Cathetosaurus lewisi and the pseudoforamen of doom

January 26, 2009

I’ve mentioned my ardent love for the Big Bone Room at BYU before. One of the cool things that you can find there and nowhere else is BYU 9047, the holotype of Cathetosaurus lewisi, referred in 1996 to Camarasaurus. In referring to the beast as Cathetosaurus in the title I’m not casting aspersions on that referral. I’m just wondering. Other ‘camarasaurids’ have been promised from time to time, but so far none have panned out. So for now it’s just Camarasaurus….but. With all the species floating around out there, Camarasaurus is getting to be a pretty big tent. I wonder if this most common of American dinosaurs will continue to be a single genus forever, or if new discoveries and reanalysis of old material will break it up into several.

Anywho, I spent some quality time with BYU 9047 when I was in Utah in 2006, on my last or next-to-last dissertation data-gathering trip. As always, I was keeping an eye out for pneumaticity and especially for pneumatic hiatuses. And I  got pretty darn excited when I took this photo of the C. lewisi sacrum in right lateral view.


As you can see, it has a foramen on the last centrum, but not on any of the preceding centra. Pneumatic hiatus city–lookout Nature, here I come!

I approached with shuffling steps and ‘bated breath. The acolyte of an eldritch cult, I knelt in the dust before the object of reverence, ducked my head beneath the vasty sweep of its sacral yoke, and dared to poke a finger into the holy of holies. Inside it was….smooth.

Like, freakishly smooth. And perfectly tubular.

In Bill, the Galactic Hero: On the Planet of Bottled Brains, Harry Harrison wrote that “Nature cares nothing for equilateralism, and indeed has a hard time drawing a straight line” (oh yeah, I just went there). What is true of straight lines is true in spades of perfect cylinders, especially in the asymmetric osteological playgrounds of sauropod vertebrae.  Like cold fusion and cheap mortgages, the foramen was Too Good To Be True.


At some point someone must have planned to mount BYU 9047, but AFAIK it was never actually put up. Must have gotten pretty close, though, because they went to the trouble of drilling a long core out of the sacrum, presumably to house a steel support rod. And the coring wasn’t perfect, either–the borehole nicked the right wall of the last centrum, producing the pseudoforamen that got me all hot and bothered for about 180 seconds. The above photo shows the entrance to the tunnel at the front end of the sacrum. You can look down this hole and see light shining in from the pseudoforamen in the last sacral (the hole does not extend all the way out the posterior end of the sacrum). Somehow I had completely missed it while wheeling the sacrum out, sketching, and taking the first round of photos. So much for the vaunted powers of observation.

You know what this is like? Everyone’s first dig, where they’re running to the dig leader every five minutes with a piece of “bone” that is actually leverite (as in, “leave ‘er right there”). This was my dry well, my leverite mine, my fool’s gold.

Real gold came along later, first a trickle, then a flood. But those are tales for other campfires. Stay tuned…

P.S. Check out how the neural spines all lean together so that they cover much less ground, antero-posteriorly, than the centra. I don’t think it’s distortion–the whole sacrum is in pretty good shape, pretty symmetrical, no obvious crushing or shearing. ‘Sup with that?

21 Responses to “Cathetosaurus lewisi and the pseudoforamen of doom”

  1. Mike Taylor Says:

    Yes, the inward-leaning neural spines are what immediately caught my eye, here too. What does the last dorsal do? Assuming its neural arch and spine are not WAY inclined, does that mean a huge gap between the last dorsal and first sacral spines, or does it mean a sharp upward angle in the vertebral column, of the type often reconstructed for the sacro-caudal junction, but never for the dorso-sacral?

    OK, having now looked at Jensen (1988:fig. 2A), I see that Jensen reconstructed the sacrum as canted strongly upwards with respect to the ilium. I don’t see why he did this, since your photo shows a nice, well-behaved sacricostal yoke that is parallel to the axis of the centra. I guess it’s time I read that paper again. And the McIntosh et al. (1996) redescription. So much to do, so little time.

  2. Marcel Says:

    one short question from a “non-scientist dino fan”. Do you think that Cathetosaurus is a own genus or do you believe its really a Camarasaurus Species.
    Whats your opinion depending on your examinations?

    Best wishes

  3. Scott Hartman Says:

    FWIW so does the sacrum of “M.” youngi. Seems to indicate a strong upwards slope to the dorsal series in life.

  4. Graham King Says:

    Hi Matt! Happy 2009… so do tell, why is it called Cathetosaurus, if not in connection with some conspicuous tubularity or other? ;-)

    Re inward-canted neural spines over sacrum, I am reminded of shoulder-regions of ungulate mammals and wonder if it is not associated (a) with notable cantilevering and (b) with less flexure occurring/needed between those sacral vertebrae compared to vertebrae elsewhere along the column (so less intervening soft-tissue) and (c) with progressive change in orientation during life of the individual as osteoclasts’n’blasts (I’m presuming sauropods had such cells) reconfigure and reinforce bone according to predominant experienced stresses.
    (Any or all of those, a-c).

    I was going to ask you SV guys anyway today: what can you say about little-sauropod vertebrae (as in younglings, or tinies)? Mussaurus commentary anyone? Growth series? Would seem good to compare, to infer how pneumaticity, say, developed progressively during life of individual; or how skeleton otherwise morphed, with use.

    Of course I’m sure there’s a whole series of posts that could potentially be written on such topics as: bone scars (muscle-attachment points), healed (or unhealed) breaks (mating injuries?), asymmetries (reflecting functional ‘handedness’?), predator toothmarks (and embedded teeth?) etc etc. :-D

  5. (((Billy))) Says:

    Is that 5 or 6 fused vertebrae in the sacrum (I’m a public historian, so I don’t always know what to look for).

  6. DD Says:

    Pseudopneumatic sacrum. dino spino tap? whodathunk~

  7. Five vertebae: count the upward-directed concavities along the bottom margin — each is the waisted part of one centrum.

  8. Matt Wedel Says:

    Marcel, for now I am undecided about Cathetosaurus. I don’t have strong reservations about the referral to Camarasaurus, but I also wouldn’t be surprised if what we currently call Camarasaurus got blown apart in a future phylogenetic analysis.

    Graham, baby verts are coming…someday. I never quite got around to finishing that chapter of my dissertation. But I have some pretty pictures.

    (((Billy))), that’s five fused verts. But other camarasaurs have been found with the last dorsal incorporated into the sacrum. A topic for another post, for sure.

  9. […] the ilia–you can see them on either side of the apatosaur sacra in the image above, and in this post on the sacrum of Camarasaurus lewisi. Since the sacricostal yokes are the bony interfaces between […]

  10. Vahe demirjian Says:

    Cathetosaurus is considered generically distinct from Camarasaurus based on a new skeleton from Wyoming sharing autapomorphies with BYU 9047 (Mateus and Tschopp 2013). There is no doubt that all the Morrison camarasaurids are in need of revision (the synonymy of Caulodon with Camarasaurus may be untenable because the brachiosaurid skull from Felch Quarry 1 has the same tooth shape as the Caulodon teeth).

    Mateus, O., & Tschopp E. (2013). Cathetosaurus as a valid sauropod genus and comparisons with Camarasaurus. Journal of Vertebrate Paleontology, Program and Abstracts, 2013. 173.

  11. Mike Taylor Says:

    Thanks for that, Vahe, we should have mentioned the Mateus and Tschopp abstract, which I remember both Matt and me being quite excited about when it came out. I’ve always been unhappy about the synonymisation of Cathetosaurus, and I’ll be fascinated to see the paper when it eventually comes out.

  12. LeeB Says:

    should shake up the taxonomy of morrison sauropods when it is published based on what it says in the abstract.
    It looks like there are going to be a number of new genera and species; and fewer species in Apatosaurus and Diplodocus.


  13. Mike Taylor Says:

    Yes, this is important work, which I am pleased to say is currently in review or maybe even in press at a good open-access journal. Really looking forward to seeing it!

  14. LeeB Says:

    I guess bringing back Brontosaurus will get the paper lots of publicity.
    But bringing back Elosaurus and giving D. hayi a genus of it’s own are interesting too.
    I guess A. louisae will need it’s own genus too.
    If it’s a large open access journal I guess we won’t have to wait too long for the paper.


  15. Mike Taylor Says:

    I didn’t say large, I said good!

    And yes, you’re right, though it hadn’t occurred to me: the line that the secular world is going to take on this paper is “Brontosaurus is back!” Which in one sense is a shame, as there’s so much more good stuff in the paper, but I guess it’s better for the public to seize on one aspect of a great work than on none of it.

  16. LeeB Says:

    Sorry about the word large; my bad.

    The publicity it’s going to get could be useful.
    Good specimens of diplodocines have recently been sold to museums in Denmark and Singapore; if they haven’t been included in the study then perhaps a steady stream of small children asking the curators what type of sauropod(s) the one(s) in the museum are could lead to them being studied.
    One can but hope.


  17. sublunary Says:

    I really want to know what the “newly developed numerical approach to reduce subjectivity in the decision of specific or generic separation” is.

  18. LeeB Says:

    Based on this it looks like Camarasaurus taxonomy just got more complicated; and Cathetosaurus isn’t a separate genus after all.


  19. Vahe demirjian Says:

    Not so fast. I read the SVP abstract by Tschopp et al. (2014) and it says that Cathetosaurus is distinct from Camarasaurus, in contrast to what is said in the website you mentioned. We’ll have to wait for Tschopp et al. to publish their results to see if they changed their mind about the generic distinctness of Cathetosaurus or whether it may be an error in the presentation at and Tschopp still considers Cathetosaurus distinct.

  20. LeeB Says:

    Well yes, the abstract says one thing and the copy of the poster presented at the meeting (according to the website) says another.
    I guess it is a case of wait for the paper.


  21. […] The Camarasaurus lewisi holotype BYU 9047 (thanks to John D’Angelo) […]

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