Etymology: "lizard of divine earthquakes, perfected before the end (of its age)"
Time horizon: end of Early Cretaceous, Aptian-Albian epochs ~113 mya
Length: 32m (~106 ft.), perhaps more depending on proportions and maturity.
Probable mass: 60+ tons
The first hi-fi skeletal of the giant brachiosaur Sauroposeidon proteles, which dominated the coastal forests of North America's Cretaceous inland sea from Oklahoma all the way to Montana. Described bones are white, their missing portions light gray, and the likely shapes of missing neck vertebrae are dark gray.
Here you see the huge neck vertebrae of the type specimen described by Matt Wedel and co., as well as a referred juvenile neck centrum from Montana originally described by John Ostrom as an unknown sauropod. This is my first version of Sauroposeidon, without the new juvenile material described by D'emic. Whether the type specimen is fully adult is still up for debate, though it's downright huge any way you look at it.
D'emic (among others) considers Sauroposeidon a basal somphospondylian rather than a brachiosaur, and lumps it together with Paluxysaurus. I don't agree with either hypothesis at the present time, but it is interesting to note that both Sauroposeidon and Paluxysaurus do converge with somphospondyli and titanosaurs in a number of important ways (long dorsals, high internal pneumaticity, tall posterior dorsal spines, linear dorsal slope, shoulder blade shape, etc.) - as do several other derived cretaceous brachiosaurs, which appear to form a sub-clade within brachiosauridae. This sub-clade (which I tentatively call Pleurocoelinae) includes Pleuroceolus, Astrodon, Eucamerotus, Cedarosaurus, Abydosaurus, Sauroposeidon, Angloposeidon, Paluxysaurus and possibly Sonorasaurus.
A number of these, such as Eucamerotus, Cedarosaurus and Paluxysaurus, also have a slight retrograde tilt on the posterior dorsal neural spines, though the spines look vertical when the dorsal column is drawn tilted up as it should be in brachiosaurs. This odd tilt is not found in the juvenile Sauroposeidon material. Interpret that as you will.
For those who are wondering - no, Sauroposeidon is not the biggest dinosaur, and it's not even the biggest brachiosaur. "Brachiosaurus" nougaredi from Algeria (scaling from a partial sacrum) and Breviparopus from Morocco (scaling from footprints) were larger than the Sauroposeidon holotype, and both likely topped 120 feet in length, assuming average proportions similar to Giraffatitan (more conservative than Sauroposeidon). Among Somphospondyli, Daxiatitan is roughly the same length as Sauroposeidon, however the neck morphology is far more derived (in addition to having the typical somphospondyli bifid spines, which Sauroposeidon totally lacks).
Wedel, Mathew J.; Cifelli, Richard L. (Summer 2005). "Sauroposeidon: Oklahoma's Native Giant". Oklahoma Geology Notes 65 (2): 4057
Wedel, Mathew J.; Cifelli, R.L. and Sanders, R..K. (2000). "Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon". Acta Palaeontologica Polonica 45: 3433888.
Wedel, Mathew J.; Cifelli, R.L. and Sanders, R.K. (March 2000). "Sauroposeidon proteles, a new sauropod from the Early Cretaceous of Oklahoma". Journal of Vertebrate Paleontology 20 (1): 109114. doi:10.1671/0272-4634(2000)020[0109:SPANSF]2.0.CO;2.