Balaam, I think you mean the polar Ice caps were larger which allowed species to migrate more easilly. Beacause if the ice caps shrink, ocean levels should rise and if the ice cap grows, ocean levels should lower. Lower ocean levels exposes land bridges or even great areas of open land and that allows animals to move freely where they couldn't before. Erosion eats away at coastlines and mountain ranges but some rocks are harder than others and take longer to erode, so some coastlines have not changed much at all in human history and others are changing every time the tide comes in.

I don't have an opinion on super-continents one way or the other. But if you are going to make arguments at least get the basic science right.