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

 Famemaster Acrocanthosaurus Schleich Brachiosaurs
Giants rivaling the size of the Late Jurassic predecessors like the Sauroposeidon also continued to exist. Sauroposeidon lived about 110 million years ago and probably inhabited a swampy river delta.  The Gulf of Mexico had swamped most of Texas, bringing the shoreline to Oklahoma. The neck is about a third longer than that of Brachiosaurus, at 60 feet, tall and weighing around 60 tons.

Battat and Wild Safari Acrocanthosaurus with CollectA and Schleich BrachiosaurusMacronarian 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.