The geological state, fauna and wildlife are very different from Ecco's own time. One of the largest and most obvious differences is the presence of animals which are extinct in Ecco's time period. These include but are not limited to Pteranodons, Dunkleosteus, Trilobites and a unique species of jellyfish.
No terrestrial dinosaurs are even seen in the background or on any patch of solid land. The places Ecco visits are mainly in a volcanic state with shallow erupted islands spread throughout the area.
There is no evidence of a human presence in this time period. Perhaps the Atlanteans fled even further into the past, or to an entirely different time period.