 The change in rainfall levels is likely due to the advancing shoreline of the Skull Creek Seaway, a cycle of the Western Interior Seaway which, later in the Cretaceous period, would completely divide North America.This dramatic shift in climate coincided with an apparent increase, rather than decrease, in the abundance of "Tenontosaurus".This shows "Tenontosaurus" to have been a remarkably adaptable animal, which persisted for a long span of time in one area despite changes to its environment.