Early Cretaceous
Cedar Mountain Formation
The dinosaurs in the lower part of the formation differ from those in the upper part. These two dinosaur assemblages, characterized by distinct dinosaurs, show the replacement of older, European-like dinosaurs with younger, Asian-like dinosaurs during the last half of the Early Cretaceous. Three faunal zones have been proposed. One is the Acrocanthosaurus Astrodon Zone with fauna descended from the Late Jurassic fauna contained with broken forests and open prarries that existed along the Gulf Coast to Maryland.
updated 010916
Macronarian sauropods survive the the transition in the Early Cretaceous and become more diverse but are uncommon in the fossil record. Track evidence in Texas and Oklehoma shows groups of up 12 animals moving together. They 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 Acrocanthosaurus.