PREHISTORIC DALLAS Reverse the clock over millions of years and we'll uncover the secrets of Dallas, Texas. From the ancestors of the famous Longhorn cattle that brought us the cowboys, to the mammoths, large cats and overgrown armadillos of the Ice Age, everything about Dallas was always BIG. Dive in to Ocean Dallas and swim with the Great White Sharks of the Cretaceous Period and the mosasaurs that battled them for dominance--right where downtown Dallas stands today. Then head west to Fort Worth and the home of the largest dinosaur to walk the earth in North America: Paluxysaurus -- the State Dinosaur of Texas. And if you think Texas is oil country, think again. At 325 million years old, it's the biggest natural gas field in North America -- and it's right beneath the city of Dallas.