Dinosaurs such as the fearsome tyrannosaurus rex ruled the animal kingdom on land. Smaller reptiles such as snakes and lizards populated the undergrowth. Mammals, about the size of squirrels and somewhat like modern possums, struggled to survive, with no anticipation of some day ruling the earth.
Crocodiles held domain over the animal kingdom in the murky waters of the marshes and ponds and in the channels of huge and sluggish rivers. A profusion of other life forms, such as salamanders, shellfish, rays, frogs and turtles, filled their biological niches in this dim watery world. SAY WHAT? Continuing from DesertUSA: If we can judge by modern rain forests, the primal Bisti rain forest represented a community of plant and animal life forms more complex and diverse than any other kind of land-based ecosystem on earth.