The even more enigmatic taphonomy of Sauroposeidon
April 1, 2010
Update
This is an actual page from the late, lamented Weekly World News, from December 14, 1999. I always thought it was pretty darned funny that they had the alien remains discovered in the “belly” of an animal known only from neck vertebrae. Now, subjecting a tabloid story to technical scrutiny really is like dancing about architecture, but…it just tickles me. As does the entire story. I haven’t been able to get hold of Dr. Posvby to confirm his findings, but it’s been over a decade and he still hasn’t published, so I’m not holding my breath.
Incidentally, the WWN archives are available on Google Books: go here to read about Bat Boy siring a 3-headed alien Elvis baby on a female Sasquatch. Or something to that effect.
Say hello to Abydosaurus mcintoshi
February 26, 2010
The hot news on the block right now is the description of the new sauropod Abydosaurus mcintoshi, which, amazingly, is known from four more or less complete skulls (Chure et al. 2010). This is unheard of — absolutely unprecedented. There are few enough sauropods for which a skull is known at all; but four of them, all in decent nick, is breathtaking.
And here is one of them, the holotype:
Abydosaurus mcintoshi holotype skull DINO 16488, from Chure et al. (2010:fig. 3)
It’s a real shame that, presumably due to space limitations, this is the only one of the skulls that’s figured in the paper; but the good news is that some of the referred material is illustrated in the supplementary information, which — like the paper itself — is freely available, thanks to the wonder of open-access publishing.
According to the phylogenetic analysis in the paper, Abydosaurus is a brachiosaurid — it is recovered in all MPTs as the sister taxon to Chure et al.’s “Brachiosaurus” OTU (on which, see below). Since it’s from the mid Cretaceous (Cenomanian-Albian, from the Mussentuchit Member of the Cedar Mountain Formation), it’s likely about 105 million years old, which means it lived the best part of 50 million years after the better known brachiosaurs Brachiosaurus and Giraffatitan. It was evidently attracted by the Giraffatitan component of the compound OTU, since the skull and neck are effectively unknown in Brachiosaurus (see Taylor 2009 for a review of the holotype and referred material). Because it lived in pretty much the same time and place as Sauroposeidon, there is the tantalising possibility that it is actually the skull of that animal; on the other hand, the four recovered skulls are all too small to fit the Sauroposeidon holotype, so unless they were all subadult, that appealing idea is probably wrong.
Unlike Giraffatitan — the only other brachiosaur with decent cranial material, so far as I recall — Abydosaurus has narrow teeth , superficially similar to those of diplodocids and titanosaurs. Chure et al. show that this seems to be part of a general trend of sauropods evolving progressively narrower tooth crowns through time, perhaps because narrow teeth can be replaced more quickly and turnover rate is more important than robustness.
Abydosaurus mcintoshi, reconstruction of skull and anterior neck based on holotype and referred specimens (from Chure et al. 2010:fig. 4). Note your weekly helping of sauropod-vertebra goodness in the upper-right corner, in the form of a transverse slice though cervical 3 just behind the diapophyses.
One aspect of this paper particularly pleases me, and that is that the new species is named after John McIntosh. For anyone out there who doesn’t know who McIntosh is, he’s been working on sauropods since forever: he’s produced a stream of important papers on the skulls of diplodocids, among many other things, and wrote the Sauropoda chapter in the original The Dinosauria (McIntosh 1990). All of this in his spare time, mind you, because as his day-job he was a professor of theoretical physics at Yale and Princeton. He’s probably seen more sauropod material than anyone else alive. And on top of all that, he is one of the good guys. I drew the long straw at the Austin SVP in 2007, and got to sit next to him at the informally convened sauropod-workers’ lunch, and it was a revelation to see his face light up as I tried to describe the weird morphology of the as-yet-unpublished vertebra that we now know as Xenoposeidon. At an advanced age — I don’t know exactly how old he is, but you can get some idea from the fact that he flew over Hiroshima and Nagasaki less than a week after the bombs were dropped — his enthusiasm remains undimmed, and he is truly an inspiring example to every avocational palaeontologist.
So it’s sort of scandalous that it took so long before McIntosh got a sauropod of his own. (Jensen did name Ultrasaurus after him, but as has been much discussed, that ended up synoymised with Supersaurus). I know there’s at least one more new sauropod in the works that’s slated to be named after him, and I’m in favour.
Brooks Britt (a co-author on the paper) with one of the skulls of Abydosaurus. Stolen from Science Daily.
A note on brachiosaur taxonomy
I suppose I ought to mention this, only because if I don’t, everyone will just ask me about it. Chure et al. (2010) refer to Giraffatitan by the old name “Brachiosaurus” brancai throughout, and explain why they do so on page 2:
Taylor (2009) recently suggested that the North American species Brachiosaurus altithorax is generically distinct from the African species Brachiosaurus brancai, which is known from abundant material including a complete skull and many craniodental elements. Based on numerous differences between overlapping parts of both holotypes, Taylor (2009) proposed that the African species should be known as Giraffatitan brancai. While we are open to this possibility, we do not believe that it is sufficiently justified at present because the identified differences have not been defended as separating genera, rather than species, populations, or individuals. The sister-taxon relationship between the two species recovered in the phylogenetic analysis performed by Taylor (2009) neither supports nor refutes their generic-level separation. At this point, we consider the decision to recognize the African species as a genus apart to be arbitrary. We choose to retain the original nomenclature in this contribution, distinguishing between the two species where appropriate.
I am sort of nonplused by this. I’m certainly not saying that my 2009 paper is unassailable: as soon anyone comes along with evidence that Brachiosaurus and Giraffatitan should after all be considered congeneric, I’ll be first in line to hear them out. But I do feel that now 26 osteological differences have been described between the species, the null hypothesis has shifted, and the burden of proof is now on those who wish to synonymise the genera. ”We choose to retain the original nomenclature” is not an argument, and doesn’t really advance understanding. So I’m afraid I think this was a regrettable misstep.
Anyway — I don’t want to end on that note! The big deal here is that we now have four fantastic new brachiosaur skulls, no doubt to be described in more detail hereafter, and John McIntosh has a beautiful sauropod named after him. Happy days!
References
- Chure, Daniel, Brooks B. Britt, John A. Whitlock and Jeffrey A. Wilson. 2010. First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition. Naturwissenschaften (online, unpaginated). doi:10.1007/s00114-010-0650-6
- McIntosh, John S. 1990. Sauropoda. pp. 345-401 in: D. B. Weishampel, P. Dodson and H. Osmólska (eds.), The Dinosauria. University of California Press, Berkeley and Los Angeles.
- 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 Vertebrate Paleontology 29(3):787-806.
Tutorial 8: how to photograph big bones
February 12, 2010
Since I started taking photographs of sauropod vertebrae back in 2004, I’ve got much, much better at it, and for the last few months I’ve been meaning to write an article about what I’ve learned along the way. A few weeks ago, fellow SV-POW!er Ranger Matt Wedel posted an article on his 10 Minute Astronomy blog on how to photograph the moon through binoculars, and that served as a prod to get back into blogging gear in the post-Christmas season.
Before I launch in, let me be really clear that I am not a proper photographer — not at all. I don’t even know what an F-stop is or what Single Lens Reflex means. Probably I should invest some time into learning some of this, since specimen photographs are so important in the world of sauropod vertebrae. (After all, the specimens are more than a little cumbersome to loan, so photos often have to stand as proxies for the actual specimens.) Nevertheless, what I’ve learned in the last five or six years has got me to the point where I am producing much, much better specimen photographs than when I started, and I hope at least some of you can benefit from what I’ve learned.
The very best (and still very bad) of the first batch of Archbishop photographs I took, back in July 2004. Note that it's not square on, doesn't fit in the frame, that it's over-exposed and (as you'll see if you click through to the full-sized version) both blurry and infested with artifacts. Compare with the recent photo at the end of this article. Copyright the NHM since it's their material.
Equipment
Camera
First up, get a decent camera. However skilled you are, you can’t take better photos than the hardware allows. Although I am to blame for the composition above and for some of blurriness, the over-exposure, poor definition and artifacts are the fault of the camera. I was using a truly horrible camera back then — some super-cheap list-of-features-on-a-discount-website piece of kit.
The good news is that a “decent” camera doesn’t need to break the bank: for our purposes you don’t need to spend a fortune on professional-photographer standard equipment. I am looking on ebay right now, and it seems you can get my model of camera for £100 in the UK or $150 in the US (second-hand of course) which is a level of investment we really should be prepared to put into one of the most important aspects of descriptive work.
What constitutes a decent camera? Mostly, optics. These days, every camera has more than enough megapixels for most purposes, so you can just forget about that statistic altogether. It’s about the quality of the lens and the size of the CCD — those are the factors that determine how much information the camera can capture, and if it puts out more bits than that, then all it’s doing is wasting disk-space and bandwidth.
Can I justify the claim that all modern cameras have enough megapixels? I think so. Suppose you’re preparing a full-page plate for the Journal of Vertebrate Paleontology. In practice, plates are nearly always composites of several photos, but suppose you want a single shot filling the whole plate. The printable area of a JVP page is 182 x 233 mm, which is 7.2 x 9.2 inches. At 300 dpi, that’s 2161 x 2752 pixels, which is 5947072, or a slice under 6 megapixels. So 6 Mp is enough for a full-page plate. (For what it’s worth, my camera does 2272 x 1704 = 3.8 megapixels, and I have never found myself feeling a need for more resolution.)
For the same reason, you definitely want optical zoom rather than digital zoom, which really amounts to just blowing up the image.
Accessories
Another big win: get a spare battery, so that one can be recharging while you’re using the other. If you don’t do that, your camera is out of commission half the time.
And get a big enough memory card. What’s “big enough”? For me, that means enough space to hold a whole day’s images so I can do a single dump onto the laptop in the evening, rather than having to keep stopping to transfer. I can take maybe a maximum of 300 photos a day. With 1 Mb images, that means I need a 300 Mb card, which is chickenfeed. You literally can’t buy cards that small any more, so this is not really a factor these days and I might just as well not have mentioned it. (The reason I did mention it is that my camera originally came with a 16 Mb card or something similarly stupid, which meant ten minutes or so of photography before downloading.)
Horrible photograph of a Brachiosaurus altithorax dorsal (holotype specimen FMNH P25105, natch), showing how NOT to compose a picture.
Composition
Get the specimen in frame
Shoot from cardinal directions
Don’t put anything in front of the specimen
Use a plain background when possible.
But the good news is that all these problems can be ameliorated if you follow the last and most important rule in this section which is:
Take many shots and keep only the good ones
I remember reading once, long ago, that the single biggest factor in the difference of quality between a professional photographer’s work and an amateur’s is that the pro takes ten times as many shots and throws 90% of them away. In these days of digital cameras with huge memory cards, we can all make like professionals now. When Matt and I were at the Field Museum in Chicago, we took 168 photos of those Brachiosaurus dorsals alone. Of those, maybe a dozen or so are really worth keeping. But at least I have those dozen.
In general, I take every photograph twice. As I’ve got better at taking the photos, I am increasingly finding that both come out well and it’s a toss-up which to keep, but maybe one time in ten or twenty, one of them just doesn’t come out right — something is wrong with the focus, or the camera shakes, or something — and that’s when I’m glad I have the spare.
Another terrible photo, this time with the flash washing out all the detail of the neural spine of Giraffatitan brancai lectotype HMN SII, 8th cervical, in left lateral view.
Lighting
Flash
On the other hand, my camera’s built-in flash is pretty lame. Expensive flash units might do much better.
Other lights
As with flash, it seems that the only thing to do is try photos with and without external lights, and with the lights in various different positions, and see what comes out best.
Giraffatitan brancai paralectotype HMN SI, cervical vertebra 6 in right anterolateral view. Not a bad photo -- click through to the full-sized version to appreciate the awesome.
Stability
So what can you do? Well, there are several levels of compensation.
Simply being aware of remaining still
When I have to hold the camera in my hands and I know it’s going to be a long exposure I find myself going into a sort of zen state — I become aware of my heartbeat and try to time the shutter release so that the camera doesn’t get moved by my pulse. It’s error-prone, but at least being aware of it can help.
Brace against a door-frame or similar
Tripods
Shutter delay
The combination of tripod mounting and shutter delay means that you can get good exposure in almost any light.
The Archbishop in all its glory, with everything working right. The much-loved dorsals 8 and 9 in right lateral view. Click through to see the detail. Compare with the horrible photo of the same bones at the top of this article. Copyright the NHM since it's their material.
Summary
… And finally …
From: Carol Brown<bcarol83@gmail.com>
Hi Michael,
We just posted an article, “100 Best (Free) Science Documentaries Online” (http://www.onlineuniversities.com/blog/2010/01/100-best-free-science-documentaries-online/). I thought I’d drop a quick line and let you know in case you thought it was something you’re audience would be interested in reading. Thanks
Enjoy!
Sauropod-related travel: Utah, 2008
February 5, 2010
Here’s one of those text-light photo posts that we always aspire to but almost never achieve. In the spring of 2008 I flew to Utah to do some filming for the History Channel series “Evolve”, in particular the episode on size, which aired later that year. I always intended to post some pix from that trip once the show was done and out, and I’m just now getting around to it…a bit belatedly.
Here’s the view out the back door of the BYU Earth Sciences Museum in Provo, Utah. Not bad–the mountains actually made me drag my eyes away from sauropod vertebrae for a few seconds here and there.
Here’s the view in other direction, with Brooks Britt using a forklift to retrieve the big Supersaurus cervical.
And here is said cervical, with a mid-cervical of a giraffe for scale. You may remember the big cervical from this post (and if you click that link, notice how much nicer the new collections area is than the off-site barn where I first encountered the Cervical of Doom). Sauropods FTW!
While the film crew were shooting Brooks and picking up some establishing shots, I was ransacking the collections for pretty vertebrae. We took our treasures up to the University of Utah med center in Salt Lake for CT scanning. Here Kent Sanders is helping me tape down a Diplodocus cervical.
And here’s Kent in the CT reading room playing with the data. Like old times–I spent most of my Saturdays in 1998 and 1999 scanning verts with Kent when he was at the University of Oklahoma Health Sciences Center.
The next morning we went to the North American Museum of Ancient Life in Lehi. Here’s a view down the main drag, with the mounted Supersaurus on the left, mounted Brachiosaurus in the center, and original Supersaurus sacrum (on loan from BYU) in the case on the right.
The highlight of my day trip year.
I was back at BYU just a few months ago shooting another documentary, but that story will have to wait for the dramatically appropriate moment. Stay tuned!
What’s up with the Brachiosaurus coracoid?
January 25, 2010
In my not-long-quite-so-recent-any-more paper on Brachiosaurus and Giraffatitan, I gave as one of the autapomorphies of Brachiosaurus proper that the glenoid articular surface of its coracoid is laterally deflected. Although we’ve discussed this a little in comments on SV-POW!, it’s not yet made it into one of our actual articles. I hestitated to feature it here since it’s so darned appendicular, but in the end I concluded that it was too interesting and potentially important to overlook.
So here it is!
Brachiosaurus altithorax holotype FMNH P25107, left coracoid in lateral, posterior and ventral views (oriented as though the scapular blade were horizontal). Modified and composed from photographs by Phil Mannion; used with permission.
The deflected surface is most apparent in the posterior view at the right of the fiigure, in which it appears deflected about 55 degrees from the horizontal. That’s misleading, though — partly because the shape is more complex in three dimensions than can be easily visualised from these orthogonal shots, and partly because of course the coracoid was not held perfectly vertical in life. In fact, the orientation of the coracoid in sauropods, and of the entire shoulder girdle, remains rather controversial. It’s not an area I’ve got involved in so far, but this Mystery Coracoid Of Weirdness (hereafter MCOW) might just be my gateway into the wacky world of pectoral girdles.
The ventral view at the bottom of the figure is also informative: as you can see from that angle, the articular surface extends a long way laterally (i.e. towards the top of the figure in this orientation). Once you’ve got your eye in with those images, it’s easy to see the facet in the lateral-view photo, despite the less than ideal saturated lighting: it’s shaped like a raindrop falling towards bottom left. (Well, not really: raindrops are actually vertically flattened spheroids rather then raindrop-shaped, but that’s not the point.)
Observations and interpretations on this oddity will be very welcome.
Finally, here is your regularly scheduled sauropod vertebra:
Brachiosauridae incertae sedis NHM R5937 "The Archbishop", cervical S. Top to bottom: left lateral; dorsal with anterior to right; posterior, right lateral and anterior. Images copyright the NHM since it's their specimen.
Another mystery: embossed laminae and “unfossae”
December 7, 2009
Broadly speaking, pneumatic sauropod vertebrae come in two flavors. In more primitive, camerate vertebrae, modeled here by Haplocanthosaurus, the centrum is a round-ended I-beam and the neural arch is composed of intersecting flat plates of bone called laminae (lam above; fos = fossa, nc = neural canal, ncs = neurocentral suture; Ye Olde Tyme vert pic from Hatcher 1903).
In more derived, camellate vertebrae, the centrum and neural arch are both honeycombed with many small air spaces. This inflated-looking morphology is very similar to that seen in birds, like the turkey we recently discussed. The fossae and foramina on the outside tend to be smaller and more numerous than in camerate vertebrae, as shown here in a titanosauriform axis from India (Figure 3 from Wilson and Mohabey 2006). The green arrows show that the fossae visible on the external surface are excavations or depressions into the honeycombed internal structure of the bone.
External fossae on bones can house many different soft tissues, including muscles, pads of fat or cartilage, and pneumatic diverticula (O’Connor 2006). Pneumatic fossae are often strongly lipped and internally subdivided and may contain pneumatic foramina, which makes them easier to diagnose (but they may also be simple, smooth, and “blind”, which makes them harder to diagnose as pneumatic). But in all of these cases we are usually talking about the same thing: a visible excavation into a corpus of bony tissue, which may have marrow spaces inside if it is apneumatic, or air spaces inside if it is pneumatic (the corpus of bone, not the dent). That’s probably how most of us think about fossae, and it would hardly need to be explained…except that sometimes, something much weirder happens.
Consider this cervical of Brachiosaurus (this is BYU 12866, from Dry Mesa, Colorado). Brachiosaurus and Giraffatitan have an in-between form of vertebral architecture that my colleagues and I have called semicamellate (Wedel et al. 2000); the centrum does have large simple chambers (camerae), but smaller, thin-walled camellae are also variably present, especially along the midline of the vertebra and in the ends of the centrum. As in Haplocanthosaurus, the neural arch is composed of intersecting plates of bone; unlike Haplocanthosaurus, these laminae are not flat or smooth but are instead highly sculpted with lots of small fossae. Janensch (1950) called these “Aussenkaverne”, or accessory outside cavities, because and they are smaller and more variable than the large fossae and foramina that invade the centrum.
And that’s the weird thing. As the red arrows in the above image show, the “Aussenkaverne” are not excavations or depressions into anything, except the space on the other side of the lamina (which in life would have been occupied by another diverticulum). The neural arches of Brachiosaurus and Giraffatitan are not excavated by fossae, they’re embossed, like corporate business cards and fancy napkins.
What’s up with that!? We tend to think of pneumaticity as reducing the mass of the affected elements, but the shortest distance between two vertebral landmarks is a smooth lamina. These embossed laminae actually require slightly more bony material than smooth ones would.
As you can see above, the outer edges of the laminae are thick but the bone everywhere else is very thin. Maybe, like the median septa in pneumatic sauropod vertebrae, the thin bone everywhere except the edges of the laminae was just not loaded very much or very often, and was therefore free to get pushed around by the diverticula on either side, in the sense of being continually and quasi-randomly remodeled into shapes that don’t strike us as being very mechanically efficient. But also like the median septa, the thin parts of the laminae are only rarely perforated (but it does happen), for possible (read: arm-wavy) reasons discussed in the recent FEA post. And maybe the amount of extra bone involved in making embossed laminae versus smooth ones was negligible even by the very light standards of sauropod vertebrae.
Another question: since these thin sheets of bone were sandwiched in between two sets of diverticula, why are the “unfossae” always embossed into them, in the medial or inferior direction? Why don’t any of them pop out laterally or dorsally, looking like domes or bubbles instead of holes, like Mount Fist-of-God from Larry Niven’s Ringworld? Did the developmental program get accustomed to making fossae that went down and into a corpus of bone, and just kept on with business as usual even when there was no corpus of bone to excavate into? I’m only half joking.
I don’t have good answers for any of these questions. I scanned this vert a decade ago and I only noticed how weird the “unfossae” were a few months ago. I’m putting all this here because “Hey, look at this weird thing that I can only wave my arms about” is not a great basis for a peer-reviewed paper, and because I’d like your thoughts on what might be going on.
In Other News
The Discovery Channel’s Clash of the Dinosaurs premiered last night. I would have given you a heads up, except that I didn’t get one myself. I only discovered it was on because of a Facebook posting (thanks, folks!).
COTD is intended to be the replacement, a decade on, for Walking With Dinosaurs. I’m happy to report that one of the featured critters is Sauroposeidon. I grabbed a couple of frames from the clips posted here.
I haven’t seen the series yet, because I don’t have cable. But I’m hoping to catch it at a friend’s place next Sunday night, Dec. 13, when the entire series will be shown again. With any luck, I’ll have more news next week.
Finally, I got to do an interview at Paw-Talk, a forum for all things animal. I’m very happy with how it turned out, so thanks to Ava for making it happen. While you’re over there, have a look around, there’s plenty of good stuff. Brian Switek, whom you hopefully know from this and this, is a contributor; check out his latest here.
References
- Hatcher, J.B. 1903. Osteology of Haplocanthosaurus, with a description of a new species, and remarks on the probable habits of the Sauropoda, and the age and origin of Atlantosaurus beds. Memoirs of the Carnegie Museum 2:1–72.
- Janensch, W. 1950. Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica (Suppl. 7) 3:27-93.
- O’Connor, P.M. 2006. Postcranial pneumaticity: an evaluation of soft-tissue influences on the postcranial skeleton and the reconstruction of pulmonary anatomy in archosaurs. Journal of Morphology 267:1199-1226.
- Wedel, Mathew J., Richard L. Cifelli and R. Kent Sanders. 2000. Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon. Acta Palaeontologica Polonica 45(4): 343-388.
- Wilson, J. A. and Mohabey, D. M. 2006. A titanosauriform axis from the Lameta Formation (Upper Cretaceous: Maastrichtian) of central India. Journal of Vertebrate Paleontology 26:471–479.
Finite Element Analysis of sauropod vertebrae
October 27, 2009
Figure 3 from Schwarz-Wings et al. 2009. A is Diplodocus, B-D are Giraffatitan.
Earlier this month Daniela Schwarz-Wings and colleagues published the first finite element analysis (FEA) of sauropod vertebrae (Schwarz-Wings et al. 2009). Above is one of the figures showing some of their results. Following standard convention, stresses are shown on a gradient with cooler colors indicating lower stresses and hotter colors indicating higher stresses. I’m not going to dwell on the on the nuts-n-bolts of FEA in general or of this study in particular. Instead, I want to talk about how sauropod vertebrae are built.
CT cross sections of BYU 12866, a mid-cervical of Brachiosaurus sp.
In cross-section, sauropod vertebrae often have thick bone at the outer edges of the laminae and in the walls and especially the floor of the centrum, as shown in this Brachiosaurus cervical. The bone everywhere else is pretty thin. If you hit one of these vertebrae with some magical forumula that would dissolve away all the bone thinner than, say, 1 cm, all that would be left would be the various apophyses, the outer margins of the laminae connecting them, and probably the bottom half of the centrum. It would be like the outline of a vertebra constructed from tent poles, or tinkertoys.
This is weird because most pneumatic sauropod vertebrae have at least something approaching an I-beam shape in cross-section. You might think that the median septum would be mechanically important, but it’s usually very thin, sometimes perforated (see Hatcher’s [1901] Diplodocus cervicals, for example), and often asymmetrically deviated to one side or the other. Not what you would expect for a piece of bone that was doing any work.
And indeed, Schwarz-Wings et al. (2009) found that:
Comparative stresses are distributed evenly around the vertebrae and mainly on the bone cortex. Peak stresses occur only at points where the tendons and muscles are inserting because the insertion areas used were small resulting in extreme localized stresses. The interior of both vertebrae is nearly stress free. Almost no stresses occur around the cavities and in their bony walls (figure 3).
This reminds me not of I-beams but of the long bones of the limbs of terrestrial vertebrates. There’s a reason why you’ve got a big honkin’ marrow cavity running through the middle of your femur: the stresses are being borne by the walls of the bone. It makes sense that vertebrae would function similarly, especially sauropod cervicals which sometimes approximate limb bones in their proportions.
So how about that median septum? Why aren’t sauropod vertebrae just hollow tubes? My guess–and it is a guess–is that they got as close to being hollow tubes as their evolutionary and developmental origins allowed. The pneumatic diverticula invaded the centra from either side and pushed in lateral-to-medial, and I think the median septum is just the wimpy little bit of bone left in between the two sets of diverticula when they almost meet up in the middle.
Even if that’s correct, there’s another mystery: why don’t the diverticula just go ahead and erode away the median septum? I can think of two possible reasons. One is that, for reasons I don’t know and I’m not sure if anyone else does either, pneumatic diverticula are good at getting into bones but pretty lousy at getting back out. There are comparatively few cases of diverticula inside bones making foramina to get out into the surrounding tissue. It does happen–in humans, the mastoid air cells sometimes bust out and make subcutaneous pneumatocoels, basically bubbles of air under the skin (Anorbe et al. 2000)–but it seems to be rare. Maybe median septa fall under the same inscrutable rule.
(Incidentally, this makes the perforate laminae in Giraffatitan all the weirder.)
Another, more mundane possibility is that the median septa (and other oddly thin bits of bone) are not never loaded, just infrequently loaded. Not enough to make them straight, thick, or normal-lookin’, but enough to make sure they don’t get resorbed entirely.
Sauropod vertebrae are just loaded with these growth-and-form-related mysteries. Kudos to Schwarz-Wings et al. for pushing us a little farther down the road toward solving them.
References
- Anorbe, E., Aisa, P. and Saenz de Ormijana, J. 2000. Spontaneous pneumatocele and pneumocephalus associated with mastoid hyperpneumatization. European Journal of Radiology 36:158–160. [abstract only for free]
- Hatcher, J.B. 1901. Diplodocus (Marsh): its osteology, taxonomy and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1: 1-63 and plates I-XIII.
- Schwarz-Wings, D., Meyer, C.A., Frey, E., Manz-Steiner, H.-R., and Schumacher, R. 2009. Mechanical implications of pneumatic neck vertebrae in sauropod dinosaurs. Proceedings of the Royal Society B. doi: 10.1098/rspb.2009.1275
What a 23% longer torso looks like
September 20, 2009
Just checking: no-one’s bored of brachiosaurs yet, are they?
Thought not. Right, then, here we go!
Greg Paul’s (1988) study of the two “Brachiosaurus” species — the paper that proposed the subgenus Giraffatitan for the African species — noted that the trunk is proportionally longer in Brachiosaurus than in Giraffatitan due to the greater length of its dorsal centra. Paul (p. 7) stated that the difference is “25%-30%” on the basis of his figure 2.
Having seen the dorsal vertebrae of the type specimens of both species, my gut reaction was that the difference was nowhere near this great, so I recalculated it for myself (Taylor 2009:table 3). Dorsal column length is the sum of the “functional length” of the centra of the dorsal vertebrae, where functional length is the length of the centrum not counting the condyle (which of course is nestled in the preceding vertebra’s cotyle when the column is articulated). For Brachiosaurus, Riggs (1904) did not give this measurement, but did give total heights, and using these for scale I was able to measure the functional lengths from his plate LXXII. For Giraffatitan, Janensch’s (1950:44) superbly comprehensive table supplied measurements for D4 and D8; for D11 and D12 I was able to determine the length by measuring from Janensch’s (1950:fig. 62) figure, knowing the height from his table; and for D5-D7, D9 and D10, I interpolated linearly between the measurements that I had. Summing the functional lengths of D6-D12, I got 226 cm for Brachiosaurus and 183 cm for Giraffatitan. So Brachiosaurus is 226/183 = 1.23 times as long as Giraffatitan — in other words, 23% longer, which is pretty much what Greg Paul said. So I learned something there.
(Yes, brachiosaurs probably had 12 dorsals.)
So: is a 23% longer torso a big deal? Back when I was trying to answer that question for myself, I figured it would help to take an image of a familiar animal and stretch it — so here is a horse, stolen from here and stretched:
Horse (top); and evil mutant horse with 23% longer torso (bottom).
To me, that second picture is wrong enough to hurt my eyes a little; your mileage may vary, but I suspect those among you who love horses will feel ill when you look at it. This image was one of the reasons — one of many — that I concluded that generic separation was unavoidable.
But here’s an odd thing: tonight, for this blog post, I did the same thing to a human body, expecting it to seem even more horrible in light of how familiar we are with our own bodies. Here it is:
Flayed Homo sapiens in orthograde anatomical position, from Vesalius (1543) "Tertia Musculorum Tabula". Modified from Wilson (2006:fig. 1). Left, as drawn; right, with torso elongated by 23%.
To my surprise, the elongated human doesn’t look appallingly wrong to me. It doesn’t look right, of course, but it seems within the realms of, for example, what might appear as a representation of a human body in the early issues of Fantastic Four. I am not sure what to make of that fact. I don’t believe I have a more finely tuned sense of horse anatomy than human anatomy: it might be that I am more used to badly drawn humans than badly drawn horses; or that there is more variation in human proportions than in horse proportions; or maybe weirdness just looks less weird when it’s upright than when it’s horizontal. I’ll be interested to hear in the comments whether the Long Horse or the Long Human looks most wrong to readers.
(By the way, I casually talk about the type specimens of both “Brachiosaurus” species: while the situation is simple in the case of Brachiosaurus altithorax, whose holotype is FMNH P25107, things are more complex in the case of Giraffatitan brancai. Janensch nominated “Skelett S” as the holotype of his new species “Brachiosaurus” brancai, but that turned out to be a chimera, composed of the two skeletons which he subsequently designated SI and SII — but Janensch never designated one of these as the type, and so far as I’ve been able to determine, neither has anyone else done so. SI is represented by cranial elements and the first seven cervicals, but that’s all; SII is a much larger animal and is represented by most of the skeleton, and has been informally treated as though it were the type specimen most of the while, so I formally proposed HMN SII as the lectotype of the species (Taylor 2009:788) — just a bit of housekeeping.)
Here’s our old friend, the 8th cervical vertebra of HMN II, in a rare posterodorsal aspect, showing just how thin and, well, lamina-like the spinopostzygapophyseal laminae are. All that space in between them? Filled with diverticula, mostly. Amazing.
Giraffatitan brancai lectotype HMN SII, 8th cervical vertebra, in posterodorsal view
Meanwhile some good news:
Remember the good news and bad news about the all-dinosaurs special volume of The Anatomical Record? Well, since we posted that, the entire issue has been made open access! Fantastic stuff there: details from D. Schachne of the Wiley-Blackwell Communications Team. It’s not clear why the articles were all paywalled when originally posted, but all’s well that ends well.
And finally …
There’s been a gratifying amount of discussion in the comments on recent articles. It can be hard to keep track of, but it helped a lot when I found an RSS feed for comments, which is what I now use. For anyone else who wants it, it’s at http://svpow.wordpress.com/comments/feed/
References
-
Janensch, Werner. 1950. Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica (Suppl. 7) 3: 27-93.Paul, Gregory S. 1988. The brachiosaur giants of the Morrison and Tendaguru with a description of a new subgenus, Giraffatitan, and a comparison of the world’s largest dinosaurs. Hunteria 2 (3): 1-14.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 Vertebrate Paleontology 29(3):787-806.Vesalius, A. 1543. Andreae Vesalii Bruxellensis, Scholae medicorum Patauinae professoris, de Humani corporis fabrica Libri septem [facsimile]. Ex Officina Ioannis Oporini, Basel, 659 pp.Wilson, Jeffrey A. 2006. Anatomical nomenclature of fossil vertebrates: standardized terms or “lingua franca”? Journal of Vertebrate Paleontology 26(3): 511-518.
- Janensch, Werner. 1950. Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica (Suppl. 7) 3: 27-93.
- Paul, Gregory S. 1988. The brachiosaur giants of the Morrison and Tendaguru with a description of a new subgenus, Giraffatitan, and a comparison of the world’s largest dinosaurs. Hunteria 2 (3): 1-14.
- 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 Vertebrate Paleontology 29(3):787-806.
- Vesalius, A. 1543. Andreae Vesalii Bruxellensis, Scholae medicorum Patauinae professoris, de Humani corporis fabrica Libri septem [facsimile]. Ex Officina Ioannis Oporini, Basel, 659 pp.
- Wilson, Jeffrey A. 2006. Anatomical nomenclature of fossil vertebrates: standardized terms or “lingua franca”? Journal of Vertebrate Paleontology 26(3): 511-518.
To B.b. or not to B.b — or — So what is a “genus” anyway?
September 12, 2009
Introduction
Back when the Xenoposeidon paper came out, we suggested that Xeno could be the first repesentative of a new sauropod “family”, and then discussed at some length: what is a “family” anyway? Now that the Brachiosaurus paper is out, and I’ve argued that the species “Brachiosaurus” brancai is generically distinct from Brachiosaurus altithorax, it’s time to talk about what a genus is (and so what “generically distinct” means).
In an unnecessarily snarky aside at the end of the last entry, I implied that Randy Irmis would be the one to say that, because my phylogeny recovered “Brachiosaurus” brancai as the sister taxon to Brachiosaurus altithorax, it could and should remain in the genus Brachiosaurus, irrespective of the morphological differences between the genera. He didn’t quite do that — although Daniel Madzia very nearly did — but Jaime Headden certainly did over on the Dinosaur Mailing List, and even ended up asking: “So my question is this: Why do we need Giraffatitan, and cannot have a Brachiosaurus proteles etc.?”
There are plenty of possible responses to this, but before we plough into that, here is a pretty picture:
Ligament rugosities on the neural spines of Brachiosaurus dorsals
Brachiosaurus altithorax holotype FMNH P25107, presacral vertebrae 5-7, neural spines in right posterolateral view
The more retentive among you SV-POW! veterans might remember way back in the very first month of this blog when I showed you what I said were the last four presacral vertebrae of the Brachiosaurus altithorax holotype FMNH P25107. Actually, I don’t know what I was thinking — they were presacrals 4-7, not 1-4, but that’s not the point. The point is that Mike From Ottawa (whatever happened to him?) asked about the very rugose anterior surfaces of the neural spines, and I replied:
What the photo doesn’t show (but if you stay tuned long enough you’ll probably see one that does) is that the posterior faces of the neural spines have very similar rugosities. In life, these would have been the anchor points for epaxial muscles and ligaments. In Brachiosaurus altithorax (but not B. brancai) these have a distinctive inverted-triangle shape. In the most posterior pair of B. brancai dorsals, which are co-ossified, the ligament joining their neural spines is itself ossified. Picture to follow some time, I guess :-)
I am finally following up on the first half of that promise: the picture above shows the three most anterior of those same four presacral vertebrae from the Brachiosaurus altithorax holotype, but this time in right posterolateral view, so you can see the posterior faces of the neural spines. And you’ll notice that on the back of each spine, as well as on the front, there’s a large and extremely rough inverted triangle. I’ve yet to see anything at all like that in any other sauropod — Giraffatitan and the Archbishop included. Very distinctive.
Right then — back to genera!
Rampant genera on the loose!
Here’s a practical reason to reject the idea that if two taxa are sisters, then they should be regarded as congeneric: Jaime wants to retain the species brancai within Brachiosaurus because it is (in the current analysis) the sister to the type species Brachiosaurus altithorax. He then wants to put the species proteles into Brachiosaurus because the species we all know as Sauroposeidon proteles is (presumably) the sister to the Brachiosaurus-altithorax-and-brancai clade. But by induction, if we accept Jaime’s policy, whatever is sister to that clade must also be subsumed into Brachiosaurus, so that we end up losing Titanosauria, Camarasauridae, Diplodocoidea, etc. — Diplodocus carnegii becomes a species of Brachiosaurus. The good side of this scheme is that eventually, we’ll work our way up to the base of Amniota, at which point I become a member of the species Brachiosaurus sapiens. That, I could get on board with. But in other respects, this classification would not be so hot.
I’m assuming that no-one really wants this, and so that advocates of the Sister-Taxa-Are-Congeneric school (hereafter STAC) recognise that you have to draw a line somewhere. But where? And how do you choose where? [Only time will tell whether I just coined an AHATWNUABPANTA.]
How to choose between specific and generic separation
At this point, I am reminded of when I used to be on a mailing list for wannabe writers. Lots of dogma on that list — people saying “don’t overdo adverbs” and “make sure you have enough incidental detail” and so. People trying to nail down an algorithm for good writing. But the best advice I saw on that list was from Jane MacDonald: ”My personal advice is don’t overdo, or underdo, anything in your writing. Do it exactly right.”(*) That’s my attitude to drawing genus boundaries. It is, frankly, an art; and there are no substitutes for taste, experience, judgement, familiarity with the group in question and all those other touchy-feely qualities that uber-cladists would love to find a way to abolish if they could. But they can’t. There is no algorithm for this. I also think of an observation by computer scientist Bjarne Stroustrup, the inventor of the C++ programming language: “Design and programming are human activities; forget that and all is lost.” The same is true of palaeontology. (And of, well, everything.)
Here’s the thing, folks: a genus, just like any other taxon, is there to be useful. Its purpose is not to conform to a dogma, but to inform and enlighten. In the new paper, I wrote that “generic separation is warranted since the two species are more different from each other than, for example, Diplodocus and Barosaurus Marsh, 1890″ (Taylor 2009:798). I stand by that as a great way to figure out when the morphological differences between two species merit generic separation: it’s all about conveying degrees of difference. And, yes, of course I know that the morphological extent of a genus in sauropods is completely different from its extent in, say, botany, where the genus Quercus (oaks) has 700 species or something stupid. Yes, I fully accept that there is no rigorous and absolute standard by which we can determine The Right Place to drop a genus boundary. Sure. But that doesn’t let us out from the responsibility of making the best judgements that we can, based on relevant prior art, recognised conventions, congruence with similar decisions and — there it is again — good taste.
(*) Actually, that is only the second best advice I saw on the wannabe writers’ mailing list. The best advice of all came second-hand, and was passed on by Greg Gunther: “I was on an [email] list with Tom Clancy once. Mr. Clancy’s contribution to the list was, ‘Write the damn book’.” Top advice.
Nomenclatural stability
And so finally I come to Randy’s comment. In response to his question, I guessed that when I put them all in a matrix together, the Archbishop will form a clade with Brachiosaurus, and Sauroposeidon with Giraffatitan. Like this: ((Brachiosaurus altithorax, “The Archbishop”), (Giraffatitan brancai, Sauroposeidon proteles)).
And Randy said:
For the sake of discussion, if the topology is as you say, then I do support the generic separation of altithorax and brancai. Now, of course, as you might surmise, if the two sub-clades are well-supported, I would also advocate putting altithorax and the NHM Tendaguru taxon in the same genus, and brancai and Sauroposeidon in the same genus.
Now I yield to no man in my respect for Randy, whose work exceeds my own humble output by a truly humiliating factor, and who makes it even worse by being such a nice guy. But I hope he will not take it the wrong way if I say that here, he is talking the purest arsegravy. Suppose the topology came out the way I guessed, and we adopted his suggested nomenclature. Then five minutes later Paul Upchurch comes along with a new analysis that finds the Archbishop closer to Giraffatitan after all: and suddenly Brachiosaurus archbishopus becomes Giraffatitan archbishopus. Five more minutes pass and Jeff Wilson publishes his new phylogeny, in which “Sauroposeidon” proteles is sister to Brachiosaurus altithorax, and so what was briefly Giraffatitan proteles becomes Brachiosaurus proteles. Later that afternoon Jerry Harris shows that Cedarosaurus is more closely related to Brachiosaurus altithorax than the species proteles is: at this point, presumably, either Cedarosaurus gets sunk into Brachiosaurus, as B. weiskopfae, or My Big Fat Brachiosaurus Genus gets smashed up and suddenly, woah, proteles needs its own genus after all and Sauroposeidon is back!
Hands up who wants to deal with tracking all that nomenclatural shifting back and forth? Hmm, thought not. Folks, when we name a new species of an existing genus we are betting the nomenclature on the phylogenetic hypothesis. This is just a dumb thing to do in this day and age — especially if you work on dinosaurs which (A) are big and usually very incomplete and so their positions can’t be known with certainty; (B) are trendy enough to be subject to a stream of new phylogenetic analyses; and (C) are in a field where pretty much everyone seems to be hot for mandatory monophyly of genera.
So I end with a plea: unless you know for certain that your new taxon is super-closely related to the type species of an existing genus, and unless you are sure that this isn’t going to change with subsequent discoveries, please put your new species in its own monospecific genus. That way, nomenclature is independent from phylogeny, which is surely how we all want it. A new monospecific genus is essentially a uninomial that happens to be spelled with a space in the middle. And uninomials are nice: they rescue us from Linnaeus’s dumb mistake in lumbering nomenclature with binomials.
This has been an Unwelcome Education Product.
Acknowledgements
Many thanks to Jim Farlow for suggesting the title of this post, which I have cheerfully stolen. I have no idea whether he agrees with the arguments presented in this article.
References
“Brachiosaurus” brancai is not Brachiosaurus
September 9, 2009
Today sees the publication of the new Journal of Vertebrate Paleontology, and with it my paper on the two best-known brachiosaurs and why they’re not congeneric (Taylor 2009). This of course is why I have been coyly referring to “Brachiosaurus” brancai in the last few months … I couldn’t bear to make the leap straight to saying Giraffatitan, a name that is going to take me a while to get used to.
But before we go lunging into the details, here is my skeletal reconstruction of Brachiosaurus proper, taken from the paper:
Skeletal reconstruction of Brachiosaurus altithorax, with Homo sapiens and Canis familiaris for scale, from Taylor (2009:fig. 7). White bones represent the elements of the holotype FMNH P 25107. Light grey bones represent material referred to B. altithorax: the Felch Quarry skull USNM 5730, the cervical vertebrae BYU 12866 (C?5) and BYU 12867 (C?10), the “Ultrasauros” scapulocoracoid BYU 9462, the Potter Creek left humerus USNM 21903, left radius and right metacarpal III BYU 4744, and the left metacarpal II OMNH 01138. Dark grey bones modified from Paul’s (1988) reconstruction of Giraffatitan brancai. Scale bar equals 2 m.
Those of you familiar with Greg Paul’s classic reconstruction of Giraffatitan brancai will immediately recognise that Real Brachiosaurus is rather differently proportioned, especially in having a longer torso and tail.
This paper has been in the works for some time, and while it was in review and then in press at JVP, it led a double life as Chapter 2 of my dissertation. (For most of its gestation period, the paper’s title was just “Brachiosaurus brancai is not Brachiosaurus“, and the folder where I keep all the project files is still called “bb-is-not-b”). In the end, I chickened out and went for a longer, more formal, title.
So why are the two species not congeneric? Well, it’s a long story, and you can read about the detail in the paper, but the bottom line is that virtually every bone that is known from both species differs in significant respects between them.
Of course, I am not the first to suggest that the African brachiosaurid that we know and love isn’t exactly Brachiosaurus. Credit for that goes to Greg Paul, who more than twenty years ago executed a then-new skeletal reconstruction of that species (the very same reconstruction that is now considered the classic), and in doing so noticed some differences between the American type species Brachiosaurus altithorax and the African referred species “Brachiosaurus” brancai (Paul 1988). Paul hedged his bets, though: rather than erect a new genus for the African animal, he proposed a subgenus Brachiosaurus (Giraffatitan), so that the full name of the species would become Brachiosaurus (Giraffatitan) brancai; and that of the type species would become Brachiosaurus (Brachiosaurus) altithorax. Unsurprisingly, this cumbersome nomenclatural scheme did not catch on, and I have not been able to locate a single subsequent reference to these subgenera in the literature.
Second caudal vertebrae of Brachiosaurus altithorax and Brachiosaurus brancai, equally scaled, from Taylor (2009:fig. 3). A, B, B. altithorax holotype FMNH P 25107; C-G, B. brancai referred specimen HMN Aa. A, C, posterior; B, D, F, right lateral; E, G, anterior. A-B modified from Riggs (1904:pl. LXXV); C-E modified from Janensch (1950a:pl. 2), F-G modified from Janensch (1929:fig. 15). Scale bar equals 50 cm.
That didn’t mean the idea was dead, though: three years later, George Olshevsky’s self-published mega-revision of dinosaur taxonomy proposed raising the name Giraffatitan to genus level (Olshevsky 1991). Although this genus became popular on the Internet (it cropped up, for example, in Mike Keesey’s much-lamented Dinosauricon web-site), it was almost completely ignored in the technical literature, and even Greg Paul himself subsequently seems to have reverted to using the name Brachiosaurus brancai (e.g. Paul 1994:246).
Why was the new name overlooked? Partly, I suspect, just because it’s so butt ugly — everyone knows and loves Brachiosaurus brancai, and the name itself has a definite poetry to it that Giraffatitan sorely lacks. But mostly it’s because Paul didn’t really make a case for the separation that he proposed — wrongly stating, for example, that “the caudals, scapula, coracoid, humerus, ilium, and femur of B. altithorax and B. brancai are very similar” (Paul 1988:7).
That’s how things stood a few years back when I started to take a serious interest in Migeod’s Tendaguru brachiosaurid, which lives in the basement of the Natural History Museum in London. It quickly started to seem to me that it wasn’t the same thing as what everyone means by Brachiosaurus, but to make sense of it all, I needed first to figure out what the Brachiosaurus actually does mean. That meant visiting the type material of both species, in Chicago and Berlin, and really looking closely.
Well, I don’t want to go on all day — apart from anything, England play Croatia in a World Cup qualifier in just over an hour — so I’ll just show you some of the the differences between the dorsal vertebrae of the two species. (You’ll have seen the caudals up above — I just threw them in to break up all that text).
Dorsal vertebrae of Brachiosaurus altithorax and Brachiosaurus brancai in posterior and lateral views, equally scaled, from Taylor (2009:fig. 1). A, B, E, F, I, J, M, N, B. altithorax holotype FMNH P 25107, modified from Riggs (1904:pl. LXXII); C, D, G, H, K, L, O, P, B. brancai lectotype HMN SII, modified from Janensch (1950a:figs. 53, 54, 56, 60-62, 64) except H, photograph by author. Neural arch and spine of K sheared to correct for distortion. A, D, E, H, I, L, M, P, posterior; B, F, G, J, N, right lateral; C, K, O, left lateral reflected. A, B, dorsal 6; C, D, dorsal 4; E-H, dorsal 8; I-L, dorsal 10; M, N, P, dorsal 12; O, dorsals 11 and 12. Corresponding vertebrae from each specimen are shown together except that dorsal 4 is not known from B. altithorax so dorsal 6, the most anterior known vertebra, is instead shown next to dorsal 4 of B. brancai. Scale bar equals 50 cm.
Lots and lots of differences here — I will quote from the Systematic Paleontology section on the type species: “Postspinal lamina absent from dorsal vertebrae (character 130); distal ends of transverse processes of dorsal vertebrae transition smoothly onto dorsal surfaces of transverse processes (character 142); spinodiapophyseal and spinopostzygapophyseal laminae on middle and posterior dorsal vertebrae contact each other (character 146); posterior dorsal centra subcircular in cross-section (character 151); posterior dorsal neural spines progressively expand mediolaterally through most of their length (“petal” or “paddle” shaped) (character 155); mid-dorsals about one third longer than posterior dorsals (see Paul, 1988:7); middorsals only about 20% taller than posterior dorsals (see Paul, 1988:8); dorsal centra long (Janensch, 1950a:72) so that dorsal column is over twice humerus length (Paul, 1988:8); transverse processes of dorsal vertebrae oriented horizontally (Paul, 1988:8); dorsal neural spines oriented close to vertical in lateral view; dorsal neural spines triangular in lateral view, diminishing smoothly in anteroposterior width from wide base upwards; deep inverted triangular ligament rugosities on anterior and posterior faces of neural spines” …. *gasp*
So anyway: the upshot of all this is that “Brachiosaurus” brancai differs from Brachiosaurus altithorax more than, say, Barosaurus does from Diplodocus; and so it must be placed in its own genus … and that genus has to be Giraffatitan, because of the ICZN’s principle of priority. And THAT is why the very end of the paper — the last sentence of the Acknowledgements — reads:
Finally, I beg forgiveness from all brachiosaur lovers, that so beautiful an animal as “Brachiosaurus” brancai now has to be known by so inelegant a name as Giraffatitan.
Anyway, go and read the paper; full-resolution figures are freely available if you want to look more closely than the JVP’s PDF allows.
References
- Olshevsky, George. 1991. A Revision of the Parainfraclass Archosauria Cope, 1869, Excluding the Advanced Crocodylia. Mesozoic Meanderings #2 (1st printing): iv + 196 pp.
- Paul, Gregory S. 1988. The brachiosaur giants of the Morrison and Tendaguru with a description of a new subgenus, Giraffatitan, and a comparison of the world’s largest dinosaurs. Hunteria 2(3):1-14.
- Paul, Gregory S. 1994. Dinosaur reproduction in the fast lane: implications for size, success and extinction. pp. 244–255 in: K. Carpenter, K. F. Hirsch, and J. R. Horner (eds.), Dinosaur Eggs and Babies. Cambridge University Press, Cambridge.
- 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 Vertebrate Paleontology 29(3):787-806.
(And, yes, Randy, I know what your comment is going to say; go ahead and say it anyway, it’ll give me a chance to explain why your approach is wrong :-))
