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.

Hey sports fans! I met David Lindblad at Beer ‘N Bones at the Arizona Museum of Natural History last month, and he invited me to talk dinosaurs on his podcast. So I did (LINK). For two hours. Some of what I talk about will be familiar to long-time readers – dinosaur butt-brains and the Clash of the Dinosaurs saga, for example. But I also just sorta turned off my inhibitions and let all kinds of speculative twaddle come gushing out, including the specter of sauropod polyphyly, which I don’t believe but can’t stop thinking about. David was a gracious and long-suffering host and let me yap on at length. It is more or less the kind of conversation you could have with me in a pub, if you let me do most of the talking and didn’t want to hear about anything other than dinosaurs.

Is it any good? Beats me – I’m way too close to this one to make that call. Let me know in the comments.

Oh, I didn’t have any visuals that really fit the theme so I’m recycling this cool image of speculative sauropod display structures by Brian Engh. Go check out his blog and Patreon and YouTube channel.

Anterior view. Dorsal is to the upper right. The neural spine and left transverse process are missing.

Here’s a closeup of the condyle. The outer layer of cortical bone is gone, allowing a glimpse of the pneumatic chambers inside the vert. The erosion of the condyle was probably inflicted post-excavation by relatively unskilled WPA workers, whose prep tools were limited to chisels, penknives, and sandpaper. Because the bones from the Kenton localities are roughly the same color as the matrix, the preparators sometimes did not realize that they were sanding into the bones until the internal structure was revealed. Bad for the completeness of this specimen, but good for pneumaticity junkies like me, because this baby is too big to be scanned by any but the largest industrial CT machines.

For other posts on the giant Oklahoma apatosaur, see:

The best-preserved presacral vertebra of Vouivria damparisensis (Mannion et al. 2017: fig. 10).

New goodies out today in PeerJ: Tschopp and Mateus (2017) on the new diplodocid Galeamopus pabsti, and Mannion et al. (2017) redescribe and name the French ‘Bothriospondylus’ as Vouivria damparisensis.

C7 of Galeamopus pabsti (Tschopp and Mateus 2017: fig. 24).

Both papers are packed with interesting stuff that I simply don’t have time to discuss right now. Possibly Mike and I will come back with subsequent posts that discuss these critters in more detail. We both have a connection here besides our normal obsession with well-illustrated sauropods – Mike reviewed the Galeamopus paper, and I reviewed Vouivria. Happily, both sets of authors chose to publish the peer-review histories, so if you’re curious, you can go see what we said.

For now, I’ll just note that C7 of Galeamopus pabsti, shown above, is intriguingly similar in form to Vertebra ‘R’ of YPM 429, the ‘starship’ Barosaurus cervical (illustrated here). Mike and I spent a lot of time puzzling over the morphology of that vert before we convinced ourselves that much of its weirdness was due to taphonomic distortion and a restoration and paint job that obscured the fact that the metapophyses were missing. Given our ongoing project to unravel the wacky morphology of Barosaurus, I’m looking forward to digging into the morphology of G. pabsti in more detail.

I’ll surely irritate Mike by saying this, but my favorite figure in either paper is this one, Figure 4 from Tschopp and Mateus (2017). I can’t remember ever seeing an exploded skull diagram like this for a sauropod before, but it’s extremely helpful and I love it.

And that’s all for now. Go read these papers – they’re both substantial contributions with intriguing implications for the evolution of their respective clades. Congratulations to both sets of authors for producing such good work.

References

  • Mannion PD, Allain R, Moine O. (2017) The earliest known titanosauriform sauropod dinosaur and the evolution of Brachiosauridae. PeerJ 5:e3217 https://doi.org/10.7717/peerj.3217
  • Tschopp E, Mateus O. (2017) Osteology of Galeamopus pabsti sp. nov. (Sauropoda: Diplodocidae), with implications for neurocentral closure timing, and the cervico-dorsal transition in diplodocids. PeerJ 5:e3179 https://doi.org/10.7717/peerj.3179

Turns out that if Mike and I don’t post about sauropods for a while, people start doing it for us! This very interesting project by Tom Johnson of Loveland, Colorado, first came to my attention when Tom emailed Mark Hallett about it and Mark kindly passed it on to me. I got in touch with Tom and asked if he’d be interested in writing it up for SV-POW!, and here it is. Many thanks to Tom for his willingness to share his work with us. Enjoy! – Matt Wedel

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The sauropod formerly known as Apatosaurus in the American Museum of Natural History was the first permanently mounted sauropod dinosaur in the world, and for many years, the most famous (Brinkman 2010). The greater part of the skeleton consists of the specimen AMNH 460 from the Nine Mile Crossing Quarry north of Como Bluff, Wyoming, supplemented with bones from other AMNH specimens from Como Bluff, Bone Cabin Quarry, and with plaster casts of the forelimbs of the holotype specimen of Brontosaurus excelsus (YPM 1980) at the Yale Peabody Museum.

A herd of Brontosaurus skeleton models parading before four box covers issued between the 1950s and 1990s.

Like many aging boomer dinophiles, my dinosaur epiphany was the result of books, movies, and toys available in the 1950s, but especially a series of plastic model dinosaur skeletons that appeared around 1958. The Brontosaurus was my personal favorite, and, like the Tyrannosaurus and Stegosaurus models in the series, was very obviously based on the AMNH mount. The models were reissued at least three times over the years and can still be found either “mint in box” or more often in various stages of completion.

Apatosaurus lousiae 1/12 scale skeleton, modelled by Phil Platt, assembled and photographed by Brant Bassam. Image courtesy of BrantWorks.com.

The crème de la crème today, of course, is the 1:12 scale Apatosaurus skeleton model by Phil Platt, available from Gaston Design in Fruita, Colorado. A particularly nice example is the one completed and mounted by Brant Bassam of BrantWorks. The Platt skeleton is a replica in the true sense of the word. The plastic models are pretty crude in comparison, as cool as they appeared to us as kids.

I was interested in skeletal illustrations I have seen of Tyrannosaurus rex, which compare the completeness of various specimens by showing the actual bones included by coloring them red. A 2005 study of Apatosaurus by Upchurch et. al. examined eleven of the most complete Apatosaurus individuals, and I was interested to see the actual bones known for each specimen. Using published descriptions, red markers, and copies of a skeletal silhouette of Apatosaurus (permission obtained from the artist), I prepared a comparison of the most completely known Apatosaurus specimens. It was clear, of course, that Apatosaurus louisae (CM 3018) is the most complete specimen of the Apatosaurus/Brontosaurus group. But it also was apparent that old AMNH 460 included a substantial portion of the skeleton, even if it is a composite.

I grabbed some additional markers and, using the illustration of the mount in William Diller Matthew’s popular book Dinosaurs (Matthew 1915, fig. 20, which I trust is in the public domain by now), I color-coded the bones according to the composition as listed in Matthew’s (1905) article:

  • AMNH 460, Nine-Mile Crossing Quarry: 5th, 6th, 8th to 13th cervical vertebrae; 1st to 9th dorsal; 3rd to 19th caudal; all ribs; both coracoids; “parts of” sacrum and ilia; both ischia and pubes; left femur and astragalus; and “part of” the left fibula. RED
  • AMNH 222, Como Bluff: right scapula, 10th dorsal vertebra, right femur and tibia. GREEN
    (Visitors to AMNH: you can see the rest of AMNH 222 under the feet of the hunched-over Allosaurus)
  • AMNH 339, Bone Cabin Quarry: 20th to 40th caudal vertebrae. LIGHT BLUE
  • AMNH 592, Bone Cabin Quarry: metatarsals of the right hind foot. VIOLET
  • YPM 1980, Como Bluff: left scapula, forelimb long bones (casts). YELLOW
  • The remaining parts of the skeleton are either modeled in plaster or are unspecified (“a few toe bones”). BLACK

It occurred to me that I might have sufficient spare parts of old ITC and Glencoe Brontosaurus models to create a three-dimensional version. I did, and painting prior to assembly definitely made the job easier.

There are obviously limitations to using Matthew’s (1915) reconstruction (e.g., only 13 cervicals) and the model (12 cervicals). It is also not clear from Matthew’s description how much of the sacrum and ilia were restored. Nevertheless, the painted model does provide a colorful, if crude, visualization of the composition of the composite.

Here are some more photos of the finished product:

A view from the front of the model, compared with a historical AMNH photo of the forelimbs and pelvic girdle.

Long considered a specimen of Brontosaurus excelsus or Apatosaurus excelsus, AMNH 460 was referred to Apatosaurus ajax by Upchurch et. al. in 2005. In the most comprehensive analysis of diplodocid phylogeny to date, Tschopp et. al. (2015) found AMNH 460 to be an “indeterminate apatosaurine” pending a “detailed analysis of the specimen.” What to call it? Oh, yeah, that’s been covered in another post!

This is a nostalgia shot for the old brontophiles. Notice that the Triceratops is entering the lake for a swim!

Tom Johnson with the mounted skeleton of Amphicyon, a Miocene “bear-dog”,
in the Raymond Alf Museum of Paleontology in Claremont, California.

References

  • Brinkman , Paul D. (2010). The Second Jurassic Dinosaur Rush, University of Chicago Press, 2010.
  • Matthew, William Diller, (1905). “The Mounted Skeleton of Brontosaurus,” The American Museum Journal, Vol. V, No. 2, April.
  • Matthew, W.D. (1915). Dinosaurs, With Special Reference to the American Museum Collections, American Museum of Natural History, New York.
  • Tschopp, Emanuel, Octávio Mateus, and Roger Benson. (2015). “A Specimen-Level Phylogenetic Analysis and Taxonomic Revision of Diplodocidae (Dinosauria, Sauropoda).” Ed. Andrew Farke. PeerJ 3 (2015): e857.
  • Upchurch, P., Tomida, Y., Barrett, P.M. (2005). “A new specimen of Apatosaurus ajax (Sauropoda: Diplodocidae) from the Morrison Formation (Upper Jurassic) of Wyoming, USA”. National Science Museum Monographs (Tokyo) 26 (118): 1–156.

In the summer of 2015, Brian Engh and I stopped at the Copper Ridge dinosaur trackway on our way back from the field. The Copper Ridge site is 23 miles north of Moab, off US Highway 191. You can find a map, directions, and some basic information about the site in this brochure. The BLM has done a great job of making this and other Moab-area dinosaur trackways accessible to the public, with well-tended trails and nice interpretive signage. Brian has gotten to do the art for interp signs at several sites now, including Copper Ridge, and he put together this video to explain a bit about the site, what we know about the trackmaker, and the lines of evidence he used in making his life restoration. I’m in there, too, yammering a bit about which sauropod might have been responsible. We weren’t sure what, if anything, we would end up doing with the footage at the time, so I’m basically thinking out loud. But that’s mostly what I do here anyway, so I reckon you’ll live.

Stay tuned (to Brian’s paleoart channel) for Part 2, which will be about the Copper Ridge theropod trackway. And the next time you’re in the Moab area, go see some dinosaur tracks. This is our heritage, and it’s cool.

jvp-fig-12

Fig. 14. Vertebrae of Pleurocoelus and other juvenile sauropods. in right lateral view. A-C. Cervical vertebrae. A. Pleurocoelus nanus (USNM 5678, redrawn fromLull1911b: pl. 15). B. Apatosaurus sp. (OMNH 1251, redrawn from Carpenter &McIntosh 1994: fig. 17.1). C. Camarasaurus sp. (CM 578, redrawn from Carpenter & McIntosh 1994: fig. 17.1). D-G. Dorsal vertebrae. D. Pleurocoelus nanus (USNM 4968, re- drawn from Lull 1911b: pl. 15). E. Eucamerotus foxi (BMNH R2524, redrawn from Blows 1995: fig. 2). F. Dorsal vertebra referred to Pleurocoelus sp. (UMNH VP900, redrawn from DeCourten 1991: fig. 6). G. Apatosaurus sp. (OMNH 1217, redrawn from Carpenter & McIntosh 1994: fig. 17.2). H-I. Sacral vertebrae. H. Pleurocoelus nanus (USNM 4946, redrawn from Lull 1911b: pl. 15). I. Camarasaurus sp. (CM 578, redrawn from Carpenter & McIntosh 1994: fig. 17.2). In general, vertebrae of juvenile sauropods are characterized by large pneumatic fossae, so this feature is not autapomorphic for Pleurocoelus and is not diagnostic at the genus, or even family, level. Scale bars are 10 cm. (Wedel et al. 2000b: fig. 14)

The question of whether sauropod cervicals got longer through ontogeny came up in the comment thread on Mike’s “How horrifying was the neck of Barosaurus?” post, and rather than bury this as a comment, I’m promoting it to a post of its own.

The short answer is, yeah, in most sauropods, and maybe all, the cervical vertebrae did lengthen over ontogeny. This is obvious from looking at the vertebrae of very young (dog-sized) sauropods and comparing them to those of adults. If you want it quantified for two well-known taxa, fortunately that work was published 16 years ago – I ran the numbers for Apatosaurus and Camarasaurus to see if it was plausible for Sauroposeidon to be synonymous with Pleurocoelus, which was a real concern back in the late ’90s (the answer is a resounding ‘no’). From Wedel et al. (2000b: pp. 368-369):

Despite the inadequacies of the type material of Pleurocoelus, and the uncertainties involved with referred material, the genus can be distinguished from Brachiosaurus and Sauroposeidon, even considering ontogenetic variation. The cervical vertebrae of Pleurocoelus are uniformly short, with a maximum EI of only 2.4 in all of the Arundel material (Table 4). For a juvenile cervical of these proportions to develop into an elongate cervical comparable to those of Sauroposeidon, the length of the centrum would have to increase by more than 100% relative to its diameter. Comparisons to taxa whose ontogenetic development can be estimated suggest much more modest increases in length.

Carpenter & McIntosh (1994) described cervical vertebrae from juvenile individuals of Apatosaurus and Camarasaurus. Measurements and proportions of cervical vertebrae from adults and juveniles of each genus are given in Table 4. The vertebrae from juvenile specimens of Apatosaurus have an average EI 2.0. Vertebrae from adult specimens of Apatosaurus excelsus and A. louisae show an average EI of 2.7, with an upper limit of 3.3. If the juvenile vertebrae are typical for Apatosaurus, they suggest that Apatosaurus vertebrae lengthened by 35 to 65% relative to centrum diameter in the course of development.

The vertebrae from juvenile specimens of Camarasaurus have an average EI of 1.8 and a maximum of 2.3. The relatively long-necked Camarasaurus lewisi is represented by a single skeleton, whereas the shorter-necked C. grandis, C. lentus, and C. supremus are each represented by several specimens (McIntosh, Miller, et al. 1996), and it is likely that the juvenile individuals of Camarasaurus belong to one of the latter species. In AMNH 5761, referred to C. supremus, the average EI of the cervical vertebrae is 2.4, with a maximum of 3.5. These ratios represent an increase in length relative to diameter of 30 to 50% over the juvenile Camarasaurus.

If the ontogenetic changes in EI observed in Apatosaurus and Camarasaurus are typical for sauropods, then it is very unlikely that Pleurocoelus could have achieved the distinctive vertebral proportions of either Brachiosaurus or Sauroposeidon.

apatosaurus-cm-555-c6-centrum-and-arch-united

C6 of Apatosaurus CM 555 – despite having an unfused neural arch and cervical ribs, the centrum proportions are about the same as in an adult.

A few things about this:

  1. From what I’ve seen, the elongation of the individual vertebrae over ontogeny seems to be complete by the time sauropods are 1/2 to 2/3 of adult size. I get this from looking at mid-sized subadults like CM 555 and the hordes of similar individuals at BYU, the Museum of Western Colorado, and other places. So to get to the question posed in the comment thread on Mike’s giant Baro post – from what I’ve seen (anecdata), a giant, Supersaurus-class Barosaurus would not necessarily have a proportionally longer neck than AMNH 6341. It might have a proportionally longer neck, I just haven’t seen anything yet that strongly suggests that. More work needed.
  2. Juvenile sauropod cervicals are not only shorter than those of adults, they also have less complex pneumatic morphology. That was the point of the figure at the top of the post. But that very simple generalization is about all we know so far – this is an area that could use a LOT more work.
  3. I’ve complained before about papers mostly being remember for one thing, even if they say many things. This is the canonical example – no-one ever seems to remember the vertebrae-elongating-over-ontogeny stuff from Wedel et al. (2000b). Maybe that’s an argument for breaking up long, kitchen-sink papers into two or more separate publications?

Reference

Wedel, M.J., Cifelli, R.L., and Sanders, R.K. 2000b. Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon. Acta Palaeontologica Polonica 45:343-388.