One of the newest sauropods (if not the newest, in terms of publication date) is the Brazilian titanosaur Uberabatitan ribeiroi Salgado & Carvalho, 2008 from the Maastrichtian Marília Formation. Uberabatitan scores reasonably high in the ‘quality and quantity of vertebral information preserved’ stakes, with a few nicely preserved cervicals known, some complete and partial dorsals, and an assortment of caudals (Salgado & Carvalho 2008). As is the case with virtually all titanosaurs that include good vertebrae, several characters of the vertebrae are diagnostic. And one of these characters interests me in particular: the podls (postzygodiapophyseal laminae) in the cervicals are described as being ‘segmented’, consisting of separate diapophyseal and zygapophyseal segments. The zygapophyseal segment extends anterodorsally over the diapophyseal segment, and there appears to be a space of flattened bone in between the two segments (you should be able to see this in A in the figure here; the zygapophyseal segment is labelled podl (z) and the diapophyseal segment is labelled podl (d). This is Text-fig. 5 from Salgado & Carvalho (2008)). This is all a bit weird and hasn’t been reported in a sauropod before, and what’s really weird is that the presence of an ‘incomplete’ lamina would seem to fundamentally contradict the reason for a lamina to exist in the first place.
Two primary hypotheses have been entertained as explanations for the presence of laminae. One is that laminae serve a mechanical role, and somehow help to support the weight of the rest of the vertebra (and its associated soft tissues) by being aligned along the primary axes of stress. At the same time, their ‘supporting’ function may have allowed bone in other areas of the vertebra to become reduced, thereby lightening the whole structure. As Wilson (1999) stated, this hypothesis has never really been tested and the fact that laminae are present in saurischians with small, lightweight vertebrae (like birds and other coelurosaurs) counts against a strictly mechnical role for the laminae. However, the fact that laminae increase in complexity and number as sauropods become longer-necked might suggest at least some supportive role for them.
However, laminae also seem to play a crucial role in pneumaticity, in that they partition the different air sacs. Actually, as Witmer (1997) noted, it may be that, as air sacs develop during growth, they act as opportunistic pneumatising machines, resorbing as much bone as is possible and hence leaving the laminae behind as key supportive elements. I don’t really fancy getting involved in an intricate discussion of evo-devo (one of my least favourite subjects, sorry), so will stop there on that line of inquiry but – whatever the developmental process – the end result is that laminae bound air sacs. Here’s where we come back to Uberabatitan. If the laminae form the bony ‘boundaries’ that ‘contain’ the air sacs, what the hell is going on when a lamina is split into two and has a big gap in the middle? Maybe the air sac here (it would have been bound ventrally by the posterior centrodiapophyseal lamina) was reduced, and only tucked away under the anterior, diapophyseal part of the podl. Maybe the air sac was absent: to confirm this, you’d need detailed information on the medial wall of that part of the vertebra bound ventrally by the pcdl and dorsally by the podl. Whatever, we seem to have something else new, and weird going on here. Your thoughts would be appreciated.
References
- Salgado, L. & Carvalho, I. S. 2008. Uberabatitan riberoi, a new titanosaur from the Marília Formation (Bauru Group, Upper Cretaceous), Minas Gerais, Brazil. Palaeontology 51, 881-901.
- Wilson, J. A. 1999. A nomenclature for vertebral laminae in sauropods and other saurischian dinosaurs. Journal of Vertebrate Paleontology 19, 639-653.
- Witmer, L. M. 1997. The evolution of the antorbital cavity of archosaurs: a study in soft-tissue reconstruction in the fossil record with an analysis of the function of pneumaticity. Journal of Vertebrate Paleontology 17 (Supplement to No.1), pp. 73.
The enigmatic taphonomy of Sauroposeidon
July 24, 2008
This figure is stolen from Wedel et al. (2000:fig. 5). A shows the first 11 cervical vertebrae* of Sauroposeidon in articulation. B shows how the holotype specimen, OMNH 53062, must have disarticulated, and C shows it as it was found. Shaded vertebrae and bits of vertebrae were not found. The thickness of the cervical ribs is greatly exaggerated for clarity.
*We assume that Sauroposeidon had 13 cervicals like Brachiosaurus. It is not beyond the bounds of possibility that it had more, but it is unlikely that it had fewer. Sauroposeidon seems to be all about crazy neck elongation, and it doesn’t make sense to make some vertebrae longer while losing others.
Some facts:
- In life, the long cervical ribs formed overlapping bundles, just like the long neck tendons of birds, and that is how the preserved cervical ribs are arrayed–in vertically stacked bundles.
- Each cervical rib is about 4 cm in diameter where it attaches to its vertebra, and tapers to a point about 3 meters away. The last meter or so of each rib goes from being the diameter of a pencil to the diameter of a mechanical pencil lead. They just sort of peter out into nothingness.
- The fact that even the pencil-lead-sized wisps of the cervical ribs are still in articulation suggests pretty strongly that the neck was buried with the muscles intact.
- If the neck had simply been broken transversely (like a guillotine cut), the two most anterior vertebrae in the preserved block of four should have the cervical ribs of even more anterior vertebrae beneath them, and the cervical ribs from the two most posterior vertebrae would not stick out the back of the preserved block.
- The facts that the cervical ribs from the missing anterior vertebrae are also missing, and that the cervical ribs from the preserved vertebrae trail behind the articulated block, suggest that the neck was pulled apart lengthwise, as shown in B.
- None of the vertebrae have any teeth marks or any sign of mechanical damage, other than the missing neural spine from the third preserved vertebra. The front third of the first preserved vertebra was eroded away before the vertebrae were discovered in the field.
- Assuming that Sauroposeidon was built like Brachiosaurus, it must have had a body mass somewhere between 40 and 60 tons. Even if it was built more like Mamenchisaurus—hellacious neck tacked on fairly dinky body–it was still probably a 20-ton critter.
- After 14 years of subsequent erosion and fieldwork, no other sauropod bones have been discovered at the site.
Some questions:
- How did the neck get separated from the body? The body was presumably too big to move, and the neck is too well preserved to have been moved very far.
- What pulled the neck apart?
- How did the neck come apart without disturbing those little pencil-lead cervical rib ends?
I don’t know the answers to those questions, by the way. And I’m open to suggestions.
Here’s my best guess. I think the body stayed put, and the neck floated away. Not far–a few hundred feet would be enough to put the body outside the outcrop area at the holotype site, but not so far that the neck would be all beat up. I think it floated rather than being dragged (by an Acrocanthosaurus, for example) because the vertebrae are all in such good shape and none of them have any tooth marks. I think it floated in calm water because the preservation is so good. I think the neck muscles rotted enough to let the force of the current rip part of the neck away from the base, just like you can pull a cooked chicken neck apart lengthwise without messing up the articulations among the vertebrae in the chunk that breaks free.
All of that will suffice to get the neck separated from the body. What really bugs me is the separation of the anterior part of the neck from the preserved block of vertebrae. It is tempting to think that the anterior part never came off, and that those vertebrae simply eroded away before they were found, like the front third of the most anterior preserved vert. But that can’t be; if those vertebrae were in articulation and just eroded away, we should still have their cervical ribs below the first two preserved verts.
Who knows, maybe the scenario I outlined above is good enough to explain both breaks. For some reason it is just easier to image most of the neck coming off the carcass than to imagine one part of the neck coming off the other part of the neck. But maybe the anteriormost vertebrae were ripped off and floated away first, and then the preserved block came free and floated off on its own later. (The head probably exploded, as these things were wont to do.)
It is worth noting that there are probably only a handful of people alive who have any first-hand experience with how multi-ton animal carcasses are dispersed, and zero people alive who have ever seen a dead sauropod rot. So, like too much in paleontology, what seems plausible or reasonable to me may not line up with objective reality.
BTW, this post fulfills a promise I made in a comment thread here. If we promise a post, we deliver. (We just don’t specify a due date.)
Comments, suggestions, hypotheses, rants, and crank fringe theories welcome.
References:
Mike with BOBA
July 17, 2008
Mike and Darren and I correspond a LOT. Like people in any long-running friendship, we’ve developed a lot of private shorthand. We also share an inordinate fondness for acronyms. One of our favorites is POOP, Prioritized Ordering Of Projects. As in, “What piece of POOP are you working on now?” or “I’ll get back to you on that as soon as I get this load of POOP in the mail.” There are even subdivisions of POOP. Some little projects that we never got around to finishing are STAINs: Short, Timely, Adequately Interesting, Nixed. And of course every now and then we feel compelled to attempt Long Overdue Grand Syntheses, or LOGS. And we’re prone to making up Ad Hoc Acronyms That We’ll Never Use Again But Put A Name To Anyway (henceforth AHATWNUABPANTA, which involves more than a little reciprocal humor and is actually not bad as these things go, but it’s goodness is wasted because it is, of course, an AHATWNUABPANTA–or was, until I used it again. Darn).
One of our oldest acronyms in regular use is BOBA, of Mike’s coining, which stands for Boring Old Brachiosaurus altithorax. Now, Brachiosaurus altithorax is not actually boring, and if anyone had the colossal stupidity and supreme bad taste to say that it is, Mike and I would probably beat the crap out of each other to see who would get to be first to beat the crap out of the offender. Still, it is hard for us to get away from using BOBA as a yardstick for comparison to, well, just about everything (including some stinkin‘ mammals), and occasionally even we get jaded about its inherent blinding awesomeness. Also, ‘boring’ here is a relative measure. With all the exotic brachiosaurids out there, like Sauroposeidon, MIWG.7306, and, uh, some secret stuff we can’t talk about yet, BOBA is comparatively tame. So the name stuck.
After briefly flirting with the truly boring BOBB, we nicknamed the African Brachiosaurus, B. brancai, JANGO. It’s just a nickname, not an acronym, but it seemed appropriate since it’s almost the same as BOBA (or is it?–another mystery to be revealed at the proper time) and it shares its first three letters with Janensch, as in Werner, who described it in exhaustive and exhausting detail. Incidentally, translations of several of Janensch’s monographs on the Tendaguru sauropods are available for free from the Polyglot Paleontologist.
Anyway, this is another one of those times that I intended to post just a picture and a couple of lines of description but ended up squirting logorrhea over most of a page. I’m not sure if that’s a good thing or not. Keeps the blog turning over, I suppose. The picture is of Mike measuring the BOBA holotype dorsals in the Field Museum in the summer of 2005, working at such blinding speed that I was unable to get a crisp picture of him. He really is like that when he’s in collections, too–ask Darren.
And now that I’ve finally got around to saying that, I find that I have nothing more to say. Maybe it’s BOBA after all.
Just kidding! Mike, seriously, put down the tire iron. Ouch! You bast-THUD!
Up till now, I’ve tried to remain completely dispassionate about Aetogate, restricting my public comments to statements of fact and reports of what others have said. In particular, the site that I maintain linking to other people’s commentary on this issue contains no opinions of my own (or at least, if any have leaked through, it’s been inadvertent).
But now that the SVP has released its findings and others have had a month to make their own comments in response, I am going to use SV-POW! to say it how I see it. (The fact that the SVP’s so-called “permalink” has changed in the last few days, if you can imagine anything so dumb, may itself tell you something.) [Update, July 2013: it’s changed again, and this link is now a 404.] [Update 2, October 2015: I made my own copies of the SVP documents, in case they vanish permanently] For brevity’s sake, I’m going to concentrate my comments on Bill Parker’s case, but most of this also applies to Jeff Martz’s case.
Please note that I am speaking only for myself here. (That’s why I am putting this on SV-POW! rather than on the Aetogate site, which remains an objective summary of the case and its coverage, with no opinions expressed.) Matt and Darren have not even seen this posting, let alone agreed to it or contributed to it.
First up, everyone agrees that the SVP did well to take this case on, and that their report contains, in Kevin Padian’s much-quoted words, “something for everyone to like — and dislike”. But the dislikeable part is very problematic. A private correspondent whose name I will not state wrote to me:
The EEC just demonstrated vividly that Lucas can get away with anything, and they practically declared open season on Parker and Martz and anyone else who dares speak up about this.
By blaming the victims, or at least by allowing Lucas’s blaming of the victims to stand unrefuted, the SVP has left Bill and Jeff in a worse position than they were in before all this started. Back then, they’d only had their work stolen. Now, they’ve had their work stolen and have a wholly undeserved reputation as trouble-makers. In effect, the SVP have shown that all those people were quite right who warned Bill and Jeff not to get involved, just to lie down quietly like good little boys and not to think they could go up against The Man. To be sure, I am quite certain that was not the SVP’s intention; but when their statement leaves Stuart Ashman of the New Mexico DCA enough wiggle-room to express “appreciation and satisfaction with the Society’s conclusions regarding these allegations”, and when The Santa Fe New Mexican can interpret the SVP statement as “a completely independent body has cleared the scientists of plagiarism”, there seems little point in pretending that’s not how it’s being read.
In light of this, what can be done to prevent repeats of the transgressions? It’s almost impossible to say. The SVP’s Executive Committee statement on Aetogate suggests on one hand that it’s Bill’s fault he got claim-jumped because he didn’t tell the NMMNHS people enough about his work, but Jeff’s fault that he got plagiarised because told them too much! It’s tempting to conclude that the only safe approach is to keep your dissertation completely secret, let no-one know what you’re working on, and not even to hint about its contents in your published work.
But that in itself won’t necessarily stop all abuses: the broader problem is that there are lots of good reasons for work to be known about before it’s formally published, of which dissertations are only one. Talks at conferences, grant proposals, informal discussions with colleagues — all the things that help to incubate work, to prevent it from becoming isolated, to mitigate against the possibility of inadvertent duplication — in short all the things that foster a collegial spirit, and that show we are working together on the great project of vertebrate palaeontology rather than fighting against each other. Most of the while this sort of pre-publication sharing works well. The problem is that it only takes a few rogue bludgers to piss in the pool, and everyone is affected. And if the professional body that has a mandate to oversee these things starts blaming the victim, it’s hard to see any other consequence than a clamming up, a tendency for everyone who feels vulnerable to plagiarism and claim-jumping (not just students) to stop talking about their work until it’s actually published. I don’t see how inculcating that culture of paranoia will benefit any of us, but it does seem to be where we’re headed right now. *sigh*
One suggestion posted to the VRTPALEO mailing list is that a preprint server, like arxiv.org, used in physics, would help the field of vertebrate palaeontology to sort out priority issues. Unfortunately, I don’t think it would help much (although of course it would be good for other reasons). The problem is plausible deniability. The SVP’s ruling on Aetogate has set a grotesque precedent that if you have a taxonomic reassignment in press, then circulating it widely as an “unpublished” thesis and alluding to it (with citations of both the thesis and the in-press paper) in three published papers and two SVP abstracts is NOT enough to establish your priority. If someone else wants to go ahead and reassign the material while your own work is in press, it suffices for that person simply to claim that neither he nor either of his co-authors was aware of the work in progress. That defence, we now know, is sufficient to deflect the SVP from reaching a firm conclusion, even if the claim-jumper included one of the original author’s relevant papers in the journal that he edits, even if he peer-reviewed it and explicitly commented on the matter in hand in his review, and even cited it in his own work. We now know that even in those circumstances, the SVP will conclude:
Faced with conflicting testimonies, the Ethics Education Committee was not able to resolve these allegations in favor of either side, a position that does not absolve either party of responsibility.
[…]
Parker noted that he expressed his intention to publish on the new genus in a number of venues (abstracts, talks, other papers), but Lucas et al. state that they were unaware of his intentions to publish a new name.
(These are direct quotes. Read their statement yourself if you, like me, find this difficult to believe.)
Just think about that. Provided you are an established vertebrate palaeontologist, you may read papers written by a graduate student from another institution, publish them in your own in-house journal, peer-review them, and even comment on the taxonomic reassignment in the peer-review, and STILL claim that neither you nor either of your two co-authors took any of the six opportunities IN THE LITERATURE ALONE to understand that the grad-student in question plans to reassign the genus. You can claim this, and the SVP will believe you.
What. The. ??!
I have to ask: is there anything Lucas could have done that would have forced the SVP to recognise wrongdoing? Short of a signed statement, I can’t think of anything. And even then, all it would take would be for him to say “I never signed that”, and the SVP would no doubt conclude that “faced with conflicting testimonies, the Ethics Education Committee was not able to resolve these allegations”.
Which is why I am fully resigned to seeing a one-pager in the next NMMNHS bulletin about the Tendaguru brachiosaurid that I’ve been working on, and assigning it to the new genus Rioarribaposeidon. Lucas knows that the SVP won’t pronounce guilt, so what’s to stop him from taking his revenge on me in this way? After all, I only have one widely available abstract to point to in establishing my priority. If Bill’s three papers, two abstracts and thesis weren’t enough, what chance does my poor abstract stand?
So where are we left? The good news is that the SVP’s statement on these cases included, along with their spineless lack-of-verdict, a much more useful document, Professional Conduct: Best Practices Regarding Research, Publication, and Museum Work. We can hope that the availability of these guidelines will go some way towards preventing repeats. But since the SVP has set an impossibly high bar for demonstrating that violations have taken place, it hardly makes any difference. The message to plagiarisers and claim-jumpers, loud and clear, is “go ahead, do what you want! We may not like it, but we’ll never call you on it. Leave a paper-trail if you like — we don’t care. Go nuts!”
As another private correspondent noted:
The EEC may get some teeth for dealing with these cases in the future. Even if they actually can’t or won’t do anything now, someday the extremely naive people running the show will be replaced by a generation of people who lived through this when they were still students and felt helpless and abandoned, and maybe THEY will do something about it.
But is that really the best we have to look forward to? It’s a pretty depressing thought, but I suppose better than nothing, to think that the generation of future VPs who are being born right about now can look forward to working in a cleaner field — one where professional ethics isn’t just something that we talk about.
So I have to conclude by saying that the SVP really dropped the ball here. They had an opportunity to send out a clear message: “You may NOT take advantage of less established scientists by plagiarising their conclusions and claim-jumping the taxa they recognise, and anyone who does will find us coming down hard on them.” The good news is, they did send out a clear message. The bad news is, it was “Feel free to plagiarise and claim-jump. And you victims had better keep quiet about it, or we’ll say that we Can’t Absolve You Of Responsibility”.
How could the SVP committees do this?
I am really unhappy about this last part of my post, and have nearly deleted it several times, but I think it needs to be said. How could the SVP committees have responded as they have? I can only think of three explanations, and I don’t like any of them:
1. They are too dumb to understand the very straightforward and overwhelming evidence in the freakin’ published literature for goshsakes.
2. They’re too cowardly to admit to what it means.
3. (I mention this only for completeness), They’re too corrupt to respond to what they see.
Even if we discount possibility 3 (which I think we can, and which I am very happy to do), I am still left horrified by either of the first two possibilities. I truly don’t know which is worse.
Now let me be clear that I have nothing but respect for the individuals who make up the SVP Ethics Committee and Executive Committee. Whatever’s happened here, it’s obviously akin to a Dilbertesque committee effect: it’s said that the IQ of a committee is that of its least intelligent members divided by the total number of members. But I would really, really, really like to hear from those individuals. I’d like to hear some explanation of how we ended up in this ridiculous state where Bill and Jeff are actually now worse off than they would have been if they’d kept as silent as previous victims (whose wisdom, if not courage, is now shown to have been greater than Bill’s and Jeff’s).
Please, committee members, comment on this blog. We’re all waiting to hear your explanations, and longing for them to be good.
Thanks for listening.
Oh, yeah, and here’s a sauropod vertebra.
If I say Amargasaurus cazaui, you say ‘long spines on cervical vertebrae’. Yes yes, it’s true that Amargasaurus had weird neck spines (and spines that, judging from their shape, really were spines rather than parts of continuous sail-like structures), but have you ever looked at its dorsals? That’s what we’re doing here: this is a posterior dorsal (from Salgado & Bonaparte (1991)) and, in contrast to the cervicals and anterior dorsals, its neural spine is not bifurcated.
Two things are really obvious. For starters, the neural spine is incredibly tall, being at least four times taller than the length of the centrum. It is in fact among the tallest of neural spines within Sauropoda. Secondly, seen in anterior or posterior view, the spine flares outwards towards its tip, forming a broad, rounded apex. Wilson (2002) and Rauhut et al. (2005) described this as ‘petal-shaped’, but it’s also been referred to as ‘paddle-shaped’ (Upchurch et al. 2004). Amargasaurus isn’t unique in these features: it’s a dicraeosaurid, and the other dicraeosaurids we know of (Dicraeosaurus hansemanni and D. sattleri, both from the Tendaguru Formation, and Brachytrachelopan mesai from the Upper Jurassic Cañadón Cálcareo Formation of Patagonia) have extremely similar vertebrae. Some rebbachisaurids also have paddle-shaped neural spines, but this presumably arose convergently because dicraeosaurids and rebbachisaurids are not close relatives within Diplodocoidea.
Finally, note the laminae. A prominent prespinal lamina (PRSL) is obvious. Given that the anterior dorsals have bifurcate neural spines (and given that both halves of the spine sport spinoprezygapophyseal laminae [SPRLs] on their anterior faces), the PRSL looks like a composite formed from the fusing of the two SPRLs (Wilson 1999). We can also see a prominent lamina running from the diapophysis to the neural spine apex, and it looks like a spinodiapophyseal lamina (SPDL). What’s unclear from the diagram is how extensive the spinopostzygapophyseal lamina (SPOL) was: did it contact the SPDL at its base? In Brachytrachelopan, Rauhut et al. (2005) described how the SPDL was short, and how it’s the SPOL that extends up the side of the neural spine. What appears more common however, is for the SPOL to merge with the more extensive SPDL, and for both to then form the so-called lateral lamina complex. It’s pretty clear that this is what happened in D. hansemanni (Janensch 1929), and it looks to me like it’s the case in Amargasaurus too.
All in all, these animals had pretty funky dorsal neural spines. As usual, the big question is: why?
References
- Janensch, W. 1929. Die Wirbelsäule der Gattung Dicraeosaurus. Palaeontographica Suppl. 7 (1), 3 (2), 37-133.
- Rauhut, O. W. M., Remes, K., Fechner, R., Cladera, G. & Puerta, P. 2005. Discovery of a short-necked sauropod dinosaur from the Late Jurassic period of Patagonia. Nature 435, 670-672.
- Salgado, L. & Bonaparte, J. F. 1991. Un nuevo sauropodo Dicraeosauridae, Amargasaurus cazaui gen. et sp. nov., de la Formacion La Amarga, Neocomiano de la Provincia del Neuquen, Argentina. Ameghiniana 28, 333-346.
- 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.
- Wilson, J. A. 1999. A nomenclature for vertebral laminae in sauropods and other saurischian dinosaurs. Journal of Vertebrate Paleontology 19, 639-653.
- Wilson, J. A. 2002. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136, 217-276.
Sauropod Vertebra Picture of the Week 
