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. It is somewhat older than the Tyrannosaur
although still of the late Cretacic period, and may have been ancestral
to it. A fine series of limbs and feet as also skull, tail, etc., are
in the Museum's collections. At or about this time carnivorous
dinosaurs of slightly smaller size are known to have inhabited New
Jersey; a fragmentary skeleton of one secured by Professor Cope in 1869
was described as _Laelaps_ (=_Dryptosaurus_).[10]
_Ornitholestes._ In contrast with the _Allosaurus_ and _Tyrannosaurus_
this skeleton represents the smaller and more agile carnivorous
dinosaurs which preyed upon the lesser herbivorous reptiles of the
period. These little dinosaurs were probably common during all the Age
of Reptiles, much as the smaller quadrupeds are today, but skulls or
skeletons are rarely found in the formations known to us.
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