Prehistoric mammals began migrating to, as well as evolving in Florida during the Early Miocene epoch. Due to lack of a glacial sheet and temperate to warm climate, many species of mammals thrived in what is now Florida.
Prior to 23-24 million years ago, no land mammals were present in what is now Florida. The first mammalian fossils are from the Eocene and are that of the extinct whales †Basilosaurus (44.9—33.9 Ma) and †Basilosaurus cetoides (37.2—33.9 Ma). Land mammals were prevented access to the forming peninsula by a natural water barrier known as the Gulf Trough which flowed over northern Florida and southern Georgia carrying sediments away and prevented migration. Though Florida was forming, this process was taking place over the central to north central part of the state.
As the trough filled in, the first mammals were able to move from the north and in to the forming peninsula.[1] North Florida became the first part of the future state to receive sediments. As the area began filling in from deposited sediments from rivers to the north and as sea level dropped during glaciation, these two processes eventually exposed the peninsula or the upper most areas of the Florida Platform.
- Also see: Choctaw Sea
Florida, a rather flat state, has an abundance of phosphate and it is the mining of this mineral which has yielded most of the fossil specimens.
Most specimens have been dated using Appearance Event Ordination.