The sauropod heresies: my Tate 2024 ‘abstract’ and handout

I gave my keynote talk last evening at the 28th Annual Tate Conference. I also passed out the handout shown above so people could have a handy reference for sauropod biology while I was talking. I have a link to a PDF version at the bottom of this post if you’d prefer it that way.

Now that the talk’s done, I’m letting my “abstract” out into the world, here (link) and at the bottom of this post. I put “abstract” in scare quotes because it’s a short paper with references and figures. The freedom to go big with the abstract is what convinced me to take on what were for me new and ambitious subjects.

A few caveats. Just on this trip I’ve seen and heard some things that make me question the usefulness of postcranial fusions — of the neurocentral joints, sacrum, scapulocoracoid, and cervical ribs — for assessing sauropod ontogeny. I don’t think fusions are completely useless, just highly variable, even more so than I thought in previous years (see tables and discussions in Wedel and Taylor 2013a and Hone et al. 2016). But some things I’ve been calling “subadults” based on unfused joints may actually have been done growing. And on the flip side, I think some things with fused joints may have still been growing. We need more histology!

Apaldetti et al. (2021: fig. 1). Note the restricted morphospace of post-Toarcian sauropods. Compare to Benson et al. (2013: fig. 13).

Two papers I should have cited in the abstract are Benson et al. (2018) and Apaldetti et al. (2021), who showed with math what I argued in the abstract on qualitative grounds: after a period of experimentation with different shapes, sizes, and body forms in the Late Triassic and Early Jurassic, sauropodomorphs settle down into the sauropod body form by sometime in the Early Jurassic, and they never go back. 

One thing I want to make clear: the fact that sauropods have a more conserved body plan that many other dinosaurian clades doesn’t make them bad dinosaurs, it makes them weird dinosaurs. Sauropods were phenomenally successful, precisely because they did everything right that big mammals do wrong — I started typing the list but just look at the handout up top. But that ecological and evolutionary success happened within pretty strict morphological boundaries; the shortest-necked sauropods were still long-necked compared to most other animals, the shortest-tailed were still long-tailed, and the smallest (as adults) were still pretty big. That sauropods didn’t transgress those boundaries, and as far as we can tell never went back to being prosauropod-like, in 135 million years of making bucket-loads of fast-growing, morphologically variable offspring, is interesting to me. And if it turns out that sauropods did transgress those boundaries, either because we find weird new sauropods, or dinosaur phylogeny gets some seismic shake-ups (you’ve read the new Lovegrove et al. paper, yeah?), that will be even more interesting.

Three sauropods from different times, places and clades, showing the conserved sauropod body plan. The basal eusauropod Spinophorosaurus from the Middle Jurassic of Niger, the turiasaur Mierasaurus from the Early Cretaceous of Utah, and a saltasaurine titanosaur Ibirania from the Late Cretaceous of Brazil (not to scale). Can you guess which is which? The 7th, 8th and 9th letters in the following sequence give the Left/Center/Right positions of Spinophorosaurus, Mierasaurus, and Ibirania, respectively: LCRCLRCRLRLC. Traced and lightly reposed from Remes et al. (2009), Royo-Torres et al. (2017), and Navarro et al. (2022). Wedel (2024: fig. 1).

My friend and colleague Jeremiah Scott helped me thrash through the literature on evolutionary ratchets, Mike Taylor and Brian Engh helped me refine my thinking on the science, its limits, and how to present it, and Jenny Adams helped me make the handout. Any errors are mine.

A big thanks to all of the other speakers at Tate 2024. I’d list them by name but it’s late, I’m tired, and the talks were uniformly excellent, so I’ll just go with this: every one of you gave me new facts to ponder and new ideas to think about. It was probably the most consistently interesting day of talks I’ve seen in my life.

I ended the talk with something that’s not in the abstract but should be: all of the ideas in the abstract are hypotheses, not conclusions. They’re crying out to be tested. In the last paragraph of the abstract I highlighted some recent work that I admire, that gives us examples to emulate in attacking the outstanding problems in sauropod paleobiology. 

The closing slide from my talk.

I’ve been doing this for about a quarter century, and in that time the landscape of dinosaur science has shifted dramatically. I don’t know where we’ll be in another quarter century, but it won’t be where we are now, and that’s really cool and really exciting. Let’s roll.

References

• Apaldetti, C., Pol, D., Ezcurra, M.D. and Martínez, R.N., 2021. Sauropodomorph evolution across the Triassic–Jurassic boundary: body size, locomotion, and their influence on morphological disparity. Scientific Reports 11(1): 22534.
• Benson, R.B., Hunt, G., Carrano, M.T. and Campione, N., 2018. Cope’s rule and the adaptive landscape of dinosaur body size evolution. Palaeontology 61(1): 13-48.
• Hone, D.W.E., Farke, A.A., and Wedel, M.J. 2016. Ontogeny and the fossil record: what, if anything, is an adult dinosaur? Biology Letters 2016 12 20150947; DOI: 10.1098/rsbl.2015.0947.
• Lovegrove, J., Upchurch, P. and Barrett, P.M., 2024. Untangling the tree or unravelling the consensus? Recent developments in the quest to resolve the broad-scale relationships within Dinosauria. Journal of Systematic Palaeontology 22(1): 2345333.
• Wedel, M.J. 2024. The sauropod heresies: evolutionary ratchets, the taphonomic event horizon, and all the evidence we cannot see. The Jurassic: Death, Diversity, and Dinosaurs, 28th Annual Tate Conference abstract book: 35-38. (PDF handout: Wedel 2024 Tate handout FINAL)
• Wedel, Mathew J., and Michael P. Taylor. 2013. Neural spine bifurcation in sauropod dinosaurs of the Morrison Formation: ontogenetic and phylogenetic implications. Palarch’s Journal of Vertebrate Palaeontology 10(1): 1-34.