FROM THE MOMENT the early-morning fog had begun to lift, they sensed they were being watched. The herd of Shantungosaurus had been grazing along the misty shoreline all morning. Measuring more than 40 feet from their duckbilled heads to the end of their tails, these reptiles, the largest of the hadrosaurs, gorged themselves on the abundant supply of kelp and seaweed that continued to wash up along the shoreline with the incoming tide. Every few moments the gentle giants raised their heads like a herd of nervous deer, listening to the noises of the nearby forest. They watched the dark trees and thick vegetation for movement, ready to run at the first sign of approach.
Across the beach, hidden among the tall trees and thick undergrowth, a pair of red reptilian eyes followed the herd. Tyrannosaurus rex, the largest and most lethal of all terrestrial carnivores, towered 22 feet above the forest floor. Saliva oozed from the big male's mouth, its muscles quivering with adrenaline as it focused on two duckbills venturing out into the shallows, isolating themselves from the herd.
With a blood-curdling roar, the killer crashed through the trees, its eight tons pounding the sand and shaking the earth with every step. The duckbills froze momentarily, then rose on their hind legs and scattered in both directions along the beach.
The two hadrosaurs grazing in the surf saw the carnivore closing in on them, its jaws wide, fangs bared, its bone-chilling trumpet drowning the crash of the surf. Trapped, the pair turned and plunged into deeper water to escape. They strained their long necks forward and began to swim, their legs churning to keep their heads above water.
Driven by hunger, T. rex crashed through the surf after them. Far from buoyant, the killer waded into deeper waters, snapping its jaws at the incoming swells, but as it neared its prey, the T. rex's clawed feet sank deep into the muddy sea floor, its weight driving it into the mire.
The hadrosaurs paddled in 30 feet of water, safe for the moment--but, having escaped one predator, they now faced another.
The six-foot gray dorsal fin rose slowly from the sea, its unseen girth gliding silently across the dinosaurs' path. If the T. rex was the most terrifying creature ever to walk the earth, then Carcharodon megalodon easily was lord and master of the sea. Sixty feet from its conical snout to the tip of its half-moon-shaped caudal fin, the shark moved effortlessly through its liquid domain, circling its outmatched prey. It could feel the racing heartbeats of the hadrosaurs and the heavier thumpa, thumpa of...