Sauroposeidon (pronounced /ˌsɔrɵpɵˈsaɪdən/ sor-o-po-sy-dən; meaning "earthquake god lizard", after the Greek god Poseidon) is a genus of sauropod dinosaur known from four neck vertebrae that were found in the southeastern portion of the US state of Oklahoma. The fossils were found in rocks dating to the Early Cretaceous, a period when the sauropods of North America had diminished in both size and numbers, making it the last known giant dinosaur on the continent. While the fossils were discovered in 1994, due to their unexpected age and unusual size they were initially misclassified as pieces of petrified wood. A more detailed analysis in 1999 revealed their true nature which resulted in a minor media frenzy, and formal publication of the find the following year.
Paleoecological analysis indicates that Sauroposeidon lived on the shores of the Gulf of Mexico, in a river delta. Like other brachiosaurids, Sauroposeidon was a quadrupedal herbivore with longer forelimbs than hindlimbs, a similar body design to the modern giraffe. Extrapolations based on its more completely known relative Brachiosaurus indicate that the head of Sauroposeidon could reach 17 m (56 ft) in height with its neck extended, making it the tallest known dinosaur. With an estimated length of up to 34 m (112 ft) and a mass of 50–60 t (55–66 short tons), it also ranks among the longest and heaviest.
It's truly astonishing. It's arguably the largest creature ever to walk the earth.—Richard Cifelli, discoverer of SauroposeidonThe press release in 1999 immediately garnered international media attention, which led to many (inaccurate) news reports of "the largest dinosaur ever!". While it is true that Sauroposeidon is probably the tallest known dinosaur, it is neither the longest nor the most massive. Argentinosaurus is a better candidate for the title "World's Largest Dinosaur" (presuming to ignore, as is conventional, Amphicoelias), though weak fossil evidence makes an exact ranking impossible.
The Sauroposeidon find was composed of four articulated, mid-cervical vertebrae (numbers 5 to 8), with the cervical ribs in place. The vertebrae are extremely elongated, with the largest one having an overall length of 1.4 m (4.6 ft), making it the longest sauropod neck vertebra on record. Examination of the bones revealed that they are honeycombed with tiny air cells, and are very thin, like the bones of a chicken or an ostrich, making the neck lighter and easier to lift. The cervical ribs were remarkably long as well, with the longest measurable rib (on vertebra 6) measuring 3.42 m (11.2 ft) – about 18% longer than the longest rib reported for Giraffatitan, but exceeded in length by the cervical ribs of Mamenchisaurus.
Estimates of Sauroposeidon's size are based on a comparison between the four Sauroposeidon vertebrae and the vertebrae of the HM SII specimen of Giraffatitan brancai, located in the Humboldt Museum in Berlin. The HM SII is the most complete brachiosaur known, though since it is composed of pieces from different individuals its proportions may not be totally accurate. Comparisons to the other brachiosaurid relatives of Sauroposeidon are difficult due to limited remains.
The neck length of Sauroposeidon is estimated at 11.25–12 m (37–39 ft), compared to a neck length of 9 m (30 ft) for the HM SII Giraffatitan. This is based on the assumption that the rest of the neck has the same proportions as Giraffatitan, which is a reasonably good conjecture.
Sauroposeidon was probably able to raise its head 17 m (56 ft) above the ground, which is as high as a six-story building. The long neck and the high brachiosaurid shoulders are what makes it the tallest known dinosaur. In some ways, its build is similar to the modern giraffe, with a short body and an extremely long neck. In comparison, Giraffatitan could probably raise its head 13.5 m (44 ft) into the air.
The mass of Sauroposeidon is estimated at 50–60 t (55–66 short tons). While the vertebrae of Sauroposeidon are 25–33% longer than Giraffatitan', they are only 10–15% larger in diameter. This means that while Sauroposeidon probably has a larger body than Giraffatitan its body is smaller in comparison to the size of its neck, so it did not weigh as much as a scaled-up Giraffatitan. By comparison, Giraffatitan might have weighed 36–40 t (40–44 short tons). This estimate of the Giraffatitan is an average of several different methodologies.
However, Sauroposeidon has a gracile neck compared to Giraffatitan. If the rest of the body turns out to be similarly slender, the mass estimate may be too high. This could be similar to the way the relatively robust Apatosaurus weighs far more than the longer but much slimmer Diplodocus. In addition, it is possible that sauropods may have had an air sac system, like those in birds, which could reduce all sauropod mass estimates by 20% or more. Sauroposeidon was an unexpected discovery, because it was a huge, gas-guzzling barge of an animal in an age of subcompact sauropods.—Matt Wedel, Sauroposeidon team leaderSauropods, which include the largest terrestrial animals of all time, were a very wide ranging and successful group. They first appeared in the Early Jurassic and soon spread across the world. By the time of the late Jurassic, North America and Africa were dominated by the diplodocids and brachiosaurids and, by the end of the Late Cretaceous, titanosaurids were widespread (though only in the southern hemisphere). Between these periods, in the Early Cretaceous, the fossil record is sparse. Few specimens have been found in North America from that time and those specimens that do exist are often fragmentary or represent juvenile members of their species. Most of the surviving sauropods at the time were also shrinking in size to a mere 15 m (49 ft) in length, and maybe 10–15 t (11–17 short tons), which makes the discovery of an extremely specialized super-giant like Sauroposeidon very unusual.
Sauroposeidon lived on the shores of the Gulf of Mexico, which ran through Oklahoma at that time, in a vast river delta, similar to the Mississippi delta today. There were probably no predators which could attempt to attack a full-grown Sauroposeidon, but juveniles were likely to be preyed on by the contemporary Acrocanthosaurus atokensis (a carnosaur slightly smaller than a Tyrannosaurus) and the small coelurosaur Deinonychus antirrhopus.
Xenoposeidon, a giant brachiosaurid similar to Sauroposeidon was described in 2004, by Darren Naish and colleagues, and is from the Early Cretaceous period of England. Known only from two neck vertebrae, it was apparently similar in some details to Sauroposeidon and perhaps similar in size. Its discovery highlights the similarity seen between Early Cretaceous North American and European dinosaurs.
Credit to Wikipedia for the article.