Just when you thought it was safe to go back into the Humboldt bone-room … hot on the heels of Part 1: Spinoparapophyseal Laminae!, comes another dose of terror thanks to everyone’s favourite mid-to-posterior brachiosaurid dorsal vertebra, HMN SII:D8. First, here is a pretty picture of the whole vertebra in right lateral view:

D8 in right lateral view

And here is the same bone in the same view, as figured by Janensch (1950:fig. 56):fig. 56)

Before I start laying the laminae on you, I should say what an awesome moment it was when I first came face to face with this vertebra, having been so intimately familiar with Janensch’s figures. It was weird — like meeting Cameron Diaz or something. Seeing D4 was even stranger, because it’s so much bigger than you think from the figure — but that’s another story for another day. I promised you laminae, or, rather, the absence of one particular lamina, and that’s what you’re going to get.

Look at the neural spine. You’ll see a prominent lamina running down the side facing you, sticking out of the page. That of course is the spinodiapophyseal lamina, and it comes down and joins the horizontal lamina complex(*) at the diapophysis. But now look below the horizontal laminae, and you will see that there is nothing supporting the diapopophysis from below. Doesn’t that make you feel sort of ill? Yes, there is a sort of vertical lamina below the horizontal lamina complex, but before it reaches the diapophysis, it forks into anterior and posterior branches, which (A) reach the horizontal laminae ahead of and behind the diapophysis, and (B) extend so tiny a distance out from the vertebra that their mechanical supporting function must have been negligible.

Now what the heck is that all about?

(*) The “horizontal lamina complex” is the set of, uh, horizontal laminae that connect the prezygapopophysis, via the parapophysis and diapophysis, to the postzygapophysis. In pre-Wilson (1999) days, these three laminae were sometimes referred to individually as the horizontal laminae, in a semi-formal way, but this term has been quite rightly supplanted by Wilson’s much more explicit PRPL, PPDL and PODL. Still, the term Horizontal Lamina Complex is still useful for referring to them as a unit, in those dorsals that are sufficiently posterior for the four landmarks to be roughly in a horizontal line.

References

Same as last time.

Of all the sauropod vertebrae in the world, perhaps the single most intriguing is a dorsal vertebra of the Brachiosaurus brancai type specimen HMN SII. It was designated the 20th presacral (i.e. 7th dorsal) by Janensch (1950), but that was on the assumption that the dorsal column consisted of 11 vertebrae. Since Janensch never had any actual reason for assuming 11 dorsals, and Migeod’s (1931) Tendaguru brachiosaurid had 12 dorsals, it seems best to assume for now that brachiosaurids in general had 12 dorsals, so that the vertebra Janensch thought was D7 (i.e. the fifth-last dorsal) was more likely D8. Anyway, that’s what I’ll be calling it.

Here is that vertebra in right anterodorsolateral view — that is, from above, in front, and to the right.

Brachiosaurus brancai type specimen HMN SII, dorsal vertebra 8 in right anterodorsolateral view

It’s a bit of a close-up, so you can hardly see the centrum down there, and only the bottom half of the neural spine is included. On the positive side, you get a good view of those honking great prezygapophyses and the nice, big gap between them. You also see the neat, parallel spinoprezygapophyseal laminae (SPRLs) running up the front of the neural spine.

But I want to draw your attention to that lamina coming down towards us from the side of the SPRL. What is it? It can’t be a nice, well-behaved spinodiapophyseal lamina (SPDL), because we already have one of those over on the left-hand side, coming down from the side of the neural spine and flaring out laterally towards the diapophysis. No indeed: the lower end of the lamina I’m interested in here is actually running towards the parapophysis. OK, it’s broken off, but you can see where it would be if it was there. So this thing is a spinoparapophyseal lamina, or SPPL for short.

Well, this is weird. Wilson (1999) listed, illustrated and discussed nineteen different vertebral laminae, but there is no hint of an SPPL anywhere in that paper. So far as I’m aware, this feature is unique to this one vertebra. So is it just a one-off freak? I don’t think so, because on the other side of the neural spine, you see its mate, the left SPPL, heading off towards its parapophysis. But then why don’t we see this on any of the other dorsals of the same specimen? Well, it might have been there in life. The truth is that the B. brancai dorsals are rather more smushed up than you’d gather from the rather lovely drawings in Janensch (1950) — remind me some time to show you my photos of the co-ossified D11/D12 pair — and the relevant portion is only really preserved in D8. It’s possible that it was SPPLs all along the dorsal sequence.

Stay tuned for more hot news about how weird HMN SII:D8 is!

References

Update

To help you get your bearings, here is a photo that I should have included in the original post: the same vertebra from nearly the same angle, but taken from further out so that you can see the whole thing. The big photo was taken from a little higher up, looking slightly down on the vert.

First, some horn-tooting. A few years ago I realized that I good lateral-view photos of lots of big stuff–a blue whale skeleton, a Brachiosaurus skeleton, a big bull elephant, myself–and I put together a composite picture that showed everything together and correctly scaled. Various iterations of the project, which I undertook solely for my own amusement, are here, here, and here. Here’s the final product:

From left to right by skull position those are:

  • the mounted skeleton of Balaenoptera musculus at the Long Marine Lab in Santa Cruz, California;
  • the mounted six-ton (not ten-ton; see the comments from June 3 and 4, below) bull Loxodonta africana from the Field Museum in Chicago, Illinois;
  • the mounted skeleton of Brachiosaurus altithorax from the same museum;
  • yours truly;
  • and Mike Taylor.

Everything is scaled correctly, and none of the critters in the picture represent the maximum size attained by their species (although I come pretty close). The whale is, at 87 feet, about 80% of the size of the largest known individuals. The Brachiosaurus skeleton is about 85% of the size of the largest known specimens in the genus, and the elephant is 77% of the size of the world record (these are all in linear terms).

I often blog like I’m in a vacuum but somehow people do find out about this stuff, and the good folks at the University of British Columbia’s Beaty Biodiversity Museum asked if they could use the photo on their blue whale page. Naturally I agreed.

Then last week I was contacted by them again. The museum’s blue whale project was to be featured on the evening news and they wanted to use the photo in the story. I’m never one to turn down free publicity in the interests of science. Here’s the clip (after a brief ad).

Since it comes up frequently (for me, at least), and since we’re talking about blue whales anyway, I’ll tackle the age-old question about which is bigger, a blue whale or the largest dinosaur.

In this corner, the defending champion: Balaenoptera musculus

Everyone “knows” that blue whales are 100 feet long and weigh 100 tons, right?

Wrong. According to Wood (1982, p. 7), “The largest accurately measured blue whale on record (length taken in a straight line parallel to the body axis from the tip of the upper jaw to the notch in the tail flukes) was a female…which measured 107 Norwegian fot (= 110 ft 2 1/2 in 33.59m).” Wood also lists numerous other confirmed records of blue whales over 100 feet long. Apparently they were not that uncommon in the Antarctic before the intensive whaling of the early 20th century.

The common perception of the 100ft/100 ton whale is even farther off when it comes to maximum weight. Weighing big whales is a pain in the ass. The biggest whale that has ever been weighed intact was a 59 ft (18m) sperm whale that was picked up by three floating cranes and weighed at 58 tons (53 metric tons; all of these data are from Wood 1982). Much larger sperm whales are known; the largest possibly being 84 ft (25.6m) long and weighing perhaps 88 tons (80 metric tons). All whales larger than that 58-ton sperm whale have had to be weighed piecemeal, by chopping them up and weighing the bits. Inevitably lots of blood and fluid are lost this way, so the piecemeal weight is usually about 6% less than the true body weight.

Nevertheless, there are lots of records of big blues weighing more than 150 tons, and the heaviest one on record is a pregnant female that weighed a jaw-dropping 209 tons (190 metric tons), more than twice the commonly quoted maximum size for this animal. Surely, surely, one thinks, that is the ne plus ultra of vertebrate mass.

Not so. Wood (1982, p. 9) describes a ‘very fat’ female, 91 ft (27.7m) long, which “yielded a record 305 barrels of oil weighing 51.85 tonnes [57 English or short tons]. Unfortunately this enormous whale was not weighed piecemeal, but on the basis of its oil yield it must have scaled at least 200 tonnes [220 short tons; emphasis in the original]!

And in this corner, the contenders: sauropods!

The longest sauropod known from decent remains is Supersaurus, for which Lovelace et al. (2007) estimate a total length of 33-34 meters (108-111 ft) for Jimbo, the new specimen from Wyoming. The Dry Mesa specimen is apparently slightly larger. Seismosaurus has now been sunk into Diplodocus, and was apparently no more than 30m (98 ft) long, enthusiastic estimates to the contrary notwithstanding (see Lovelace et al. 2007 for details, and also check out Scott Hartman’s site for lots of good info and cool skeletal reconstructions). Because it was so slender, Supersaurus weighed less than you might think; Lovelace et al. estimate Jimbo’s mass at 35-40 tons.

The most massive sauropod for which a reasonably secure mass estimate is possible is Argentinosaurus, which Mazzetta et al. (2004) estimated to have weighed 80.5 tons (73 metric tons). Old estimates of up to 80 tons for Brachiosaurus are based on models that can most charitably be described as just horribly, stupidly fat; all of the recent sane estimates put the better-known big specimens of Brachiosaurus between about 30 and 45 tons, with the very largest known specimens possibly getting up to 50 or 60 tons. Irritatingly, during the 1980s a bunch of mass estimates for “Ultrasauros” came out that were based on the ridiculous 80-ton estimate for Brachiosaurus, and put the mass of “Ultrasauros” at 180 tons. As we shall see, there is no good evidence that any sauropod ever got within 40 tons of that mark.

Then there are the semi-apocryphal gigapods, Bruhathkayosaurus and Amphicoelias fragillimus. Bruhathkayosaurus is reported to have a 2-meter-long tibia, which would make it perhaps 20% larger than Argentinosaurus in linear terms, and 70% more massive (mass scales with the cube of the linear dimension, and 1.2 x 1.2 x 1.2 = 1.728). Assuming that the proposed tib is really a tib and not an eroded femur or something, and that Bruhathkayosaurus was built like the very robust Argentinosaurus and not like, say, the very slender Brachiosaurus, and that the mass estimate for Argentinosaurus is accurate, Bruhathkayosaurus may have weighed as much as 139 tons (126 metric tons).

Amphicoelias fragillimus appears to have been built like a big Diplodocus–well, okay, an extremely mind-blowingly immense Diplodocus–and assuming the sole surviving drawing is legit and correctly scaled, it was just completely nuts (way more so than Apatosaurus; see Darren’s thoughts here and here). The femur may have been anywhere from 3-4.6 meters long (Carpenter 2006), and was more likely in the upper part of that range. In the big mounted skeletons of Diplodocus, the femora are just a little over 1.5 meters long. So Amphicoelias may have been 2-3 times the size of Diplodocus in linear terms. Carpenter (2006) posited a length of 190ft (58m) and a weight of 135 tons (122.4 metric tons).

Interlude: world record animals

The biggest known whales really are probably close to being the biggest representatives of their species. The individuals listed above are the largest known from a sample of more than 300,000 blue whales killed in the early 20th century. That’s a big pool. Supersaurus and Argentinosaurus are both known from two specimens, and Bruhathkayosaurus and A. fragillimus from one specimen each. The chances that these largest-known sauropods are really the largest sauropods that ever lived is vanishingly small.

And the winner is…

For mass, no question, the blue whale. Even our most liberal estimates of the most poorly known gigapods don’t come close to the 200-ton mark, which blue whales are known to exceed.

For length, probably a sauropod. A huge sample of blue whales included none longer than 110 feet, while our comparatively pathetic sample of sauropods has already turned in one animal (Supersaurus) that may have just edged that out, and another (A. fragillimus) that–assuming it was really as big as we think–blows it out of the water (so to speak).

References

In this article I’d like look at something that I’ve just spoken about at a conference: the ‘Dinosaurs – A Historical Perspective’ meeting held in London on May 6th and 7th (my thoughts on the conference can be found here and here). Mike attended too (and, like me, gave a talk), but Matt couldn’t make it. Anyway…

 

 

Today, the idea that sauropods (and non-avian theropods) were pneumatic animals is well established and universally accepted (a minority view – promoted by those who insist that birds cannot be dinosaurs – maintains that non-avian dinosaurs were not pneumatic, but I see no indication that the workers concerned know what they’re talking about). Indeed, sauropod pneumaticity has been discussed a lot here at SV-POW! But have people always regarded sauropods as pneumatic? As someone particularly interested both in pneumaticity and in the dinosaurs of the Lower Cretaceous Wealden Supergroup of southern England, the whole ‘Pneumaticity: the Early Years’ story is of special interest to me. I hope you get something out of it too…

 

Actually, the very first dinosaur (not just sauropod, but dinosaur) identified as exhibiting skeletal pneumaticity is from the Wealden, and it’s a theropod: it’s the large tetanuran Becklespinax altispinax, discovered prior to 1855 in the Hastings Beds Group of East Sussex (the Hastings Beds Group is the oldest unit in the Wealden Supergroup: for more see the Tet Zoo article here). Consisting only of three articulated posterior dorsal vertebrae, Becklespinax exhibits deep fossae on the sides of the neural arches (by now you’ll all be familiar with the names for the different vertebral laminae present in saurischians, but the fossae have names too: in Becklespinax, we’re talking about the infraprezygapophyseal fossa, the infradiapophyseal fossa, and the infrapostzygapophyseal fossa). The key thing is that, in describing these vertebrae, Richard Own (1804-1892) realised that these fossae were probably pneumatic as they are in birds, and in his 1856 article on Megalosaurus (he assumed that the Becklespinax vertebrae belonged to Megalosaurus), he wrote that ‘Three deep depressions, probably receiving parts of the lungs in the living animal, divide these lamelliform butresses from each other’ (Owen 1856, p. 5). His ‘lamelliform butresses’ are what we call laminae. This is the very first reference to pneumaticity in any Mesozoic dinosaur (Britt 1993), so Becklespinax is the first non-avian dinosaur for which pneumaticity was ever suggested.

 

The next milestone in pneumaticity came from Harry Seeley (1839-1909) in his description of the Wealden sauropod Ornithopsis hulkei (Seeley 1870). O. hulkei was named for two dorsal vertebrae: BMNH R2239 from East Sussex and BMNH R28632 from the Isle of Wight, but the former was later removed from O. hulkei (then becoming the type for Bothriospondylus elongatus), leaving BMNH R28632 alone associated with this name and as the lectotype* [the specimen is shown below, from Seeley 1870]. The strong opisthocoely, large lateral foramina and camellate internal anatomy show that BMNH R28632 is from a titanosauriform (it can’t really be identified more precisely than that and whether it’s diagnostic is arguable: see Naish & Martill 2007. For previous SV-POW! comments on the specimen go here). It’s often noted that Seeley suggested that these vertebrae belonged to an animal ‘of the Pterodactyle kind’. However, he did not think that these vertebrae belonged to a giant pterosaur (as, oops, Naish & Martill (2001) said): rather, he thought that O. hulkei represented something entirely new, the first member of a ‘new order of animals which will bridge over something of the interval between birds and Pterodactyles, and probably manifest some affinity with the Dinosaurs’ (Seeley 1870, p. 280).

 

* When a species is erected for more than one specimen, the specimens are all called syntypes. When one syntype from a series is later elected to serve as the type specimen for the species, it is called the lectotype.

 

 

 

Seeley – who has been described as ‘the most defiant’ of Victorian palaeontologists, of exhibiting ‘anarchic tendencies’, and of being considered ‘strikingly individualistic’, even in his own day (Desmond 1982) – gets a lot of flack these days, in particular for his rampant taxonomic splitting and naming of new dinosaur and pterosaur species, and also for his unusual views on how vertebrate groups were related to one another. But I often think that his conclusions on lifestyles and comments on palaeobiology are really not unreasonable in view of what we think today, and in fact often seem quite far-sighted.

 

Here’s where we come back to pneumaticity: Seeley (1870) was very impressed with the enormous lateral foramina present in O. hulkei (these were the main feature which led him to regard O. hulkei as allied to pterosaurs and birds), and he wrote: ‘Seeing that in living animals these foramina exist for the prolongation of the peculiarly avian respiratory system into the bones, and that no other function is known for them, we are compelled to infer for this animal bird-like heart and lungs and brain’ (Seeley 1870, p. 280). In describing the worn condyle of BMNH R28632, Seeley noted the presence within the bone of ‘enormous honeycomb-like cells of irregular polygonal form … divided by exceedingly thin and compact films of bone’ (Seeley 1890, p. 281). Elsewhere in the paper, he referred to the internal cavities as ‘air-cells’, and he also wrote of the Ornithopsis vertebrae (both BMNH R2239 and BMNH R28632) as ‘being constructed after the lightest and airiest plan’. He never explicitly stated it, but I infer from these statements that Seeley imagined the internal cavities of the centrum to be pneumatic: he was describing what today we call the camellae (that is, the numerous small pneumatic cavities that occupy the centrum in mamenchisaurs and titanosauriforms). So, all in all, I say well done Seeley for correcting inferring vertebral pneumaticity in O. hulkei.

 

Like most Victorian palaeontologists, Seeley did not get on particularly well with the most prolific, most respected and most politically powerful Victorian palaeontologist, Richard Owen [although it’s not really accurate to regard Owen just as a palaeontologist: sure, he did palaeontology, but his contribution to mainstream zoology and anatomy was massive and equally significant, if not more so]. In 1876, Owen described another Wealden sauropod and, like the O. hulkei lectotype (BMNH R28632), it was from the Isle of Wight’s Wessex Formation: it’s based on two cervical vertebrae (BMNH R46869 and BMNH R46870: one is shown below). Today, it is obvious that these vertebrae are from sauropods, and their enormous lateral foramina and camellate internal anatomy show that they’re from titanosauriforms (and not from camarasaurs as has been suggested in the past: see Naish & Martill 2001, 2007). However, Owen couldn’t be this confident that identified the material as ‘Dinosauria (?)’.

 

 

 

The big deal for our story is that these vertebrae have massive lateral fossae housing large lateral foramina, and again Owen correctly interpreted them as pneumatic, writing: ‘The whole of the side of the centrum is occupied by a deep oblong depression which, probably, lodged a saccular process of the lung’ (Owen 1876, p. 6). So far so good. But Owen had one of these two Wessex Formation specimens (BMNH R46870) sectioned, revealing its incredible (and beautiful) interior [it’s the image shown at the very top]. The internal anatomy of this specimen illustrates camellate texture so well that it’s almost becoming a poster-child in talks and articles on sauropod vertebrae. But while, as we just saw, Seeley had implied that camellae were pneumatic, Owen interpreted them quite differently. He wrote ‘I deem it much more probable that the large cancelli obvious at every fractured surface of this vertebra were occupied in the living reptile by unossified cartilage, or chondrine, than by air from the lungs, and consequently have no grounds for inferring that the whale-like Saurian, of which the present vertebrae equals in length the largest one of any Cetacean recent or fossil, had the power of flight, or belonged to either Pterosauria or Aves’ (Owen 1876, p. 6). To reflect the presence of ‘chondrine-filled’ spaces in the vertebrae of this animal, Owen coined for it the new name Chondrosteosaurus gigas, meaning ‘giant cartilage and bone lizard’.

 

Quite why Owen was happy with pneumatic lateral fossae, but not with pneumaticity within the body of the centrum itself, seems odd, especially when Owen was very familiar with avian anatomy (he specifically referred to the internal anatomy of avian vertebrae in, for example, his 1859 article on pterosaur vertebrae [Owen 1859]). As you can see in Tutorial 3, the internal anatomy of bird and sauropod centra are so similar that it is difficult not to conclude that what applies for one applies for the other. However, it is clear from Owen’s quote given above that, when interpreting C. gigas, he was not just doing an objective description, but also had an axe to grind: he was specifically refuting Seeley’s statements on O. hulkei, hence the rejection of the idea that C. gigas might have been capable of flight, or that it might be allied to pterosaurs or birds. For whatever reason, Owen was also making note of the fact that he disagreed with Seeley’s idea of a pneumatic vertebral interior: the name Chondrosteosaurus itself almost seems like a snub to Seeley.

 

Despite this one-upmanship, ultimately, both Seeley and Owen come out of this early phase in research pretty well, as both workers still win citations for having made key early statements on saurischian pneumaticity (e.g., Wedel 2003, O’Connor 2006). Edward Cope (1840-1897), who liked Seeley and said nice things about him, was to note during the 1870s that sauropod vertebrae were probably pneumatic, and Othniel Marsh (1831-1899) did likewise. What happened in the field of dinosaur pneumaticity after this? Well, that’s a story for another time: for the time being I will direct you to Wedel (2003).

 

References

 

  • Britt, B. 1993. Pneumatic Postcranial Bones in Dinosaurs and Other Archosaurs. Unpublished PhD thesis, University of Calgary (Alberta).
  • Desmond, A. J. 1984. Archetypes and Ancestors: Palaeontology in Victorian London 1850-1875. The University of Chicago Press, Chicago. 
  • Naish, D. & Martill, D. M. 2001. Saurischian dinosaurs 1: Sauropods. In Martill, D. M. & Naish, D. (eds) Dinosaurs of the Isle of Wight. The Palaeontological Association (London), pp. 185-241.
  • Naish, D. & Martill, D. M. 2007. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia. Journal of the Geological Society, London 164, 493-510.
  • 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.
  • Owen, R. 1856. Monograph on the fossil Reptilia of the Wealden and Purbeck Formations. Part III. Dinosauria (Megalosaurus). Palaeontographical Society Monographs 9, 1-26.
  • Owen, R. 1859. On the vertebral characters of the Order Pterosauria, as exexmplified in the genera Pterodactylus (Cuvier) and Dimorphodon (Owen). Philosophical Transactions of the Royal Society of London 149, 161-169.
  • Owen, R. 1876. Monograph on the fossil Reptilia of the Wealden and Purbeck Formations. Supplement 7. Crocodilia (Poikilopleuron). Dinosauria (Chondrosteosaurus). Palaeontographical Society Monographs 30, 1-7.
  • Seeley, H. G. 1870. On Ornithopsis, a gigantic animal of the pterodactyle kind from the Wealden. Annals and Magazine of Natural History, Series 4, 5 279-283.

Hottt news

May 15, 2008

Mike Taylor has a loooong interview up at Laelaps. It’s sauropawesome.

The picture above has nothing to do with that, we just like to put sauropod vertebrae in every post. Here are some CT sections of a Haplocanthosaurus cervical (abbreviations: fos - fossa, lam - laminae, nc - neural canal, ncs - neurocentral suture). I like them because they look nothing like what I expected. Not that the internal structure or laminae are unusual for sauropods, just that sauropod vertebrae themselves are unusual and sometimes the best way to be confronted with that is to see them from new vantages. I recycled this from Wedel (2007:fig. 13), and it basically just a rearrangement of Wedel (2005:fig. 7.3). The nice drawing of the Haplo cervical is from Hatcher (1903:pl. 2).

Well, now I’ve blabbed on for a paragraph and managed to cite myself twice in a post that is ostensibly about Mike. Seriously, go read the interview, it’s great.

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. Mem Carn Mus 2:1-72.

Wedel, M.J. 2005. Postcranial skeletal pneumaticity in sauropods and its implications for mass estimates; pp. 201-228 in Wilson, J.A., and Curry-Rogers, K. (eds.), The Sauropods: Evolution and Paleobiology. University of California Press, Berkeley.

Wedel, M.J. 2007. Aligerando a los gigantes (Lightening the giants). ¡Fundamental! 12:1-84. [in Spanish, with English translation]

Pursuant to a comment I just made on the previous post, here is cervical 8 of YPM 1980, the holotype of Brontosaurus excelsus, now of course known as Apatosaurus excelsus, in anterior and left lateral views, scanned from plate 12 of Ostrom and McIntosh 1966. Look on my cervicals, ye mighty, and despair.

You see? I wasn’t kidding. This thing is beyond crazy. The dorsoventral height of its parapophyses alone exceeds that of the centrum and neural spine together. What the heck was it doing with that thing? Seriously.  It makes no mechanical sense whatsoever.  To the best of my knowledge no-one has ever even advanced a hypothesis about those honkin’ great cervical ribs … and I am not about to break that streak.

Just enjoy.

Reference

  • Ostrom, John H., and John S. McIntosh.  1966.  Marsh’s Dinosaurs.  Yale University Press, New Haven and London.  388 pages including 65 absurdly beautiful plates.

Long-time SV-POW! readers will have detected a brachiosaurid bias in our writings, and this is for a good reason: it is because brachiosaurids are best. They just are. But there are a few diplodocids that really get our juices flowing — not just Amphicoelias fragillimus (which we would post on, except that Darren did such a good job on it a while back on Tet Zoo [part 1, part 2]) but also the enigmatic Supersaurus. Until very very recently, this genus was known just from a single specimen, recovered by “Dino” Jim Jensen, and formally described by him in 1985, twelve long years after the name first appeared in print, in that well-known international journal Reader’s Digest. (No, I am not kidding.)

I don’t want to say too much about Jensen’s specimen right now, because I plan to cover it in more detail soon, but I do need to say that Jensen suffered from two debilitating conditions. The first was a congenital inability to see a scapulocoracoid without lying down in the dirt next to it for a photographer. Exhibit A is Jensen (1985:fig 4A), which also appears as Jensen (1987:fig 6A):

And Exhibit B is figure 6B from the very same paper:

fig 6b -- Jensen lying next to another big scapulocoracoid

(“What is this?”, I hear you cry. “Sauropod Scapulocoracoid Picture of The Week?” Sorry for the appendicularity, we’ll be getting you back to your regularly scheduled programme of vertebrae RSN, but the plain fact is that vertebrae are just not as good for lying down next to as scaps and humeri — though heaven knows we’ve done our best.)

Jensen’s second handicap was a tendency to figure fossils the way he thought they ought to be rather than how they actually were. For example, Jensen (1985:fig 2A) shows the very same Supersaurus cervical that Matt covered last week. Jensen’s version is influenced, we might charitably conclude, by a certain amount of imagination:

The taxonomic history of the various Supersaurus elements in Jensen’s specimen is baroque and Byzantine even by the standards of sauropod taxonomy, and I won’t go into it just now (again, stay tuned), but the result of all the to-ing and fro-ing is that a fair sample of elements is available (the cervical, two dorsals, a crushed sacrum, a handful of caudals, two scaps and pelvic elements). But many aspects of its anatomy remain obscure, and the most that can be said about its affinities is that it seems to be similar to, but distinct from, the diplodocine diplodocid Barosaurus.

No longer! As of six days ago, a new paper by Lovelace, Hartman and Wahl is — finally — out. It’s no exaggeration to describe this as one of the most eagerly awaited sauropod papers of the last decade, because it describes a brand new specimen of Supersaurus, WDC DMJ-021, from a quarry in Wyoming. It’s a little smaller than Jensen’s specimen, but very much in the same size class, that is, bigger than “Seismosaurus” and a lot bigger than any of the common-or-garden diplodocids you might see in museums, such as the Carnegie Diplodocus that seems to follow me around the museums of Europe. The paper contains some nice skeletal reconstructions (figs. 7-8 ) which show this well.

The new specimen consists of nine cervicals (in various conditions), six dorsals (ditto), nine or so caudals including the two most proximal, ribs, pelvic fragments and tibiae and fibulae. And here — tah-dah! — is the proximal caudal (lacking neural spine) in right lateral view, courtesy of Scott Hartman:

Take a moment to look at those scale bars, by the way. On my screen, if I blow the image up to full size, it’s roughly life-sized. Scroll around a bit and take in the topography. You may gulp a little if you wish. A certain amount of gasping may also be in order.

Lovelace et al. do a convincing job of showing that, while Supersaurus does resemble Barosaurus in gross proportions, it is in fact more closely related to Apatosaurus — a big surprise given that Apato is freakishly robust, and really stands alone among non-titanosaurian sauropods in terms of being absurdly over-engineered. As pointed out in the paper, however, this is more true in Apatosaurus excelsus and Apatosaurus louisae than in the type species, Apatosaurus ajax — and, indeed, if you check out the reconstruction of A. ajax in the frontispiece to Upchurch et al.’s (2005) monograph on a specimen of that species, you’ll notice that it’s not so crazy-fat as the Greg Paul apatosaur reconstruction we’ve all grown used to.

So what does this mean? For one thing, it means that Taylor and Naish’s (2005) rather obvious phylogenetic definition of Apatosaurinae as (Apatosaurus not Diplodocus) now has some substance to it, as the clade includes not only Apatosaurus but also Supersaurus and — it turns out, according to Lovelace et al’s analysis — Jerry Harris’s Suuwassea. The latter result is not wholly unexpected, as Jerry’s (2006a) abominable(*) paper on Suuwassea‘s axial skeleton did point out similarities to Apatosaurus, but this is the first time such a topology has been recovered by a published phylogenetic analysis, Jerry’s own (2006b) analysis having found Suuwassea as an unresolved basal flagellicaudatan in a trichotomy with Diplodocidae and Dicraeosauridae.

[(*) Why is the Jerry's axial osteology paper "abominable"? Because it uses a nomenclatural system unique to a small group of workers consisting of, uh, Jerry, and is therefore near-incomprehensible to everyone who's grown used to the standard Wilson (1999) nomenclature for vertebral laminae. If I had time to burn, I'd do a translation of Harris (2006a) and submit it to the Polyglot Paleontologist. Let me clearly say that, in other areas, I have nothing but respect for Jerry, whose work is both comprehensive and readable -- a glorious combination -- and whose reviews are the best and most useful I have ever seen. But this is one of those sad occasions when a very clever person has done a very dumb thing. I now await a rebuttal in the comments :-) ]

Another interesting consequence is that Apatosaurus‘s characteristically robust morphology now seems to be autapomorphic for the genus Apatosaurus itself, so that the ancestor of apatosaurines had a slender build, similar to that of Diplodocus, which was inherited by basal apatosaurines. It’ll be interesting to know what Jerry makes of this, and specifically how well Suuwassea fits this model.

One odd side-effect in the phylogeny of Lovelace et al. (2008:fig. 14) is that (Barapasaurus + Patagosaurus + (Mamenchisaurus + Losillasaurus)) form a clade, which is the outgroup to (Jobaria + Neosauropoda). Omeisaurus falls outside this group, which is a surprise as it has sometimes been thought congeneric with, or at least mixed up with, Mamenchisaurus. (Both Mamenchi and Omei have multiple species, all based on lovely material but described in only the most cursory fashion, and it’s thought that some species of each genus may belong in the other.) It’s not obvious why adding a deeply nested apatosaurine diplodocid diplodocoid should have such a dramatic effect on so much more basal a part of the tree, but that’s what happens. I’d like to hear thoughts on this.

Well, that’s enough for now, in what has become a much longer post than I intended. I finish by noting that Lovelace et al. also added “Seismosaurus” to their matrix, but found that not only did it clade with Diplodocus, it was scored identically! Accordingly, they concur with another recent paper that “Seismosaurus” is a junior subjective synonym of Diplodocus. In fact, they go further than that other paper did, and argue that poor old Sam is not just congeneric but conspecific with Diplodocus longus. That’s sort of sad — “Seismosaurus” was a pretty cool name. On the other hand, it does mean that NMMNH 3690 is the world’s biggest Diplodocus, and by some distance.

And finally, there are a couple of neat photos of a Supersaurus mount, based largely on the WDC specimen, over on Scott Hartman’s site. I recommend them. Strongly.

References

Unbelievably, despite the fact that it is one of my favorite places in the world, despite the fact that it is just 10 fast hours away by car, across some of the most desolate and beautiful country on the planet, I have not been to BYU since the fall of 2005.

The highlight of my last trip was spending a little quality time with the Dry Mesa Supersaurus cervical. You’ve seen it here before so you know it’s dimensions…sorta. As I am always saying, there is a big difference between knowing something in your head and knowing it in your gut. So here are a couple of gut-level facts about this vert.

First, it’s so darn big that once the forklift has it down from it’s shelf, it can’t turn or maneuver, and the driver has to crawl out through the window (true; I watched him do it). I have no idea how they got this thing up there in the first place. It’s not there anymore, it’s been moved to the gigantic shiny white new big bone storage room (a.k.a. the Vault of Awesome) that was just about completed when I was there last. How they moved it is another mystery, since the forklift can’t turn.

Second, if you want to get it all in one frame with minimal distortion, you have to get up on a very tall ladder and shoot straight down. Which I did. The scale bar is in cm (top) and inches (bottom).

This is one of my hand-full of favorite fossils in the world, and I’m looking forward to seeing it again in its new home. The barn it was in before was not air-conditioned, and the two hours I spent in there on a hot August afternoon had me sweating like a fat kid in a garbage sack. But it was more than worth it. Dirty is temporary. Science last forever (or close enough for me).

STOP THE PRESSES!! (May 7)

The paper describing the new Supersaurus specimen from Wyoming has finally been made public. It’s Lovelace et al., with a claimed date of 2007, which for all I know is when the thing actually came out. I’d appreciate details on that from those in the know. In any case, the paper is freely available by emailing co-author Scott Hartman on dinoboygraphics@aol.com – I haven’t even had a chance to read it yet, but I salute the authors for getting it out, and salute them for offering it to interested parties. Everyone should be so kind.

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