Mounted sauropods in dorsal view!
March 13, 2019
Mike’s and Matt’s excellent adventure in Pittsburgh continues! Today was Day 4, and just as yesterday offered us a unique opportunity to see the mounted Dipodocus and Apatosaurus skeletons up close on a lift, so today we got to look the two mounts from directly above!
Thanks to our host Amy Henrici and to Calder Dudgeon, we were able to go up to the maintenance balconies above the dinosaur hall, and from there we were able to see this:
It was a little bit scary up there: here’s Matt’s vertical panorama photo of me. Just below the balcony I’m standing on you can see another, which is actually far below up but further back. Below that is the main balcony that overlooks the hall. And below that, the hall itself, showing Diplodocus from above:
We think this is a first: we don’t know of any published photos of mounted sauropods from above — but now, there are some. Let’s take a closer look at the torsos:
Diplodocus carnegii holotype CM 84, torso, in dorsal view, anterior to right.
Apatosaurus louisae holotype CM 3018, torso, in dorsal view, anterior to left.
You can immediately see from here that Apatosaurus is a much broader animal than Diplodocus. That much, we could have guessed. What’s more interesting is that Apatosaurus seems to be slightly broader at the shoulders than at the hips, whereas the opposite is the case in Diplodocus.
This observation left us wondering what’s known about the relative widths of the forelimb and hindlimb articulations in extant animals. What, from the modern bestiary, has hips broader than its shoulders, and what has shoulders wider than its hips? We have no idea. Does anyone know if this has been studied, or better yet summarised?
Sauropod Vertebra Picture of the Week 
March 14, 2019 at 3:18 am
Uh oh, the noob didn’t mean to be first, at least when I loaded the page to ask a clarifying Q:
Before I do the deep dive of ignorance, let me say that is a fabulous collection of pictures this week! I guess you can pretend to be a pterosaur, except they didn’t really care about these things. I think various animated features have had aerial views, but this was unexpected!!
Let me also say to your actual question, no clue – but thinking about quadrupeds and the balancing act of staying upright during locomotive gaits: the feet usually end up quite close together, no matter what the hips and shoulders are up to, right? That way you ensure your CoG is always over your feet – thinking of cows and elephants I’ve seen head on, they look like a stiff breeze might push them over, and you don’t have to waste energy waddling to awkwardly compensate for the wide stance.
Counterexample: a cousin’s pit bull type dog I met last week, has a such a wide front paw stance that it immediately struck me as REALLY weird: it literally was doing a push up pose to drink from its bowl, and reminded me of a crocodile – it seems dino-mania runs in the family, he understood why I thought mammals had diverged beyond that. Really looked like a cartoon weightlifter, since its pectorals were immense, and its hindquarters are comparatively teeny.
But I did have a Q: The apatosaur ribcage is MOUNTED to suggest a wider torso, but is that correct? Now, 1. I know you asked about hips and shoulders in particular and didn’t actually mention ribs at all; 2. I get the apatosaur cervical verts’ projections ARE wider (unless I’m misremembering camarasaurus? Or are they simply more closely related?) and the picture seems to show their ribs are thicker… and it makes plausible developmental sense that whatever codes for “thicker” and what codes for “wider” in one place, plausibly does the same in other parts of the skeleton. I’m trying to be explicit about the hand waving here, given the sheer complexities of developmental chemistry. But having realized that the dandelion I grew up with has fairly smoothly jagged leaves and one flower per stem, I noticed the ones with very similar bauplan but multiple flowers per stem, also had VERY jagged leaves ….but is it possible the diplodocids simply got by with the same size gut supported by thinner bones… …somehow?
March 14, 2019 at 3:33 am
I mean, there is a theropod there, so a wide stance would be expected in a defensive (offensive?) pose, but I’m thinking Bellettini might say, “it’s really just to make sure the toy stays standing – but it’s still WRONG!” And this is somewhat more than the usual toy…
But speaking of theropods and stances, that they seem to have moved like birds ….actually, do the ostriches actually walk like birds, mostly from the knees? You’d think they might have reason to use their femurs for more than rebalancing the lack of tail… And the larger theropods did have tails, and large caudal-femoral muscles, did they simply accelerate by standing more upright, instead of leaning forward like we have to? But now I’m way off topic, so please ignore me.
March 15, 2019 at 4:45 am
Seen from above, the Diplodocus sacrum is a remarkable structure: th “see-through” holes between the sacral ribs are quite dramatic. The Apatosaurus sacrum doesn’t have these openings, though there are markings suggestive of plugged openings. Is the difference something real, or a preservation/”preparational” artifact?
(Nice to see pictures from CMP. I lived litarally across the street from the museum part of the time I was in graduate school, but when I went back to visit a few years ago there had been MAJOR upgrades to the vert paleo exhibits!)
March 15, 2019 at 12:04 pm
Allen, you are right that sauropod sacra in general are remarkable and much overlooked. They have taught Matt and me and interesting morphological detail that turns out to apply through the dorsal column. Details to follow in a short note — note, I say!
The top surface of the Carnegie Apatosaurus pelvis, sad to relate, pure fiction. You an forgive them for not having gone the extra mile to sculpt in the spaces between the sacral ribs given that no-one can see that part of the mount. (Matt and I speculated that, with the possible exception of Matt Lamanna, CM’s assistant curator of vertebrate paleontology, we may be the first people ever to see a complete mounted sauropod skeleton from above.)
March 17, 2019 at 9:45 pm
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March 18, 2019 at 2:18 pm
Nice shots. Apatosaurus is awesome.
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