Acrocanthosaurus atokensis

  • Pronounced:  ak-ro-KANTH-uh-sawr-us

  • Diet:  Carnivore (Meat-Eater)

  • Name Means:  "High Spined Lizard"

  • Length:  40 feet (13 m)

  • Height:  16 feet (5 m)

  • Weight:  3.5 to 5 tons (3,200 to 4,500 kg)

  • Time:  Early Cretaceous - 110 mya

Fossil remains for this Dinosaur have been found in Southwestern United States

Called Acro for short, this dinosaur is a Therapod (a two-legged meat-eater) which had 68 long, knife-like teeth in its 5 foot long head. At 40 feet long, this dinosaur ruled the land about 35 million years before there were any T. rex's. Unlike T. rex, this dinosaur had larger, more powerful arms that could grab, hold and crush other dinosaurs. It could probably lift a small car off the ground!

There is one very interesting feature about the Acro, and that is the high spines along its back and neck. In fact the name Acrocanthosaurus means 'high spined lizard' in Greek (the last part of its name, atokensis, refers to Atoka County in Oklahoma where the only full skeleton was discovered).

The spines are not nearly as big as those on some dinosaurs that have 'sails' on their back, like Spinosaurus  Instead, Acro's spines, the longest of which is about 2 feet, were anchors to which huge muscles were attached. This made Acro very strong and powerful. And Acros probably needed to be very strong because there is evidence that it hunted huge sauropod dinosaurs. In Texas, there are dinosaur tracks that show a large Acro tracking and hunting a large brachiosaur called Pleurocoelus  Some modern animals have a similar type of spine along their back to give them strength: horses, elephants and buffaloes all have this type of muscle suspension.

Acro had relatively small feet for a large dinosaur. This was because it lived in a drier climate and did not need a large surface area to keep it from sinking in mud. Although similar in size and weight to T. rex, its feet were only about half the size. T. rex lived in a much wetter environment and probably spent a lot of time walking through marshy ground. The teeth of an Acro were typical of the large meat-eaters of the late Jurassic and Early Cretaceous. They were long (as much as 9 or 10 inches if you include the root) and fairly thin, curving slightly inward with serrations along the front and back edges. This means that Acro did not necessarily use its teeth as a killing tool. Teeth like this were most likely used to rip big pieces of flesh from prey which it was holding with its powerful arms and feet. Unlike T. rex, Acro teeth could not have been used to crunch bone as they would break too easily. When its teeth did break, Acro had new teeth waiting. Like many dinosaurs, it was constantly shedding old teeth and replacing them with new.

Acrocanthosaurus is in the same family of dinosaurs as the Allosaurus  which was a very successful family of dinosaurs. It was most likely the dominant North American predator of the Early Cretaceous. It is known primarily from one specimen, nicknamed 'Fran' which was discovered in Atoka County, Oklahoma by Cephis Hall and Sid Love in 1983. The specimen showed a number of interesting pathologies, including a hole in the right scapula (shoulder blade) that had become infected. The ribs beneath and in front of this scapula appear to have been broken and healed, indicating that the animal had been injured. Scattered remains of Acrocanthosaurus have been found in Oklahoma, Texas, Utah and Arizona.

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