The giant Oklahoma Apatosaurus: OMNH 1670 redux

April 30, 2012

In the recent post on OMNH 1670, a dorsal vertebra of a giant Apatosaurus from the Oklahoma panhandle, I half-promised to post the only published figure of this vertebra, from Stovall (1938: fig. 3.3). So here it is:

And in the second comment on that post, I promised a sketch from one of my notebooks, showing how much of the vertebra is reconstructed. Here’s a scan of the relevant page from my notebook. Reconstructed areas of the vert are shaded (confusingly, using strokes going in opposite directions on the spine and centrum, and the dark shaded areas on the front of the transverse processes are pneumatic cavities), and measurements are given in mm.

Next item: is this really a fifth dorsal vertebra?

Apatosaurus louisae CM 3018 D4 and D5, in anterior (top), left lateral, and posterior views, from Gilmore (1936: plate 25).

Here are D4 and D5 of A. louisae CM 3018. They sort of bracket OMNH 1670 in terms of morphology. D4 has a broader spine, and D5 has a narrower one. The spine of D5 lacks the slight racquet-shaped expansion seen in OMNH 1670, but the overall proportions of the spine are more similar. On the other hand, the transverse processes of D4 taper a bit in anterior and posterior view, as in OMNH 1670, and unlike the transverse processes of D5 with their more parallel dorsal and ventral margins. But honestly, neither of these verts is a very good match (and the ones on either side, D3 and D6, are even worse).

Apatosaurus parvus UWGM 15556 (formerly A. excelsus CM 563) D4 (left) and D3 (right) in anterior (top), right lateral, and posterior views, from Gilmore (1936: plate 32).

Here are D3 and D4 of A. parvus UWGM 15556. D3 is clearly a poor match as well–it is really striking how much the vertebral morphology changes through the anterior dorsals in most sauropods, and Apatosaurus is no exception. D3 looks like a dorsal in lateral view, but in anterior or posterior view it could almost pass for a posterior cervical. If I was going to use the term “cervicodorsal”, indicating one of the vertebrae from the neck/trunk transition, I would apply it as far back as D3, but not to D4. That thing is all dorsal.

And it’s a very interesting dorsal from the perspective of identifying OMNH 1670. It has fairly short, tapering transverse processes. The neural spine is a bit shorter and broader, but it has a similar racquet-shaped distal expansion. I’m particularly intrigued by the pneumatic fossae inscribed into the anterior surface of the neural spine–in Gilmore’s plate they make a broken V shapen, like so \ / (or maybe devil eyes). Now, OMNH 1670 doesn’t have devil eyes on its spine, but it does have a couple of somewhat similar pneumatic fossae cut into the spine just below the distal racquet–perhaps a serially modified iteration of the same pair of fossae as in the A. parvus D4. It’s a right sod that D5 from this animal has its spine blown off–but it still has its transverse processes, and they are short and tapering as in OMNH 1670.

Apatosaurus sp. FMNH P25112, dorsal vertebrae 1-10 and sacrals 1 and 2, Riggs (1903: plate 46)

Here are all the dorsals and the first couple sacrals of FMNH P25112, which was originally described as A. excelsus but in the specimen-level analysis of Upchurch et al. 2005) comes out as the sister taxon to the A. ajax/A. parvus/A. excelsus clade. Note the striking similarity of the D5 here with D4 of the A. parvus specimen in Gilmore’s plate (until the careful phylogenetic work up Upchurch et al. 2005, that A. parvus specimen, once CM 563 and now UWGM 15556, was considered to represent A. excelsus as well). But  also notice the striking similarity of D6 to OMNH 1670. It’s not quite a dead ringer–the transverse processes are longer and have weird bent-down “wingtips” (XB-70 Valkyrie, anyone?)–but it’s pretty darned close, especially in the shape of the neural spine.

So what does this all mean? First, that trying to specify the exact serial position of an isolated vertebra is nigh on to impossible, unless it’s something that is one-of-a-kind like an axis. Second, after doing all these comparos I think it’s unlikely that OMNH 1670 is a D4–those are a bit too squat across the board–but it could plausibly be either a D5 or a D6. Third, I’m really happy that it doesn’t seem to match any particular specimen better than all the rest. What I don’t want to happen is for someone to see that this vertebra looks especially like specimen X and therefore decide that it must represent species Y. As I said in the comments of the previous post, what this Oklahoma Apatosaurus material needs is for someone to spend some quality time seeing, measuring, and photographing all of it and then doing a phylogenetic analysis. That sounds like an ambitious master’s thesis or the core of a dissertation, and I hope an OU grad student takes it on someday.

If you were intrigued by my suggestion that the big Oklahoma Apatosaurus rivalled Supersaurus in size, and wanted to see a technical comparison of the two, I am happy to report that Scott Hartman has done the work for you. Here’s one of his beautiful Apatosaurus skeletal reconstructions, scaled to the size of OMNH 1670, next to his Supersaurus silhouette. This is just a small teaser–go check out his post on the subject for a larger version and some interesting (and funny) thoughts on how the two animals compare.

References

  • Gilmore, C.W. 1936. Osteology of Apatosaurus with special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum 11:175-300.
  • Riggs, E.S. 1903. Structure and relationships of opisthocoelian dinosaurs, part I: Apatosaurus Marsh. Field Columbian Museum Publications, Geological Series 2(4): 165–196.
  • Stovall, J.W. 1938. The Morrison of Oklahoma and its dinosaurs. Journal of Geology 46:583-600.
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14 Responses to “The giant Oklahoma Apatosaurus: OMNH 1670 redux”

  1. Kattato Garu Says:

    All our Christmasses are come at once! Now THAT’s a Sauropod Vertebra Picture of the Week post!

  2. Nima Says:

    That is one big beast. How do the mass figures come out on that one? (Assuming, lets say, 20 tons for the Carnegie Museum’s Apatosaurus and 33 tons for Giraffatitan HMN SII?)

  3. Nima Says:

    A 40-ton Apatosaurus? Well that just blows all my dreams of Brachiosaurus being more massive than Apatosaurus out of of the water. Or does it… On the other hand mass estimates being as murky as they are, and given that no fully mature Brachiosaurus has turned up, it’s possible they did get a lot bigger.

    If, going by Giraffatitan’s HMN XV2, adult Brachiosaurus were even just 15% bigger than the holotype (assuming a mass of 35 tons), they could easily outclass the OK Apatosaurus.
    (1.15^3 = 1.52) x 35 = 53.23 tons and for Giraffatitan, 33 tons x 1.52 = 50.16 tons (HMN XV2). Not that these are by any means correct, just my current estimates.

  4. Dean Says:

    I love how paleontology works these days. Look! The Brachiosaurus, Apatosaurus, and Diplodocus are the biggest, no, wait, there are some other ones that were even bigger! Wait those first three are huge again!!!!!!


  5. [...] and Scott let us use their art a lot–even the goofy stuff–and get a shout-out now and then, and I’ve been awed by the work of Memo–a.k.a. Nemo Ramjet–for longer than [...]


  6. [...] Next to it is D5 of CM 3018, the holotype specimen of Apatosaurus louisae (from Gilmore 1936: plate 25), which has served as the basis for many of the published mass estimates of the genus Apatosaurus. OMNH 1670 is 135 cm tall, compared to 106 cm for D5 of CM 3018. If the rest of the animal scaled the same way, it would have been 1.27^3 = 2 times as massive. Mass estimates for CM 3018 are all over the map, from about 18 tons up to roughly twice that, so the big Oklahoma Apatosaurus was probably in Supersaurus territory, mass-wise, and may have rivaled some of the big titanosaurs (Update: see the two giant diplodocids square off in a cool follow-up post by Supersaurus wrangler Scott Hartman). Here’s a fun rainy-day activity: take any skeletal reconstruction of Apatosaurus, clone it in Photoshop or GIMP, scale it up by 27%, and park it next to the original. It looks a lot bigger. So I’m continually surprised that Apatosaurus is so rarely mentioned in the various roundups of giant sauropods, both in the technical literature and in popular articles online. This vertebra was figured by Stovall (1938)–if I get inspired, I’ll dig up that figure and post it another day (hey, look, I did!). [...]

  7. Bryan Riolo Says:

    Can anyone tell me why so many restorations of dinosaurs assume that the legs and forelimbs are practically fleshless? Scott Hartman’s beautiful work strikes me as a prime example of this trend. Both the Supersaurus and Apatosaurus legs in the outlined skeletals shown here are so lacking in musculature as to be almost impossible. It also seems to me that taking this point of view of fleshing out the animals skews the data badly on their mass AND their proportions. Frankly, I do not give a rodent’s tokus how much they weighed, the lighter, the better for the beasts in question, actually.

    I have seen too many dinosaur documentaries in which dinosaurs are often fleshed out in ways that would have crushed the bones. HOW can a Tyrannosaurus leg when alive be thinner than the bones? Is an assumption being made that the bones swelled in diameter after death? Where is the cartilage? Is it also thought that because we do not see the flesh, fat, skin, blood vessels and skin on the fossil bones that they must not have existed?

    If these factors are so often ignored, how can we trust ANY of the estimates given on any position pertaining to the matter of linear size and the mass of any of the animals being talked about?

  8. Mike Taylor Says:

    You can’t, and shouldn’t, trust any length or mass estimates.

  9. Bryan Riolo Says:

    Mike Taylor Says:

    March 31, 2013 at 9:05 pm

    “You can’t, and shouldn’t, trust any length or mass estimates.”

    Never said I did. Since the same skeletal frame (human) can be shown to have had to support many different adult weights, I view attempts to pinpoint sauropod weights with a lot of amusement. I support the stating of a range of possible weights for a given critter.

    As an artist who often draws dinosaurs, I have had to contend with the opinions of those who want to, on the one hand, say science has pinpointed the looks of these creatures, and, on the other hand, virtually completely ignore the available bones we do have.

    There are many examples of highly skilled and highly qualified individuals whose flesh restorations ignore the bones…the KNOWN bones…of prehistoric animals, yet are touted as accurate, almost to the point of dogma. I will not name names and you might want to ignore me, but it is true.

    I am not going to insist that I am correct in all my own interpretations, but I would at least like to see the bones of these magnificent animals be respected. Tyrannosaurus rexes with Allosaurus necks might look good, but seem to me to fly in the face of available information. Correct me if I am wrong.

  10. Mike Taylor Says:

    You’re not wrong :-)


  11. […] * “My” giant is the big Oklahoma Apatosaurus, which I gave a talk on at SVPCA a couple of weeks ago. See these posts for more details (1, 2, 3). […]


  12. […] the juvenile apatosaurus, or by scaling sideways from Sauroposeidon (since a big Apatosaurus was in the same ballpark, size-wise)–and we get similar answers either […]


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