You were being too literal. I and I believe Barry as well were talking about the overall size of the LAND animal population. The size of water animals is irrelevant to Barry's theory due to bouyancy. Elephants and Giraffe's are not as big as their dinosaur analogues. I believe even the number and size of large mammals has decreased since the first mega-mammals arose. Off course that impression could be due to biased documentation due to the popularity of large mamals in books and documentaries.

I agree fully there is no tendency for a specific lineage to increase or decrease in size. That is simply a matter of random natural selection forces. There are many examples of size increases followed by decreases. That is part of why I think there must have been something in the environment favoring larger size during the period of the dinosaurs. It may have also had to do with a difference in metabolism. Perhaps they weren't fully warm blooded and it is harder for large fully warm blooded animals not to overheat due to the smaller surface to volume ratio.

Regards,
Mark