Carnivora of much larger size would be too slow and heavy in movements to catch small prey, while the larger herbivores by intelligent use of their defensive weapons could still fend them off successfully.

In consequence giant carnivores would find no field for action in the Cenozoic world, and hence they have not been evolved.
But the giant herbivorous dinosaurs, well armed or well defended though they were, had not the intelligence to use those weapons effectively under all circumstances.

Thus they might be successfully attacked, at least sometimes, by the powerful although slow moving Megalosaurians.
The suggestion has also been made that these giant carnivores were carrion-eaters rather than truly predaceous.

The hypothesis can hardly be effectively supported nor attacked.

It is presented as a possible alternate.
_Albertosaurus._ Closely allied to the _Tyrannosaurus_ but smaller, about equal in size to _Allosaurus_, was the _Albertosaurus_ of the Edmonton formation in Canada.