Behold! The glory that is CM 555

March 12, 2019

Matt and I have completed Day 2 of our excursion to the Carnegie Musuem in Pittsburgh. Day 1 was spent in the public galleries, because collections aren’t open on Sunday, but today we got into the Big Bone room.

One of our targets was CM 555, a very nice nearly complete neck (C1-C14) from a subadult apatosaurine — quite possibly Brontosaurus excelsus, which is what John McIntosh catalogued it as, though I am not yet 100% convinced it’s the same thing as YPM 1980, the holotype of that species.

We were able to lay out the full sequence on the floor, on styroforam sheets, and spend quality time just looking at it and thinking about it. I don’t just mean documenting it for later analysis, but making use of that precious time right there with the physical specimen to think through together what it’s telling us. We have a bunch of new insights, which we’ll share when we’re not completely exhausted.

Here’s Matt with the first six cervicals. C1 (the atlas) is as usual an unprepossessing lump, but then things get interesting. C2 to C6 are all unfused, so the centra and neural arches are separate.

Behind C6, the arches are fused to the centra (though the fusion lines are still apparent in C7 and C8). This is a nice example of how, in sauropods, serial position recapitulates ontogeny — one of the great confounding factors when studying isolated vertebrae.

We’ve learned a lot already from CM 555. Tomorrow will be spent with the two big mounted diplodocids (Diplodocus carnegii CM 84 and Apatosaurus louisae CM 3018). We’ll let you know how it goes. I predict: awesome.

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8 Responses to “Behold! The glory that is CM 555”


  1. Very nice! Did you guys take any new lateral view images of the series or just Cv2-6 we’ve seen previously?

  2. Matt Wedel Says:

    I actually have left and right lateral photos of all of the CM 555 vertebrae from previous visit, just haven’t gotten them out into the wild yet. I was sadly lacking in the other views, though – I was young and dumb the last time I visited – so today we got dorsal view photos and made a start on anterior and posterior. We’ll get ventral, too, for the ones that we can, although several of the posterior vertebrae are too unwieldy and too fragile to probably get good ventral views. We’ll see what we can do.

    Stay tuned for a LOT more hot diplodocid action in the very near future.

  3. Mark Evans Says:

    Styroforam? Now you’re doing micropalaeontology!

  4. Emanuel Tschopp Says:

    Nice! A completely different fusion pattern compared to Galeamopus… very interesting


  5. […] spend much of the last few days playing with the cervical vertebrae of a subadult apatosaur, and trying to make sense of those of the mounted adult, neck ontogeny is much on our minds. […]


  6. […] remember that we’ve been playing with CM 555, a subadult apatosaurine of indeterminate species, though John McIntosh assigned is to Brontosaurus […]


  7. […] real colossus of the trip was CM 555, which we’ve already blogged about a couple of times. Just laying out all of the vertebrae and logging serial changes was hugely […]


  8. […] Behold! The glory that is CM 555 Four huge beasts Mounted sauropods in dorsal view! Walking around the mounted skeleton of <i>Diplodocus carnegii</i> Walking around the mounted skeleton of <i>Apatosaurus louisae</i> […]


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