Acrocanthosaurus

Acrocanthosaurus meaning "high-spined lizard") 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. 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, reaching 11.5 meters (38 ft) in length, and weighing up to 6.2 metric tons (6.8 short tons). 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.*Acrocanthosaurus* is named after its tall neural spines, from the Greek *ɑκρɑ*/ ('thorn' or 'spine') *sauros* ('lizard'). There is one named species (*A. atokensis*), which is named 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 Langston had proposed the name "Acracanthus atokaensis" for the genus and species in his unpublished 1947 master's thesis, but the name was changed to *Acrocanthosaurus atokensis* for formal publication.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, and is now housed at the North Carolina Museum of Natural Sciences in Raleigh. This specimen is the largest and includes the only known complete skull and forelimb. Skeletal elements of OMNH 10147 are almost the same size as comparable bones in NCSM 14345, indicating an animal of roughly the same size, while the holotype and SMU 74646 are significantly smaller. The presence of *Acrocanthosaurus* in the Cloverly Formation was established in 2012 with the description of another partial skeleton, UM 20796. This specimen, consisting of parts of two vertebrae, partial pubic bones, a femur, a partial fibula, and fragments, represents a juvenile animal. It came from a bonebed in the Bighorn Basin of north-central Wyoming, and was found near the shoulder blade of a *Sauroposeidon*. An assortment of other fragmentary theropod remains from the formation may also belong to *Acrocanthosaurus*, which may be the only large theropod in the Cloverly Formation. *Acrocanthosaurus* may be known from less complete remains outside of Oklahoma, Texas, and Wyoming. A tooth from southern Arizona has been referred to the genus, and matching tooth marks have been found in sauropod bones from the same area. Several teeth from the Arundel Formation of Maryland have been described as almost identical to those of *Acrocanthosaurus* and may represent an eastern representative of the genus. Many other teeth and bones from various geologic formations throughout the western United States have also been referred to *Acrocanthosaurus*, but most of these have been misidentified; there is, however, some disagreement with this assessment regarding fossils from the Cloverly Formation. *Acrocanthosaurus* was among the largest theropods known to exist. The largest known specimen (NCSM 14345) is estimated to have measured 11.5 m (38 ft) from snout to tail tip and weighed 5.7 to 6.2 metric tons (6.3 to 6.8 short tons), with an upper maximum weight of 7.25 metric tons (7.99 short tons) within the realm of possibility for this specimen. Its skull alone was nearly 1.3 m (4.3 ft) in length.