The earth was smaller in the past era by less oceans and big Dinos as a result.

 Interesting article on: Scitechdaily. com about the earth. see: https://scitechdaily.com/new-understanding-of-earths-architecture-updated-maps-of-tectonic-plates/?fbclid=IwAR1TphzTCIqkoD_-LUij_zGNm4SjTFNtxud9LGIKZSr8FdxSuypYnfvVNrA

See below:

According to Q-FFF Theory ( Quantum Function Follows Form model,

It is assumed that Black Holes come in different sizes, they  repel all matter and form tails of plasma water ice out of the particle vacuum itself.

Secondly all Comets are equipped with one or more micro black holes in its nucleus which also produce water ice and water tails.

So ancient comets seem to have bombarded our earth by the millions, creating more ocean water and more gravity, a possible reason for Dino extinction.

The size of the Dino population on earth seem to have made advantage out of this minimized  gravity, phenomenon and were able to grow large.