Australia has considerably fewer species of carnivorous mammals than any other continent does but about as many carnivorous reptile species as other continents do  This is probably a consequence of the unusual sparseness of Australia' s ecosystems
To survive, carnivorous mammals must eat much more than carnivorous reptiles need to; thus carnivorous mammals are at a disadvantage in ecosystems in which there is relatively little food
The unusual sparseness of Australia's ecosystems is probably the reason Australia has considerably fewer carnivorous mammal species than other continents do but about as many carnivorous reptile species.