User blog comment:Gladh/My Dino collection/@comment-5116140-20130111112553

It is really interesting how the results alternate between the two biomes in time.

This pattern has been seen by many - but no one has given a proper analysis of what it means. For example, all of the last 4 results are Tundra.

Forest -> Tundra -> Forest -> Forest -> Tundra ->Tundra ->Tundra ->Tundra

Condensing you have just the 4 time intervals:

Forest -> Tundra -> Forest -> Tundra