The most complete caudal vertebra of the Snowmass Haplocanthosaurus (Foster and Wedel 2014) in right lateral view: specimen photo, CT scout, 3D model, 3D print at 50% scale. The photos of the specimen and the 3D print probably match the worst with the others, because they are subject to perspective distortions that the digital reconstructions are free from.

Here’s one nice thing about having a 3D print of a specimen that you’re working on: you can hand it to other anatomists and paleontologists and get their take on its weird features, and it’s small enough and light enough that you can bring it halfway across the country to show in person to an entirely different set of colleagues. For all that we hear about humans being a visual species, we are also a tactile one, and in my admittedly limited experience, grokking morphology by handling 3D printed fossils is almost as good as – and for big, heavy, fragile sauropod vertebrae, sometimes better than – handling the real thing.

Many thanks to Julia McHugh at Dinosaur Journey for access to the specimen, John Yasmer at the Hemet Valley Medical Center for CT scanning, Thierra Nalley at Western University of Health Sciences for help with segmenting and visualization in Amira, and Gary Wisser, WesternU’s 3D visualization specialist, for the sweet print. Further bulletins as events warrant.

Reference

Foster, J.R., and Wedel, M.J. 2014. Haplocanthosaurus (Saurischia: Sauropoda) from the lower Morrison Formation (Upper Jurassic) near Snowmass, Colorado. Volumina Jurassica 12(2): 197–210. DOI: 10.5604/17313708 .1130144

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Back in business

May 31, 2018

Many thanks to all of the good folks in the radiology department at the Hemet Valley Medical Center, especially John Yasmer, DO, my partner in crime, and Heather Salzwedel, who did all of the actual work of scanning while the rest of us stood around making oooh and aaah noises.

Further bulletins as events warrant.

Last Wednesday, May 9, Brian Engh and I bombed out to Utah for a few days of paleo adventures. Here are some highlights from our trip.

We started at a Triassic tracksite on Thursday. But I’m not going to post any pictures of the tracks – those will be coming to a Brian Engh joint near you in the future. Instead, I’m going to talk about this little male collared lizard whose territory included the tracksite. He was fearless – didn’t want to run off and leave us yahoos wandering around his patch of desert unsupervised. Brian tickled his chin at one point.

Getting this close to him is how I got shots like this one:

Click through to the big version, it’s worth it.

One more shot of a couple of cool desert dwellers. I was so fixated on the lizard that I didn’t realize until later that Brian was in the frame, taking a much-needed hydration break.

On Friday we had a temporary breaking of the fellowship. I went to Fruita, Colorado, to visit the Dinosaur Journey museum. You’ve seen photos from DJ here before, from the 2014 Mid-Mesozoic Field Conference and the 2016 Sauropocalypse. Here’s an apatosaur pubis with some obvious bite marks on the distal end. This is on display next to a similarly-bitten ischium, which is shown in the MMFC14 post linked above.

Here’s a big apatosaur cervical, in antero-ventral view, with a dorsal rib draped over its left side. The cervical ribs are not fused in this specimen, so it was probably still growing. Here’s a labeled version:

The short centrum and nearly-vertical transverse processes indicate that this is a pretty posterior cervical, possibly a C13 or thereabouts. This specimen was over the fence in the exhibit area and I couldn’t throw a scale bar at it, but I’d describe it as “honkin'”. Like most of the apatosaur material at DJ, this vert is from the Mygatt-Moore Quarry.

Of course the real reason I was at Dinosaur Journey was to see the Snowmass Haplocanthosaurus that John Foster and I described back in 2014. You may remember that its caudal vertebrae have wacky neural canals. You may also have noticed a recent uptick in the number of posts around here about wacky neural canals. The game is afoot.

But as cool as they were, the Triassic tracks, the collared lizard, and even the Snowmass Haplo were only targets of opportunity. Brian and I had gone to Utah for this:

That photo was taken by Paige Wiren of Salt Lake City, on the day that she discovered that bone eroding out of a riverbank, just as you see it.

Here’s Paige with the element, which proved to be the left femur of an apatosaurine sauropod. It’s face down in these photos, so we’re looking at the medial side. The articular head is missing from the proximal end – it should be facing toward Paige’s right knee in the above photo – but other than that and a few negligible nicks and dings, the femur was complete and in really good shape.

Paige did the right thing when she found the femur: she contacted a paleontologist. Specifically, she asked a friend, who in turn put her in touch with Carrie Levitt-Bussian, the paleontology Collections Manager at the Natural History Museum of Utah. Based on Paige’s photos and maps, Carrie was able to identify the element as a dinosaur femur, probably sauropod, within the territory of the BLM Hanksville Field Office. John Foster, the Director of the Museum of Moab, has a permit to legally collect vertebrate fossils from that area, and he works on sauropods, so Carrie put Paige in touch with John and with ReBecca Hunt-Foster, the district paleontologist for the BLM’s Canyon Country District in Utah.

Now, I know there’s a lot of heated rhetoric surrounding the Bureau of Land Management, but whatever your political bent, remember this: those are our public lands. Therefore the fossils out there are the collective property of all of us, and we should all be upset if they get poached or vandalized. Yes, that is a big problem – the Brontomerus type quarry was partially poached before the bones we have now were recovered, and vandalism at public fossil sites in Utah made the national news while we were out there.

So that’s what we went to do: salvage this bone for science and education before it could be lost to erosion or asshats. Brian and I were out there to assist John, ReBecca, and Paige, who got to see her find come out of the ground and even got her hands dirty making the plaster jacket. Brian and John headed out to the site Friday morning and met up with Paige there, and ReBecca and I caravanned out later in the day, after I got back from Fruita.

But I’m getting ahead of myself a bit. We didn’t have to jacket the whole thing. It had naturally broken into three pieces, with thin clay infills at the breaks. So we just slid the proximal and middle thirds away as we uncovered them, and hit any loose-looking pieces with consolidant. The distal third was in more questionable shape, so we did make a partial jacket to hold it together.

We also got to camp out in gorgeous country, with spectacular (and welcome) clouds during the day and incredible starry skies at night.

We floated the femur out of the site using the Fosters’ canoe at the end of the day on Saturday, and loaded up to head back to Moab on Sunday. At one point the road was empty and the sky was not, so I stood on the center line and took some photos. This one is looking ahead, toward I-70 and Green River.

And this one is looking behind, back toward Hanksville.

Here are John and Brian with the femur chunks in one of the back rooms of the Museum of Moab. The femur looks oddly small here, but assembled it was 155 cm (5’1″) long and would have been 160 (5’3″) or more with the proximal head. Smaller than CM 3018 and most of the big mounted apatosaurs, but nothing to sneeze at.

What happens to it next? It will be cleaned, prepped, and reassembled by the volunteers and exhibit staff at the Museum of Moab, and eventually it will go on public display. Thousands of people will get to see and learn from this specimen because Paige Wiren made the right call. Go thou and do likewise.

That was the end of the road for the femur (for now), but not for Brian and me. We had business in Cedar City and St. George, so we hit the road Sunday afternoon. Waves of rainclouds were rolling east across Utah while we were rolling west, with breaks for sunlight in between. I miiiight have had to swerve a couple of times when all the scenery distracted me from driving, and I definitely made an obnoxious number of stops to take pictures.

I don’t remember which scenic overlook this was, but it was a pretty darned good view. This is another one that will reward embiggening – check out those mesas marching off into the distance.

In Cedar City we were guests of Andrew R.C. Milner, Site Paleontologist and Curator at the St. George Dinosaur Discovery Site at Johnson Farm (SGDS). We spent most of Monday at SGDS, getting our minds comprehensively blown by the amazing trace and body fossils on display. It was my first time visiting that museum, but it sure as heck won’t be the last.

I didn’t take nearly enough photos in St. George – too busy helping Brian do some filming for a future project – but I did get this gem. This is a Eubrontes track, from a Dilophosaurus-sized theropod. This is a positive track, a cast of the dinosaur’s foot made by sandy sediment that filled the natural mold formed when the dino stepped into mud. The high clay content of the mud recorded the morphology of the foot in fine detail, including the bumps of individual scales on the foot pads. The vertical streaks were cut into the side of the track by similar scales as the animal’s foot pushed into the mud.

The full story of the Johnson Farm tracks and trackmakers is beautifully told in the book Tracks in Deep Time: The St. George Dinosaur Discovery Site at Johnson Farm, by Jerry Harris and Andrew Milner. I hadn’t read it before, so I picked up a copy in the gift shop and I’ve been devouring it. As a professional scientist, educator, and book author myself, I’m jealous of what Jerry and Andrew produced – both the text and the abundant full-color illustrations are wonderfully clear, and the book is well-produced and very affordable.

From St. George we hit the road home, and rolled into Claremont just before midnight on Monday. It was a whirlwind tour – 1800 miles, three museums, and two fossil sites in six days – and my brain is still fizzing with all of the things we got to see and do.

One of the many pros of having a professional artist as a friend is that minimal hospitality, like letting him crash on my couch, is sometimes rewarded with original art. Brian was already gone when I got up Tuesday morning, but this was waiting for me on the dining room table. (Want your own? Help Brian make more monsters here.)

I owe plenty of thanks myself: to the Foster and Milner families for their near-maximal hospitality, to Julia McHugh of Dinosaur Journey for assistance in collections, to Diana Azevedo, Jalessa Spor, Jerry Harris, and the rest of the SGDS staff for being such gracious hosts, to Brian for being such a great friend and traveling companion, and most of all to Paige Wiren for finding the apato femur and helping us save it for science. You’re all top-notch human beings and I hope our paths cross again soon.

Left side, posterolateral oblique view, wide shot.

Same thing, close up.

Right side, lateral, wide.

Same thing, close up.

For more on this and other pneumatic sauropod tails, please see Wedel and Taylor (2013, here). And for more on the currently unresolved taxonomic status of FMNH P25112, see this post.

Here’s another vertebra from the big Oklahoma apatosaurine. Based on the size and shape of the transverse process, and the large pneumatic chambers on either side of the neural canal, I think this is probably a 4th caudal, but it could plausibly be a 3rd or a 5th. The centrum is 33 cm tall by 36 cm wide.

For other elements of the big Oklahoma apatosaurine, please see:

In the first installment in this series (link), we looked at a couple of weird sauropod vertebrae with neurocentral joints that were situated either entirely dorsal or ventral to the neural canals. This post has more examples of what I am calling “offset” neurocentral synchondroses.

I decided it made more sense to refer to the synchondrosis as being offset, instead of referring to the neural canal as offset. Because the neural canal in all of these vertebrae is right where it pretty much always is, just dorsal to the articular surfaces of the centrum. In an adult, fused vertebra, there’d be no sign that anything unusual had ever happened. So I think it makes more sense to talk about the neurocentral joint having migrated dorsally or ventrally relative to the canal, rather than vice versa. If you know differently, or if these weirdos have been addressed before elsewhere and I’ve just missed it, please let me know in the comments!

Here’s a plate from Marsh (1896) showing caudal vertebrae of Camarasaurus (“Morosaurus” in O.C. Marsh parlance), which echo the Alamosaurus caudal from the first post in having the neurocentral joint almost entirely ventral to the neural canal. The neural arch here doesn’t just arch over the canal dorsally, it also cuts under it ventrally, at least in part.

This plate is also nice because it shows the relationships among the arch, centrum, and caudal ribs before they fuse. Here’s the caption, from Marsh (1896):

Here’s the preceding plate, Plate 33, with illustrations of an unfused Camarasaurus sacrum.

And its caption:

This plate not only shows how the sacral ribs fuse to the arch and spine medially, and to each other laterally (forming the sacrocostal yoke), it also shows a last sacral that is very similar to the aforementioned caudals in the position of the neurocentral joint. But interestingly that neurocentral joint offset only seems to be present in the last caudal sacral – the lower figure shows widely-separated neurocentral joint surfaces in the more anterior centra, indicating that the neural arches (not figured in this dorsal view) did not wrap around the neural canal to approach the midline. (I think we’re looking at S2 through S5 here, and missing a dorso-sacral.)

So now I’m freaked out, wondering if this neural arch wrap-around in the caudals is common to most sauropods and I just haven’t looked at enough juvenile caudals to have spotted it before. As always, feel free to ablate my ignorance in the comments, particularly if you know of more published examples. I’m a collector.

The neural canal of that last sacral also has a very interesting cross-sectional shape, like a numeral 8. I have some thoughts on that, but they’ll keep for a future post in this series.

Here’s a dorsal vertebra of Camarasaurus in anterior view (from Ostrom & McIntosh 1966, modified by Wilson & Sereno 1998). It is one of the most disturbing things I have ever seen in a sauropod. It makes my skin crawl.

Here’s why: the centrum and the thing we habitually call the ‘neural arch’ aren’t fully fused, and as this modified version makes clear, the ‘neural arch’ is neither neural nor an arch. Instead of being bounded ventrally by the centrum and dorsally and laterally by the neural arch, the neural canal lies entirely below the synchondrosis between the not-really-an-arch and the centrum.

Why?! WHY WOULD YOU DO THAT, CAMARASAURUS? This is not ‘Nam. This is basic vertebral architecture. There are rules.

Look at c6 of Apatosaurus CM 555 here, behaving as all good vertebrae ought to. Neural arch be archin’, as the kids say.

And if you are seeking solace in the thought that maybe the artist just drew that Cam dorsal incorrectly, forget it. I’ve been to Yale and examined the original specimen. I’ve seen things, man!

Camarasaurus isn’t the only pervert around here. Check this out:

Unfused neural arch of a caudal vertebra of a juvenile Alamosaurus from Big Bend. And I mean, this is a neural arch. This may be the most neural of all neural arches, in that it contains the entire neural canal. It’s more of a neural…ring, I guess. That’s right, this Alamosaurus caudal is batting for the opposite team from the Cam dorsal above. And it’s a team that neither you nor I play on, because we have well-behaved normal-ass vertebrae with neural arches that actually arch, and then stop, like God and Richard Owen intended.

Scientifically, my question about these vertebrae is: well, that is, I mean to say, what!? I think they have damaged me in some fundamental way.

If you have anything more intelligent to add (or even less intelligent – consider the gauntlet thrown down!), the comment thread is open.

References

  • Ostrom, John H., and John S. McIntosh. 1966. Marsh’s Dinosaurs. Yale University Press, New Haven and London. 388 pages including 65 absurdly beautiful plates.
  • Wilson, J. A. and Paul C. Sereno. 1998. Early evolution and higher-level phylogeny of sauropod dinosaurs. Society of Vertebrate Paleontology, Memoir 5: 1-68.