Your torso is also pretty lame

February 21, 2008

Following on from Your neck is pathetic, I offer you the fifth presacral vertebra of the Brachiosaurus altithorax holotype specimen FMNH P25105, in right lateral view, with a complete human dorsal column for scale.

Why is this vertebra designated “presacral 5”? Because the Brachiosaurus holotype specimen included an articulated set of the last seven dorsal vertabrae (and the sacrum, two caudals, a coracoid, humerus, ilium, femur and some ribs) but none of the more anterior dorsals. Rather than guess how many dorsals there were in life, so that he could assign serial positions to the seven that were preserved, Riggs (1903) very sensibly just counted forward from the sacrum.

So how many dorsals did Brachiosaurus have? We must have plenty of better specimens by now, right? Wrong: despite more than a century of fossil-hunting in North America, Riggs’s specimen, which he described in detail in 1904, remains by far the best and most complete that has been described in the published literature. All the other specimens that are of any scientific value consist of isolated or doubtfully associated elements, and in any case have not been described anywhere near as well as Riggs dealt with his material. There are apparently some much better specimens in private hands, but, well, they are effectively lost to science — at least until the owners die.

When Janensch (1914, 1950) described the African species Brachiosaurus brancai from Tendaguru in Tanzania, he reconstructed it with 11 dorsals, and that number has been pretty much accepted ever since. However, as pointed out by Paul (1988), Migeod’s (1931) description of a Tendaguru brachiosaurid that has been generally accepted as a specimen of B. brancai indicated that it had at least 12 dorsals. Although Migeod’s specimen is probably generically distinct from both B. altithorax and B. brancai (Taylor 2005), it still provides the best evidence we have of the vertebral formula in brachiosaurids. So, twelve it is, until better evidence turns up. Distressingly, none of the other brachiosaurids or putative brachiosaurids that we know about (Sonorasaurus, Cedarosaurus, Sauroposeidon, etc.) have specimens with complete dorsal columns.

Oh, and how many dorsals do humans have? Twelve thoracics and five lumbar vertebrae, for a grotesquely inflated total of 17. The distinction between thoracics (which bear ribs) and lumbar vertebrae (which do not) is standard for mammals, but does not apply for reptiles, in which all dorsals bear ribs. (At least, that’s true in sauropods, which is all that matters.)

Bibliography

  • Janensch, Werner. 1914. Ubersicht uber der Wirbeltierfauna der Tendaguru-Schichten nebst einer kurzen Charakterisierung der neu aufgefuhrten Arten von Sauropoden. Archiv fur Biontologie, Berlin, III, 1(1):81-110.
  • Janensch, Werner. 1950. Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica (Suppl. 7) 3:27-93.
  • Migeod, Frederick W. H. 1931. British Museum East Africa Expedition: Account of the work done in 1930. Natural History Magazine 3(19): 87-103.
  • Paul, Gregory S. 1988. The brachiosaur giants of the Morrison and Tendaguru with a description of a new subgenus, Giraffatitan, and a comparison of the world’s largest dinosaurs. Hunteria 2(3):1-14.
  • Riggs, Elmer S. 1903. Brachiosaurus altithorax, the largest known dinosaur. American Journal of Science 15(4):299-306.
  • Riggs, Elmer S. 1904. Structure and relationships of opisthocoelian dinosaurs: Part II, the Brachiosauridae. Field Columbian Museum, Geological Series 2, 6:229-247, plus plates LXXI-LXXV.
  • Taylor, Michael P. 2005. Sweet seventy-five and never been kissed: the Natural History Museum’s Tendaguru brachiosaur; p. 25 in Paul. M. Barrett (ed.), Abstracts volume for 53rd Symposium of Vertebrae Palaeontology and Comparative Anatomy. The Natural History Museum, London. (Yes, it’s bad form for me to cite my own abstract. Sorry: the key point has yet to appear in “proper” published literature.)
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26 Responses to “Your torso is also pretty lame”


  1. The distinction between thoracics (which bear ribs) and lumbar vertebrae (which do not) is standard for mammals, but does not apply for reptiles, in which all dorsals bear ribs.

    Huh. Odd that all the vertebrae between the cervicals and sacrals in birds bear ribs, yet they’re called thoracics. Birds, being dinosaurs, are also reptiles; ergo, reptiles also have thoracics (but lack lumbars, of course)…

    NOTE TO READERS UNFAMILIAR WITH THE HISTORY OF THIS ISSUE: Really, I’m just teasing Mike, Matt, and Darren here. They’ve chosen not to see the light on issues of homology, which is, of course, their prerogative since there aren’t any rules supporting one or the other anatomical nomenclature system, and we’ve all discussed it in the past. I just couldn’t pass up an opportunity to needle them about it here… ;-D

  2. Mike Taylor Says:

    As I was writing this article, I was thinking to myself “I wonder what Jerry will have to say about this” :-)

    Maybe we’ll do a post specifically on the potayto-potahto issue some time (or is the tomayto-tomahto issue? And, come to think of it, does anyone actually say “potahto”? I’ve never heard it.)

    For those who want to know what the heck we’re talking about, this is all in reference to Jerry’s paper:

    Harris, J.D. 2004. Confusing dinosaurs with mammals: tetrapod phylogenetics and anatomical terminology in the world of homology. Anatomical Record Part A 281: 1240-1246. doi: 10.1002/ar.a.20078

    Which, happily, can be freely downloaded from his site: http://cactus.dixie.edu/jharris/Anatomical_Nomenclature.pdf

  3. Zach Miller Says:

    You know, Scott (of Coherent Lighthouse) was asking me the other day if reptile finger bones were still called “phalanges.” I replied: “Duh, they’re homologous structures.” He remained unconvinced, somehow believing that reptile finger bones were known by some other name. Although I called hooey, this thoracic/lumbar issue that Jerry brings up (I realize he’s kidding around) makes me question my dismissiveness!

  4. John Conway Says:

    I feel so… inadequate.

    Honestly though, people have BRACHIO-FREAKIN-SAURUS skeletons in private collections?(!) What the hell do they do with them? Build dino-bone gazebos? Or is it more like: “hey baby, wanna check out my ‘thigh’ bone?”

  5. Graham Peter King Says:

    Re nomenclature and homology…

    Since tetrapod fore- and hindlimbs are homologous (both being pentadactyl limbs) shouldn’t we harmonise their respective bones’ names (eg pre- and post-, or cranial and caudal, humerofemur… etc)?

    And since homology reveals descent, which limb girdle came first? What was the ancestral condition? Fore-limbed, or hind-limbed, only? (Presumably at some time a Homeobox-gene-doubling mutation caused a dipod species to give rise to the first tetrapod species.)

    And what about left and right limbs? Ditto?

    “To the fossil beds! Let us seek the monolimbic ancestor of all tetrapods!”

    Which came first, the dextrolateral or craniocaudal doubling? Did fore- and hind-limbs double up separately?

    Here’s tantalising evidence that the craniocaudal replication was followed by forelimb doubling before paired hindlimbs arose:-
    http://en.wikipedia.org/wiki/Monopod_(creature)

    I am of course just having mad fun. Surreal tho innit? ;-D

  6. Graham Peter King Says:

    Duh! I meant “dextroSINISTRAL”, of course. (I think it’s important to speak only ACCURATE nonsense…)

  7. Marcel Says:

    Hi!
    Did i get it right? There are two different Brachiosaurids in the Tendaguru Formation?

    Best wishes

    Marcel

  8. Mike Taylor Says:

    Hi, Marcel. Yes, that’s what I argued in my 2005 SVPCA talk. After that talk, I briefly discussed my findings with Paul Upchurch and Paul Barrett, both sauropod experts, and they both seemed convinced — though you’ll have to wait for the paper for the full case to be made.

    Of course, the existence of two brachiosaurids in the Tendaguru Formation should not be that much of a surprise, given the existence of at least four and probably five or six diplodocids in the Morrison.

    You ask, “Did I get it right?” — so did you independently reach this conclusion? Interesting! How and when? Is it published?


  9. […] 5, 2008 Every once in a while it’s good to remember that no matter how big you end up, everybody starts out […]

  10. Marcel Says:

    Hello Mike,

    =) no i havent anything to publish. This was only a error. I thought “Did i get it right?” is the same as “Have i understand it right?”. I think its time to for me to read more english literature. =)

    Thanks for the answer.

    Marcel


  11. […] 24, 2008 In the spirit of Your neck is pathetic and Your torso is also pretty lame, I note that your sacrum is […]


  12. […] away from using BOBA as a yardstick for comparison to, well, just about everything (including some stinkin‘ mammals), and occasionally even we get jaded about its inherent blinding awesomeness. Also, […]

  13. David Marjanović Says:

    Huh. Odd that all the vertebrae between the cervicals and sacrals in birds bear ribs, yet they’re called thoracics.

    That’s because ornithologists actually believe that birds have a thoracic-lumbar distinction — it just so happens that the lumbars have all fused to the sacrum.

    Really. I’ve had one trying to teach me that.

    And no, they’ve never looked at, say, Archaeopteryx. Not ever. Neontologists.

    ————-

    BTW, crown-group crocodiles have such a distinction, too. And so did the, uh, possible anthracosaur Eldeceeon in the Early Carboniferous.

    ————-

    And since homology reveals descent, which limb girdle came first? What was the ancestral condition? Fore-limbed, or hind-limbed, only?

    Forefinned only, as seen in osteostracans. However, the left-right symmetry is much older than the fins; there never was an asymmetric condition.


  14. […] series: it would have to be the four posts of axial-anatomy humiliation, Your neck is pathetic, Your torso is also pretty lame, Your sacrum is negligible and Your coccyx is […]


  15. […] in the neck are called cervical vertebrae, or cervicals for short; those in the trunk are called dorsal vertebrae (in crocs and mammals these are further broken down into the thoracic vertebrae, which bear mobile […]


  16. […] Regarding the number of dorsal vertebrae: it may have been circumstances that forced P.A.S.T to give the mount 12 dorsals, but Migeod’s pre-description of the NHM’s Tendaguru brachiosaur gives good reason to think this is likely the correct count. […]

  17. MBH Says:

    Where is the human spine image taken from? the image is currently used on Wikipedia, but we need to know where the diagram is from too to be sure the image is truly “free”.

  18. Mike Taylor Says:

    That’s a good question. I have no idea, of course — it was more than ten years ago, after all. If you’ll point me to the relevant Wikipedia image, I’ll replace it with with a suitably licenced version.

  19. Mike Taylor Says:

    My records show that the human spine in this image was taken from https://www.cedars-sinai.edu/Images/468325_SPINE_CURVES_OF.jpg — but, as is so often the case on the Internet, the page has vanished without trace. It seems that https://www.cedars-sinai.edu/Patients/Programs-and-Services/Spine-Center/The-Patient-Guide/Anatomy-of-the-Spine/Images/468325_SPINE_CURVES_OF.jpg is the same page, and it appears on https://www.cedars-sinai.org/health-library/diseases-and-conditions/c/curves-of-the-spine.html but nothing on there says anything about permissions. So I guess I have to go with https://www.cedars-sinai.edu/Website-Terms-and-Conditions.aspx which says “All information contained within this website is the copyright of Cedars-Sinai Health System (“CSHS”) unless otherwise noted.”

    The upshot: I think I need to remake this image using an unambiguously public domain or CC By spine. Rats.

  20. MBH Says:

    Thanks a lot! I have now updated the Commons image.

  21. MBH Says:

    Oh, I see we both updated the image within a minute, thanks again!


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