Sauropod Vertebra Picture of the Week

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

• Carpenter, K. 2006. Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus Cope, 1878. New Mexico Museum of Natural History and Science Bulletin 36:131-137.
• Lovelace, David M., Scott A. Hartman and William R. Wahl. 2008. Morphology of a specimen of Supersaurus (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of diplodocid phylogeny. Arquivos do Museu Nacional, Rio de Janeiro, 65 (4): 527-544.
• Mazzetta, G.V., Christiansen, P., and Farina, R.A. 2004. Giants and bizarres: body size of some southern South American Cretaceous dinosaurs. Historical Biology 2004:1-13.
• Wood, G.L. 1982. The Guinness Book of Animals Facts & Feats. Guinness Superlatives Ltd., Enfield, Middlesex. 252 pp.