Rapetosaurus is Just Plain Wrong

January 31, 2013

You may remember this:

Rapetosaurus mount at Field Museum

…which I used to make this:

Rapetosaurus skeleton silhouette

…and then this:

Rapetosaurus skeleton silhouette - high neck

The middle image is just the skeleton from the top photo cut out from the background and dropped to black using ‘Levels’ in GIMP, with the chevrons scooted up to close the gap imposed by the mounting bar.

The bottom image is the same thing tweaked a bit to repose the skeleton and get rid of some perspective distortion on the limbs. The limb posture is an attempt to reproduce an elephant step cycle from Muybridge.

That neck is wacky. Maybe not as wrong as Omeisaurus, but pretty darned wrong. As I mentioned in the previous Rapetosaurus skeleton post, the cervicals are taller than the dorsals, which is opposite the condition in every other sauropod I’ve seen. All in all, I find the reposed Rapetosaurus disturbingly horse-like. And oddly slender through the torso, dorsoventrally at least. The dorsal ribs look short in these lateral views because they’re mounted at a very odd, laterally-projecting angle that I think is probably not correct. But the ventral body profile still had to meet the distal ends of the pubes and ischia, which really can’t go anywhere without disarticulating the ilia from the sacrum (and cranking the pubes down would only force the distal ends of the ilia up, even closer to the tail–the animal still had to run its digestive and urogenital pipes through there!). So the torso was deeper than these ribs suggest, but it was still not super-deep. Contrast this with Opisthocoelicaudia, where the pubes stick down past the knees–now that was a tubby sauropod. Then again, Alamosaurus has been reconstructed with a similarly compact torso compared to its limbs–see the sketched-in ventral body profile in the skeletal recon from Lehman and Coulson (2002: figure 11).

I intend to post more photos of the mount, including some close-ups and some from different angles, and talk more about how the animal was shaped in life. And hopefully soon, because history has shown that if I don’t strike while the iron is hot, it might be a while before I get back to it. For example, I originally intended this post to follow the last Rapetosaurus skeleton post by  about a week. So much for that!

Like everything else we post, these images are CC BY, so feel free to take them and use them. If you use them for the basis of anything cool, like a muscle reconstruction or life restoration, let us know and we’ll probably blog it.

About these ads

8 Responses to “Rapetosaurus is Just Plain Wrong”

  1. Blair Says:

    I thought this was going to be in reference to its name…

  2. Andy Farke Says:

    From Malagasy…pronounced “ruh-PAY-too-SOR-us”


  3. Matt, you partly fell for perspective. The lowest ribs go noticeably below the glenoid, but not in your drawing!

    Do you have many photos? If so I’d like to try and throw them into a photogrammetry program to see if we can get out a prespective corrected outline.

  4. Matt Wedel Says:

    Matt, you partly fell for perspective. The lowest ribs go noticeably below the glenoid, but not in your drawing!

    Based on what? I have photos from all around the mount, and none of them show the ribs going down very far. The anteriormost ribs go a bit below the glenoid, but not much–maybe a few cm max. These ribs are obscured in the silhouettes because of the sternals and shoulder apparatus behind them. But the overall idea that the ribs look short primarily because of perspective won’t fly: first, the ribs on both sides of the skeleton end at about the same level, and second, if anything the vertical offset between the feet on the near and far sides suggests I was too high here, not too low.

    Do you have many photos? If so I’d like to try and throw them into a photogrammetry program to see if we can get out a prespective corrected outline.

    I have quite a few, but I didn’t take them with photogrammetry in mind so the coverage is probably inadequate. But I will DropBox them to you anyway–it’s definitely worth a shot.


  5. Strawman alert! Matt, I never said that
    the ribs look short primarily because of perspective
    I said “partly”, and gave no indication how big a part (because I do not know).

    However, I also need to point out this:
    I am an idiot, I looked at the wrong fucking skeleton!

  6. Matt Wedel Says:

    Thanks for the clarification. You got me on the strawman. :-)

    More impetus to get some more photos posted soonish!


  7. hm, no snide remark on my HUGE goof….. I guess you are saving that for later occasions ;)


  8. […] here’s the same thing in silhouette. It may be informative to compare this to the very different silhouette of the mounted Rapetosaurus krausei, also at the Field […]


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Follow

Get every new post delivered to your Inbox.

Join 376 other followers

%d bloggers like this: