopp and colleagues have published a monstrous specimen-level phylogenetic analysis of Diplodocidae and, among other things, resurrected Brontosaurus as a valid genus. The paper is in PeerJ so you can read it for free (here).
I’ve already been pinged by lots of folks asking for my thoughts on this. I know that the return of Brontosaurus is what’s going to catapult this paper into the spotlight, but I hope what everyone takes away from it is just what a thorough piece of work it is. I’ve never seen so many phylogenetic characters illustrated so well. It sets a new standard, and anyone who wants to overturn this had better roll up their sleeves and bring a boatload of data. I’m also very, very happy that it’s open-access so everyone in the world can see it, use it, question it, tear it apart or build on it. Getting Brontosaurus back is just gravy. Although, being pro-brontosaur enough to have named a dinosaur in honor of Brontosaurus, I’m also pretty happy about that. If you need a quick guide to who’s who now, A. ajax and A. louisae are still Apatosaurus, and B. excelsus, B. yahnahpin (formerly Eobrontosaurus), and B. parvus (originally Elosaurus) are all Brontosaurus. For more details, go read the paper.
My personal feelings aside, a lot of people are asking how solid is this generic re-separation. I haven’t read the entire paper yet – it’s 299 pages long, for crying out loud – but the separation of Brontosaurus and Apatosaurus seems solid enough. Tschopp et al. didn’t do it lightly, they justify their decision in detail. I don’t hold with the idea that just because two taxa are sisters, means that they cannot be separated generically. As usual in phylogenetic taxonomy, it comes down to what we decide as a community constitutes “diagnosably distinct”. Tschopp et al. have actually put some thought into what that might mean here, and whether you agree with them or not, they’ve at least made all of their evidence and reasoning explicit. That’s both an opportunity and a challenge for critics: an opportunity to pin down exactly where and why you may disagree, and a challenge to do exactly that. You can’t just sit back and say, “I think the analysis is flawed” or “I wouldn’t have coded that character that way” (well, you can, but if that’s all you say, no-one is obliged to take that kind of lazy, drive-by criticism seriously). There are 477 characters here, most of them illustrated, for 81 OTUs, and a lot of post-hoc discussion of the results. So whether you agree with the authors or not, in whole or in part, both fans and critics should dig in and build on this work. Is it the last word on diplodocid taxonomy? Of course not. But it does move the field forward significantly, and the Tschopp et al. should be applauded for that.
There’s a lot more in there than just bringing back Brontosaurus. “Diplodocus” hayi is elevated to its own genus, Galeamopus. Neither of those things are super surprising. There have been rumors since the 90s at least that Brontosaurus might be coming back, and everyone has known for a while that D. hayi was a bit wonky. I was also not surprised to see Australodocus returned to Diplodocidae – when I saw the type material in 2011, it looked diplodocid to me (based on some characters I’ll have to unpack in some other post). More surprising to me are the sinking of Dinheirosaurus into Supersaurus, the finding that Tornieria is not particularly close to Diplodocus, and the uncertain positions of AMNH 460, the American Museum mount, which is an indeterminate apatosaurine pending further study, of FMNH 25112, the Field Museum “Apatosaurus”, which might not even be an apatosaurine at all(!). In several cases, Tschopp et al. come right out and say that X is going to need further study, so if you want to work on sauropods and you’re stuck for project ideas, go see what needs doing.
As I was scanning the paper again while composing the last paragraph, I almost fell down the rabbit hole. So much interesting stuff in this paper. Even if all you care about is morphology, the hundred or so figures illustrating the phylogenetic characters ought to keep you happy for a very long time. I look forward to reading through the vertebral characters in detail and seeing what I’ve been missing all these years.
I’m contractually obliged to point out that the authors chose to publish the complete peer-review history of the paper, so you can see what the editor (Andy Farke) and reviewers had to say. As always, I think this transparency (and credit for the reviewers) is great for science, and I can’t wait until it’s the norm at more journals.
In addition to the paper, there’s also an interview with lead author Emanuel Tschopp on the PeerJ blog, and a nice shout-out for SV-POW!
Parting shot: why did Tschopp et al. get different results than anyone had previously? Because they used more specimens and more taxa – more data full stop. That’s also why their paper warrants serious consideration. It’s serious work. Let’s go stand on their shoulders.
In 2012, Matt and I spent a week in New York, mostly working at the AMNH on “Apatosaurus” minimus and a few other specimens that caught our eye. But we were able to spend a day at the Yale Peabody Museum up in New Haven, Connecticut, to check out the caudal pneumaticity in the mounted Apatosaurus (= “Brontosaurus“) excelsus, YPM 1980, and the bizarrely broad cervicals of the Barosaurus lentus holotype YPM 429.
While we there, it would have been churlish not to pay some attention to the glorious and justly famous Age of Reptiles mural, painted by Rudolph F. Zallinger from 1944-1947.
So here it is, with the Brontosaurus neck for scale:
Click through for high resolution (3552 × 2664).
And here is a close-up of the most important, charismatic, part of the mural:
Again, click through for high resolution (3552 × 2664).
That’s your lot for now. We’ve long promised a proper photo post of the Brontosaurus mount itself, and I’ll try to get that done soon. For now, it’s just scenery.
March 6, 2015
We have a new page on the sidebar – here – where we’re collecting as many museum abbreviations as possible, the idea being that you can copy and paste them into your papers to rapidly populate the ‘Museum Abbreviations’ section. I grabbed about 100 from my own previous papers and a handful of others, so currently the list is highly skewed toward museums with (1) sauropods (2) that I’ve had reason to yap about. I’ve probably missed tons of museums that are important for people working on hadrosaurs or stegosaurs or (shudder) mammals. From here on out the list will grow as people suggest additions and edits in the comments on that page. So please get on over there and contribute!
Completely unrelated eyeball-bait art courtesy of Brian Engh, who writes,
I don’t even remember drawing this, I just found it lying around and spruced it up a bit today. It’s supposed to be some kinda diplodocid, maybe Kaatedocus, but I think the main goal of the drawing was to draw one with a sense of weight that felt right given that their center of mass is supposed to be so far back. I like the idea of them getting startled and popping up every now and again… [see also–MJW]
February 22, 2015
One thing that I’ve never understood is why some people are skeptical about sauropods using their tails defensively, when lizards do this all the time. I’ve been digging through the literature on this for a current project, and there are some really great accounts out there, and by ‘great’ I mean ‘scary’.
Here’s a key passage from Murphy and Mitchell (1974: p. 95):
V. salvator uses the tail to strike repeatedly in combination with biting for defense…Captive Varanus (varius, spenceri, mertensi, and salvadorii) use the tail for defense, but only salvadorii appears to aim directly for a handler’s eye. An adult male V. salvadorii accurately struck the senior author’s eye with the tip of the tail as he was attempting to maneuver the lizard. On many subsequent occasions, the monitor tried to strike the eye of the handler with accuracy.
Not being a monitor expert, I was initially thrown by the V. salvator/V. salvadorii issue. V. salvator is the water monitor, V. salvadorii is the crocodile monitor. Both get pretty darned big; Wikipedia lists 3.21 m (10.5 ft) for V. salvator and 2.44-3.23 m (8.0-10.6 ft) for V. salvadorii.
Anyway, I’d heard of lots of anecdotal reports of lizards from many clades using their tails to lash at rivals, predators, or handlers, but I’d never read about a lizard aiming directly for the target’s eyes. It immediately made me think about (1) sauropod tails, especially the whip-lash tails of flagellicaudan diplodocoids and at least some titanosaurs (Wilson et al. 1999), and (2) the supraorbital crests and ridges in many theropods, especially big Morrison forms like Allosaurus and Ceratosaurus. Of course, supraorbital crests in theropods could serve many functions, including shading the eyes and social and sexual display, but it’s interesting to speculate that they might have had a defensive function as well. Has anyone ever proposed that in print?
Most of the papers that pooh-pooh the use of whiplash tails in defense (e.g., Myhrvold and Currie 1997) argue that the tail-tip would be too small to do any serious damage to a multi-ton attacker, and too fragile to survive an impact. This seems wrong-headed to me, like arguing that unless you find putative animal weapons broken and caked in their adversaries’ blood, they aren’t used as weapons. A structure doesn’t have to do lethal damage or any damage at all to serve as a weapon, as long as it dissuades a predator from attacking. I’d think that getting hit in the eye by a 35-foot bullwhip might convince an allosaur to go have a look at Camptosaurus instead.
Now, one could argue that if the whip-lash doesn’t do any serious damage, predators will learn to blow them off as dishonest signals (we’re assuming here that having your eye possibly knocked out doesn’t count as ‘serious damage’ to an allosaur). But it’s not like the whiplash was the only weapon a diplodocid could bring to bear: the proximal tail could probably deliver a respectable clobberin’, and then there’s the zero fun of being stomped on by an adversary massing a dozen tons or more. In that sense, the whip-lash is writing checks the rest of the body can certainly cash. It’s saying, “Getting hit with this will be no fun, and if that isn’t enough, there’s plenty more coming.”
All of this is leaving aside more obvious defensive adaptations of the tail in Shunosaurus, maybe Omeisaurus and Mamenchisaurus, and probably Spinophorosaurus (although I’d feel better about Spinophorosaurus if the association of the spikes and the tail was more secure). I suspect that all sauropod tails were useful in defense, but only some sauropod taxa used that behavior enough for a morphological enhancement (club, spikes, whiplash) to have evolved. Similarly, common snapping turtles, Chelydra serpentina, will wiggle their unspecialized tongues to attract fish (I’ve witnessed this myself in captive specimens) but lack the worm-shaped tongue lure found in the more ambush-specialized alligator snappers, Macrochelys temminckii. On reflection, there are probably few morphological changes in evolution that aren’t preceded by behavior. Not in a Lamarckian sense, just that certain variations aren’t useful unless the organism is already (suboptimally) performing the relevant function.
Bonus observation: Mike noted back when that Shunosaurus and Varanus retain complex caudal vertebrae all the way out to the end. Since in this case ‘complex’ means ‘having processes that muscles can attach to’, maybe that has something to do with keeping up relatively fine motor control in your bad-guy-whomping organ. Would be interesting to compare caudal morphology between tail-whomping lizards and committed caudal pacifists (assuming we can find any of the latter that we’re certain about – maybe tail-whomping just doesn’t get used very often in some taxa, like those that have caudal autotomy). Anyone know anything about that?
- Murphy, J. B., & Mitchell, L. A. (1974). Ritualized combat behavior of the pygmy mulga monitor lizard, Varanus gilleni (Sauria: Varanidae). Herpetologica, 90-97.
- Myhrvold, N. P., & Currie, P. J. (1997). Supersonic sauropods? Tail dynamics in the diplodocids. Paleobiology, 23(4), 393-409.
- Wilson, J. A., Martinez, R. N., & Alcober, O. (1999). Distal tail segment of a titanosaur (Dinosauria: Sauropoda) from the Upper Cretaceous of Mendoza, Argentina. Journal of Vertebrate Paleontology, 19(3), 591-594.
February 13, 2015
According to Rare Historical Photos from the 1860s to the 1960s, this is the iceberg that sank the Titanic:
Clearly this was no iceberg, but a gigantic Apatosaurus vertebra, most of it hidden under water. Here is an artist’s impression:
They get everywhere, don’t they?
February 10, 2015
Go to Google and do a picture search for “natural history museum”. Here are the results I get. (I’m searching the UK, where that term refers to the British museum of that name — results in the USA may very.)
In the top 24 images, I see that half of them are of the building itself — rightly so, as it’s a beautiful and impressive piece of architecture that would be well worth visiting even if it was empty. Of the rest, ten are of specimens inside the museum: and every single one of them is of the Diplodocus in the main hall. (The other two photos are from the French natural history museum, so don’t really belong in this set. Not coincidentally, they are both primarily photos of the French cast of the same Diplodocus.)
The NHM’s Diplodocus — I can’t bring myself to call it “Dippy” is the icon of the museum. It’s what kids go to see. It’s what the museum used as the basis of the logo for the 2005 SVPCA meeting that was held there. It’s essentially the museum mascot — the thing that everyone thinks of when they think of the NHM.
And rightly so: it’s not just a beautiful specimen, it’s not just sensational for the kids. As the first cast ever made of the Carnegie specimen CM 84, it’s a historically important object in its own right. It was the first mounted Diplodocus ever, being presented in 1905 before the the original material was even on display in Pittsburgh.
As a matter of fact, this cast was the very first mounted sauropod to be publicly displayed: that honour is usually given to the AMNH Apatosaurus, but as museum-history expert Ilja Nieuwland points out:
The London ‘Dippy’ was in fact the first sauropod on public display, if only for three days in early July of 1904, in the Pittsburgh Exposition Society Hall.
There you have the Natural History Museum Diplodocus: the symbol of the museum, an icon of evolution, a historical monument, a specimen of great scientific value and unparalleled symbolism.
So naturally the museum management want to tear it down. They want to convert the Diplodocus hall into a blue whale hall. Because the museum doesn’t already have a blue whale hall.
Or, no — wait — it does already have a blue whale hall. That’s it. That’s what I meant to say. And very impressive it is, too.
I don’t mind admitting that the whale hall is my second favourite room in the museum. Whenever I go there as a tourist (rather than as a scientist, when I spend all my time in the basement), I make sure I see it. It’s great.
The thing is, it’s already there. A museum with a whale hall does not need another whale hall.
Obviously anticipating the inevitable outcry, the museum got all its ducks in a row on this. They released some admittedly beautiful concept artwork, and arranged to have opinion pieces written in support of the change — some by people who I would have expected to know better.
One of the more breathtaking parts of this planned substitution is the idea that Diplodocus is no longer relevant. The NHM’s director, Sir Michael Dixon says the change is “about asking real questions of contemporary relevance”. He says “going forward we want to tell more of these stories about the societally relevant research that we do”. This “relevance” rhetoric is everywhere. The museum “must move with the times to stay relevant”, writes Henry Nicholls in the Guardian.
There was a time when Diplodocus was relevant, you know: waaay back in the 1970s. But time has moved on, and now that’s 150,000,035 years old, it’s become outdated.
Conversely, the rationale for the whale seems to be that they want to use it as a warning about extinction. But could there ever be a more powerful icon of extinction than a dinosaur?
The thing is, the right solution is so obvious. Here’s what they want to do:
Clearly the solution is, yes, hang the whale from the ceiling — but don’t remove the Diplodocus. Because, seriously, what could be a better warning about extinction than the juxtaposition of a glorious animal that we lost with one that we could be about to lose?
All this argument about which is better, a Diplodocus or a blue whale: what a waste of energy. Why should we have to choose? Let’s have both.
I’ve even had an artist’s impression made, at great expense, to show how the combination exhibit would look. Check it out.
(If anyone would like to attempt an even better rendering, please by my guest. Let me know, and I’ll add artwork to this page.)
So that’s my solution. Keep the museum’s iconic, defining centrepiece — and add some more awesome instead of exchanging it. Everyone wins.
February 2, 2015
Introduction and Background
I have three goals with this post:
- To document the range of variation in epipophyses in the cervical vertebrae of sauropods.
- To show that the “finger-like processes” overhanging the cervical postzygapophyses in the newly described Qijianglong are not novel or mysterious structures, just very well developed epipophyses.
- Finally, to show that similar long, overhanging epipophyses are present in other mamenchisaurids, although as far as I can tell no-one has noted them previously.
Epipophyses are muscle attachment points dorsal to the postzygapophyses, for the insertion of long, multi-segment epaxial (dorsal) neck muscles in birds and other dinosaurs. I know that they turn up occasionally in non-dinosaurian archosaurs, and possibly in other amniotes, but for the purposes of this post I’m only considering their distribution in sauropods. For some quick background info on epipophyses and the muscles that attach to them, see the second half of this post, and see Wedel and Sanders (2002) and Taylor and Wedel (2013a) for further discussion and more pictures.
Before we start with the pictures, a fiddly nomenclatural point: this muscle attachment point dorsal to the postzyg has traded under at least six names to date.
- The ‘Owenian’ term, used by virtually all non-avian theropod workers, by Sereno et al. (1999) for Jobaria, and probably by loads of other sauropod workers (including myself, lately) is epipophysis.
- Beddard (1898) referred to this feature in birds as the hyperapophysis; this term seems to have fallen completely out of use.
- Boas (1929), again referring to birds, called it the processus dorsalis. Zweers et al. (1987: page 138 and table 1) followed this terminology, which is how I learned of it when I was an undergrad at OU.
- Baumel and Witmer (1993) called this feature in birds the torus dorsalis (note 125 on page 87), which some authors have informalized to dorsal torus (e.g., Harris 2004: page 1243 and fig. 1). Baumel and Witmer (1993: page 87) note that, “the use of ‘Torus’ is preferable since it avoids confusion with the spinous [dorsal] process of the neural arch”.
- In my own early papers (e.g., Wedel et al. 2000b) and blog posts I called this feature the dorsal tubercle, which was my own attempt at an informal term matching ‘processus dorsalis’ or ‘torus dorsalis’. That was unfortunate, since there are already several other anatomical features in vertebrates that go by the same name, including the dorsal-facing bump on the dorsal arch of the atlas in many vertebrates, and a bump on the humerus in birds and some other taxa. In more recent papers (e.g., Taylor and Wedel 2013a) I’ve switched over to ‘epipophysis’.
- In the last post, Mike coined the term parapostzygapophysis for this feature in Qijianglong. [Note: he now regrets this.]
As usual, if you know of more terms for this feature, or additional history on the ones listed above, please let us know in the comments.
Now, on to the survey.
I haven’t seen very many prominent epipophyses in basal sauropodomorphs. Probably the best are these in the near-sauropod Leonerasaurus, which is very sauropod-like in other ways as well. Modifed from Pol et al. (2011: fig. 5).
This combination of photograph and interpretive drawing neatly shows why it’s often difficult to spot epipophyses in photos: unless you can make out the postzygapophyseal facet, which is often located more anteriorly than you might guess, you can’t tell when the epipophysis projects further posteriorly, as in the last of these vertebrae. In this case you can make it out, but only because the interpretive drawing shows the facet much more clearly than the photo.
The most basal sauropod in which I have seen clear evidence of epipophyses is Tazoudasaurus. They’re not very apparent in lateral view, but in posterior view the epipophyses are clearly visible as bumps in the spinopostzygapophyeal laminae (SPOLs). Modified from Allain and Aquesbi (2008: fig. 9).
In addition to Qijianglong, some other basal eusauropods have prominent epipophyses. Probably the best known is Jobaria; Sereno et al. (1999: fig. 3) figured and labeled the epipophysis in one of the cervical vertebrae. The vertebra image in that figure is tiny (nice work, glam-magz!), so here are some sketches of Jobaria mid-cervicals (from two different individuals) that I made back in the day when I was doing the research for Gary Staab’s Jobaria neck sculpture (see Sanders et al. 2000 for our SVP abstract about that project).
Turiasaurus also has prominent, overhanging epipophyses in at least some of its cervical vertebrae. You can just make one out as a tiny spike a few pixels long in Royo-Torres et al. (2006: fig. 1K). I have seen that cervical firsthand and I can confirm that the epipophyses in Turiasaurus are virtually identical to those in Jobaria.
It’s not air-tight, but there is suggestive evidence of projecting epipophyses in some other mamenchisaurids besides Qijianglong.
If you’re really hardcore, you may remember that back in 2005, Mike got to go up on a lift at the Field Museum of Natural History to get acquainted with a cast skeleton of Mamenchisaurus hochuanensis that was mounted there temporarily. During that adventure he took some photos that seem to show projecting epipophyses in at least two of the mid-cervicals. At least, if they’re not epipophyses, I don’t know what they might be.
Here they are again in medial view. My only reservation is that these vertebrae were distorted to begin with, and some features of the cast are very difficult to interpret. So, probably epipophyses, but it would be nice to check the original material at some point.
Something similar may be present in some posterior cervical vertebrae of Mamenchisaurus youngi. Here’s Figure 17 from Ouyang and Ye (2002). The “poz” label does not not seem to be pointing to the articular facet of the postzygapophysis, which looks to be a little more anterior and ventral, below the margin of the PODL. If that’s the case, then C15 has long, overhanging epipophyses like those of Jobaria. C16 has a more conservative bump, which is to be expected – the epipophyses typically disappear through the cervico-dorsal transition.
Finally, here’s a cervical vertebra of Omeisaurus junghsiensis from Young (1939: fig. 2). I don’t want to hang very much on just a few pixels, but my best guess at the extent of the postzygapophyseal articular facet is shown in the interpretation above. If that’s correct, then this specimen of Omeisaurus had really long epipophyses, rivaling those of Qijianglong. Unfortunately that’s impossible to check, because this specimen has been lost (pers. comm. from Dave Hone, cited in Taylor and Wedel 2013).
Haplocanthosaurus nicely shows that the epipophyses can be large in terms of potential muscle attachment area without projecting beyond the posterior margins of the postzygapophyses. Here is C14 of H. priscus, CM 572, in posterior and lateral views, modified from Hatcher (1903: plate 1).
Epipophyses that actually overhang the postzygapophyses are not common in Diplodocidae but they do occasionally occur. Here are prominent, spike-like epipophyses in Diplodocus (upper left, from Hatcher 1901: plate 3), Barosaurus (upper right), Kaatedocus (lower left, Tschopp and Mateus 2012: fig. 10), and Leinkupal (lower right, Gallina et al. 2014: fig. 1).
Of course, the champion epiphysis-bearer among diplodocoids is the weird little rebbachisaurid Nigersaurus. Here’s a Nigersaurus mid-cervical, from Sereno et al. (2007: fig. 3). Note that the projecting portions of the epipophysis is roughly as long as the articular surface of the postzygapophysis.
The epipophysis in this cervical of Australodocus just barely projects beyond the posterior margin of the postzygapophysis.
In Giraffatitan, epipophyses are absent or small in anterior cervicals but they are prominent in C6-C8. Here’s a posterolateral view of C8, showing very large epipophyses that are elevated several centimeters above the postzygapophyses. You can also see clearly in this view that the spinopostzygapophyseal lamina (SPOL) and postzygodiapophyseal lamina (PODL) converge at the epipophysis, not the postzygapophysis itself.
The holotype of Sauroposeidon, OMNH 53062, is similar to Giraffatitan in that the two anterior cervical vertebrae (possibly C5 and C6) have no visible epipophyses, but epipophyses are prominent in the two more posterior vertebrae (possibly C7 and C8). Click to enlarge – I traced the articular facet of the postzygapophysis in ?C8 to more clearly separate it from the epipophysis. For a high resolution photograph of that same vertebra that clearly shows the postzyg facet and the epipophysis dorsal to it, see this post.
Oddly enough, I’ve never seen prominent epipophyses in a titanosaur. In Malawisaurus, Trigonosaurus, Futalognkosaurus, Rapetosaurus, Alamosaurus, and Saltasaurus, the SPOLs (such as they are – inflated-looking titanosaur cervicals do not have the same crisply-defined laminae seen in most other sauropods) merge into the postzygapophyseal rami and there are no bumps sticking up above or out beyond the articular facets of the postzygs. I don’t know what to make of that, except to note that several of the animals just mentioned have mediolaterally wide, almost balloon-shaped cervical neural spines. In our 2013 PeerJ paper, Mike and I argued that the combination of tall neural spines and tall epipophyses in the cervical vertebrae of sauropods made them functionally intermediate between crocs (huge neural spines, no epipophyses) and birds (small or nearly nonexistent neural spines, big epipophyses). Perhaps most titanosaurs reverted to a more croc-like arrangement with most of the long epaxial neck muscles inserting on the neural spine instead of the postzygapophyseal ramus. I’ve never seen that possibility discussed anywhere, nor the apparent absence of epipophyses in most titanosaurs. As usual, if you know otherwise, please let me know in the comments!
And as long as we’re discussing the phylogenetic distribution of epipophyses, it is interesting that long, overhanging epipophyses are so broadly but sporadically distributed. They turn up in some non-neosauropods (Jobaria, Turiasaurus, Omeisaurus) and some diplodocoids (Nigersaurus, the occasional vertebra in Diplodocus and Leinkupal), but not in all members of either assemblage, and they seem to be absent in Macronaria (although many non-titanosaurs have shorter epipophyses that don’t overhang the postzygs). I strongly suspect that a lot of this is actually individual variation that we’re not perceiving as such because our sample sizes of almost all sauropods are tiny, usually just one individual. Epipophyses are definitely muscle attachment sites in birds and no better hypothesis has been advanced to explain their presence in other archosaurs. Muscle attachment scars are notoriously variable in terms of their relative development and expression among individuals, and it would be odd if epipophyses were somehow exempt from that inherent variability.
It also seems more than likely that ontogeny plays a role: progressive ossification of tendons attached at the epipophyses would have the effect of elongating the preserved projection. And since for some aspects of sauropod vertebral morphology, serial position recapitulates ontogeny (Wedel and Taylor 2013b), it shouldn’t be surprising that we see differences in the prominence of the epipophyses along the neck.
Back to Qijianglong
By now it should be clear that the “finger-like processes” in Qijianglong are indeed epipophyses, and although they are quite long, they aren’t fundamentally different from what we see in many other sauropods. I haven’t gone to the trouble, but one could line up all of the vertebrae figured above in terms of epipophysis size or length, and Qijianglong would sit comfortably at one end with Omeisaurus and Mamenchisaurus, just beyond Nigersaurus and Jobaria.
The strangest thing about the epipophyses in Qijianglong is that they seem to be bent or broken downward in two of the vertebrae (B and H in the figure above). I assume that’s just taphonomic distortion – the cervical shown in H wouldn’t even be able to articulate with the vertebra behind it if the epipophysis really drooped down like that. The epipophyses in Qijianglong seem to mostly manifest as thin spikes of bone (or maybe plates, as shown in B and I), so it’s not surprising that they would get distorted – most of the vertebrae shown above have cervical ribs that are incomplete or missing as well.
One more noodle-y thought about big epipophyses. I wrote in the last section that I’ve never seen them in titanosaurs, possibly because titanosaurs have big neural spines for their epaxial muscles to attach to. Maybe long, overhanging epipophyses are so common in mamenchisaurids because their neural spines are so small and low. Although we tend to think of them as a basal group somewhat removed from the “big show” in sauropod evolution – the neosauropods – mamenchisaurids did a lot of weird stuff. At least in terms of their neck muscles, they may have been the most birdlike of all sauropods. Food for thought.
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