Sauroposeidon

Sauroposeidon (meaning "earthquake god lizard", after the Greek god Poseidon) is agenus of sauropod dinosaur known from several incomplete specimens including a bone bed and fossilized trackways that have been found in the American states of Oklahoma, Wyoming, and Texas. The fossils were found in rocks dating from near the end of the Early Cretaceous (Aptian-early Albian), a time when sauropod diversity in North America had greatly diminished. It was the last known North American sauropod prior to an absence of the group on the continent of roughly 40 million years that ended with the appearance of Alamosaurus during the Maastrichtian.

Description
Paleoecological analysis indicates that Sauroposeidon lived on the shores of the Gulf of Mexico, in a river delta. Extrapolations based on the more completely known Brachiosaurus indicate that the head of Sauroposeidon could reach 18 m (59 ft) in height with its neck extended, which would make 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. However, this animal may not be as closely related to Brachiosaurus as previously thought, so these estimates may be inaccurate.

While initially described as a brachiosaurid closely related to Brachiosaurus and Giraffatitan, the discovery of additional remains in theCloverly Formation of Wyoming suggested that it was in fact more closely related to the titanosaurs, in the group Somphospondyli. Analysis of these remains and comparison with others from Texas supported this conclusion, and demonstrated that the more completely known sauropods from the Twin Mountains Formation (including a partial skull and fossil trackways) previously named Paluxysaurus jonesi also belonged to Sauroposeidon.

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 relatives ofSauroposeidon 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 17–18 m (56–59 ft) above the ground, which is as high as a six-story building. In comparison, Giraffatitan could probably raise its head 13.5 m (44 ft) into the air.

Sauroposeidon's shoulder height has been estimated at 6–7 m (20–23 ft) based on an interpretation of the animal as a brachiosaurid. Estimates of its total possible length have ranged from 28 m (92 ft) to 34 m (112 ft).