The fossils were found in rocks dating from near the end of the Early Cretaceous (Aptian–early Albian), from about 113 to 110 million years ago, 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.

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.

Extrapolations based on the more completely known Brachiosaurus indicate that the head of Sauroposeidon could reach 16.5–18 m (54–59 ft) in height with its neck extended, which would make it one of the tallest known dinosaurs.

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.

In the mid 1980s, students from the University of Texas at Austin discovered a bonebed on a ranch in Hood County, but early work stopped in 1987.

The site was fluvial when its rocks were being deposited, with channel sands and muds, and concretions of calcite-cemented sandstone containing fossils.

[8] The name Paluxysaurus was based on the specimen FWMSH 93B-10-18, a partial skull including an associated left maxilla, nasal, and teeth.

The genus was limited to the bonebed remains; for example, the partial skeleton from Wise County known as Pleurocoelus sp.

[6] The original Sauroposeidon find was composed of four articulated, mid-cervical vertebrae (numbers 5 to 8), with the cervical ribs[clarification needed] in place.

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.

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.

This paleoenvironment, which has been preserved in the Antlers Formation, also stretches from southwest Arkansas through southeastern Oklahoma and into northeastern Texas.

Scientists have used biostratigraphic data and the fact that it shares several of the same genera as the Trinity Group of Texas, to surmise that this formation was laid down during the Aptian and Albian stages of the Early Cretaceous Period, approximately 110 mya.

The paleoenvironment of Sauroposeidon consisted of tropical or sub-tropical forests, river deltas, coastal swamps, bayous and lagoons, probably similar to that of modern-day Louisiana.

Other vertebrates present during this time included the amphibian Albanerpeton arthridion, the reptiles Atokasaurus metarsiodon and Ptilotodon wilsoni, the cartilaginous fish Hybodus buderi and Lissodus anitae, the ray-finned fish Gyronchus dumblei, the crocodilians Goniopholis, Bernissartia, and Paluxysuchus, and the turtles Glyptops and Naomichelys.