Acrocanthosaurus ( ; ) is a genus of carcharodontosaurid dinosaur that existed in what is now North America during the Aptian and early Albian stages of the Early Cretaceous, from 113 to 110 million years ago. Like most dinosaur genera, Acrocanthosaurus contains only a single species, A. atokensis. Its fossil remains are found mainly in the U.S. states of Oklahoma, Texas, and Wyoming, although teeth attributed to Acrocanthosaurus have been found as far east as Maryland, suggesting a continent-wide range. Acrocanthosaurus was a bipedal predator. As the name suggests, it is best known for the high neural spines on many of its vertebrae, which most likely supported a ridge of muscle over the animal's neck, back, and hips. Acrocanthosaurus was one of the largest theropods, with the largest known specimen reaching in length and weighing approximately . Large theropod footprints discovered in Texas may have been made by Acrocanthosaurus, although there is no direct association with skeletal remains. Recent discoveries have elucidated many details of its anatomy, allowing for specialized studies focusing on its brain structure and forelimb function. Acrocanthosaurus was the largest theropod in its ecosystem and likely an apex predator which preyed on sauropods, ornithopods, and ankylosaurs. Discovery and naming Acrocanthosaurus is named after its tall neural spines, from the Greek ɑκρɑ/akra ('high'), ɑκɑνθɑ/akantha ('thorn' or 'spine') and σɑʊρος/sauros ('lizard'). There is one named species (A. atokensis), after Atoka County in Oklahoma, where the original specimens were found. The name was coined in 1950 by American paleontologists J. Willis Stovall and Wann Langston Jr. Langston had proposed the name "Acracanthus atokaensis" for the genus and species in his unpublished 1947 master's thesis, but the name was changed to Acrocanthosaurus atokensis for formal publication. The holotype and paratype (OMNH 10146 and OMNH 10147), discovered in the early 1940s and described at the same time in 1950, consist of two partial skeletons and a piece of skull material from the Antlers Formation in Oklahoma. Two much more complete specimens were described in the 1990s. The first (SMU 74646) is a partial skeleton, missing most of the skull, recovered from the Twin Mountains Formation of Texas and currently part of the Fort Worth Museum of Science and History collection. An even more complete skeleton (NCSM 14345, nicknamed "Fran") was recovered from the Antlers Formation of Oklahoma by Cephis Hall and Sid Love, prepared by the Black Hills Institute in South Dakota,