 Definite Acrocanthosaurus fossils have been found in the Twin Mountains Formation of northern Texas , the Antlers Formation of southern Oklahoma , and the Cloverly Formation of north @-@ central Wyoming and possibly even the Arundel Formation in Maryland and in Florida . These geological formations have not been dated radiometrically , but scientists have used biostratigraphy to estimate their age . Based on changes in ammonite taxa , the boundary between the Aptian and Albian stages of the Early Cretaceous has been located within the Glen Rose Formation of Texas , which may contain Acrocanthosaurus footprints and lies just above the Twin Mountains Formation . This indicates that the Twin Mountains Formation lies entirely within the Aptian stage , which lasted from 125 to 112 million years ago . The Antlers Formation contains fossils of Deinonychus and Tenontosaurus , two dinosaur genera also found in the Cloverly Formation , which has been radiometrically dated to the Aptian and Albian stages , suggesting a similar age for the Antlers . Therefore , Acrocanthosaurus most likely existed between 125 and 100 million years ago . 
