About 105 million years ago, a small herd of four-footed, plant-eating dinosaurs fled southward along an ancient shoreline while a two-footed, meat-eating dinosaur pursued them closely. The evidence of their passage was buried and turned to stone, and today the rock lies exposed in the bed of the Paluxy River at Dinosaur Valley State Park. When the river is full and muddy after a rain, replicas of the tracks may be seen at the headquarters exhibit. The tracks include those of Pleurocoelus, a plant-eating, lizard-hipped dinosaur forty feet long, and Acrocanthosaurus, a meat-eating, lizard-hipped dinosaur twenty-five feet long. Other animals shown from this early Cretaceous setting are Tenontosaurussa, Iguanodon, Pappotberium, Holoclemensia, Naomichelys, Goniopholis (Dakotasuchus), Theriosuchus, and an unnamed pterosaur or flying reptile. Pleurocoelus, a type of sauropod related to brontosaurs, had big, flat hindfeet with four claws and small, hoof-like forefeet without claws, while Acrocanthosaurus, a type of carnosaur related to tyrannosaurs, had feet with three clawed toes.