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''Acrocanthosaurus'' (pronunciation: ak-ro-KAN-tho-SAWR-us; meaning: "high-spined lizard") is a Genus of Carnosauria n Theropod Dinosaur from the mid- Cretaceous Period of North America . It was one of the largest Bipedal Carnivorous dinosaurs, with one mounted specimen reaching a length of 11.5 meters (38 feet). Many of its Vertebra e had high spines on top. GENERAL INFORMATION ''Acrocanthosaurus'' is named for the spines on its back, from the Greek ''akro'' ("high"), ''akantha'' ("spine"), and ''sauros''("lizard"). There is one named Species (''A. atokensis''), which is named after Atoka County in Oklahoma , where the original specimens were found. It was named in 1950 by American Paleontologists J. Willis Stovall and Wann Langston, Jr. . The Holotype and Paratype , described at the same time in 1950, consist of two partial skeletons and a bit of skull material from the Antlers Formation in the U.S. state of Oklahoma. Two more complete skeletons have recently been described. The first is a skeleton about 70% complete, including some of the skull, recovered from the Twin Mountain Formation of Texas (Harris, 1998). An even more complete skeleton, with an intact skull (nicknamed "Fran") was recovered from the Antlers and is now housed at the North Carolina Museum Of Natural Sciences (Currie & Carpenter, 2000). Many other fragments and individual bones have been found all over north Texas and Oklahoma. The Antlers Formation is composed of sediment from the Aptian through Albian stages of the Cretaceous Period, while the Twin Mountain is restricted to the Aptian. Therefore, ''Acrocanthosaurus'' lived between 125 and 100 million years ago. Other dinosaurs from this time and place include '' Deinonychus '', '' Sauroposeidon '', and '' Tenontosaurus ''. Another species from England was at one point named ''Acrocanthosaurus altispinax'', but has since been removed to its own genus, '' Becklespinax ''. Modern Phylogenetic analyses put ''Acrocanthosaurus'' inside the group Allosauroidea , but there is some dispute over the exact position of ''Acrocanthosaurus'' within that group. It was originally placed in Allosauridae with '' Allosaurus '', an arrangement supported by some later studies (Stovall & Langston, 1950; Currie & Carpenter, 2000). Many other scientists put it in Carcharodontosauridae with '' Carcharodontosaurus '' and '' Giganotosaurus '' (Sereno et al., 1996; Harris, 1998; Naish et al., 2001; Holtz et al., 2004; Franzosa & Rowe, 2005). DORSAL SPINES The most notable feature of ''Acrocanthosaurus'' are the tall spines, located on the back, hips, and upper tail, which can be more than 2.5 times the height of the vertebrae they extend from. Other dinosaurs also had high spines on the back, sometimes much higher than ''Acrocanthosaurus''. For instance, the Africa n '' Spinosaurus '' had spines nearly 1.5 meters tall, which is about 15 times taller than the centra (bodies) of the vertebrae they are attached to. The spines may have been covered in muscle or fat like those of a modern Bison , forming a tall, thick ridge down its back. Alternatively, the spines may have supported a skin sail as in dinosaurs like ''Spinosaurus'', or non-dinosaurs like '' Dimetrodon '', albeit much lower in profile. The function of the spines remains unknown, although they may have been involved in Communication , Fat storage, or Temperature Control . POSSIBLE FOOTPRINTS The famous Glen Rose Trackway site in Dinosaur Valley State Park of north Texas contains many footprints, including three-toed theropod prints that some paleontologists have associated with ''Acrocanthosaurus''. It is impossible to say what animal made the prints, since no Fossil bones were discovered there. However, the footprints are of an appropriate size, and the Glen Rose Formation is near the Antlers and Twin Mountain Formations, and roughly the same age, so it is quite possible that the footprints do indeed belong to ''Acrocanthosaurus''. The theropod footprints belong to several individuals moving in the same direction as several individual Sauropod dinosaurs. The theropod prints are sometimes found on top of the sauropod footprints, indicating that they were formed later. This has been put forth as evidence that a small Pack of ''Acrocanthosaurus'' was stalking a Herd of sauropods. While interesting and plausible, this Hypothesis is difficult to prove and other explanations exist. For example, several solitary theropods may have moved through in the same direction at different times after the sauropods had passed, creating the appearance of a pack stalking its Prey . The same can be said for the purported "herd" of sauropods, who also may or may not have been moving as a group. BRAIN STRUCTURE In 2005 , scientists digitally reconstructed an Endocast (replica) of the Brain and Cranial Nerves of ''Acrocanthosaurus'' using Computed Tomography (CT) scanning technology to analyze the spaces within the holotype braincase. This allowed them to make several observations:
Digital endocasts have also been created for several other large theropods: '' Tyrannosaurus '', '' Ceratosaurus '', ''Allosaurus'', and ''Carcharodontosaurus''. POPULAR CULTURE ''Acrocanthosaurus'' appears in the '' for PC and Console platforms. REFERENCES
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