In the light of all this distortion and uncertainty, what can be said about the largest genera of dinosaurs? What are the heaviest and longest genera that we can speak of with confidence?
If we require totally unambiguous evidence for measurements, then the longest dinosaur is still boring old Diplodocus carnegiei, at a relatively modest 27m (89 feet) - because it's the longest dinosaur for which we have a complete skeleton. Nevertheless, we can be confident that other dinosaurs, for which we have more fragmentary remains, were longer. For example, consider Supersaurus:
By contrast, when we consider the heaviest dinosaur, data is harder to come by. Different scientists are liable to give wildly differing weight estimates for any given genus (see ``Why do mass estimates vary so much?'' ); and the weight of any species will vary between individuals, and the weight of any individual will vary through its life and seasonally. However, we can still make estimates, and compare what we know of various genera.
Here, then, are the ``biggest dinosaur'' candidates, in something akin to descending order of credibility:
Argentinosaurus is currently the conventional answer to the ``biggest dinosaur'' question. The sacrum, vertebrae and tibia that we have indicate that it is a member of the titanosaur family, and comparison with better-known titanosaur genera give us a good indication of its scale, suggesting a total length of 35m (114 feet) or longer. Given the bulkiness of titanosaurs, its likely weight was in the region of 80-100 tons.
### What particular better-known genera are used for this comparison?
This recently-discovered Egyptian titanosaur was announced in June 2001, and widely described as ``the second biggest ever discovered''. Its humerus, at 1.69m in length, is somewhat smaller than that of Argentinosaurus, at 1.81m, suggesting that if the animals were simialrly proportioned, it was 93% a long as Argentinosaurus, that is, about 32m (104 feet). This would suggest a weight in the region of 65-80 tons.
Another titanosaur, estimated at about 28m (92 feet) and 45-55 tons.
Closely related to Brachiosaurus, but with a substantially longer neck - about 12m (39 feet) in length, compared with maybe 9m (30 feet) in the better-known genus.
Sauroposeidon is only known from a series of four well-preserved cervical vertebrae, so it's impossible to be certain about the size of the rest of the animal. However, features of those vertebrae suggest that it was particularly specialised towards supporting a long neck, which suggests that the rest of its body may have been proportionally somewhat smaller than in Brachiosaurus. Accordingly length is estimated in the region of perhaps 30m (97 feet) with a mass in the region of 50-60 tons.
Perhaps a more interesting Sauroposeidon statistic is that its long neck and high brachiosaurid shoulders mean that it would have been the tallest known dinosaur, able to raise its head perhaps 18m (58 feet) above ground level.
This large diplodocid is known from relatively fragmentary remains: one cervical vertebra, several dorsals, a few cordals and a scapulocoracoid. That's enough to tell a pretty impressive story, though.
Consider the sole Supersaurus cervical. Its long, low shape suggests that it can't be from any further back than C9 or C10, yet it's 1.35m long. This compares with a length of .6m for C10 of the Diplodocus carnegiei specimen CM84. We can conclude, then that Supersaurus's neck was 2.25 times as long as Diplodocus's six-meter neck, which suggests a neck of 13.5m (44 feet). Wow. That's longer than Sauroposeidon's neck (but it probably couldn't be raised as high.)
It's tempting to think that the whole animal was 2.25 times as long as Diplodocus, but that won't do: the height of its dorsal vertebrae is ``only'' 1.5 times that of Diplodocus's, suggesting that the neck of Supersaurus was disproportionately long for its body, as in Barosaurus. Nevertheless, it's hard to imagine the animal's total length as much less than 40m (130 feet), with a weight in the region of 40-50 tons.
Another large diplodocid from the same period as Supersaurus, but probably rather smaller - opinions differ. David Gillette, its describer, estimated its length at about 45m (150 feet), based in part on on comparison of tail vertebrae to juvenile elements in the Smithsonian's mounted Diplodocus, which is actually a composite. More recent estimates tend to be in the range of 33-37m (110-120 feet).
(It's also recently been argued that hallorum is actually a large species of Diplodocus, in which case Seismosaurus would be a junior synonym.)
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Amphicoelias fragilimus- 56-62 meters, 125-170 tons
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Bruhathkayosaurus matleyi- 44.1 meters, 175-220 tons http://www.cmnh.org/dinoarch/2001Jun/msg00626.html http://www.cmnh.org/dinoarch/2001Jun/msg00665.html
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