nesters simply because big things are easier to find. Ostriches are very good at hiding, but they depend on a medium which did not exist, i.e., grass. ...
You keep forgetting: bracken fern is every bit as good as grass for hiding.
Again, a change in dentition has been observed. Dental diversification increases in the latter part of the Cretaceous: from specialized insectivorous to omnivorous types.
-------------- May the peace of God be with you. sarima@ix.netcom.com