Equatorial Minnesota on Alamosaurus

February 21, 2021

Figure 3. BIBE 45854, articulated series of nine mid and posterior cervical vertebrae of a large, osteologically mature Alamosaurus sanjuanensis. Series is estimated to represent the sixth to fourteenth cervical vertebrae. A, composite photo-mosaic of the cervical series in right lateral view; identification of each vertebra indicated by C6 to C14, respectively. B, line drawing based on the photo-mosaic in A. C, line drawing in B with labels shown and vertebral fossae indicated by solid grey fill; cross-hatching represents broken bone surfaces and reconstructive material. Abbreviations: C, cervical vertebra; cdf, centrodiapophyseal fossa; clf, centrum lateral fossa; pocdf, postzygapophyseal centrodiapophyseal fossa; prcdf, prezygapophyseal centrodiapophyseal fossa; prcdf1, dorsal prezygapophyseal centrodiapophyseal fossa; prcdf2, ventral prezygapophyseal centrodiapophyseal fossa; sdf, spinodiapophyseal fossa; spof, spinopostzygapophyseal fossa; sprf, spinoprezygapophyseal fossa. (Tykoski and Fiorillo 2016)

Have you been reading Justin Tweet’s series, “Your Friends the Titanosaurs“, at his awesomely-named blog, Equatorial Minnesota? If not, get on it. He’s been running the series since June, 2018, so this notice is only somewhat grotesquely overdue. The latest installment, on Alamosaurus from Texas and Mexico, is phenomenal. I have never seen another summary or review that pulled together so much of the relevant literature and explained it all so well. Seriously, that blog post deserves to be a review paper; it could be submitted pretty much as-is, although it would be even better with his two other Alamosaurus posts integrated (this one, and this one). It’s great work, is what I’m saying, and it needs to be acknowledged.

In particular, I was struck by the note by Anonymous in 1941 on the discovery of a cervical vertebra 1.2 meters long. I’d never heard of that ref, and I’ve never seen that vert, but at 120cm it would be in the top 7 longest cervical vertebrae on the planet (see the latest version of the list in this post), narrowly beating out the 118-cm cervical of Puertasaurus. In fairness, the preserved cervical of Puertasaurus is probably a posterior one, and more anterior cervicals might have been longer. Then again, in the big Alamosaurus neck the longest verts are pretty darned posterior, so…we need more Puertasaurus.

EDIT a few hours later: Thanks to the kind offices of Justin Tweet, I’ve now seen Anonymous (1941), and the exact wording is, “A single vertebra, or neck joint bone, is three feet across, only two inches less than four feet long, and in its present fossilized state weighs 600 pounds.” ‘Two inches less than four feet long’ is 46 inches or a hair under 117cm, which puts the supposed giant cervical just behind Puertasaurus after all, but still firmly in the top 10. And depending on how one interprets the passage in Anonymous (1941), it might not have been any bigger than BIBE 45854–see this comment for details.

Big cervical showdown. From the top left: BYU 9024, originally referred to Supersaurus but more likely representing a giant Barosaurus (137cm); the single available cervical of Puertasaurus (118cm); a world-record giraffe neck (2.4m); Alamosaurus referred cervical series BIBE 45854, longest centra are ~81cm; Sauroposeidon holotype OMNH 53062, longest centrum is 125cm. This image makes it very clear that whatever Sauroposeidon was doing, it was a way different thing from Alamosaurus.

Crucially, the longest vertebrae in the BIBE 45854 series are about 80 or 81 cm long, which means that a 1.2-meter cervical would be half again as large. That is a pretty staggering thought, and that individual of Alamosaurus–assuming it was the same taxon as BIBE 45854, and not some other, longer-necked critter–would definitely be a contender for the largest sauropod of all time.

Illustrations here are of the big Alamosaurus cervical series from Big Bend, which was comprehensively described by Ron Tykoski and Tony Fiorillo in 2016, and which we have covered in these previous posts:

References

  • Anonymous. 1941. Find dinosaur neck bone nearly four feet long. The Science News-Letter 39(1):6–7.
  • Tykoski, R.S. and Fiorillo, A.R. 2016. An articulated cervical series of Alamosaurus sanjuanensis Gilmore, 1922 (Dinosauria, Sauropoda) from Texas: new perspective on the relationships of North America’s last giant sauropod. Journal of Systematic Palaeontology 15(5):339-364.
Posted by Matt Wedel
Filed in Alamosaurus, Barosaurus, cervical, credit where it's due, diplodocids, giraffe, Sauroposeidon, showdown, size, stinkin' mammals, Things I should have posted a year ago, titanosaur
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Werner Janensch, Wannabe, Lovefool

November 22, 2019

The Man Himself, taking notes on what look like Giraffatitan caudals.

Here’s how I got my start in research. Through a mentorship program, I started volunteering at the Oklahoma Museum of Natural History in the spring of 1992, when I was a junior in high school. I’d been dinosaur-obsessed from the age of three, but I’d never had an anatomy course and didn’t really know what I was doing. Which is natural! I had no way of knowing what I was doing because I lacked training. Fortunately for me, Rich Cifelli took me under his wing and showed me the ropes. I started going out on digs, learned the basics of curatorial work, how to mold and cast fossils, how to screenwash matrix and then pick microfossils out of the concentrate under a dissecting microscope, and—perhaps most importantly—how to make a rough ID of an unidentified bone by going through the comparative element collection until I found the closest match.

All set, right? Ignition, liftoff, straight path from there to here, my destiny unrolling before me like a red carpet.

No.

It could have gone that way, but it didn’t. I had no discipline. I was a high-achieving high school student, but it was all to satisfy my parents. When I got to college, I didn’t have them around to push me anymore, and I’d never learned to push myself. I went off the rails pretty quickly. Never quite managed to lose my scholarships, without which I could not have afforded to be in college, period, but I skimmed just above the threshold of disaster and racked up a slate of mediocre grades in courses from calculus to chemistry. I even managed to earn a C in comparative anatomy, a fact which I am now so good at blocking out that I can go years at a time without consciously recalling it.

After three years of this, I had the most important conversation of my life. Because I was a zoology major I’d been assigned a random Zoology Dept. faculty member as an undergrad advisor. I was given to Trish Schwagmeyer, not because we got on well (we did, but that was beside the point) or had similar scientific interests, just luck of the draw. And it was lucky for me, because in the spring of 1996 Trish looked at my grades from the previous semester, looked me in the eye, and said, “You’re blowing it.” She then spent the next five minutes explaining in honest and excruciating detail just how badly I was wrecking my future prospects. I’ve told this story before, in this post, but it bears repeating, because that short, direct, brutal-but-effective intervention became the fulcrum for my entire intellectual life and future career.

The holotype specimen of Sauroposeidon coming out of the ground in 1994.

Roughly an hour later I had the second most important conversation of my life, with Rich Cifelli. While I’d been lost in the wilderness my museum volunteering had petered out to zero, and Rich would have been completely justified in telling me to get lost. Not only did he not do that, he welcomed me back into the fold, in a terrifyingly precise recapitulation of the Biblical parable of the prodigal son. When I asked Rich if I could do an independent study with him in the next semester, he thought for a minute and said, “Well, we have these big dinosaur vertebrae from the Antlers Formation that need to be identified.” Which is how, at the age of 21, with a rubble pile of an academic transcript and no real accomplishments to stand on, I got assigned to work on OMNH 53062, the future holotype of Sauroposeidon proteles.

I was fortunate in four important ways beyond the forgiveness, patience, and generosity of Richard Lawrence Cifelli:

  • OMNH 53062 was woefully incomplete, just three and a half middle cervical vertebrae, which meant that the project was small enough in concept to be tractable as an independent study for an undergrad. Rich and I both figured that I’d work on the vertebrae for one semester, come up with a family-level identification, and maybe we’d write a two-pager for Oklahoma Geology Notes documenting the first occurrence of Brachiosauridae (or whatever it might turn out to be) in the vertebrate fauna of the Antlers Formation.
  • Because the specimen was so incomplete, no-one suspected that it might be a new taxon, otherwise there’s no way such an important project would have been assigned to an undergrad with a spotty-to-nonexistent track record.
  • Despite the incompleteness, because the specimen consisted of sauropod vertebrae, it held enough characters to be identifiable–and eventually, diagnosable. Neither of those facts were known to me at the time.
  • All of Rich’s graduate students were already busy with their own projects, and nobody else was about to blow months of time and effort on what looked like an unpromising specimen.

NB: this guy is not a prodigy.

There is a risk here, in that I come off looking like some kind of kid genius for grasping the importance of OMNH 53062, and Rich’s other students look like fools for not seeing it themselves. It ain’t like that. The whole point is that nobody grasped the importance of the specimen back then. It would take Rich and me a whole semester of concentrated study just to come to the realization that OMNH 53062 might be distinct enough to be diagnosable as a new taxon, and a further three years of descriptive and comparative work to turn that ‘maybe’ into a paper. People with established research programs can’t afford to shut down everything else and invest six months of study into every incomplete, garbage-looking specimen that comes down the pike, on the off chance that it might be something new. Having the good judgment to not pour your time down a rat-hole is a prerequisite for being a productive researcher. But coming up with a tentative ID of an incomplete, garbage-looking specimen is a pretty good goal for a student project: the student learns some basic comparative anatomy and research skills, the specimen gets identified, no existing projects get derailed, and no-one established wastes their time on what is most likely nothing special. If the specimen does turn out to be important, that’s gravy.

So there’s me at the start of the fall of 1996: with a specimen to identify and juuuust enough museum experience, from my high school mentorship, to not be completely useless. I knew that one identified a fossil by comparing it to known things and looking for characters in common, but I didn’t know anything about sauropods or their vertebrae. Rich got me started with a few things from his academic library, I found a lot more in OU’s geology library, and what I couldn’t find on campus I could usually get through interlibrary loan. I spent a lot of time that fall standing at a photocopier, making copies of the classic sauropod monographs by Osborn, Hatcher, Gilmore, Janensch, and others, assembling the raw material to teach myself sauropod anatomy.

The sauropod monographs live within arm’s reach of my office chair to this day.

In addition to studying sauropods, I also started going to class, religiously, and my grades rose accordingly. At first I was only keeping up with my courses so that I would be allowed to continue doing research; research was the carrot that compelled me to become a better student. There was nothing immediate or miraculous about my recovery, and Rich would have to give me a few well-deserved figurative ass-kickings over the next few years when I’d occasionally wander off course again. But the point was that I had a course. After a few months I learned—or remembered—to take pride in my coursework. I realized that I had never stopped defining myself in part by my performance, and that when I’d been adrift academically I’d also been depressed. It felt like crawling out of a hole.

(Aside: I realize that for many people, depression is the cause of academic difficulty, not the reverse, and that no amount of “just working harder” can offset the genuine biochemical imbalances that underlie clinical depression. I sympathize, and I wish we lived in a world where everyone could get the evaluation and care that they need without fear, stigma, crushing financial penalties, or all of the above. I’m also not describing any case here other than my own.)

What fresh hell is this? (Apatosaur dorsal from Gilmore 1936)

Out of one hole, into another. The biggest problem I faced back then is that if you are unfamiliar with sauropod vertebrae they can be forbiddingly complex. The papers I was struggling through referred to a pandemonium of laminae, an ascending catalog of horrors that ran from horizontal laminae and prespinal laminae through infraprezygapophyseal laminae and spinopostzygapophyseal laminae. Often these features were not labeled in the plates and figures, the authors had just assumed that any idiot would know what a postcentrodiapophyseal lamina was because, duh, it’s right there in the name. But that was the whole problem: I didn’t know how to decode the names. I had no map. SV-POW! tutorials didn’t exist. Jeff Wilson’s excellent and still-eminently-useful 1999 paper codifying the terminology for sauropod vertebral laminae was still years in the future.

Then I found this, on page 35 of Werner Janensch’s 1950 monograph on the vertebrae of what was then called Brachiosaurus brancai (now Giraffatitan):

It was in German, but it was a map! I redrew it by hand in my very first research notebook, and as I was copying down the names of the features the lightbulb switched on over my head. “Diapophyse” meant “diapophysis”, and it was the more dorsal of the two rib attachments. “Präzygapophyse” was “prezygapophysis”, and it was one of the paired articular bits sticking out the front of the neural arch. And, crucially, “Präzygodiapophysealleiste” had to be the prezygodiapophyseal lamina, which connected the two. And so on, for all of the weird bits that make up a sauropod vertebra.

It’s been 22 years and I still remember that moment of discovery, my pencil flying across the page as I made my own English translations of the German anatomical terms, my mind buzzing with the realization that I was now on the other side. Initiated. Empowered. I felt like I had pulled the sword from the stone, found Archimedes’ lever that could move the world. In the following weeks I’d go back through all of my photocopied sauropod monographs with my notebook open to the side, reading the descriptions of the vertebrae for the second or third times but understanding them for the first time, drawing the vertebrae over and over again until I could call up their basic outlines from memory. This process spilled over from the fall of 1996 into the spring of 1997, as Rich and I realized that OMNH 53062 would require more than one semester of investigation.

Interlude with a left femur of the Oklahoma apatosaurine (but not the largest individual).

My memories of those early days of my sauropod research are strongly shaped by the places and circumstances in which I was doing the work. Vicki and I had gotten married in the summer of 1996 and moved into a two-bedroom duplex apartment on the north side of Norman. The upstairs had a long, narrow bathroom with two sinks which opened at either end onto the two upstairs bedrooms, the one in which we slept and the one we used as a home office. In the mornings I could get showered and dressed in no time, and while Vicki was getting ready for work or school I’d go into the office to read sauropod papers and take notes. Vicki has always preferred to have music on while she completes her morning rituals, so I listened to a lot of Top 40 hits floating in from the other upstairs rooms while I puzzled out the fine details of sauropod vertebral anatomy.

Two songs in particular could always be counted on to play in any given hour of pop radio in the early spring of 1997: Wannabe by the Spice Girls, and Lovefool by the Cardigans. I am surely the only human in history to have this particular Pavlovian reaction, but to this day when I hear either song I am transported back to that little bedroom office where I spent many a morning poring over sauropod monographs, with my working space illuminated by the light of the morning sun pouring through the window, and my mind illuminated by Werner Janensch, who had the foresight and good grace to give his readers a map.

Figure 5 from my undergraduate thesis: OMNH 53062 in right lateral view.

If you want to know what I thought about OMNH 53062 back in 1997, you can read my undergraduate thesis—it’s a free download here. Looking back now, the most surprising thing to me about that thesis is how few mentions there are of pneumaticity. I met Brooks Britt in the summer of 1997 and had another epochal conversation, in which he suggested that I CT scan OMNH 53062 to look at the air spaces inside the vertebrae. I filed my undergrad thesis in December of 1997, and the first session CT scanning OMNH 53062 took place in January, 1998. So in late 1997 I was still a pneumaticity n00b, with no idea of the voyage I was about to embark upon.

In 2010, after I was settled in as an anatomist at Western University of Health Sciences, I wrote a long thank-you to Trish Schwagmeyer. It had been 14 years since that pivotal conversation, but when she wrote back to wish me well, she still remembered that I’d gotten a C in comparative anatomy. I’d have a chance to make amends for that glaringly anomalous grade later the same year. At ICVM in Punta del Este, Uruguay, I caught up with Edie Marsh-Matthews, who had taught my comparative anatomy course back when. I apologized for having squandered the opportunity to learn from her, and she graciously (and to my relief) shifted the conversation to actual comparative anatomy, the common thread that connected us in the past and the present.

If the story has a moral, it’s that I owe my career in large part to people who went out of their way to help me when I was floundering. And, perhaps, that the gentle approach is not always the best one. I needed to have my head thumped a few times, verbally, to get my ass in gear, when less confrontational tactics had failed. I slid easily through the classrooms of dozens of professors who watched me get subpar grades and didn’t try to stop me (counterpoint: professors are too overworked to invest in every academic disaster that comes through the door, just like paleontologists can’t study every garbage specimen). If Trish Schwagmeyer and Rich Cifelli had not decided that I was worth salvaging, and if they not had the grit to call me out on my BS, I wouldn’t be here. As an educator myself now, that thought haunts me. I hope that I will be perceptive enough to know when a student is struggling not because of a lack of ability but through a lack of application, wise enough to know when to deploy the “you’re blowing it” speech, and strong enough to follow through.

References

  • Gilmore Charles W. 1936. Osteology of Apatosaurus, with special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum 11:175–300 and plates XXI–XXXIV.
  • Janensch, Werner.  1950.  Die Wirbelsaule von Brachiosaurus brancai.  Palaeontographica (Suppl. 7) 3: 27-93.
  • Wedel, M.J. 1997. A new sauropod from the Early Cretaceous of Oklahoma. Undergraduate honor thesis, Department of Zoology, University of Oklahoma, Norman, OK. 43pp.
  • Wilson, J.A. 1999. A nomenclature for vertebral laminae in sauropods and other saurischian dinosaurs. Journal of Vertebrate Paleontology 19: 639-653.

Matt with big Apato dorsal 2000

Final bonus image so when I post this to Facebook, it won’t grab the next image in line and crop it horribly to make a preview. This is me with OMNH 1670, in 2003 or 2004, photo by Andrew Lee.

Posted by Matt Wedel
Filed in cervical, diplodocids, femur, Giant Oklahoma apatosaurine, museums, navel blogging, OMNH, Sauroposeidon, stinkin' appendicular elements, stinkin' mammals, stinkin' SV-POW!sketeers, Things I should have posted ten years ago
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Sauroposeidon, the early years: my first drawing

February 7, 2018

 

As part of a major spring cleaning operation that we started the first week of January, this week I opened the last two boxes left over from when we moved into our current house. One of them had a bundle of framed art. I knew most of what was in there before I opened the box, but I had somehow completely forgotten about this. I must have gotten it framed in late 90s, and it hung on the walls of our apartments in Norman and Santa Cruz. At some point it went into a box, and I forgot it even existed.

This is the first technical drawing I ever attempted of OMNH 53062, which would later become the holotype of Sauroposeidon. I drew it for my poster at the 1997 SVP meeting in Chicago, and it went on to become Figure 5 in my undergraduate thesis (which is preserved for posterity here). I’d do other, better drawings of the specimen in later years, but this one came first.

I know I’m biased, but that second vertebra in the preserved series, which I interpreted as C6 back when, will probably always be the most gorgeous natural object on the planet in my book. I don’t expect anyone else to feel the same. I worked on that specimen for three years – some of it seeped into my soul, and vice versa. Then again, I don’t care how jaded you are about long vertebrae, that one is still a pretty arresting sight.

For a much more recent take on the appearance of the Sauroposeidon vertebrae, see this post.

Posted by Matt Wedel
Filed in cervical, navel blogging, Sauroposeidon
2 Comments »

It’s that time of year…

December 22, 2017

This year Santaposeidon comes to you courtesy of OMNH vert paleo head preparator and 20th-level fossil conservation wizard Kyle Davies, who took the photo, composed the card, and gave me kind permission to share it here. Needless to say, we’re happy to pass on the happy holiday wishes to all of you, wherever you are and whenever you are reading this.

For previous Santaposeidon sightings, please see:

 

Posted by Matt Wedel
Filed in Christmas, goofy, hats, holidays, mounts, museums, OMNH, Santaposeidon, Sauroposeidon
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Some further thoughts on Patagotitan

August 10, 2017

A bunch of stuff, loosely organized by theme.

Media

First up, I need to thank Brian Switek, who invited me to comment on Patagotitan for his piece at Smithsonian. I think he did a great job on that, arguably the best of any of the first-day major media outlet pieces. And it didn’t go unnoticed – his article was referenced at both the Washington Post and NPR (and possibly other outlets, those are the two I know of right now). I don’t think my quotes got around because they’re particularly eloquent, BTW, but rather because reporters tend to like point-counterpoint, and I was apparently the most visible counterpoint. They probably would have done the same if I’d been talking complete nonsense (which, to be fair, some people may think I was).

Paleobiology vs Records

The most commonly reproduced quote of mine is this one, originally from Brian’s piece:

I think it would be more accurate to say that Argentinosaurus, Puertasaurus and Patagotitan are so similar in size that it is impossible for now to say which one was the largest.

That may seem at odds with the, “Well, actually…[pushes glasses up nose]…Argentinosaurus was still biggest” tack I’ve taken both in my post yesterday and on Facebook. So let me elaborate a little.

There is a minor, boring point, which is that when I gave Brian that quote, I’d seen the Patagotitan paper, but not the Electronic Supplementary Materials (ESM), so I knew that Patagotitan was about the same size as the other two (and had known for a while), but I hadn’t had a chance to actually run the numbers.

The much more interesting point is that the size differences between Argentinosaurus, Puertasaurus, and Patagotitan are astonishingly small. The difference between a 2.5m femur and a 2.4m one is negligible, ditto for vertebrae with centra 59cm and 60cm in diameter. OMNH 1331, the biggest centrum bit from the giant Oklahoma apatosaur, had an intact max diameter of 49cm, making it 26% larger in linear terms than the next-largest apatosaur. The centra of these giant South American titanosaurs are more than 20% bigger yet than OMNH 1331, just in linear terms. That’s crazy.

It’s also crazy that these three in particular – Argentinosaurus, Puertasaurus, and Patagotitan – are so similar in size. Dinosaur developmental programs were ‘messy’ compared to those of mammals, both in having weird timings for things like onset of reproduction, and in varying a lot among closely related taxa. Furthermore, sauropod population dynamics should have been highly skewed toward juveniles and subadults. So is the near-equality in size among Argentinosaurus, Puertasaurus, and Patagotitan just a coincidence, or does it mean that something weird was going on? There’s really no third option. I mean, even if some kind of internal (biomechanical or physiological) or external (ecological, food or predation) constraint forced those three to the same adult body size, it’s weird then that we’re finding only or at least mostly near-max-size adults. (If the available specimens of these three aren’t near-max-size, then any hypothesis that they’re forced to the same size by constraints is out the window, and we’re back to coincidence.)

BUT

With all that said, the title of “world’s largest dinosaur” is not handed out for effort expended, number of specimens collected, skeletal completeness, ontogenetic speculation, or anything other than “the dinosaur with the largest measured elements”. And that is currently Argentinosaurus. So although for any kind of paleobiological consideration we can currently consider Argentinosaurus, Puertasaurus, and Patagotitan to all be about the same size – and Alamosaurus, Paralititan, Notocolossus, and probably others I’ve forgotten should be in this conversation – anyone wanting to dethrone Argentinosaurus needs to actually show up with bigger elements.

So, if you’re interested in paleobiology, it’s fascinating and frankly kind of unnerving that so many of these giant titanosaurs were within a hand-span of each other in terms of size. Patagotitan is one more on the pile – and, as I said yesterday, exciting because it’s so complete.

But if you want to know who holds the crown, it’s still Argentinosaurus.

Humeri

In a comment on the last post, Andrea Cau made an excellent point that I am just going to copy here entire:

Even Paralititan stromeri humerus is apparently larger than Patagotitan humerus (169 cm vs 167.5 cm). I know humerus length alone is bad proxy of body size, but at least this shows that even in that bone Patagotitan is just another big titanosaur among a well known gang of titans, not a supersized one.

That made me want to start a list of the longest sauropod humeri. Here goes – if I missed anyone or put down a figure incorrectly, I’m sure you’ll let me know in the comments.

  • Giraffatitan: 213cm
  • Brachiosaurus: 203cm
  • Ruyangosaurus: 190cm (estimated from 135cm partial)
  • Turiasaurus: 179cm
  • Notocolossus: 176cm
  • Paralititan: 169cm
  • Patagotitan: 167.5cm
  • Dreadnoughtus: 160cm
  • Futlognkosaurus: 156cm

Admittedly the Patagotitan humerus is from a paratype and not from the largest individual, but that is true for some others on the list, including Giraffatitan. And we have no humeri from Argentinosaurus, Puertasaurus, and some other giants.

Dorsal Vertebrae

A couple of further thoughts on how the dorsal vertebrae of Patagotitan compare to those of Argentinosaurus. First, now that I’ve had some time to think about it, I have a hard time seeing how the dorsal polygon method used by Carballido et al. in the Patagotitan paper has any biological meaning. In their example figure, the polygon around the Puertasaurus vertebra is mostly full of bone, and the one around Patagotitan has a lot of empty space. It’s easy to imagine an alternative metric, like “area of the minimum polygon actually filled by bone”, that would lead to a different ‘winner’. But that wouldn’t mean much, either.

Something that probably does have a real and important biomechanical meaning is the surface area of the articular face of the centrum, because that’s the area of bone that has to bear the compressive load, which is directly related to the animal’s mass. The biggest Patagotitan centrum is that of MPEF-PV 3400/5, which is at least a local maximum since has smaller centra both ahead and behind. The posterior face measures 59cm wide by 42.5cm tall. Abstracted as an ellipse, which may not be perfectly accurate, those measurements give a surface area of (pi)(29.5)(21.25)=1970 cm^2. For Argentinosaurus, the largest complete centrum has a posterior face measuring 60cm wide by 47cm tall (Bonaparte and Coria 1993: p. 5), giving an elliptical surface area of (pi)(30)(23.5)=2210 cm^2. (I’d use hi-res images of the centra to measure the actual surface areas if I could, but AFAIK those images either don’t exist or at least have not yet been made public, for either taxon.) So although the Argentinosaurus dorsal seems like it is only a bit bigger in linear terms, it’s 12% larger in surface area, and that might actually be a meaningful difference.

Cervical Vertebrae

One thing I haven’t commented on yet – Patagotitan is the newest member of the “world’s longest vertebrae” club. The longest Patagotitan cervical, MPEF-PV 3400/3, is listed in the ESM as having a centrum length of 120cm, but it’s also listed as incomplete. In the skeletal recon in the paper, the centrum is colored in as present, but the neural spine is missing. So is the centrum complete in terms of length? I don’t think it’s clear right now.

Anyway, here’s the current rundown of the longest cervical centra of sauropods (and therefore, the longest vertebrae among animals):

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

You may be surprised to see the Price River 2 cervical in there. It was reported in an SVP abstract a few years ago (I’ll dig up that ref and update this post), and Mike and I saw it last year on the Sauropocalypse. We measured the centrum at 129cm, making it just a bit longer than the longest centrum of Sauroposeidon, and therefore the second-longest vertebra of anything ever.

Aside – I’m probably getting a reputation as a big ole meanie when it comes to debunking “world’s largest dinosaur” claims. If I’m willing to take the lead in kicking my own dinosaur down the ladder, don’t expect me to be kind to yours. I follow where the numbers lead.

Now, here’s an interesting thing – now that Sauroposeidon is coming out as a basal titanosaur, rather than a brachiosaur, it might not have been a skinny freak. The 120cm cervical of Patagotitan makes the 125cm cervical of Sauroposeidon and the 129cm cervical from Price River 2 look even more tantalizing. Maybe it’s super-giant sauropods all the way down.

Posted by Matt Wedel
Filed in Alamosaurus, Argentinosaurus, cervical, dorsal, Notocolossus, Paralititan, Patagotitan, Puertasaurus, Sauroposeidon, size, titanosaur
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A quick stop at the Oklahoma Museum of Natural History

December 21, 2016

aquilops-display-omnh-dec-2016-1

I’m back in Oklahoma for the holidays, and anytime I’m near Norman I pop in to the OMNH to see old friends, both living and fossil. Here’s the Aquilops display in the hall of ancient life, which has been up for a while now. I got some pictures of it when I was here back in March, just never got around to posting them.

aquilops-close-up-omnh-dec-2016-2

Aquilops close up. You can’t see it well in this pic, but on the upper right is a cast of the Aquilops cranium with a prosthesis that shows what the missing bits would have looked like. That prosthesis was sculpted by – who else? – Kyle Davies, the OMNH head preparator and general sculpting/molding/casting sorceror. You’ve seen his work on the baby apatosaur in this post. I have casts of everything shown here – original fossil, fossil-plus-prosthesis, and reconstructed 3D skull – and I should post on them. Something to do in the new year.

ceratopsians-large-and-small-omnh-dec-2016-3

The Aquilops display is set just opposite the Antlers Formation exhibit, which has a family of Tenontosaurus being menaced by two Deinonychus, and at the transition between Early and Late Cretaceous. The one mount in the Late Cretaceous area is the big Pentaceratops, which is one of the best things in this or any museum.

pentaceratops-omnh-dec-2016-4

Evidence in support of that assertion. Standing directly in front of this monster is a breathtaking experience, which I highly recommend to everyone.

It’s just perfect that you can see the smallest and earliest (at least for now) North American ceratopsian adjacent to one of the largest and latest. Evolution, baby!

mammoth-santa-omnh-dec-2016-5

I didn’t only look at dinosaurs – the life-size bronze mammoth in the south rotunda is always worth a visit, especially in holiday regalia.

santaposeidon-omnh-dec-2016-6

No holiday post about the OMNH would be complete without a shot of “Santaposeidon” (previously seen here). I will never get tired of this!

The chances that I’ll get anything else posted in 2016 hover near zero, so I hope you all have a safe and happy holiday season and a wonderful New Year.

Posted by Matt Wedel
Filed in Aquilops, elephant, goofy, hats, museums, OMNH, public galleries, Santaposeidon, Sauroposeidon, stinkin' heads, stinkin' mammals, stinkin' ornithischians
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The epipophyses of Qijianglong and other sauropods

February 2, 2015

Introduction and Background

2005-09-27 CM 555 c6 480

An epipophysis in a neural arch of a juvenile Apatosaurus, CM 555. From this post.

I have three goals with this post:

  1. To document the range of variation in epipophyses in the cervical vertebrae of sauropods.
  2. 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.
  3. 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.

OMNH emu vert 480

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.

  1. 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.
  2. Beddard (1898) referred to this feature in birds as the hyperapophysis; this term seems to have fallen completely out of use.
  3. 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.
  4. 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”.
  5. 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’.
  6. 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.

Prosauropods

Leonerasaurus_cervical_vertebrae - Pol et al 2011 fig 5

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.

Basal sauropods

Tazoudasaurus cervical - Allain and Aquesbi 2008 fig 9i-j

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).

Jobaria epipophyes

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.

Other mamenchisaurids

It’s not air-tight, but there is suggestive evidence of projecting epipophyses in some other mamenchisaurids besides Qijianglong.

Mamenchisaurus epipophyses - lateral view

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.

Mamenchisaurus epipophyses - medial view

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.

Mamenchisaurus youngi epipophyses

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.

Omeisaurus epipophysis

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).

Diplodocoidea

Haplocanthosaurus epipophyses - Hatcher 1903

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).

diplodocid epipophyses

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).

NIgersaurus cervical - Sereno et al 2007 fig 3

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.

Macronaria

Australodocus epipophysis

The epipophysis in this cervical of Australodocus just barely projects beyond the posterior margin of the postzygapophysis.

Giraffatitan c8 epipophyses

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.

Sauroposeidon epipophyses

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!

malawisaurus-cervicals

Cervical vertebrae of Malawisaurus from Gomani (2005: fig. 9): not an epipophysis in sight. But check out the spike-like neural spines – these are so wide from side to side that from the front they look like party balloons.

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.

FIGURE 11. Anterior cervical series of Qijianglong guokr (QJGPM 1001) in left lateral views unless otherwise noted. A, axis; B, cervical vertebra 3; C, cervical vertebra 4; D, cervical vertebrae 5 and 6; E, cervical vertebra 7 and anterior half of cervical vertebra 8 (horizontally inverted; showing right side); F, posterior half of cervical vertebra 8 and cervical vertebra 9; G, cervical vertebra 10; H, cervical vertebra 11; I, close-up of the prezygapophy- sis-postzygapophysis contact between cervical vertebrae 3 and 4 in dorsolateral view, showing finger-like process lateral to postzygapophysis; J, close- up of the postzygapophysis of cervical vertebra 5 in dorsal view, showing finger-like process lateral to postzygapophysis. Arrow with number indicates a character diagnostic to this taxon (number refers to the list of characters in the Diagnosis). All scale bars equal 5 cm. Abbreviations: acdl, anterior centrodiapophyseal lamina; cdf, centrodiapophyseal fossa; plc, pleurocoel; pocdl, postcentrodiapophyseal lamina; poz, postzygapophysis; pozcdf, post- zygapophyseal centrodiapophyseal fossa; pozdl, postzygodiapophyseal lamina; ppoz, finger-like process lateral to postzygapophysis; ppozc, groove for contact with finger-like process; przdl, prezygodiapophyseal lamina; sdf, spinodiapophyseal fossa.

Cervical vertebrae of Qijianglong (Xing et al. 2015: fig. 11)

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.

References

Posted by Matt Wedel
Filed in Barosaurus, brachiosaurids, cervical, diplodocids, Diplodocus, epipophyses, Giraffatitan, Jobaria, Kaatedocus, mamenchisaur, Nigersaurus, Sauroposeidon
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Wheelbarrow handles for vertebrae? The cervical rib bundles of Sauroposeidon and other sauropods

September 22, 2014

Cervical rib cross-sections from Mamenchisaurus Giraffatitan and Diplodocus Klein et al 2012 fig 1

Klein et al. (2012: fig. 1)

We have good descriptions of the proximal parts of the cervical ribs for lots of sauropods. We also have histological cross-sections of a few, mostly thanks to the work of Nicole Klein and colleagues (Klein et al. 2012, Preuschoft and Klein 2013), although histological cross-sections of ribs were also figured as long ago as 1999, by Dalla Vecchia (1999: figs. 29 and 30), and as recently as this month, by Lacovara et al. (2014: supplementary figure 4).

What we have very, very few of is series of cross-sections that show how the cr0ss-section of a cervical rib changes along its length. There may be more out there (and if I have forgotten any, please remind me!), but at the moment I can only think of three such figures: two in Janensch (1950: figs. 83 and 85), both on Giraffatitan, and one in Klein et al. (2012: fig. 1), with cross-sections from Mamenchisaurus, Giraffatitan, and Diplodocus (shown at the top of the post).

Sauroposeidon cervical rib cross-sections v3

 

Rarer still are images that show cross-sections of overlapped cervical ribs, stacked in situ. You could use the information in Janensch (1950: figs. 83 and 85) to generate the stacked cross-sections, but you wouldn’t know the spacing between the ribs as they were in the ground. I think the image just above, of the cervical rib bundles in the Sauroposeidon holotype, OMNH 53062, may be the first of its kind–again, if you know of any others, please let me know. I took the notes for this figure back in 2004, sitting down with the holotype and some digital calipers to make sure I could scale everything correctly, I just hadn’t ever put it into a presentable form until now. The first C6 section (blue V-shape) is from right at the root where the capitulum and tuberculum meet and the posterior shaft of the rib begins.

It is by now well-understood that the long cervical ribs of sauropods and other dinosaurs are ossified tendons of the long hypaxial neck muscles, specifically the longus colli ventralis and flexor colli lateralis. We argued this back in 200o on comparative anatomical grounds (Wedel et al. 2000b: pp. 378-379), and it has now been demonstrated histologically (Klein et al. 2012, Lacovara et al. 2014). The system of stacked tendons is also found in most birds. Here’s the bundle of stacked tendons in a rhea neck, only slightly fanned out:

Rhea ventral tendons stacked - full

And the same neck, with both the epaxial and hypaxial muscles more fully separated:

Rhea neck muscles fanned - full

What I’d really like is an MRI of a rhea or ostrich neck, showing the stacked tendons and their associated belts of muscle, to compare with the stacked cervical ribs of Sauroposeidon and other sauropods. Anyone know of any?

Incidentally, I think the cervical ribs and cervical rib bundles of sauropods are one line of evidence for sauropod necks having been rather slenderly-muscled. The long, multi-segment muscles like the longus colli ventralis are the outermost components of the muscular envelope that surrounds the vertebrae, as you can see in the rhea dissection photos. In sauropod specimens with articulated cervical ribs, the ribs do not deviate from one another or fan out. Rather, they lie in vertically stacked bundles that run from one capitulum-tuberculum intersection to the next. So the depth of that intersection–the “root” of the cervical rib of any given vertebra–plus the thickness of the ribs stacked underneath it, is pretty much the thickness of the muscular envelope around the neck, or at least around the ventral half. And the cervical ribs are typically pretty close to the vertebral centra–only weirdos like Apatosaurus and Erketu displace them very far ventrally (see Taylor and Wedel 2013a: fig. 7 and this post). So, thin jackets of muscle around proportionally large vertebrae–or, if you like, corn-on-the-cob rather than shish-kebabs.

As for why sauropods have long cervical ribs, Mike and I discussed some possibilities in our 2013 PeerJ paper (Taylor and Wedel 2013a), and Preuschoft and Klein addressed the issue last fall in PLOS ONE (Preuschoft and Klein 2013). My favorite hypothesis is that long tendons allow an animal to shift the bulk of the muscle–and therefore the center of gravity–toward the base of the neck, but that long unossified tendons can be distorted through stretching, which wastes muscular energy. Ossifying those long tendons is like putting bony wheelbarrow handles on each vertebra, allowing the muscles to move the vertebra from a distance without so much wasted energy, and probably with finer positional control.

That’s a nifty hypothesis in need of testing, anyway. In fact, cervical ribs and their associated muscles could stand a lot more attention on both the descriptive and analytical fronts. I know that Liguo Li has some research in the works on different conformations of hypaxial muscles, tendons, and cervical ribs in birds (you know, when she’s not describing bizarre new titanosaurs like Yongjinglong — see Li et al. 2014). If you saw Peter Dodson give their talk at SVP last fall, you probably remember some stunning images of dissected bird necks. As a famous legislator once said, we shall watch her career with great interest.

References

 

Posted by Matt Wedel
Filed in cervical, cervical ribs, cross sections, Sauroposeidon
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Mid-Mesozoic Field Conference, Day 6: Sauroposeidon and kin

May 8, 2014

My camera had a possibly-fatal accident in the field at the end of the day on Saturday, so I didn’t take any photos on Sunday or Monday. From here on out, you’re either getting my slides, or photos taken by other people.

Powell Museum sauropod humerus

On Sunday we were at the John Wesley Powell River History Museum in Green River, Utah, for the Cretaceous talks. There were some fossils on display downstairs, including mounted skeletons of Falcarius and one or two ornithischians,* and this sauropod humerus from the Cedar Mountain Formation (many thanks to Marc Jones for the photo).

* A ceratopsian and Animantarx, maybe? They were in the same room as the sauropod humerus, so it’s no surprise that I passed them by with barely a glance.

There were loads of great talks in the Cretaceous symposium on Sunday, and I learned a lot, about everything from clam shrimp biostratigraphy to ankylosaur phylogeny to Canadian sauropod trackways. But I can’t show you any slides from those talks, so the rest of this post is the abstact from Darren’s and my talk, illustrated by a few select slides.

Wedel Naish 2014 Sauroposeidon and kin - slide 1 title

Sauroposeidon is a giant titanosauriform from the Early Cretaceous of North America. The holotype is OMNH 53062, a series of four articulated cervical vertebrae from the Antlers Formation (Aptian-Albian) of Oklahoma. According to recent analyses, Paluxysaurus from the Twin Mountain Formation of Texas is the sister taxon of OMNH 53062 and may be a junior synonym of Sauroposeidon. Titanosauriform material from the Cloverly Formation of Wyoming may also pertain to Paluxysaurus/Sauroposeidon. The proposed synonymy is based on referred material of both taxa, however, so it is not as secure as it might be.

Wedel Naish 2014 Sauroposeidon and kin - slide 34 Sauroposeidon characters

Top row, vertebrae of Paluxysaurus. From left to right, the centrum lengths of the vertebrae are 72cm, 65cm, and 45cm. Main image, the largest and most complete vertebra of the holotype of Sauroposeidon. Labels call out features that are present in every Sauroposeidon vertebra where they can be assessed, but consistently absent in Paluxysaurus. Evaluating the proposed synonymy of Paluxysaurus and Sauroposeidon is left as an exercise for the reader.

MIWG.7306 is a cervical vertebra of a large titanosauriform from the Wessex Formation (Barremian) of the Isle of Wight. The specimen shares several derived characters with the holotype of Sauroposeidon: an elongate cervical centrum, expanded lateral pneumatic fossae, and large, plate-like posterior centroparapophyseal laminae. In all of these characters, the morphology of MIWG.7306 is intermediate between Brachiosaurus and Giraffatitan on one hand, and Sauroposeidon on the other. MIWG.7306 also shares several previously unreported features of its internal morphology with Sauroposeidon: reduced lateral chambers (“pleurocoels”), camellate internal structure, ‘inflated’ laminae filled with pneumatic chambers rather than solid bone, and a high Air Space Proportion (ASP). ASPs for Sauroposeidon, MIWG.7306, and other isolated vertebrae from the Wessex Formation are all between 0.74 and 0.89, meaning that air spaces occupied 74-89% of the volume of the vertebrae in life. The vertebrae of these animals were therefore lighter than those of brachiosaurids (ASPs between 0.65 and 0.75) and other sauropods (average ASPs less than 0.65).

Wedel Naish 2014 Sauroposeidon and kin - slide 64 Mannion phylogeny

Check this out: according to at least some versions of the Mannion et al. (2013) tree, Sauroposeidon and Paluxysaurus are part of a global radiation of andesaurids in the Early and middle Cretaceous. Cool!

Sauroposeidon and MIWG.7306 were originally referred to Brachiosauridae. However, most recent phylogenetic analyses find Sauroposeidon to be a basal somphospondyl, whether Paluxysaurus and the Cloverly material are included or not. Given the large number of characters it shares with Sauroposeidon, MIWG.7306 is probably a basal somphospondyl as well. But genuine brachiosaurids also persisted and possibly even radiated in the Early Cretaceous of North America; these include Abydosaurus, Cedarosaurus, Venenosaurus, and possibly an as-yet-undescribed Cloverly form. The vertebrae of Abydosaurus have conservative proportions and solid laminae and the bony floor of the centrum is relatively thick. In these characters, Abydosaurus is more similar to Brachiosaurus and Giraffatitan than to Sauroposeidon or MIWG.7306. So not all Early Cretaceous titanosauriforms were alike, and whatever selective pressures led Sauroposeidon and MIWG.7306 to evolve longer and lighter necks, they didn’t prevent Giraffatitan-like brachiosaurs such as Abydosaurus and Cedarosaurus from persisting well into the Cretaceous.

Wedel Naish 2014 Sauroposeidon and kin - slide 65 Cloverly sauropods

The evolutionary dynamics of sauropods in the North American mid-Mesozoic are still mysterious. In the Morrison Formation, sauropods as a whole are both diverse and abundant, but Camarasaurus and an efflorescence of diplodocoids account for most of that abundance and diversity, and titanosauriforms, represented by Brachiosaurus, are comparatively scarce. During the Early Cretaceous, North American titanosauriforms seem to have radiated, possibly to fill some of the ecospace vacated by the regional extinction of basal macronarians (Camarasaurus) and diplodocoids. However, despite a flood of new discoveries in the past two decades, sauropods still do not seem to have been particularly abundant in the Early Cretaceous of North America, in contrast to sauropod-dominated faunas of the Morrison and of other continents during the Early Cretaceous.

Wedel Naish 2014 Sauroposeidon and kin - slide 66 acknowledgments

That final slide deserves some explanation. On the way back from the field on Saturday–the night before my talk–a group of us stopped at a burger joint in Hanksville. Sharon McMullen got a kid’s meal, and it came in this bag. We took it as a good omen that Sauroposeidon was the first dinosaur listed in the quiz.

For the full program and abstracts from both days of talks, please download the field conference guidebook here.

Posted by Matt Wedel
Filed in "Angloposeidon", brachiosaurids, Brachiosaurus, cervical, humerus, Sauroposeidon, stinkin' appendicular elements
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One articulated Sauroposeidon to go, hold the perspective distortion, with a side of stinkin’ mammal

April 24, 2014

Order up!

Sauroposeidon OMNH 53062 articulated right lateral composite with giraffe

Sauroposeidon is stitched together from orthographic views of the 3D photogrammetric models rendered in MeshLab. Greyed out bits of the vertebrae are actually missing–I used C8 to patch C7, C7 to patch C6, and so on forward. The cervical ribs as reconstructed here were all recovered and they are in collections, but they’re in several jackets and boxes and therefore not easily photographed.

The meter bars are both one meter as advertised. The giraffe neck is FMNH 34426 (from this post), which is actually 1.7 meters long, but I scaled it up to 2.4 meters to match that of the tallest known giraffe. I think it’s cool that a world-record giraffe neck is roughly as long as two vertebrae from the middle of the neck of Sauroposeidon.

There are loads of little morphological details in the Sauroposeidon vertebrae that are clearer now than they were in our old photographs, but those will be stories for other posts.

Posted by Matt Wedel
Filed in cervical, giraffe, Gratuitously awesome images, Sauroposeidon, stinkin' mammals
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