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Description
Named by Willis Stoval and Wann Langston, Jr., 1950
Diet: Carnivore (Prey included giant sauropods such as Astrodon johnstoni and Sauroposeidon porteles, one of the largest dinosaurs known, but will target a young or sick animal since the healthy adults are too large and dangerous for them to take down. Also preyed on smaller animals such as Tenontosaurus)
Length: 38 feet (11.5 meters)
Weight: 6.3 to 6.8 tons
Region: Oklahoma (Antlers formation), Texas (Twin Mountains and Glen Rose formation), and Wyoming (Cloverly formation) USA (Note: Teeth attributed to Acrocanthosaurus were found as far east as the Arundel Formation, Maryland)
Age: 116-110 million BC (Aptian to Early Albian stage of the Early Cretaceous)

Named in 1950 by American paleontologists Willis Stoval and Wann Langston, Jr., Acrocanthosaurus was one of the largest meat-eating dinosaurs and is second after Tyrannosaurus rex of being the largest North American theropod. An apex predator living during the Early Cretaceous period, this giant killer represents a midway in the evolution of giant theropods of North America between the Late Jurassic allosaurs of earlier and the famous tyrannosaurs that lived millions of years later in the Late Cretaceous.

Its fossils were mainly found in the Southwestern United States, but teeth attributed to this dinosaur were found as far east as Maryland.

While the original specimen of this dinosaur consists of two fragmentary remains excavated from Atoka County, Oklahoma, the most complete Acrocanthosaurus skeleton, nicknamed "Fran", was discovered by amateur collectors Cephis Hall and Sid Love in 1983 in southeastern Oklahoma. It is now housed at the North Carolina Museum of Natural Sciences in Raleigh and it is the largest specimen. It includes the only complete skull and forelimbs.

Meaning "High-spined Lizard", it had long neural spines, approximately 20 inches (50 centimeters), extending from its vertebrae, which most likely formed a ridge of muscle over it's neck, back, and tail. The purpose of the ridge is unknown. It's believed that they were used to regulate body temperature, or would've been brightley colored and attract mates, as well as warding off rival males. Others believed that they were used to store body fat when food was scarce.

Because of this, Acrocanthosaurus was once misclassed as a spinosaur, but it's now believed to be a member of the carcharodontosauridae family in the carnosauria clade, related to Giganotosaurus and Carcharodontosaurus.

The skull of this dinosaur was up to 4.3 feet (1.3 meters) long and features a large fenestra to reduce the skull's weight. It had a bony brow ridge above the eye, formed by the lacrimal and postorbital bones coming together, which is a carcharodontosaurid trait.

As in other carcharodontosaurids, the 68 thin, sharp teeth in the mouth of Acrocanthosaurus were curved and serrated, designed to cut and slice through flesh. The teeth in the lower jaw are generally smaller than those in the upper jaw.

In 2005, scientists used digital reconstructions around the brain of Acrocanthosaurus. The olfactory lobes were large and thick, indicating a good sense of smell. The reconstruction of the semicircular canals of the ear (balance organ) showed that its head was held in a 25 degree angle horizontally, usually when alerted. The brain itself was s-shaped and resemble those of a crocodile's than a bird's. It also resemble those of Giganotosaurus and Carcharodontosaurus than Allosaurus's, which strengthen the classification as a carcharodontosaurid.

The forelimbs of Acrocanthosaurus were quite unique as reconstructions of it show suggests that there would've been large amounts of cartilage between the bones. This comes from the fact that the bones themselves do not make perfect joints and to properly articulate, the bones would need extra cartilage. The arms of this dinosaur did not have a range of motion and could not fully extend. But it could only manage limited flexing. The humerus could retract back quite away, as if Acrocanthosaurus is pulling something towards its chest. As is seen in other large theropods, the arms could not twist like what human arm can and when rest, the arms would've faced inwards, like when a person clapping his (or her) hands together. Acrocanthosaurus had three fingers, with the first and second claws were probably being permanently flexed, while the third and smallest claw may have been able to retract as well.

After determining the range of motion in the joints of the forelimb, a study went on to hypothesize the predatory of this giant theropod: The arms of Acrocanthosaurus could not swing forward very far and were not likely to have used to capture prey. It probably led to its mouth when hunting. But the forelimbs were able to retract towards the body strongly. Once it lunged its head forward and caught its prey in its jaws, the Acrocanthosaurus could then impale its victims with its claws, holding the body in place while it ate.

The neck vertebrae also interlocked together for greater rigidity, meaning that this giant predator could hold on to large prey with its jaws without sustaining neck injury.

During the time this giant theropod lived, the southwestern United States was a coastal floodplain that drained into an inland sea (millions of years later, the sea would expand to the north, forming the Western Interior Seaway that split North America in two). Acrocanthosaurus was the apex predator of the region and at the top of the local food chain. Its prey included giant sauropods such as the the enormous Sauroposeidon, as well as smaller plant-eaters such as Tenontosaurus.

But its thighbone was much larger than the shinbone, meaning that Acrocanthosaurus was not a fast-running hunter. But this would've been ideal for chasing down the very large, slow-moving sauropods that it preyed on.

The famous Dinosaur State Valley Park along the Paluxy River near Glen Rose, Texas, which represents an ancient coastal shoreline during the the Early Cretaceous, contains fossil footprints that may belong to Acrocanthosaurus, though no associate skeleton was found. Associated with trackways are footprints belonging to a sauropod (probably Sauroposeidon). Scientists believed that this was evidence of a chase and attack scene, but whether if it was or not is yet to be revealed.

Note: Based on Gregory S. Paul's skeletal work!

Description
Named by Willis Stoval and Wann Langston, Jr., 1950
Diet: Carnivore (Prey included giant sauropods such as Astrodon johnstoni and Sauroposeidon porteles, one of the largest dinosaurs known, but will target a young or sick animal since the healthy adults are too large and dangerous for them to take down. Also preyed on smaller animals such as Tenontosaurus)
Length: 38 feet (11.5 meters)
Weight: 6.3 to 6.8 tons
Region: Oklahoma (Antlers formation), Texas (Twin Mountains and Glen Rose formation), and Wyoming (Cloverly formation) USA (Note: Teeth attributed to Acrocanthosaurus were found as far east as the Arundel Formation, Maryland)
Age: 116-110 million BC (Aptian to Early Albian stage of the Early Cretaceous)

Named in 1950 by American paleontologists Willis Stoval and Wann Langston, Jr., Acrocanthosaurus was one of the largest meat-eating dinosaurs and is second after Tyrannosaurus rex of being the largest North American theropod. An apex predator living during the Early Cretaceous period, this giant killer represents a midway in the evolution of giant theropods of North America between the Late Jurassic allosaurs of earlier and the famous tyrannosaurs that lived millions of years later in the Late Cretaceous.

Its fossils were mainly found in the Southwestern United States, but teeth attributed to this dinosaur were found as far east as Maryland.

While the original specimen of this dinosaur consists of two fragmentary remains excavated from Atoka County, Oklahoma, the most complete Acrocanthosaurus skeleton, nicknamed "Fran", was discovered by amateur collectors Cephis Hall and Sid Love in 1983 in southeastern Oklahoma. It is now housed at the North Carolina Museum of Natural Sciences in Raleigh and it is the largest specimen. It includes the only complete skull and forelimbs.

Meaning "High-spined Lizard", it had long neural spines, approximately 20 inches (50 centimeters), extending from its vertebrae, which most likely formed a ridge of muscle over it's neck, back, and tail. The purpose of the ridge is unknown. It's believed that they were used to regulate body temperature, or would've been brightley colored and attract mates, as well as warding off rival males. Others believed that they were used to store body fat when food was scarce.

Because of this, Acrocanthosaurus was once misclassed as a spinosaur, but it's now believed to be a member of the carcharodontosauridae family in the carnosauria clade, related to Giganotosaurus and Carcharodontosaurus.

The skull of this dinosaur was up to 4.3 feet (1.3 meters) long and features a large fenestra to reduce the skull's weight. It had a bony brow ridge above the eye, formed by the lacrimal and postorbital bones coming together, which is a carcharodontosaurid trait.

As in other carcharodontosaurids, the 68 thin, sharp teeth in the mouth of Acrocanthosaurus were curved and serrated, designed to cut and slice through flesh. The teeth in the lower jaw are generally smaller than those in the upper jaw.

In 2005, scientists used digital reconstructions around the brain of Acrocanthosaurus. The olfactory lobes were large and thick, indicating a good sense of smell. The reconstruction of the semicircular canals of the ear (balance organ) showed that its head was held in a 25 degree angle horizontally, usually when alerted. The brain itself was s-shaped and resemble those of a crocodile's than a bird's. It also resemble those of Giganotosaurus and Carcharodontosaurus than Allosaurus's, which strengthen the classification as a carcharodontosaurid.

The forelimbs of Acrocanthosaurus were quite unique as reconstructions of it show suggests that there would've been large amounts of cartilage between the bones. This comes from the fact that the bones themselves do not make perfect joints and to properly articulate, the bones would need extra cartilage. The arms of this dinosaur did not have a range of motion and could not fully extend. But it could only manage limited flexing. The humerus could retract back quite away, as if Acrocanthosaurus is pulling something towards its chest. As is seen in other large theropods, the arms could not twist like what human arm can and when rest, the arms would've faced inwards, like when a person clapping his (or her) hands together. Acrocanthosaurus had three fingers, with the first and second claws were probably being permanently flexed, while the third and smallest claw may have been able to retract as well.

After determining the range of motion in the joints of the forelimb, a study went on to hypothesize the predatory of this giant theropod: The arms of Acrocanthosaurus could not swing forward very far and were not likely to have used to capture prey. It probably led to its mouth when hunting. But the forelimbs were able to retract towards the body strongly. Once it lunged its head forward and caught its prey in its jaws, the Acrocanthosaurus could then impale its victims with its claws, holding the body in place while it ate.

The neck vertebrae also interlocked together for greater rigidity, meaning that this giant predator could hold on to large prey with its jaws without sustaining neck injury.

During the time this giant theropod lived, the southwestern United States was a coastal floodplain that drained into an inland sea (millions of years later, the sea would expand to the north, forming the Western Interior Seaway that split North America in two). Acrocanthosaurus was the apex predator of the region and at the top of the local food chain. Its prey included giant sauropods such as the the enormous Sauroposeidon, as well as smaller plant-eaters such as Tenontosaurus.

But its thighbone was much larger than the shinbone, meaning that Acrocanthosaurus was not a fast-running hunter. But this would've been ideal for chasing down the very large, slow-moving sauropods that it preyed on.

The famous Dinosaur State Valley Park along the Paluxy River near Glen Rose, Texas, which represents an ancient coastal shoreline during the the Early Cretaceous, contains fossil footprints that may belong to Acrocanthosaurus, though no associate skeleton was found. Associated with trackways are footprints belonging to a sauropod (probably Sauroposeidon). Scientists believed that this was evidence of a chase and attack scene, but whether if it was or not is yet to be revealed.

Note: Based on Gregory S. Paul's skeletal work!