April 8, 2013
Last night London and I spent the night in the Natural History Museum of Los Angeles County (LACM), as part of the Camp Dino overnight adventure. So we got lots of time to roam the exhibit halls when they were–very atypically–almost empty. Above are the museum’s mounted Triceratops–or one of them, anyway–and mounted cast of the Mamenchisaurus hochuanensis holotype, presented in glorious not-stygian-darkness (if you went through the old dino hall, pre-renovation, you know what I mean).
We got there early and had time to roam around the museum grounds in Exposition Park. The darned-near-life-size bronze dinos out front are a minor LA landmark.
The rose garden was already closed, but we walked by anyway, and caught this rainbow in the big fountain.
After we checked in we had a little time to roam the museum on our own. I’ve been meaning to blog about how much I love the renovated dinosaur halls. The bases are cleverly designed to prohibit people touching the skeletons without putting railings or more than minimal glass in the way, and you can walk all the way around the mounted skeletons and look down on them from the mezzanine–none of that People’s Gloriously Efficient Cattle Chute of Compulsory Dinosaur Appreciation business. Signage is discreet and informative, and so are the handful of interactive gizmos. London and I spent a few minutes using a big touch-screen with a slider that controlled continental drift from the Triassic to the present–a nice example of using technology to add value to an exhibit without taking away from the real stuff that’s on display. There are even a few places to sit and just take it all in. That’s pretty much everything I want in a dinosaur hall.
Also, check out the jumbotron on the left in the above photo. It was running a (blessedly) narration-free video on how fossils are found, collected, prepared, mounted, and studied, on about a five-minute loop. Lots of pretty pictures. Including this next one.
There are a couple of levels of perspective distortion going on here, both in the original photo and in my photo of that photo projected on the jumbotron.
Still, I feel confident positing that that is one goldurned big ilium. I’m not going to claim it’s the biggest bone I’ve ever seen–that rarely ends well–but sheesh, it’s gotta be pretty freakin’ big. And apparently a brachiosaurid, or close to it. Never mind, it’s almost certainly an upside-down Triceratops skull. Thanks to Adam Yates for the catch. I will now diminish, and go into the West.
Triceratops, Styracosaurus, and Einiosaurus–collect the whole set!
Of course, the centerpiece of the second dinosaur hall–and how great is it that there are two!?–is the T. rex trio: baby, juvenile (out of frame to the right), and subadult. Yes, subadult: the “big” one is not as big as the really big rexes, and from the second floor you can see unfused neural arches in some of the caudal vertebrae (many thanks to Ashley Fragomeni for pointing those out to me on a previous visit).
Awwwww! C’mere, little fella!
Still, this ain’t Vulgar Overstudied Theropod Picture of the Week. Here are some sweet pneumatic diplodocid caudals in the big wall o’ fossils (visible behind Mamenchisaurus in the overhead photo above). The greenish color is legit–in the Dino Lab on the second floor, they’re prepping a bunch of sauropod elements that look like they were carved out of jade.
Sudden violent topic shift, the reason for which will be become clear shortly: London and I have been sculpting weapons of mass predation in our spare time. In some of the photos you may be able to see his necklace, which has a shark tooth he sculpted himself. Here are a couple of allosaur claws I made–more on those another time.
The point is, enthusiasm for DIY fossils is running very high at Casa Wedel, so London’s favorite activity of the evening was molding and casting. Everyone got to make a press mold using a small theropod tooth, a trilobite, or a Velociraptor claw. Most of the kids I overheard opted for the tooth, but London went straight for the claw.
Ready for plaster! Everyone got to pick up their cast at breakfast this morning, with instructions to let them cure until this evening. All went well, so I’ll spare you a photo of this same shape in reverse.
We were split into three tribes of maybe 30-40 people each, and each tribe bedded down in a different hall. The T. rex and Raptor tribes got the North American wildlife halls, but our Triceratops tribe got the African wildlife hall, which as a place to sleep is about 900 times cooler. Someone had already claimed the lions when we got there, so London picked hyenas as our totem animals.
Lights out was at 10:30 PM, and the lights came back on at 7:00 this morning. Breakfast was out from 7:15 to 8:00, and then we had the museum to ourselves until the public came in at 9:30. So I got a lot of uncluttered photos of stuff I don’t usually get to photograph, like this ammonite. Everyone should have one of these.
London’s favorite dino in the museum is Carnotaurus. It’s sufficiently weird that I can respect that choice.
Not that there’s anything wrong with the old standards, especially when they’re presented as cleanly and innovatively as they are here.
Finally, the LACM has a no tripod policy, and if they see you trying to carry one in they will make you take it back to your car. At least during normal business hours. But no one searched my backpack when we went in last night, and I put that sucker to some good use. Including getting my first non-bigfoot picture of the cast Argentinosaurus dorsal. It was a little deja-vu-ey after just spending so much time with the giant Oklahoma Apatosaurus–elements of the two animals really are very comparable in size.
If you’re in the LA area and interested in spending a night at the museum–or at the tar pits!–check out the “Overnight Adventures” page on the museum’s website. Cost is $50 per person for members or $55 for non-members, and worth every penny IMHO. It’s one of those things I wish we’d done years ago.
March 26, 2013
Another raw photo from the road.
The Morrison fossils from the Oklahoma panhandle were dug up and prepped out by WPA workers in the 1930s, and their preparation toolkit consisted of hammers, chisels, pen-knives, and sandpaper. (Feel free to take a minute if you need to get your nausea under control.) And whereas most Morrison fossils are much darker than the surrounding matrix, in the Oklahoma panhandle the bone and matrix are about the same color. Sometimes the prep guys didn’t know they’d gone too deep until they sanded into the trabecular bone. Or in this case, into the air spaces in the condyle of this anterior dorsal of Apatosaurus.
Still, we have lots of anterior dorsals of Apatosaurus, and very few we can see inside, and they’re too darned big to scan, so this gives us useful information that a more perfect specimen would not. So I salute you, underemployed dude from eighty-odd years ago. Thanks for showing me something cool.
January 14, 2013
Matt took this photo in the basement of the Museum für Naturkunde Berlin, back in 2008 when we were there as part of the field-trip associated with the Bonn sauropod conference.
Hopefully all you long-time SV-POW! readers will recognise the specific vertebra that I’m in love with.
September 18, 2012
Friday evening I was in a pub with Mike, Darren, John Conway, and Emma Lawlor. We were killing time waiting for the Pink Giraffe Chinese restaurant down the street to open. I was chatting with John about “All Todays”, his speculative presentation with Cevdet Kosemen (a.k.a. Nemo Ramjet) on how future sentients might reconstruct Holocene animals if they were known only from fossils. Like his “All Yesterdays” presentation last year, John’s flights of scientific fancy had fired my imagination and gotten me thinking about how paleontology forms sort of a skin or membrane between the bubble of what we know and the surrounding ocean of what we don’t. I decided that we should pass a pad around and each sketch a speculative sauropod.
My own entry is based on the holotype of Mamenchisaurus hochuanensis, which was found almost complete except for the skull (naturally) and forelimbs. I have often joked that diplodocids were basically bipeds whose forelimbs happened to reach the ground. Mamenchisaurs were probably not that back-heavy, but their presacral vertebrae were extremely pneumatic and if our hypothetical future paleontologists had no other sauropod material to work with, I think it’s possible that they would reconstruct the M. hochuanensis holotype as a biped.
I’m not sure there’s much to say about Mike’s brachiosaur, beyond the Ebert-like observation that if a brachiosaur dressed up in a coat and top hat and went cruising for dames, this, I am forced to conclude, is more or less how it would look.
John Conway also drew a mamenchisaur, this time Mamenchisaurus youngi with its bizarrely bent-back sacrum. John’s explanation for the weird sacrum brings to mind ground sloths and–for those who saw “All Yesterdays” at SVPCA 2011–a certain black-feathered therizinosaur. I’d also like to note that he knocked this out in about 5 minutes, thus demonstrating the difference between a professional artist and a mere doodler like myself.
Darren’s hindlimb-less sauropod complements my bipedal Mamenchisaurus. Here the animal, evidently known from only the front half of the skeleton, has been restored as a giant bird. Dig the giant thumb claws and spreading metapodials. Surely, you say, future paleontologists of any species or machine culture would know a pectoral girdle when they saw one. But I’ll bet a sauropod scapulocoracoid could pass for an ilium, if said future paleontologists were still in the early stages of understanding the morphology and diversity of vertebrates. Remember that Seeley described the sauropod Ornithopsis as “a gigantic animal of the pterodactyle kind” based on its pneumatic vertebrae. There is also a long and honorable (?) tradition of mistaking sauropods for hadrosaurs (Sonorasaurus), theropods (Bruhathkayosaurus), and tree trunks (Sauroposeidon), so don’t be too quick to rule this out.
What I want to see next is a skeletal reconstruction of Darren’s sauro-bird, using only elements from the front half of a sauropod skeleton. Anyone want to give it a shot?
Our penultimate entry is Emma’s rendering of an evil bastard snake devouring an innocent baby sauropod. Tragically this one is not speculative–we have very good fossil evidence that the scene shown here really happened, probably a lot. She tried to make it up to us with a smiley face on the next page, but it was too late. We were so depressed after this that we could barely choke down four courses of excellent Chinese food.
One more for the road: a totally new depiction of the enigmatic sauropod Xenoposeidon by yours truly. I expect to see this incorporated into future talks and papers dealing with European sauropod diversity in the Early Cretaceous. Just credit me as you normally would.
That’s all, folks. I hope that speculative sauropod sketches get to be a Thing, and that we see lots more of them from future conferences.
September 5, 2012
Another recent paper (part 1 is here) with big implications for my line of work: D’Emic and Foreman (2012), “The beginning of the sauropod dinosaur hiatus in North America: insights from the Lower Cretaceous Cloverly Formation of Wyoming.” In it, the authors sink Paluxysaurus into Sauroposeidon and refer a bunch of Cloverly material to Sauroposeidon as well. So in one fell swoop Sauroposeidon goes from being one of the most poorly represented Early Cretaceous North American sauropods, based on just four vertebrae from a single individual, to one of the best-known, most complete, and most widespread, based on at least seven individuals from Texas, Oklahoma, and Wyoming.
The web of connections among the different sets of material is complex, and involves the Sauroposeidon holotype OMNH 53062 from the Antlers Formation of southeastern Oklahoma, the type and referred material of Paluxysaurus from the Twin Mountains Formation of northern Texas described by Rose (2007), sauropod material from the Cloverly Formation of north-central Wyoming described and illustrated by Ostrom (1970), and UM 20800, a scap and coracoid newly excavated from one of Ostrom’s old quarries. D’Emic and Foreman argue that (1) the Cloverly material is referable to Sauroposeidon based on the shared derived characters of a juvenile cervical, YPM 5294, and the Sauroposeidon holotype, and (2) Paluxysaurus is not distinguishable from the Cloverly material and in fact shares several autapomorphies with the Cloverly sauropod. Which means that (3) Paluxysaurus is Sauroposeidon.
But that’s not all! All the new material suggests different phylogenetic affinities for Sauroposeidon. Instead of a brachiosaurid, it is now posited to be a basal somphospondyl. That’s not super-surprising; as we noted back in 2000 (Wedel et al. 2000), if Sauroposeidon was a brachiosaurid it had evolved some features in parallel with titanosaurs, most notably the fully camellate internal structure of the cervical vertebrae. And it also makes sense because other basal somphospondyls include Erketu and Qiaowanlong, the cervicals of which are similar to Sauroposeidon in some features. D’Emic and Foreman (2012) cite a forthcoming paper by Mike D’Emic in the Journal of Systematic Paleontology that contains the cladistic analysis backing all this up, but the case based on comparative anatomy is already pretty strong.
If anyone is unconvinced by all of these referrals, please bear in mind that we haven’t heard the whole story yet, quite probably for reasons that are outside of the authors’ control. I am inclined to be patient because I have been in that situation myself: Wedel (2003a) was intended to stand on the foundation of evidence laid down by Wedel (2003b), but because of the vagaries of publication schedules at two different journals, the interpretive paper beat the descriptive one into press by a couple of months.
Anyway, if anyone wants my opinion as “Mr. Sauroposeidon“, I think the work of D’Emic and Foreman (2012) is solid and the hypothesis that Paluxysaurus is Sauroposeidon is reasonable. So, if I think it’s reasonable now, why didn’t I synonymize the two myself? Partly because I thought there was a pretty good chance the two were not the same, based mostly on FWMSH 93B-10-8 (which I referred to as FWMSH “A” in Wedel 2003b, since I had only seen in on display without a specimen number), which I thought looked a lot more like a titanosaur cervical than a brachiosaur cervical. But of course I thought Sauroposeidon was a brachiosaur until a couple of months ago, and if it ain’t, and if brachiosaurs and basal somphospondyls have similar cervicals, that objection is considerably diminished. And partly because I’ve had other things to be getting on with, and stopping everything else to spend what would realistically be a few months looking into a possible synonymy (that I didn’t strongly suspect) wasn’t feasible in terms of time or geography. So I’m glad that D’Emic and Foreman have done that work, and I’m excited about the new things they’ve uncovered.
And I’m honored to bring you a new life restoration of Sauroposeidon by uber-talented Bob Nicholls, which we think is the first to show Sauroposeidon in its new guise as a basal somphospondyl. Click through for the mega-awesome version.
Same critter, different views. If anyone wants to GDI this baby, you now have everything you need. Many thanks to Bob for permission to post these and the following making-of images. Please visit him at Paleocreations.com to see a ton of awesome stuff, and give him some love–or at least a few thousand “likes”–on Facebook.
This is Bob’s first foray into 3D modeling, but you’d never know from the quality of his virtual sculpt. And let me tell you, that dude works fast. He sent this initial version, showing Sauroposeidon as an attenuated brachiosaur (sorta like this) on August 23, to solicit comments from Mike and me.
I wrote back and let Bob know about the new work of D’Emic and Foreman, and suggested that he could probably be the first to restore Sauroposeidon as a somphospondyl. Mike and I also voiced our opposition to the starvation-thinned neck, and Mike suggested that the forelimb was too lightly muscled and that the ‘fingers’ were probably too prominent. The very next day, this was in our inboxes:
I wrote back:
Whatever Sauroposeidon was, its neck was fairly tall and skinny in cross-section. It looks like the neck on your model sort of tapers smoothly from the front of the body to the head. I think it would be much narrower, side-to-side, along most of its length, and would have a more pronounced shoulder-step where it met the body.The bottom view is very useful. It shows the forefeet as being about the same size as the hindfeet. AFAIK all or nearly all known sauropod tracks have much bigger hindfeet than forefeet. Certainly that is the case with Brontopodus birdi, the big Early Cretaceous sauropod tracks from Texas that were probably made by Sauroposeidon. The forefeet should be about 75-80% the width of the hindfeet, and only about half a long front-to-back. Even if you don’t quite get to those numbers, shrinking the forefeet a bit and subtly up-sizing the hindfeet would make the model more accurate.
I like how freaky it looks. It looks WRONG, but in a good way.
I had one more change to recommend:
I’m sorry I didn’t suggest this sooner, but it only just now occurred to me. With the referral of Paluxysaurus and the Cloverly material to Sauroposeidon, we now have dorsal vertebrae, and they are loooong, much more similar in proportion to the dorsals of Brachiosaurus altithorax than those of Giraffatitan brancai. So, as much as I like the compact little body on your Sauroposeidon, I think it was probably fairly long in the torso. You probably already have Mike’s Brachiosaurus paper [Taylor 2009] with the skeletal recon showing the long torso–in the absence of an updated skeletal recon for Sauroposeidon, I’d use Mike’s Figure 7 as a guide for reconstructing the general body proportions.
Bob lengthened the torso to produce the final version, which is the first one I showed above. He sent that over on August 29–the delay in getting this post up rests entirely with me.
So. It is still very weird to think of “my” dinosaur as a somphospondyl rather than a brachiosaur. I had 15 years to get used to the latter idea. But suddenly having a lot more material–essentially the whole skeleton, minus some stinkin’ skull bits–is pretty darned exciting, and the badass new life restoration doesn’t hurt, either.
Now, would it be too much to wish for some more Brontomerus?
- D’Emic, M.D., and B.Z. Foreman. 2012. The beginning of the sauropod dinosaur hiatus in North America: insights from the Lower Cretaceous Cloverly Formation of Wyoming. Journal of Vertebrate Paleontology 32(4): 883-902.
- Ostrom, J.H. 1970. Stratigraphy and paleontology of the Cloverly Formation (Lower Cretaceous) of the Bighorn Basin area, Wyoming and Montana. Peabody Museum Bulletin 35: 1-234.
- Rose, Peter J. 2007. A new titanosauriform sauropod (Dinosauria: Saurischia) from the Early Cretaceous of central Texas and its phylogenetic relationships. Palaeontologia Electronica 10(2): 8A (65 pp.)
- Taylor, Michael P. 2009. A re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropoda) and its generic separation from Giraffatitan brancai (Janensch 1914). Journal of Vertebrae Paleontology 29(3): 787-806.
- Wedel, M.J. 2003a. Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs. Paleobiology 29: 243-255.
- Wedel, M.J. 2003b. The evolution of vertebral pneumaticity in sauropod dinosaurs. Journal of Vertebrate Paleontology 23: 344-357.
- Wedel, M.J., R.L. Cifelli and R.K. Sanders. 2000. Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon. Acta Palaeontologica Polonica 45(4): 343-388.
April 30, 2012
In the recent post on OMNH 1670, a dorsal vertebra of a giant Apatosaurus from the Oklahoma panhandle, I half-promised to post the only published figure of this vertebra, from Stovall (1938: fig. 3.3). So here it is:
And in the second comment on that post, I promised a sketch from one of my notebooks, showing how much of the vertebra is reconstructed. Here’s a scan of the relevant page from my notebook. Reconstructed areas of the vert are shaded (confusingly, using strokes going in opposite directions on the spine and centrum, and the dark shaded areas on the front of the transverse processes are pneumatic cavities), and measurements are given in mm.
Next item: is this really a fifth dorsal vertebra?
Here are D4 and D5 of A. louisae CM 3018. They sort of bracket OMNH 1670 in terms of morphology. D4 has a broader spine, and D5 has a narrower one. The spine of D5 lacks the slight racquet-shaped expansion seen in OMNH 1670, but the overall proportions of the spine are more similar. On the other hand, the transverse processes of D4 taper a bit in anterior and posterior view, as in OMNH 1670, and unlike the transverse processes of D5 with their more parallel dorsal and ventral margins. But honestly, neither of these verts is a very good match (and the ones on either side, D3 and D6, are even worse).
Here are D3 and D4 of A. parvus UWGM 15556. D3 is clearly a poor match as well–it is really striking how much the vertebral morphology changes through the anterior dorsals in most sauropods, and Apatosaurus is no exception. D3 looks like a dorsal in lateral view, but in anterior or posterior view it could almost pass for a posterior cervical. If I was going to use the term “cervicodorsal”, indicating one of the vertebrae from the neck/trunk transition, I would apply it as far back as D3, but not to D4. That thing is all dorsal.
And it’s a very interesting dorsal from the perspective of identifying OMNH 1670. It has fairly short, tapering transverse processes. The neural spine is a bit shorter and broader, but it has a similar racquet-shaped distal expansion. I’m particularly intrigued by the pneumatic fossae inscribed into the anterior surface of the neural spine–in Gilmore’s plate they make a broken V shapen, like so \ / (or maybe devil eyes). Now, OMNH 1670 doesn’t have devil eyes on its spine, but it does have a couple of somewhat similar pneumatic fossae cut into the spine just below the distal racquet–perhaps a serially modified iteration of the same pair of fossae as in the A. parvus D4. It’s a right sod that D5 from this animal has its spine blown off–but it still has its transverse processes, and they are short and tapering as in OMNH 1670.
Here are all the dorsals and the first couple sacrals of FMNH P25112, which was originally described as A. excelsus but in the specimen-level analysis of Upchurch et al. 2005) comes out as the sister taxon to the A. ajax/A. parvus/A. excelsus clade. Note the striking similarity of the D5 here with D4 of the A. parvus specimen in Gilmore’s plate (until the careful phylogenetic work up Upchurch et al. 2005, that A. parvus specimen, once CM 563 and now UWGM 15556, was considered to represent A. excelsus as well). But also notice the striking similarity of D6 to OMNH 1670. It’s not quite a dead ringer–the transverse processes are longer and have weird bent-down “wingtips” (XB-70 Valkyrie, anyone?)–but it’s pretty darned close, especially in the shape of the neural spine.
So what does this all mean? First, that trying to specify the exact serial position of an isolated vertebra is nigh on to impossible, unless it’s something that is one-of-a-kind like an axis. Second, after doing all these comparos I think it’s unlikely that OMNH 1670 is a D4–those are a bit too squat across the board–but it could plausibly be either a D5 or a D6. Third, I’m really happy that it doesn’t seem to match any particular specimen better than all the rest. What I don’t want to happen is for someone to see that this vertebra looks especially like specimen X and therefore decide that it must represent species Y. As I said in the comments of the previous post, what this Oklahoma Apatosaurus material needs is for someone to spend some quality time seeing, measuring, and photographing all of it and then doing a phylogenetic analysis. That sounds like an ambitious master’s thesis or the core of a dissertation, and I hope an OU grad student takes it on someday.
If you were intrigued by my suggestion that the big Oklahoma Apatosaurus rivalled Supersaurus in size, and wanted to see a technical comparison of the two, I am happy to report that Scott Hartman has done the work for you. Here’s one of his beautiful Apatosaurus skeletal reconstructions, scaled to the size of OMNH 1670, next to his Supersaurus silhouette. This is just a small teaser–go check out his post on the subject for a larger version and some interesting (and funny) thoughts on how the two animals compare.
- Gilmore, C.W. 1936. Osteology of Apatosaurus with special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum 11:175-300.
- Riggs, E.S. 1903. Structure and relationships of opisthocoelian dinosaurs, part I: Apatosaurus Marsh. Field Columbian Museum Publications, Geological Series 2(4): 165–196.
- Stovall, J.W. 1938. The Morrison of Oklahoma and its dinosaurs. Journal of Geology 46:583-600.
April 25, 2012
Something I’ve always intended to do but never gotten around to is posting on some of the immense Apatosaurus elements from the Oklahoma panhandle. Here’s one of the most impressive, OMNH 1670, an isolated dorsal. Notice that the tip of the neural spine is ever-so-shallowly bifurcated, which in Apatosaurus indicates a D4, D5, or D6. The low parapophyses and fat transverse processes are similar to D4, but Apatosaurus D4s usually have somewhat broader spines, so I’m guessing this thing is a D5. These things vary and I could easily be off by a position in either direction.
Next to it is D5 of CM 3018, the holotype specimen of Apatosaurus louisae (from Gilmore 1936: plate 25), which has served as the basis for many of the published mass estimates of the genus Apatosaurus. OMNH 1670 is 135 cm tall, compared to 106 cm for D5 of CM 3018. If the rest of the animal scaled the same way, it would have been 1.27^3 = 2 times as massive. Mass estimates for CM 3018 are all over the map, from about 18 tons up to roughly twice that, so the big Oklahoma Apatosaurus was probably in Supersaurus territory, mass-wise, and may have rivaled some of the big titanosaurs (Update: see the two giant diplodocids square off in a cool follow-up post by Supersaurus wrangler Scott Hartman). Here’s a fun rainy-day activity: take any skeletal reconstruction of Apatosaurus, clone it in Photoshop or GIMP, scale it up by 27%, and park it next to the original. It looks a lot bigger. So I’m continually surprised that Apatosaurus is so rarely mentioned in the various roundups of giant sauropods, both in the technical literature and in popular articles online. This vertebra was figured by Stovall (1938)–if I get inspired, I’ll dig up that figure and post it another day (hey, look, I did!).
Fun fact: in Apatosaurus the tallest (most posterior) dorsals are 1.3-1.5 times as tall as D5 (Gilmore 1936: 201). So D10 from this individual was probably between 1.7 and 2 meters tall–not quite in Amphicoelias fragillimus territory but getting closer than I’ll bet most people suspected.
NB: if you try to use the scale bar lying on the centrum of OMNH 1670 to check my numbers, you will get a wonky answer. The problem is that the vertebra is so large that it is almost impossible to get far enough back from it (above it, in this case, since it is lying on a padded pallet) to get a shot free from distortion due to parallax. For this shot, the pallet with the vert was on the floor, and I was standing on top of the tallest ladder in the OMNH collections, leaning out over the vert to get centered over the prezygapophyses, and shooting straight down–in other words, I had done everything possible to minimize the visual distortion. But it still crept in. Anyway, trust the measurements, which I–and presumably Gilmore–made with a good old reliable tape measure.
- Gilmore, C.W. 1936. Osteology of Apatosaurus with special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum 11:175-300.
- Stovall, J.W. 1938. The Morrison of Oklahoma and its dinosaurs. Journal of Geology 46:583-600.