We were probably wrong about caudal pneumaticity in Ca13 of the Brontosaurus excelsus holotype YPM 1980

March 20, 2023

This is one of those posts where the title pretty much says it all, but here’s the detailed version.

Recap: the 2013 paper

In Matt’s and my 2013 paper Caudal pneumaticity and pneumatic hiatuses in the sauropod dinosaurs Giraffatitan and Apatosaurus (Wedel and Taylor 2013b), we wrote about the Brontosaurus excelsus holotype 1980:

Much more convincing, however, are two isolated lateral fossae: one on the left side of caudal 9, the other on the right side of caudal 13 (Figure 10). Both of these are much larger than the aforementioned foramina – about 6 cm across – and have distinct lips. There is absolutely no trace of similar fossae in any of the other caudals, so these fossae represent a bilateral pneumatic hiatus of at least seven vertebrae

And we illustrated the right side of Ca13 in our figure 10:

Wedel and Taylor (2013:figure 10). An isolated pneumatic fossa is present on the right side of caudal vertebra 13 in Apatosaurus excelsus holotype YPM 1980. The front of the vertebra and the fossa are reconstructed, but enough of the original fossil is visible to show that the feature is genuine.

Fast forward to 2023

The Yale Brontosaurus has been dismounted and sent to RCI in Canada for some long overdue TLC. It’s being re-prepared, and Brian Curtice has seen the material close up. The news from Brian is not good: I quote some of his emails. First, on 26 January:

The 1980 caudal 13 it isn’t pneumatic. That whole hole is plaster. The 2 verts in front of it have similar damage but on the opposite side. It looks like they were damaged during preservation, excavation, or preparation.

Then on 27 January:

Quick caudal pneumatic update: other than the fact 1980 has a large number of what I dub nutrient foramina there isn’t any shiny surfaces, no odd sculpting, fluting, etc. the bone is exquisite in these areas but will soon be painted black.

Later that day:

It was also exceptionally difficult to sometimes tell what was actual bone. Barbour [1890 — ed.] is spot on at what Marsh had done. The preparators sometimes couldn’t be sure without acetone and an air scribe… I did the best I could but my goodness it was tough and may have errors. Thus I stayed towards what I was positive on.

On 3 February, I wrote back to Brian asking:

My question about the “pneumatic fossa” in caudal 13 is: why did they sculpt it like that? It would have been the simplest thing in the world to give it a simple flat lateral aspect, like the other caudals, so what made them put the fossa in? One possible answer is that that’s what the bone was actually like, but smashed up, and they “repaired” it. I guess we are unlikely ever to know.

He replied the same day:

There are 3 caudals (11-13, pics attached) with similarly damaged bone, punky and smashed and “beat up”, with 11 and 12 having the damage on the left and ventral and 13 on the right. I suspect they were lying close to one another. I couldn’t tell if it was trampling, but it didn’t seem like it was from being hacked from the ground.
As to why they did it? I suspect because 13’s damage wasn’t as jagged, they could plaster over it easier? We’ll never know for sure.

Brian sent a photo of the re-prepared caudal 13, showing … well, see for yourself:

Truthfully, I don’t find this especially compelling. But that’s about the inadequacy of photos for this kind of work. My inclination is to trust Brian’s interpretation, while wondering how Matt and I were both fooled back in June 2012 when we visited YPM together and spent significant time gazing at this caudal.

So what now?

The good news for us is that this doesn’t really change any of our arguments or conclusion in the 2013 paper. We said that there is previously undocumented evidence of caudal pneumaticity in apatosaurines[1] — and there still is, in the other specimen we figured, FMNH P25112, in our figure 9. And the significant conclusion of the papers was the intermittent and unpredictable pneumatization along the tails of sauropods is compelling evidence for extensive “cryptic pneumaticity” — that is, for soft-tissue pneumatization alongside vertebrae that did not penetrate the bone. That conclusion is still good.

But still: one of the data-points we relied on in making that argument no longer looks solid, and it feels like the honest thing is to document that. It probably doesn’t warrant a follow-up paper or even an erratum. But it does warrant a blog-post, and this is it.

Thanks to Brian for bringing it to our attention!


[1]. In the paper we said “in Apatosaurus“, not “in apatosaurines”. But that was back when Apatosaurus was the only recognized apatosaurine, so it amounted t0 the same thing. If we were writing it in the post-Tschopp-et-al. world of today, we’d say “in apatosaurines”.



2 Responses to “We were probably wrong about caudal pneumaticity in Ca13 of the Brontosaurus excelsus holotype YPM 1980”

  1. llewelly Says:

    Good of Brian Curtice to have notified you.

    Good you posted about it.

    It seems like the skill of late 19th and early 20th century restorations have inadvertently fooled a lot of paleontologists. : (

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