![](\"https://svpow.files.wordpress.com/2023/06/haplocanthosaurus-from-across-the-morrison-curtice-et-al-2023-fig-1.jpg\")
Haplocanthosaurus tibiae and dorsal vertebrae. Curtice et al. (2023: fig. 1).
Haplocanthosaurus tibiae and dorsal vertebrae. Curtice et al. (2023: fig. 1).
Brian Curtice and Colin Boisvert are presenting our talk on this project at 2:00 pm MDT this afternoon, at the 14th Symposium on Mesozoic Terrestrial Ecosystems and Biota (MTE14) in Salt Lake City, and the related paper is in the MTE14 volume in The Anatomical Record. Here’s the citation and a direct link to the paper:
\n\nThis one is exciting to me for several reasons, both personal and scientific. I’ve been friends with Brian Curtice and Ray Wilhite since the late 90s, but I’ve never published with them before now. It’s nice to have Colin Boisvert on board as well — he’s working on his Master’s at BYU, just like Brian and Ray did back when, and he’s a keen observer of the sauropod scene.
\nTurning to the science, the number of known Haplo individuals in the entire Morrison is small, probably fewer than a dozen, so any new Haplo material is nice to get. Also, Dry Mesa is a big, famous, productive, diverse quarry, and having Haplo in that quarry is interesting and important.
\nBut to me the most exciting thing about this is that Dry Mesa now has the highest diversity of sauropod genera of any locality in the world. At least six valid, impossible-to-confuse sauropod genera are known from Dry Mesa (listed alphabetically here; we provide specimen numbers of diagnostic elements for each genus in the paper):
\n![](\"https://svpow.files.wordpress.com/2013/03/wedel-and-taylor-2013-bifurcation-figure-7-small-diplodocus-cervical1.jpg\")
BYU 12613, a posterior cervical of a diplodocid, in dorsal (top), left lateral (left), and posterior (right) views. The centrum length is 270 mm, compared to 642 mm for C14 of D. carnegii. Wedel and Taylor (2013), Figure 7.
Alert readers may also recall BYU 12613, a posterior cervical that Mike and I called Diplodocus in our 2013 neural spine bifurcation paper, but which may actually pertain to Kaatedocus. All the Diplodocus material from Dry Mesa is small, and I’m not at all confident that I could tell small Diplodocus vertebrae from Kaatedocus, so out of an abundance of caution we’re calling it all Diplodocus for the purposes of counting genera.
\n![](\"https://svpow.files.wordpress.com/2016/05/2005-07-29-byu-11617-barosaurus-right-lateral.jpg\")
BYU 11617, which sure as heck looks like Barosaurus to me, with a loooong swoopy centrum, big posterolateral flanges, and prezygs that overhang the condyle.
There are also vertebrae in the quarry that I’ve always considered to belong to Barosaurus, like BYU 11617 from this post. If Brian Curtice is right about BYU 9024 (this monster) belonging to Supersaurus rather than Barosaurus, then I’m no longer certain that we can distinguish Supes and Baro based on cervical vertebrae. So maybe those Baro verts actually belong to Supersaurus. But if they don’t — or if BYU 9024 itself belong to Barosaurus, as Mike and I have argued (in our 2016 SVPCA talk, and this post and this post) — then Barosaurus is a seventh sauropod genus from Dry Mesa.
\nThe high sauropod diversity at Dry Mesa is exciting for a couple of reasons. One, it emphasizes the ridiculous productivity of the Morrison paleoenvironment. Yes, there were droughts and fires and landslides and whatnot — at least periodically, even at Dry Mesa (Richmond and Morris 1998). But there was also an environment — or rather, a series of environments — fecund enough to support many coexisting genera of whale-sized herbivores. That’s part of the Morrison story, too.
\nAnd two, this is relevant to the “problem” of Morrison sauropod diversity — the idea that there are just too darned many sauropods in the Morrison, no environment could have supported so many, and therefore Morrison sauropod taxonomy has to be messed up, buncha dumb paleontologists oversplitting genera and species because they don’t know any better. (For more on this idea, see Darren’s brilliant series of posts at Tetrapod Zoology; the concluding post, with links to all the rest, is here.)
\nI put “problem” in scare quotes because I think it’s illusory. In addition to Dry Mesa with its six or seven sauropod genera, there are a handful of Morrison localities with five sauropod genera, more with four, and gobs with three. Not surprisingly, the diverse localities tend to be the big ones, which at least hints that more quarries would have more sauropods if they were bigger — maybe only the biggest quarries did a decent job of capturing the diversity of sauropods on the landscape.
\n![](\"https://svpow.files.wordpress.com/2023/06/engh-brushy-basin-dinos.jpg\")
Brian Engh’s assemblage of large-bodied Brushy Basin dinos for Jurassic Reimagined Part 1. Coincidentally, though, if you swap in Supersaurus for Barosaurus — or maybe just add Supersaurus alongside Barosaurus — you’ll have the known sauropod diversity of the Dry Mesa Dinosaur Quarry.
One you have five or six sauropod genera coexisting closely enough to get buried in the same hole, I think the “problem” of Morrison sauropod diversity goes away. The Morrison Formation outcrops from New Mexico to Canada, from the Oklahoma panhandle and the Black Hills of South Dakota to central Utah, and spans probably 7 or 8 million years. Even four or five distinct habitats or communities across all that space and time (which might be unrealistically conservative — it could easily be several communities at a time, turning over every 2 or 3 million years*), each with four to six sauropod species, gets the species count waaay up there.
\n*But wait — doesn’t our figure up top show that Haplocanthosaurus persisted from the lower part of the Salt Wash to the upper part of the Brushy Basin? Sure, but not as the same species right the way through. There were probably something like half a dozen species of haplocanthosaurs in the Morrison — H. priscus, H. delfsi, the as-yet-unnamed-but-definitely-distinct Bilbey Haplo (Bilbey et al. 2000), the as-yet-unnamed-but-definitely-distinct Snowmass Haplo (Foster and Wedel 2014, Wedel et al. 2021), plus I assume a couple more when and if we get better material of the more fragmentary specimens. That would be consistent with the multiple known species of Apatosaurus, Brontosaurus, Camarasaurus, Diplodocus, etc. So sequential communities of Morrison sauropods probably had a lot of the same genera — there’s nearly always a Cam of some kind, some apatosaurine lurking around, etc. — but with different species across time, space, and paleoenvironmental conditions.
\nI think a big part of the problem is that it’s (maybe too) easy to think of the Morrison Formation as a single thing — like most formations — and to think that we can hold all of it in our heads at once. But the Morrison is a monster, more comparable to a group than to other formations, and not really comparable to any other dinosaur-bearing formation in terms of extent, productivity, and likely diversity of environments and habitats. (For an overview of Morrison environments through time, see Jurassic Reimagined Part 1.)
\nSo, yeah. Morrison sauropod diversity was high, and we just have to deal with that. Plus, hey, now we have more Haplo to play with. Happy days all around!
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