The humerus of Brachiosaurus altithorax, part 3: the airport mount

May 22, 2014

Last time we looked at the humeri in the Field Museum’s mounted Brachiosaurus skeleton — especially the right humerus, which is a cast from the holotype, while the left is a sculpture. But Matt’s and my photos of that mount are all pretty much useless scientifically — partly because we were terrible photographers back then, but also partly because the very light background of sky tended to put the skeleton into silhouette and lose a lot of detail.

But fortunately there’s another Brachiosaurus in Chicago!


(We’ve featured this mount once before.)

This in fact the original Brachiosaurus mount that was erected in the Field Museum’s main hall in 1993. When a certain vulgar, over-studied theropod was installed in that hall in 2000, the surprising decision was made to remove the Brachiosaurus to “make room” for it (even though it’s objectively tiny). The mount was not built to be exposed to the elements, so it couldn’t just be moved outdoors. Instead, a new one was made from more suitable materials for the picnic area, and the original mount was moved to O’Hare Airport.

[Aside: what the heck were the museum thinking when they booted Brachiosaurus out of the main hall? However much you love T. rex, and I admit I do, Sue makes a feeble centrepiece compared with a brachiosaur. I can only assume there was some subtle political motivation for reducing their main hall’s Awesome Quotient so dramatically. The poor thing was only there seven years.]

Anyway, the original mount is now at Terminal 1 at O’Hare Airport, where it can be photographed less inadequately than outdoors. Here are those contrasting humeri again: the real cast on the right side of the animal (left side of photo) and the sculpture on the left (right side of photo):


And a zoom into the relevant section:


As it happens, I flew into a different terminal at O’Hare. But I knew that this mount was in Terminal 1, so before I get the transit to my hotel, I dragged my luggage across to Terminal 1 and begged the ticket clerk to let me through into the departure area so I could look at it. I don’t now remember exactly what the sequence of events was, but I do recall that phone-calls were made and supervisors were consulted. In the end, someone on staff gave me a platform ticket, and I was able to go and spend a quality hour with this glorious object.

It also meant I got to watch nearly every single traveller amble straight past Brachiosaurus giving it literally not even a single glance — see the first photo for an example. Truly depressing.

Anyway, I was able to get some slightly better photos of this cast humerus than I subsequently got of the outdoor mount. Though not very many, because — stop me if you’ve heard this — I was young and stupid then.

Anyway, here is the humerus in anterior view. Or as close to anterior as I could manage. By holding the camera above my head, I could get it nearly level with the distal margin of the mounted bone, so what we have here is really more like anterodistal:


And here is that some bone in lateral view (again, really laterodistal). From this angle, you can really see how shapeless parts of the lateral border of the cast are — which is odd, because there are sharp lips on the actual fossil.


In terms of general appreciation of the bone, this next one, in anterolaterodistal view,  is probably best — the light caught it in an informative way. Unfortunately, I cut off the distal margin. Sorry.


As you can see, the level of detail in the cast is mostly pretty good. For example, you can clearly make out the broken-off base of the deltopectoral crest (the tall light-coloured oval about a quarter of the way down and a third of the way across the bone). That makes the lumpenness of the distal part of the lateral aspect all the more mysterious.

Finally, here are both humeri, more or less from the left, so that the real cast is in something approaching medial view.


From this angle, you can see that the humerus is noticeably less anteroposteriorly deep than its transverse width. We’ll see this theme cropping up again with brachiosaur limb bones — stay tuned for future posts!

Also of interest: the very nice sculpted humerus on the left side has a complete deltopectoral crest — modelled, I imagine, after those of the various Giraffatitan humeri. It also has a finished distal end which is much broader than that of the cast humerus. In this, it’s probably right, as the real bone suffered from some decay.

And that, I am afraid, is all: stupidly, I neglected to photograph the humerus in posterior aspect, or any of the diagonals other than anterolateral.

Next time: exciting news about the relative breadth of humerus and femur in brachiosaurs!

12 Responses to “The humerus of Brachiosaurus altithorax, part 3: the airport mount”

  1. Haha!!! I’m flying into O’Hare soon! I will absolutely try to see this.

  2. Mike Taylor Says:

    I can’t recommend it too highly! Try to get more, and better, photos than mine!

    (If you’re not coming in through Terminal 1, it might be worth your calling ahead to arrange access. I think I got lucky back in 2005, and I wouldn’t want to gamble on that working out right if I did it again.)

  3. Ian Corfe Says:

    Hmm, so of the two mounted skeleton humeri, one is mostly sculpture and one a poor cast of an anyway somewhat eroded bone… Doesn’t look great for accurate mass reconstructions using minimum circumference!

    The flattening (less antero-posteriorly deep than transversely wide) also throws a spanner in the works, as the estimates in Benson et al 2014 are using a formula approximating an ovoid cross section, so probably overestimates the true circumference. And since they only have the transverse width measurement and estimate the antero-posterior using a regression of closely related sauropods (I think all Macronoarians but it’s not totally clear), this is also probably overestimated before being put into the formula for estimating the ovoid minimum cross section (which itself is an overestimate of the real shape)…

    Looking forwards to the relative breadth data!

  4. Mike Taylor Says:

    Hmm, so of the two mounted skeleton humeri, one is mostly sculpture and one a poor cast of an anyway somewhat eroded bone

    But the humeri in the mounted Giraffatitan in Berlin are pure goodness.

    The casting of the Chicago humerus is mostly very good, as you can see from the detail of the texture on the anterior face. It’s just that region of the bone — the distal end of the medial aspect — that looks smudged and blurred. It’s almost as though someone looked at the way the cortex had flaked away and deliberately decided to smooth it. In short, I’d pretty much completely trust a circumference measurement of the Chicago humerus.

    I really must read the Benson et al paper, and its predecessor. What do you mean by “ovoid cross section”? Do you mean with the assumption of a specific w:h ratio? It certainly is true that that ratio tends to be very high in brachiosaur femora, as the next post will show.

    All in all, it does look like the limb-bone circumference method might be giving us erroneously high values for brachiosaur mass.

  5. […] with what seems to have turned out to be Brachiosaur Humerus Week here on SV-POW! (part 1, part 2, part 3), let’s consider the oft-stated idea that brachiosaurs have the most slender humeri of any […]

  6. Gilles Danis Says:

    My company P.A.XS.T. bui8lt the Ohare Brachiosaurus as well as the one at the Field Museum, the one at Disneyworld Wild Animal Kingdom, the one at Hayashibara, Japan and the one at N.A.M.A.L. in Orem Utah. We also restored and built Seismosaurus hallorum (now Diplodocus hallei) in Kitakyushu Japan and Albuquerque NM. We also built the first two mounts of Jobaria tiguidensis, as well and hundreds of other skeletons of dinosaurs and other vertebrates

  7. Mike Taylor Says:

    Hi, Gilles, fantastic to hear from you! I had no idea there were so many Brachiosaurus mounts around the world — presumably these all based on your original for the Field Museum?

    Is there a web-site for P.A.S.T? I’ve not been able to find one, which is a real shame given all the important work you’ve done.

  8. Ian Corfe Says:

    (Mike – responded to your oval query on the Giraffatitan humeri page!)

  9. […] P.A.S.T president Gilles Danis commented on our post about the Chicago airport Brachiosaurus mount, I got into an interesting email […]

  10. […] 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 […]

  11. […] 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 […]

  12. […] our Brachiosaurus series [part 1, part 2, part 3, part 4, part 5, part 6, part 7], here is another historically important photo scanned from the […]

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