As we noted yesterday, the humerus of the Brachiosaurus altithorax holotype FMNH P25107 is inconveniently embedded in a plaster jacket — but it wasn’t always. That’s very strange. I have an idea about that which I’ll come to later.

Anyway, although the humerus is now half in a jacket and fully inside a cabinet, we can see it from all angles thanks to the cast that’s part of the mounted skeleton outside the Field Museum. (I can definitively state that this is the greatest picnic area in the universe).

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As noted in the previous post, Matt and I were idiots back when we visited Chicago, so our photos are mostly useless. We have lots that show the mounted skeleton as art, but very few that are scientifically useful. But what you can make out from the photo above (especially if you click through) is that the textures of the two humeri are very different.

You can see it more clearly from in front:

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(There I am, microscopic and easily overlooked, on the left.)

Here’s a close-up of the humeri from that photo, sharpened and contrast/brightness-balanced so you can more easily see what’s going on:

dscn9672-close-up

Contrast the scarred, pitted surface of the right humerus (on the left of the picture) with the much cleaner and bone-like texture of the left one (on the right of the picture). What’s going on here is that the right humerus of the mounted skeleton is a cast of the original element (bad preservation and all) whereas the left humerus is a sculpture. (Or possibly a cast of one of the Giraffatitan humeri, but I doubt that — it’s a bit too clean and seems more robust than those bones.) The real humerus is very distinctive, especially in the progressive flaking away on the lateral side of the distal end.

Of course you can walk all around the cast humerus and photograph it from every angle — both the posterior that is apparent in the jacket, and the anterior that’s face down and inaccessible.

You can walk all around the cast humerus and photograph it from every angle. But we didn’t. Because, as noted here and yesterday (and previously, come to think of it) we used to be idiots back then. As Matt has pithily observed:

“About every three or four months I realize that I’ve spent my entire life up until now being a dumbass; the problem is that ‘now’ keeps moving and every time I think I’ve finally got everything figured out, I later determine that I was/am still a moron.  I distinctly remember having this feeling for the first time in third grade, age of eight, and I keep hoping it will eventually go away, but that hope seems increasingly unfounded.”

That is a hauntingly familiar feeling.

It seems that this cast-right, sculped-left humerus combo is common in Brachiosaurus mounts — I guess because they’re all cloned from the Field Museum’s original. Here, for example (from this post) is the mount at BYU the North American Museum of Ancient Life:

Utah 2008 07 Matt in lift

Once you’ve seen that humerus mismatch, you can’t miss it.

Finally, then — what about this historical oddity that the humerus was once out of its jacket but is now back in? That doesn’t make a lot of sense to me. I can’t really imagine why you’d do that.

So maybe that never happened? We’ve been taking it for granted that the humerus in the old Field-Museum photo is real, but maybe it’s not. Maybe it was a cast, and that cast is still somewhere in the museum (or indeed incorporated into the mount). Maybe when the fossil humerus was brought back from the field, the jacket was removed from the anterior face and that was cast; then this face was rejacketed, the bone was flipped, the posterior face was exposed (as it still is today) and that was cast. Then the two casts were joined together to make an apparently whole humerus.

If that speculation is right, then it should be possible to detect a join running down the lateral and medial faces of the cast humerus that’s in the mount (and apparently in all other mounts). That’s something I’ll look closely for the next time I’m lucky enough to be in Chicago.

I wish it was possible to know this kind of thing. I’d love it if every time a museum mounted a skeleton they published an account of how it was done, as Janensch (1950b) did for the original Giraffatitan mount in Berlin, and Remes (2011) did for the recent remount. Unfortunately I’ve never heard of such a paper regarding the Chicago mount, and I don’t even know how long ago it was done (or if anyone who was involved is still alive). The Wikipedia page says the mount went up in 1993, but gives no reference for that and doesn’t say who did it. Does anyone know?

Update (11:38pm)

Thanks to Ben (no surname given), whose comment below points to a useful 1993 Chicago Tribune article, “Brach To The Future“. This confirms the date of the mount as 1993, unveiled on Saturday 3rd July. The mount is the work of PAST (Prehistoric Animal Structures, Inc.), who bizarrely don’t seem to have a web-site. PAST president Gilles Danis was involved in the process, so he’d be the person to contact about how it was done.

Oh, and here’s another relevant Tribune article: “Out Of The Past“. Steven Godfrey is the key player in this account, so he’s someone else to track down.

References

  • Janensch, Werner. 1950b. Die Skelettrekonstruktion von Brachiosaurus brancai. Palaeontographica (Supplement 7) 3:97-103, and plates VI-VIII.
  • Remes, Kristian, David. M. Unwin, Nicole. Klein, Wolf-Dieter Heinrich, and Oliver Hampe. 2011. Skeletal reconstruction of Brachiosaurus brancai in the Museum für Naturkunde, Berlin: summarizing 70 years of sauropod research. pp. 305-316 in: Nicole Klein, Kristian Remes, Carole T. Gee, and P. Martin Sander (eds.), Biology of the Sauropod Dinosaurs: Understanding the Life of Giants. Indiana University Press, Bloomington and Indianapolis.

In the comments on Matt’s post about the giant new Argentine titanosaur specimens, Ian Corfe wondered why Benson et al. (2014) estimated the circumference of the humerus of Brachiosaurus altithorax instead of just measuring it. (Aside: I can’t find that data in their paper. Where is it?)

I replied:

Yes, the humerus is half-encased in a jacket, face down (we should post photos some time), which would make the circumference impossible to measure directly. But the mounted Brachiosaurus skeleton right outside the Field Museum (and the identical one at O’Hare Airport) have casts of that humerus, so measuring the circumference shouldn’t require any equipment more exotic than a stepladder. Maybe the anterior aspect was sculpted — but I doubt it, as there certainly was a time when the humerus was out of its jacket and mounted vertically.

Here is the evidence that the humerus wasn’t always in that jacket (from Getty Images):

Femur of Apatosaurus and right humerus Brachiosaurus altithorax holotype on wooden pedestal (exhibit) with labels and 6 foot ruler for scale, Geology specimen, Field Columbian Museum, 1905. (Photo by Charles Carpenter/Field Museum Library/Getty Images)

Femur of Apatosaurus and right humerus Brachiosaurus altithorax holotype on wooden pedestal (exhibit) with labels and 6 foot ruler for scale, Geology specimen, Field Columbian Museum, 1905. (Photo by Charles Carpenter/Field Museum Library/Getty Images)

I have no idea why it was put back in a plaster jacket: does anyone?

Back in 2005, when Matt and I visited the Field Museum, the staff were amazingly, almost embarrassingly, helpful. They mounted a whole elaborate project to remove the humerus jacket from the cabinet that held it, so we could get a better look:

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Unfortunately, Matt and I were doofuses back in the day: terrible photographers who knew embarrassingly little about appendicular material. So nearly all of our photos are worthless. Here is a rare nice one, showing the humerus in posterodistal aspect. You can see how layers have flaked away towards this end:

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Here is the humerus in proximal view — something that’s relevant to my interests, as at tells us about the area of articular cartilage where it connected to the shoulder:

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And finally — because it would be rude not to — here is Matt, going the Full Jensen with the humerus:

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Next time: what we can learn about the humerus from the mounted skeleton outside the museum!

References

Benson Roger B. J., Nicolás E. Campione, Matthew T. Carrano, Philip D. Mannion, Corwin Sullivan, Paul Upchurch, and David C. Evans. (2014) Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem Lineage. PLoS Biology 12(5):e1001853. doi:10.1371/journal.pbio.1001853

My camera had a possibly-fatal accident in the field at the end of the day on Saturday, so I didn’t take any photos on Sunday or Monday. From here on out, you’re either getting my slides, or photos taken by other people.

Powell Museum sauropod humerus

On Sunday we were at the John Wesley Powell River History Museum in Green River, Utah, for the Cretaceous talks. There were some fossils on display downstairs, including mounted skeletons of Falcarius and one or two ornithischians,* and this sauropod humerus from the Cedar Mountain Formation (many thanks to Marc Jones for the photo).

* A ceratopsian and Animantarx, maybe? They were in the same room as the sauropod humerus, so it’s no surprise that I passed them by with barely a glance.

There were loads of great talks in the Cretaceous symposium on Sunday, and I learned a lot, about everything from clam shrimp biostratigraphy to ankylosaur phylogeny to Canadian sauropod trackways. But I can’t show you any slides from those talks, so the rest of this post is the abstact from Darren’s and my talk, illustrated by a few select slides.

Wedel Naish 2014 Sauroposeidon and kin - slide 1 title

Sauroposeidon is a giant titanosauriform from the Early Cretaceous of North America. The holotype is OMNH 53062, a series of four articulated cervical vertebrae from the Antlers Formation (Aptian-Albian) of Oklahoma. According to recent analyses, Paluxysaurus from the Twin Mountain Formation of Texas is the sister taxon of OMNH 53062 and may be a junior synonym of Sauroposeidon. Titanosauriform material from the Cloverly Formation of Wyoming may also pertain to Paluxysaurus/Sauroposeidon. The proposed synonymy is based on referred material of both taxa, however, so it is not as secure as it might be.

Wedel Naish 2014 Sauroposeidon and kin - slide 34 Sauroposeidon characters

Top row, vertebrae of Paluxysaurus. From left to right, the centrum lengths of the vertebrae are 72cm, 65cm, and 45cm. Main image, the largest and most complete vertebra of the holotype of Sauroposeidon. Labels call out features that are present in every Sauroposeidon vertebra where they can be assessed, but consistently absent in Paluxysaurus. Evaluating the proposed synonymy of Paluxysaurus and Sauroposeidon is left as an exercise for the reader.

MIWG.7306 is a cervical vertebra of a large titanosauriform from the Wessex Formation (Barremian) of the Isle of Wight. The specimen shares several derived characters with the holotype of Sauroposeidon: an elongate cervical centrum, expanded lateral pneumatic fossae, and large, plate-like posterior centroparapophyseal laminae. In all of these characters, the morphology of MIWG.7306 is intermediate between Brachiosaurus and Giraffatitan on one hand, and Sauroposeidon on the other. MIWG.7306 also shares several previously unreported features of its internal morphology with Sauroposeidon: reduced lateral chambers (“pleurocoels”), camellate internal structure, ‘inflated’ laminae filled with pneumatic chambers rather than solid bone, and a high Air Space Proportion (ASP). ASPs for Sauroposeidon, MIWG.7306, and other isolated vertebrae from the Wessex Formation are all between 0.74 and 0.89, meaning that air spaces occupied 74-89% of the volume of the vertebrae in life. The vertebrae of these animals were therefore lighter than those of brachiosaurids (ASPs between 0.65 and 0.75) and other sauropods (average ASPs less than 0.65).

Wedel Naish 2014 Sauroposeidon and kin - slide 64 Mannion phylogeny

Check this out: according to at least some versions of the Mannion et al. (2013) tree, Sauroposeidon and Paluxysaurus are part of a global radiation of andesaurids in the Early and middle Cretaceous. Cool!

Sauroposeidon and MIWG.7306 were originally referred to Brachiosauridae. However, most recent phylogenetic analyses find Sauroposeidon to be a basal somphospondyl, whether Paluxysaurus and the Cloverly material are included or not. Given the large number of characters it shares with Sauroposeidon, MIWG.7306 is probably a basal somphospondyl as well. But genuine brachiosaurids also persisted and possibly even radiated in the Early Cretaceous of North America; these include Abydosaurus, Cedarosaurus, Venenosaurus, and possibly an as-yet-undescribed Cloverly form. The vertebrae of Abydosaurus have conservative proportions and solid laminae and the bony floor of the centrum is relatively thick. In these characters, Abydosaurus is more similar to Brachiosaurus and Giraffatitan than to Sauroposeidon or MIWG.7306. So not all Early Cretaceous titanosauriforms were alike, and whatever selective pressures led Sauroposeidon and MIWG.7306 to evolve longer and lighter necks, they didn’t prevent Giraffatitan-like brachiosaurs such as Abydosaurus and Cedarosaurus from persisting well into the Cretaceous.

Wedel Naish 2014 Sauroposeidon and kin - slide 65 Cloverly sauropods

The evolutionary dynamics of sauropods in the North American mid-Mesozoic are still mysterious. In the Morrison Formation, sauropods as a whole are both diverse and abundant, but Camarasaurus and an efflorescence of diplodocoids account for most of that abundance and diversity, and titanosauriforms, represented by Brachiosaurus, are comparatively scarce. During the Early Cretaceous, North American titanosauriforms seem to have radiated, possibly to fill some of the ecospace vacated by the regional extinction of basal macronarians (Camarasaurus) and diplodocoids. However, despite a flood of new discoveries in the past two decades, sauropods still do not seem to have been particularly abundant in the Early Cretaceous of North America, in contrast to sauropod-dominated faunas of the Morrison and of other continents during the Early Cretaceous.

Wedel Naish 2014 Sauroposeidon and kin - slide 66 acknowledgments

That final slide deserves some explanation. On the way back from the field on Saturday–the night before my talk–a group of us stopped at a burger joint in Hanksville. Sharon McMullen got a kid’s meal, and it came in this bag. We took it as a good omen that Sauroposeidon was the first dinosaur listed in the quiz.

For the full program and abstracts from both days of talks, please download the field conference guidebook here.

Actually we had the Jurassic talks today, but I can’t show you any of the slides*, so instead you’re getting some brief, sauropod-centric highlighs from the museum.

* I had originally written that the technical content of the talks is embargoed, but that’s not true–as ReBecca Hunt-Foster pointed out in a comment, the conference guidebook with all of the abstracts is freely available online here.

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Like this Camarasaurus that greets visitors at the entrance.

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And this Apatosaurus ilium with bite marks on the distal end, indicating that a big Morrison theropod literally ate the butt of this dead apatosaur. Gnaw, dude, just gnaw.

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And the shrine to Elmer S. Riggs.

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One of Elmer’s field assistants apparently napping next to the humerus of the Brachiosaurus alithorax holotype. This may be the earliest photographic evidence of someone “pulling a Jensen“.

Cary and Matt with Brachiosaurus forelimb

Here’s the reconstructed forelimb of B. altithorax, with Cary Woodruff and me for scale. The humerus and coracoid (and maybe the sternal?) are cast from the B.a. holotype, the rest of the bits are either sculpted or filled in from Giraffatitan. The scap is very obviously Giraffatitan.

Matt with MWC Apatosaurus femur

Cary took this photo of me playing with a fiberglass 100% original bone Apatosaurus femur upstairs in the museum office, and he totally passed up the opportunity to push me down the stairs afterward. I kid, I kid–actually Cary and I get along just fine. It’s no secret that we disagree about some things, but we do so respectfully. Each of us expects to be vindicated by better data in the future, but there’s no reason we can’t hang out and jaw about sauropods in the meantime.

Finally, in the museum gift shop (which is quite lovely), I found this:

Dammit Nova

You had one job, Nova. ONE JOB!

So, this is a grossly inadequate post that barely scratches the surface of the flarkjillion or so cool exhibits at the museum. I only got about halfway through the sauropods, fer cryin’ out loud. If you ever get a chance to come, do it–you won’t be disappointed.

Although it would be nice to think that our site views have octupled in the last day because of Mike’s fine and funny posts about what search terms bring people to SV-POW!, the real reason is that we were blessed by incoming links from both pages of this Cracked.com article.

Now, as any person who has ever accomplished anything whatsoever knows, it is super-important to avoid Cracked.com or you’ll still be up 23 hours from now reading, “6 Mind-Blowing Ways that Comedy Writers are Secretly Destroying Your Productivity”. (I’m kidding, that article doesn’t really exist–but if it did, I’m sure it would consist entirely of descriptions and links to six other Cracked articles). But that’s only true because most of the articles there hit the sweet spot at the intersection of funny, surprisingly informative, mercifully short, and well-written. Crack.com would be a more honest URL, but I assume it was taken.

Anyway, I’d like to return the favor, so here’s a list of the 6 SV-POW! Posts Most Likely to Blow the Minds of Cracked.com Readers. If I missed some goodies or recommended some stinkers, let me know–the comment thread is open.

Amphicoelias vert reconstruction by Mike

1.How big was Amphicoelias fragillimus? I mean, really?

Who doesn’t want to read about the bizarre real-world mystery surrounding what might have been the world’s largest dinosaur? If you’re not sold, consider that the picture above shows a single vertebra that was–or at least might have been–seven and a half feet tall.

long nerves of sauropods

2. Oblivious sauropods being eaten

The mercifully short version of this much longer post, in which I consider the consequences of the world’s largest animals having the world’s longest cells.

krayt-cervicals

3. The sauropods of Star Wars

Weapons-grade anatomical pedantry.

Umbaran starfighters

4. CONFIRMED: the Umbaran Starfighter is an Apatosaurus cervical

Yes, there is a ship in Star Wars: The Clone Wars that is basically a flying dinosaur vertebra. It took us about five weeks to unravel that story–the post linked above has links to the rest of the saga.

blue-whale-and-brachiosaurus

5. SV-POW! showdown: sauropods vs whales

Our original linkbait post. Don’t miss the shorter follow-up with more critters.

Is that your flexor tubercle, Saurophaganax, or are you just hungry to see me?

Is that your flexor tubercle, Saurophaganax, or are you just hungry to see me?

6. Friday phalanges: Megaraptor vs Saurophaganax

A deliberately goofy post in which I wax poetic about the largest predatory dinosaur claws ever discovered.

So, that was a big pile of superlatives and Star Wars. If you’re hungry for more substantial fare, you might start with our Tutorials page or our Things to Make and Do series on dissecting and skeletonizing modern animals. We also blog a lot about the evils of obstructive publishers and the need for open access to the scientific literature–you can find those posts on our Shiny Digital Future page.

flaming-vagabond-in-firefly-niska-station

A parting shot in my desperate quest for attention: this Star Wars ship flying around in the background in Firefly and Serenity is at least partly my fault–full story here. Oh, and my co-blogger Mike Taylor has written an insightful and affordable book about Doctor Who; read about it here.

Illustration talk slide 39

Illustration talk slide 40

Illustration talk slide 41

Illustration talk slide 42

Illustration talk slide 43

The Sauroposeidon stuff is cribbed from this post. For the pros and cons of scale bars in figures, see the comment thread after this post. MYDD is, of course, a thing now.

Previous posts in this series.

Reference:

Wedel, M.J., and Taylor, M.P. 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. ISSN 1567-2158.

FMNH Brachiosaurus mount lateral

Here’s the mounted skeleton of Brachiosaurus altithorax outside the Field Museum in Chicago, based on the holotype FMNH P25107, with missing parts filled in from the mounted Giraffatitan brancai MB.R.2181 at the Museum für Naturkunde Berlin. To see it with humans and other animals for scale, go here.

FMNH Brachiosaurus mount lateral - silhouette

And here’s the same thing in silhouette. It may be informative to compare this to the very different silhouette of the mounted Rapetosaurus krausei, also at the Field Museum.

I’m putting these up so they can be used. Like everything on this blog, these images are released under the CC BY license, so you can do with them what you like as long as you credit us. Go nuts!

In a paper for which we’re currently handling the revisions, I and Matt cite several pieces of artwork, including Knight’s classic Brontosaurus and Burian’s snorkelling Brachiosaurus.

All we have for the references are:

  • Knight CR (1897) Restoration of Brontosaurus.
  • Burian Z (1941) Snorkelling Brachiosaurus.

But a reviewer asked us:

Please edit the reference list with additional information, e.g.: “on the NE wall of the AMNH Hall of Saurischian Dinosaurs” or whatever is appropriate for [these references].

I don’t really have any idea what the right way is to cite artwork — does anyone?

And does anyone have the necessary information? We all know that Zallinger’s “Age of Reptiles” mural is on the wall of the YPM dinosaur hall, but where are the originals of the Knight Brontosaurus and the Burian Brachiosaurus?

Help!

Brachiosaurus sp. BYU 12866 c5? in left lateral view with CT slices, some corrected for distortion.

Brachiosaurus sp. BYU 12866 c5? in left lateral view with CT slices, some corrected for distortion.

Last Tuesday Mike popped up in Gchat to ask me about sauropod neck masses.  We started throwing around some numbers, derived from volumetric estimates and some off-the-cuff guessing. Rather than tell you more about it, I should just paste our conversation, minimally edited for clarity and with a few hopefully helpful links thrown in.

Mike: Dud. Neck masses.
Matt: What about ‘em?
Mike: Taylor (2009:803) measured the neck of Giraffatitan by GDI as 4117 liters.
Matt: k
Mike: I didn’t convert that to a mass, but I guess density of 0.5 is as good as any, which gives us (say) 2 tonnes.
Matt: That works for me.
Mike: That’s for an 8.5 m neck. So Supersaurus at 15 …
Matt: Yep. Almost twice as long, and not much more slender, and from what I’ve seen, ASP about the same.
Mike: Is 1.76 times as long. If it was isometric with the G. neck, it would be 5.5 times as heavy, which is 11 tonnes.
Matt: Oh.
Mike: So first: yeesh. Like, that is the mass of a whole freaking Diplo. Now we surely have to say isometry is unlikely.
Matt: Prolly.
Mike: But just multiplying out by length is unrealistic too. So maybe I should guess at mass =~ l^2? If I went with that, I’d get 6410 kg, which is elephant mass.
Matt: Something just occurred to me. Like, just now. For my 2006 poster, I calculated the mass of the cervical series in Giraffatitan, by summing over the CT slices from Brachiosaurus sp. BYU 12866 and multiplying by appropriate scale factors for the rest of the verts. We could “skin” that in muscle, and actually figure this out, for various muscle thicknesses, for one sauropod.
Mike: We should totally do that … if we had some idea how heavily muscled it was.
Matt: Well, obviously the thing to do is what Hutch et al. did for the tyrannosaurs, and put on several soft tissue envelopes. Crazy skinny, our best guess, markedly unfit, OMG, etc. It’s not that much more work. In fact, that could be my SVPCA talk this year.
Mike: Sure, but that’s just how to mitigate our ignorance. All we’d be doing at this point is taking n guesses instead of one. But, yeah, we should do it. Or you should if you prefer.
Matt: Let’s make it a Wedel and Taylor. I’ll crunch the numbers, but I want your input.
Mike: Works for me!
Matt: Good. Now let’s file it until April at least.
BYU 12613, a posterior cervical probably referable to Diplodocus, in dorsal (top), left lateral (left), and posterior (right) views. It compares most favourably with C14 of D. carnegii CM 84/94 (Hatcher 1901: plate 3) despite being less than half as large, with a centrum length of 270 mm compared to 642 mm for C14 of D. carnegii. From Wedel and Taylor (in press).

BYU 12613, a posterior cervical probably referable to Diplodocus, in dorsal (top), left lateral (left), and posterior (right) views. It most closely resembles C14 of D. carnegii CM 84/94 (Hatcher 1901: plate 3) despite being less than half as large, with a centrum length of 270 mm compared to 642 mm for C14 of D. carnegii. From Wedel and Taylor (in press).

Matt: Oh!
Matt: Also.
Matt: You know that little Diplo cervical from BYU that we figure in our in-press paper?
Mike: I think I know the one, yeah.
Matt: I am SUCH a moron. I have CT scans of the whole thing.
Mike: Good.
Matt: I forgot that Kent and I scanned it back in 2008. Even blogged about it, fer cryin’ out loud.  So I can do the sum-over-slices, scale-for-other-verts thing for Diplodocus, too. Which is at least closer to Supes than JANGO is.
Mike: Remind me, is it from a juvenile?
Matt: Maybe, maybe not. It IS tiny, but the neural spine is fused, the internal structure is crazy complex, and it doesn’t have any obvious juvenile characters other than just being small. The ASP is about as high as it gets in diplodocids. Which, as you may remember, is not nearly as high as it gets in titanosauriforms–that’s another paper that needs writing. Damn it. To know all this stuff and not have told it yet is killing me.
Mike: PeerJ!
Matt: I know!
Mike: Bottom line, it’s nuts that no-one has ever even tried to weigh a sauropod neck.* We should definitely do it, even if we do a really crappy job, if only so that others feel obliged to rebut.
Matt: Quite. Let’s do it. For reals.
Mike: In April. Done.

* R. McNeill Alexander (1985, 1989) did estimate the mass of the neck of Diplodocus, based on the old Invicta model and assuming a specific gravity of 1.0. Which was a start, and waaay better than no estimate at all. Still, let’s pretend that Mike meant “tried based on the actual fossils and what we know now about pneumaticity”.

The stuff about putting everything off until April is in there because we have a March 31 deadline to get a couple of major manuscripts submitted for an edited thingy. And we’ve made a pact to put off all other sciencing until we get those babies in. But I want to blog about this now, so I am.

Another thing Mike and I have been talking a lot about lately is the relation between blogging and paper-writing. The mode we’ve seen most often is to blog about something and then repurpose or rewrite the blog posts as a paper. Darren paved the way on this (at least in our scientific circle–people we don’t know probably did it earlier), with “Why azhdarchids were giant storks“, which became Witton and Naish (2008). Then last year our string of posts (starting here) on neural spine bifurcation in Morrison sauropods became the guts–and most of the muscles and skin, too–of our in-press paper on the same topic.

But there’s another way, which is to blog parts of the science as you’re doing them, which is what Mike was doing with Tutorial 20–that’s a piece of one of our papers due on March 31.

Along the way, we’ve talked about John Hawks’ model of using his blog as a place to keep his notes. We could, and should, do more of that, instead of mostly keeping our science out of the public eye until it’s ready to deploy (which I will always favor for certain projects, such as anything containing formal taxonomic acts).

And I’ve been thinking that maybe it’s time for me–for us–to take a step that others have already taken, and do the obvious thing. Which is not to write a series of blog posts and then decide later to turn it into a paper (I wasn’t certain that I’d be writing a paper on neural spine bifurcation until I had written the second post in that series), but to write the paper as a series of blog posts, deliberately and from the outset, and get community feedback along the way. And I think that the sauropod neck mass project is perfect for that.

Don’t expect this to become the most common topic of our posts, or even a frequent one. We still have to get those manuscripts done by the end of March, and we have no shortage of other projects waiting in the wings. And we’ll still post on goofy stuff, and on open access, and on sauropod stuff that has nothing to do with this–probably on that stuff a lot more often than on this. But every now and then there will be a post in this series, possibly written in my discretionary blogging time, that will hopefully move the paper along incrementally.

References

Recapture Creek comparo with measurements

If you’re just joining us, this post is a follow-up to this one, in which I considered the possible size and identity of the Recapture Creek femur fragment, which “Dinosaur Jim” Jensen (1987: page 604) said was “the largest bone I have ever seen”.

True to his word, Brooks Britt at BYU got back to me with measurements of the Recapture Creek femur fragment in practically no time at all:

Length 1035 mm, width 665 mm.  However, you cannot trust the measurements because Jensen put a lot of plaster on the proximal half of the bone.

Now, taking plaster off a bone is not going to make it any larger. So the plastered-up specimen is the best case scenario for the RC femur to represent a gigapod. And I know the stated width of 665 mm is the max width of the proximal end, because I sent Brooks a diagram showing the measurements I was requesting. The length is a little less than anticipated, and doesn’t quite jibe with the max proximal width–I suspect a little might have broken off from the distal end where the preservation looks not-so-hot.

Based on those measurements, it looks like Jensen got the scale bar in Figure 8 in his 1987 paper approximately right–if anything, the scale bar is a little undersized, but only by 5% or so, which is actually pretty good as these things go (scale bars without measurements are still dag-nasty evil, though). By overlapping Jensen’s photo with the femur of the Brachiosaurus altithorax holotype (FMNH P25107) to estimate the size of the element when complete, I get a total length of 2.2 meters–exactly the same size as about 8% bigger than the Brachiosaurus holotype (actual length 2.03 m). If the Recapture Creek femur is from a Camarasaurus, which I don’t think we can rule out, it was 2 meters long when complete, or 11% longer and 37% more massive than the big C. supremus AMNH 5761–about 35 tonnes or maybe 40 on the outside. So it’s a big bone to be sure, but it doesn’t extend only slightly extends the known size range of Morrison sauropods. (Updated 2014-05-19–as I related in the first post, I somehow got it fixed in my head that the holotype B.a. femur was 2.19 m when it is actually 2.03 m.)

So, as before, caveat estimator when working from scaled illustrations of single partial bones of possibly immense sauropods.

Now, here’s a weird thing. Let’s assume for the sake of this discussion that the Recapture Creek femur is from a brachiosaur. That gives us three individual Late Jurassic brachiosaurids–the Recapture Creek animal, the Brachiosaurus altithorax holotype, and the mounted Giraffatitan brancai–that are almost exactly the same size in limb bone dimensions (although B.a. had a longer torso). But we know that brachiosaurids got bigger, as evidenced by the XV2 specimen of Giraffatitan, and based on the lack of scapulocoracoid fusion in both FMNH P25107 and the mounted Giraffatitan. So why do we keep finding these (and smaller) subadults, and so few that were XV2-sized? I know that there gets to be a preservation bias against immense animals (it’s hard to bury a 50-tonne animal all in one go), but I would not think the 13% linear difference between these subadults and XV2-class adults would be enough to matter. Your thoughts?

Reference

Jensen, J.A. 1987. New brachiosaur material from the Late Jurassic of Utah and Colorado. Great Basin Naturalist 47(4): 592-608.

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