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DrScottHartman's avatar

Something Super this way comes

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Ah, Supersaurus. I spent so...much...time with this beast when I was at the WDC that I actually hadn't bothered to do anything with it from 2006 until 2011, when I made some minor revisions for a project that Nature did on gigantism in sauropods. Anyhow, inspired by questions raised over at SVPOW [link] I went ahead and finished revising it. The bones didn't need any tweaking, but their position and the soft-tissue sure did.

A lot happens in 7 years apparently. Anyhow, the WDC specimen of Supersaurus clocks in at 32m in length, with a 12m long neck. Volumetric mass estimates placed it in the 30-35 tonne range, although it wouldn't hurt to redo them just to double check (or I could do a double integration, if I update the multi-view skeletals I did of this guy). The BYU specimen, which is the type (but much less complete) specimen was larger yet, possibly a diplodocid that exceeded 40 meters, and could easily have hit the 40-50 tonne range (note that in our paper we disregarded many of the popular mass estimates for sauropods that produced estimates of 50-80 tonnes for Brachiosaurus, or the big Diplodocus specimen that was named Seismosaurus).
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Paleo-King's avatar
Curious question Scott... this version of Supersaurus differs in a lot of ways from your early version (which I know was based on different specimens, the old BYU ones). The old version had a shorter neck and also the neural spines on the neck were not angled forward as much. Actually the two necks look completely different. Is that old skeletal with the different neural spines and shorter neck still valid for the BYU specimens, or did they turn out to be a different species in your view?
DrScottHartman's avatar
Thanks for the question, but I'm not sure which older skeletal you are referring to? Since 2006 or so the only other skeletal on Supersaurus I've had up was the one based from our description of the Thermopolis specimen: www.academia.edu/2411751/MORPH…

The neck in that one is almost identical in that one, so I'm confused. I had done one waaaay back in 2002 that I can't even find a copy of and I can't find with Google image search - if you have that one (if so congrats, that was from the days of pen and ink!) it was done before the excavation was complete and before most of the bones were prepped out. It was just meant to be a guide for the people working on it (you could color in the bones that we'd found, that were prepped, etc). 
Paleo-King's avatar
I mean this one, with the shorter neck and more brachiosaur-like neural spines in the neck: vignette2.wikia.nocookie.net/d…

Was this the 2002 version? There is a big difference in neck length and cervical shape.
DrScottHartman's avatar
Yup, that's the one. We only had about half of Jimbo's bones out of the ground none of the cervicals were prepped out all the way yet. Basically the only cervical that was relatively intact I'd seen was the classic BYU "spaceship" vertebrae, but (as the name suggests) it was a wee-bit smooshed and hard to interpret without having our cervicals to compare it to.
Paleo-King's avatar
Ok so that old version had too short of a neck. Thanks!
Megalotitan's avatar
Is it just me, or are the legs really proportionally short? :o (Eek) 
DrScottHartman's avatar
It's not just you. Luckily we found the "Jimbo" specimen in Wyoming; it was the only animal in the quarry so we can be confident in referring the shorter legs to this behemoth.
Megalotitan's avatar
A good explanation.
Although I realized that apatosaurines have fairly proportionally short legs right after I've posted that comment :P (Lick) 
thedinorocker's avatar
I noticed with pleasure you add at your skeletal index the updated skeletal of Brontosa...mmm Apatosaurus excelsus! :)
After a comparision between it and others species clearly appear that A.excelsus and A.louisae are more "brontosaurids" than A.ajax wich show similarities with the Supersaurus
DrScottHartman's avatar
I can't disagree with any of that statement.
thedinorocker's avatar
;)
I hope to se an update Diplodocus longus one day!
Hey isn't an estimate of 40-50 tonnes too low if the large one is indeed 40m long and the small one 32m? Isometric scaling would suggest 60 tonnes.
DrScottHartman's avatar
If it is indeed 40m, yes.
How long is it actually?
DrScottHartman's avatar
With so little of the vertebral column known there's no way to answer that question with any precision. Personally I suspect it's closer to 35 meters, but there are plenty of ways you could finagle the numbers to get up to 40m, so we'll just have to find more.
I remember you and the rest of the WDC crew found Supersaurus to be an apatosaurine, but I've heard that's been challenged. What's your current opinion on it?

Also, it's really a shame that Jim Jensen died before he could have seen the Wyoming specimen.
DrScottHartman's avatar
I still suspect it's an apatosaurine (the tail is a dead-on ringer), but I'm not overly attached to it.
Perhaps a weird question: could the height of the dorsal neural spines in sauropods provide an indication for the lever-action of the neck, and to what the degree the neck could be raised above the horizontal? There is quite a bit of variation in the height of this portion of the axial skeleton in sauropod dinosaurs, and all of that would have been covered by muscle, with the apical bifurcation housing both muscle and a tendon. I hope you get what I am trying to get at.. Anyway, thanks in advance for taking the time to answer it! :)
Actually, I suspect bifid neural spines point to a more horizontal neck. Compare the amount of stress on your vertebral column when your standing up or leaning over, and you'll see why the extra ligaments are needed in horizontal-necked sauropods. Also, brachiosaurs don't have bifid neural spines and they're the most "vertical" sauropods of all. I doubt that's a coincidence.
That actually makes a lot of sense! Thanks for that! 
DrScottHartman's avatar
The height of the dorsal neural spines does speak to the lever arm of any nuchal ligaments that are attached to them and the neck (really just the anterior dorsals here), but the position of the neck plays a large role as well, and that is defined by the articular surfaces more than anything else (although sauropod vertebrae are notoriously susceptible to crushing).
keesey's avatar
Very cool!

Just a note: Scott made a silhouette version and uploaded it to PhyloPic, so now you can see it a fill evolutionary lineage for Supersaurus, including other silhouettes by Scott and other artists - [link]
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