Supersaurus vs Brachiosaurus - BYU 9024 and FMNH P25107

This was inspired by an email Mike sent a couple of days ago:

Remind yourself of the awesomeness of Giraffatitan:
http://svpow.files.wordpress.com/2008/11/mike-by-jango-elbow.jpeg

Now think of this. Its neck is 8.5m long. Knock of one measly meter — for example, by removing one vertebra from the middle of the neck — and you have 7.5 m.

Supersaurus’s neck was probably TWICE that long.

Holy poo.

I replied that I was indeed freaked out, and that it had given me an idea for a post, which you are now reading. I didn’t have a Giraffatitan that was sufficiently distortion-free, so I used my old trusty Brachiosaurus. The vertebra you see there next to Mike and next to the neck of Brachiosaurus is BYU 9024, the longest vertebra that has ever been found from anything, ever.

Regarding the neck length of Supersaurus, and how BYU 9024 came to be referred to Supersaurus, here’s the relevant chunk of my dissertation (Wedel 2007: pp. 208-209):

Supersaurus is without question the longest-necked animal with preserved cervical material. Jim Jensen recovered a single cervical vertebra of Supersaurus from Dry Mesa Quarry in western Colorado. The vertebra, BYU 9024, was originally referred to “Ultrasauros”. Later, both the cervical and the holotype dorsal of “Ultrasauros” were shown to belong to a diplodocid, and they were separately referred to Supersaurus by Jensen (1987) and Curtice et al. (1996), respectively.

BYU 9024 has a centrum length of 1378 mm, and a functional length of 1203 mm (Figure 4-3). At 1400 mm, the longest vertebra of Sauroposeidon is marginally longer in total length [see this post for a visual comparison]. However, that length includes the prezygapophyses, which overhang the condyle, and which are missing from BYU 9024. The centrum length of the largest Sauroposeidon vertebra is about 1250 mm, and the functional length is 1190 mm. BYU 9024 therefore has the largest centrum length and functional length of any vertebra that has ever been discovered for any animal. Furthermore, the Supersaurus vertebra is much larger than the Sauroposeidon vertebrae in diameter, and it is a much more massive element overall.

Neck length estimates for Supersaurus vary depending on the taxon chosen for comparison and the serial position assumed for BYU 9024. The vertebra shares many similarities with Barosaurus that are not found in other diplodocines, including a proportionally long centrum, dual posterior centrodiapophyseal laminae, a low neural spine, and ventrolateral flanges that connect to the parapophyses (and thus might be considered posterior centroparapophyseal laminae, similar to those of Sauroposeidon). The neural spine of BYU 9024 is very low and only very slightly bifurcated at its apex. In these characters, it is most similar to C9 of Barosaurus. However, theproportions of the centrum of BYU 9024 are more similar to those of C14 of Barosaurus, which is the longest vertebra of the neck in AMNH 6341. BYU 9024 is 1.6 times as long as C14 of AMNH 6341 and 1.9 times as long as C9. If it was built like that of Barosaurus, the neck of Supersaurus was at least 13.7 meters (44.8 feet) long, and may have been as long as 16.2 meters (53.2 feet).

Based on new material from Wyoming, Lovelace et al. (2005 [published as Lovelace et al. 2008]) noted potential synapomorphies shared by Supersaurus and Apatosaurus. BYU 9024 does not closely resemble any of the cervical vertebrae of Apatosaurus. Instead of trying to assign its serial position based on morphology, I conservatively assume that it is the longest vertebra in the series if it is from an Apatosaurus-like neck. At 2.7 times longer than C11 of CM 3018, BYU 9024 implies an Apatosaurus-like neck about 13.3 meters
(43.6 feet) long.

Supersaurus vs Diplodocus BYU 9024 and USNM 10865 - Gilmore 1932 pl 6

Bonus comparo: BYU 9024 vs USNM 10865, the mounted Diplodocus longus at the Smithsonian, modified from Gilmore 1932 (plate 6). For this I scaled BYU 9024 against the 1.6-meter femur of this specimen.

If you’d like to gaze upon BYU 9024 without distraction, or put it into a composite of your own, here you go:

Supersaurus cervical BYU 9024

References

 

OLYMPUS DIGITAL CAMERA

This is BYU 12867–you’ve seen it here before–in dorsal view. It’s not a brilliant shot–I took it through the glass of the display case while filming a documentary at the North American Museum of Ancient Life in Lehi, Utah, in 2008. Centrum length is 94 cm, total length with the overhanging prezygapophyses is over a meter.

As promised, some thoughts on the various new brachiosaur mass estimates in recent papers and blog-posts.

Back in 2008, when I did the GDI of Giraffatitan and Brachiosaurus for my 2009 paper on those genera, I came out with estimates of 28688 and 23337 kg respectively. At the time I said to Matt that I was suspicious of those numbers because they seemed too low. He rightly told me to shut up and put my actual results in the paper.

More recently, Benson et al. (2014) used limb-bone measurements to estimate the masses of the same individuals as 56000 and 34000 kg. When Ian Corfe mentioned this in a comment, my immediate reaction was to be sceptical: “I’m amazed that the two more recent papers have got such high estimates for brachiosaurs, which have the most gracile humeri of all sauropods“.

So evidently I have a pretty strong intuition that Brachiosaurus massed somewhere in the region of 35000 kg and Giraffatitan around 30000 kg. But why? Where does that intuition come from?

I can only assume that my strongly held ideas are based only on what I’d heard before. Back when I did my 2008 estimate, I probably had in mind things like Paul’s (1998) estimate of 35000 kg for Brachiosaurus, and Christiansen’s (1997:67) estimate of 37400 for Giraffatitan. Whereas by the time the Benson et al. paper came out I’d managed to persuade myself that my own much lower estimates were right. In other words, I think my sauropod-mass intuition is based mostly on sheer mental inertia, and so should be ignored.

I’m guessing I should ignore your intuitions about sauropod masses, too.

References

In recent photo posts on the mounted Brachiosaurus skeleton and its bones in the ground, I’ve lamented that the Field Museum’s online photo archive is so unhelpful: for example, if it has a search facility, I’ve not been able to find it.

But the good news is that there’s a Field Museum Photo Archives tumblr. Its coverage is of course spotty, but it gives us at least some chance of finding useful brachiosaur images. Like this one of the sixth presacral vertebra (i.e. probably D7 in a column of 12 dorsals):

tumblr_mlrvdcANCj1s5mxl9o1_1280

It’s instructive to compare that with Riggs’s (1904: plate LXXII) illustration of the same vertebra in the same aspect, in which he almost literally airbrushed out the jigsaw-puzzle complexity of the preserved bone surface:

Riggs1904-plate-LXXII-presacral-6.right-lateral

 

More disturbing still, compare that old photograph with my own (terrible) 2005 photo of the same vertebra:

dscn1404-rotated-cropped-enhanced

It looks very much as though the vertebra itself — not just Riggs’s illustration — has been “improved” since the older photo was taken exactly a century earlier in 1905. This is a constant problem when dealing with old fossils.

Here are three more interesting photos from the Tumblr. First, the Brachiosaurus fossils in the field:

tumblr_mkxwevwaqi1s5mxl9o1_1280

This is evidently from later in the excavation process than the previous photo of this area, since much of the material is now jacketed. That’s the femur in front of shot, here seen in anteromedial view, with the top towards the right.

Next up, this photo purports to be “Thirteen men including Security Guard unloading dorsal vertebrae of type specimen Brachiosaurus fossil”:

tumblr_mk9snb7ghp1s5mxl9o1_1280

But in fact it’s not Brachiosaurus — the neural spines are too tall and slender. I am pretty sure this is Riggs’s Apatosaurus — the rightmost dorsal has that distinctive notch on the dorsal aspect of the neural spine. And indeed, checking his monograph on that specimen (Riggs 1903: plate XLVI), I see that its dorsals were distorted in this way, and that the front-centre vert is a fine match for its D10.

Finally, there’s this one of the prep room:

tumblr_mk0kgrIURE1s5mxl9o1_1280

On the far left, we have the still-jacketed Brachiosaurus femur; next to it stands Harold W. Menke, who discovered the fossil; and to his right is Elmer S. Riggs, who wrote the description.

Those are all the Brachiosaurus-related images I’ve been able to find on the tumblr. But do let me know if you find any others.

References

  • Riggs, Elmer S. 1903. Structure and relationships of opisthocoelian dinosaurs. Part I: Apatosaurus Marsh. Field Columbian Museum, Geological Series 2:165-196.
  • Riggs, Elmer S. 1904. Structure and relationships of opisthocoelian dinosaurs. Part II, the Brachiosauridae. Field Columbian Museum, Geological Series 2:229-247.

 

Continuing our Brachiosaurus series [part 1part 2part 3part 4part 5part 6, part 7], here is another historically important photo scanned from the Glut encyclopaedia: this time, from Supplement 1 (2000), page 157.

Glut2000-p157--brachiosaurus-altithorax-quarry

This is the Brachiosaurus altithorax holotype FMNH P25107 in the field, at Grand Junction, Colorado, in 1900. Clearly visible are the seven presacral vertebrae running across the middle of the photo (upside-down, so we see their ventral surfaces), several ribs on either side, and the end of a long-bone to the left — most likely the distal end of the femur.  The flat bone at bottom left is probably part of the ilium, with the circular cut-out being the acetabulum. (The caption also mentions the sacrum, which I can’t see.)

As with the photo of the mounted skeleton in the museum, this is one of the Field Museum’s own photos — neg. #4027 — but I can’t find a better copy online. It’s got to be out there somewhere — can anyone help?

References

Glut, Donald F. 2000. Dinosaurs: The Encyclopedia: Supplement 1. McFarland & Company, Inc., Jefferson, North Carolina. 442 pages.

Way back in November 2011, I got this inquiry from Keiron Pim:
I’m currently writing a popular guide to dinosaurs, to be published by Random House next autumn [Ed.: available now at amazon.com and at amazon.co.uk]. I’ve been writing about [Brachiosaurus and Giraffatitan], and have read your 2009 study vindicating the proposal to separate them into two genera.
[...]
I know you consider Brachiosaurus likely to have been bigger (and note that the specimen was not fully grown), with a longer trunk and tail – but most of the sources I can find give both animals the same body length, generally around 26m. Presumably this doesn’t reflect your work, and your calculations are different.

I replied at the time, and said that I’d post that response here on SV-POW!. But one thing and another prevented me from getting around to it, and I forgot all about it until recently. Since we’re currently in a sequence of Brachiosaurus-themed posts [part 1, part 2, part 3, part 4, part 5, part 6], this seems like a good time to fix that. So here is my response, fresh from November 2011, lightly edited.

dscn1253

Well, Giraffatitan has only been recognised as a separate animal at all in the last couple of years, and nearly everything that has been written about “Brachiosaurus“, at least in the technical literature, is actually about Giraffatitan. So existing sources that give the same length for both are probably not making a meaningful distinction between the two animals.

First, on Giraffatitan: Janensch (1950b:102) did a great job of measuring his composite mounted skeleton. His figure for the total length of Giraffatitan along the neural canal is 22.46 m, and is certainly the best estimate in the literature for an actual brachiosaur specimen (and quite possibly the best for any sauropod).

I don’t know where the figure of 26 m comes from, but as Janensch (1961:213) notes, the isolated fibula XV2 of Giraffatitan in the Berlin collection is 134 cm long, compared with 119 cm for that of the mounted skeleton. This is 1.126 times as long, which if scaled isometrically would yield a total length of 25.29 m.  So that is defensible, but 26 m is not, really.

I would advise sticking with Janensch’s published figure of 22.46 m, as it’s based on good material, and also because it forms the basis of my comparative estimate for a Brachiosaurus of similar limb length.

Now in my 2009 paper I estimated with reasonable rigour that the torso of Brachiosaurus was probably about 23% longer than that of Giraffatitan, yielding 4.82 m rather than 3.92 that Janensch gave for Giraffatitan. On much less solid evidence, I tentatively estimated that the tail of Brachiosaurus might have been 20-25% longer than that of Giraffatitan. Given the paucity of evidence I would play safer by going with the lower end of that estimate, which would give a tail length of 9.14 m compared with Janensch’s 7.62 for Giraffatitan. Riggs (1904) tells us that the sacrum of Brachiosaurus is 0.95 m long, which is slightly less than 1.07 m for Giraffatitan. Finally, since we know nothing of the head and neck of Brachiosaurus, the null hypothesis has to be that they were similar in proportion to those of Giraffatitan.

Putting it all together, Brachiosaurus may have been longer in the torso by 0.9 m, and in the tail by 1.52 m, but shorter in the sacrum by 0.12 m — for a total additional length of 2.3 m. That would make Brachiosaurus 24.76 m long, which is 10% longer than Giraffatitan.

Note that all the Brachiosaurus figures are given with much greater precision than the sparse data we have really allows.  I think you could round Janensch’s 22.46 m for Giraffatitan to 22.5 and be pretty confident in that number, but you shouldn’t really say anything more precise than “maybe about 25 m” for Brachiosaurus.

Finally, you correctly note that the Brachiosaurus specimen was not fully grown — we can tell because its coracoid was not fused to the scapula. But the same is true of the mounted Giraffatitan, so these two very similarly sized animals were both subadult. How much bigger did they get?  We know from the fibula that Giraffatitan got at least 12-13% bigger than the well-known specimen, and I’d be pretty happy guessing the same about Brachiosaurus.  And I wouldn’t rule out much bigger specimens, either.

References

Here is the wonderful Brachiosaurus altithorax mount in its original location, in the main hall of the Field Museum in Chicago. (Click through for full resolution.)

Glut1997-p215--brachiosaurus-altithorax-mount

I scanned this from Don Glut’s Dinosaurs: The Encyclopedia, page 215. There must be better quality versions somewhere, because this is one of the Field Museum’s own photos — negative #GN 86962 — but I can’t find it in their singularly unhelpful online photo archive.

I’m posting it because there’s an astonishing lack photos of this mount on the Internet. As I noted last time, I was only able to find this striking image:

The Brachiosaurus mount in its original position in the main hall of the Field Museum. I can't find a higher resolution version of this photo -- can anyone help?

The Brachiosaurus mount in its original position in the main hall of the Field Museum. I can’t find a higher resolution version of this photo — can anyone help?

at the miserably low resolution shown here (358×248). More generally, almost every photo of a mounted Brachiosaurus out there seems to be from either the picnic area outside the museum, or O’Hare Airport. If anyone’s able to find decent-resolution examples of this skeleton indoors, please do drop the links into a comment.

I mentioned this to Matt, and he commented:

I think that the mount got moved outside just a bare handful of years before digital cameras went from rare to ubiquitous. If the move had happened even five years later, I’ll bet there would be loads of photos of the old mount.

I’m sure he’s right. But someone must have half-decent photos from back then?

Seriously -- is this tiny photo the best photographic record we have?

Seriously — is this tiny photo the best photographic record we have?

Of course, the real question is: why did they shove the Brachiosaurus outside? It was mounted in 1994, and taken down again in 1999, so this marvellous mount – by any objective standard the single most awesome exhibit in the museum’s history — was only actually in residence for five paltry years.

The standard explanation is that it was removed “to make space for” Sue, the vulgar overstudied theropod. But a glance at the photo above shows that there was plenty of space to put in half a dozen T. rexes without needing to move the brachiosaur. I can only assume that someone realised having a brachiosaur next door would make Sue look feeble. It’s a tragedy.

Update

Thanks to Dean for finding this one: small, but beautiful.

chi-8sue20100512120107

References

Glut, Donald F. 1997. Dinosaurs: The Encyclopedia. McFarland & Company, Inc., Jefferson, North Carolina. 1076 pages.

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