Apatosaurus is — still — Just Plain Wrong
November 30, 2018
We’ve posted a lot here about how crazy the cervical vertebrae of apatosaurines are (for example: 1, 2, 3), and especially the redonkulosity of their cervical ribs. But I think you will agree with me that this is still an arresting sight:
That’s MWC 1946, a mid-cervical from the Mygatt-Moore Quarry that was figured by Foster et al. (2018: fig. 18 A-B) and referred with the rest of the Mygatt-Moore apatosaur material to Apatosaurus cf. louisae (entirely correctly, in my view). This is a ventral view, with the condyle down by the scale bar.
Here’s the same thing cropped from the background to emphasize its unbelievableness:
and mirrored and restored a bit in GIMP to give a taste of its probable appearance in life (if you had an apatosaur, an x-ray machine, and a lot of confidence about not getting stepped on):
For obvious reasons, my nickname for this specimen is the Brontosmasher.
Keep in mind that the centrum was full of air in life, whereas the cervical ribs and the bony struts that support them are just huge slabs of bone. I strongly suspect that the volume of bone in the cervical ribs and their supporting struts is vastly more than in the centrum and neural arch. I will soon have the ability to test that hypothesis–I have this specimen on loan from Dinosaur Journey for CT scanning and 3D modeling. Watch this space.
Many thanks to Julia McHugh at Dinosaur Journey for access to the specimen and assistance during my frequent visits.
Reference
- Foster, J.R., Hunt-Foster, R.K., Gorman, M.A., II, Trujillo, K.C., Suarez, C.A., McHugh, J.B., Peterson, J.E., Warnock, J.P., and Schoenstein, H.E. 2018. Paleontology, taphonomy, and sedimentology of the Mygatt-Moore Quarry, a large dinosaur bonebed in the Morrison Formation, western Colorado—implications for Upper Jurassic dinosaur preservation modes: Geology of the Intermountain West 5: 23–93.
Sauropod Vertebra Picture of the Week 
November 30, 2018 at 5:33 pm
How sure are we that the diapophyseal and parapophyseal rami, and the cervical ribs, were not themselves pneumatised in apatosaurines? Definitely something to look for in the CT!
November 30, 2018 at 5:47 pm
Diapophyses and parapophyses usually are pneumatized, out to the fusion line. As for the rib itself, I’ve seen some fossae and sculpting at the intersection where the capitulum, tuberculum, and shaft come together, but no internal chambers in apatosaurines. I think that the CRs past the fusion points will still have more bone the centrum and arch, even including the diapophyes and parapophyses.
But yeah, will be interesting to see what turns up on the CT. Definitely going to run this thing through sideways and hope for minimal artifacts.
December 1, 2018 at 4:01 am
Hate to be “that guy,” but you mistyped MWC 1916 as 1946.
December 1, 2018 at 9:51 am
Maxwell, what makes you say that? The tiny paper labels on the specimen itself say 1946.
December 1, 2018 at 11:09 am
I think from the caption to Foster et al. (2018: fig. 18), which refers to this specimen as “MWC 1916”. But I am confident that’s a typo because the paper label on the specimen, the specimen card, and the database entry for it all say MWC 1946. I know because I had to fill out the paperwork to get it on loan.
December 1, 2018 at 8:57 pm
I apologize, that was my mistake.
I did get that number from Foster et al., and I did a quick Google search to see which was the misspelling, and it seems that “1916” is given in several other sources. When I searched for “MWC 1946” Apatosaurus the only link I got was to this post, so I assumed that yours was the mistake. Sorry, about that.
December 2, 2018 at 12:26 am
Hey, no need to apologize, all the info you had access to said otherwise!
I also did a search for “MWC 1916” and I got John Foster’s (2005) chapter in the Thunder-Lizards book about juvenile sauropod material from Western Colorado. He lists MWC 1916 as a cervical centrum 104mm long (about 4 inches), so I think that clinches it as MWC 1916 belonging to a different specimen. MWC 1946 is 360mm long, and about 650mm max width across the cervical ribs.
But seriously, if you ever think we’re in error, _say so_. It won’t hurt our feelings, and we only get smarter if our mistakes get caught and fixed.
December 2, 2018 at 2:24 pm
Is the variable robustness and orientation of the cervical ribs amongst Apatosaurus significant for species recognition? I’ve seen more gracile forms, even with variability of the anterior processes of the ribs on supposed Apatosaurine species.
December 2, 2018 at 9:13 pm
Good question. I’d have to check Tschopp et al. 2015. I know the size and orientation changes A LOT along the column.
December 3, 2018 at 10:44 am
My sense is that different apatosaurine specimens have wildly different cervical morphology, even if you allow for serial changes. How that maps onto species or genera, I couldn’t say.
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