MEANING: High spined lizard
PERIOD: Early Cretaceous
CONTINENT: North America
Acrocanthosaurus is a carcharodontosaurid dinosaur from the Early Cretaceous of what is now North America. Large theropod footprints discovered in Texas are theorized to have been made by Acrocanthosaurus. It had a long narrow skull, with low ridges rising from the nasal bones, running along each side of the snout from the back toward the eye. Acrocanthosaurus is best known for the tall neural spines on the vertebrae down the neck, back, and upper tail. These spines likely supported a ridge of muscle down its back. It was one of the largest theropods, reaching around 11 m in length and weighing up to 7 t.
Acrocanthosaurus is from the Cretaceous. The Cretaceous is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period.
The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct flora and fauna, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth by the end of the Cretaceous, coincident with the decline and extinction of previously widespread gymnosperm groups.
The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary (K–Pg boundary), a geologic signature associated with the mass extinction that lies between the Mesozoic and Cenozoic Eras.
Acrocanthosaurus is a carcharodontosaur. Carcharodontosauridae is a family of large carnivorous theropod dinosaurs. The group includes some of the largest land predators ever known. Carcharodontosaurids were present on nearly every continent through the Early Cretaceous, and in the Late Cretaceous they were replaced by the abelisaurids in Gondwana and tyrannosaurids in North America and Asia.
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