1. Obviously, marine creatures only interact with their outside world through the water.
2. Icthyosaurs shared the seas with plesiosaurs and other marine creatures starting about 250 million years ago.
3. First, they found that the minimum size of marine creatures decreased by a factor of 10, the maximum size exploded 100,000 times during the same period.
4. Which is not good, because remember, most marine creatures are adapted to survive at narrow temperature ranges.