Acrocanthosaurus (Greek for "high-spined lizard"); pronounced ACK-roe-CANTH-oh-SORE-us
Woodlands of North America
Early Cretaceous (125 million years ago)
Size and Weight:
About 40 feet long and 6 tons
Large size; narrow ridge on back
In most ways--except for the prominent ridge along its back, from which its name ("high-spined lizard") derives--Acrocanthosaurus was a typical large theropod dinosaur, with big, powerful legs, equally powerful jaws, and relatively stunted arms. The big difference is that, while huge predators like Tyrannosaurus Rex and Giganotosaurus dominated the later Cretaceous period, Acrocanthosaurus was an apex predator of the early Cretaceous, about 125 million years ago.
As with other sail-backed dinosaurs, such as the slightly later Spinosaurus, experts are unsure about the function of Acrocanthosaurus' distinctive back ridge. It may have served as a storage place for fat (like the hump of a modern camel), as a temperature-control device (depending on whether Acrocanthosaurus was cold- or warm-blooded), or as a sexual display (that is, males with bigger, more prominent ridges had the opportunity to mate with more females).