10 Ridged Facts About Acrocanthosaurus

This intimidating predator would look great on the big screen. Ahem, Steven Spielberg...

1. Acrocanthosaurus is the Official State Dinosaur of Oklahoma.

Acrocanthosaurus was discovered in Oklahoma’s Atoka County in the 1940s, and in 2006, it was declared the state’s official dinosaur—even though it already had a state fossil (another big carnivore named Saurophaganax).

2. It Wasn’t Much Smaller than T. Rex.

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While there aren't any complete specimens, most paleontologists estimate that a fully-grown Acrocanthosaurus would have been around 35 to 38 feet long. By comparison, Tyrannosaurus rex could reach about 40 feet. Both rank among the biggest meat-eating dinosaurs ever found.

3. Those Arms Might Have Helped it Ensnare Prey.

Orin Zebest, Flickr // CC BY 2.0

According to one 2006 study, Acrocanthosaurus’ forelimbs had a very limited range of motion. Still, despite that shortcoming, analysis revealed that the arms would have been quite adept at pulling things toward the animal's torso. Perhaps Acrocanthosaurus came up to victims from behind, sank its claws into them, and held on tight while chomping like mad.

4. Acrocanthosaurus Didn’t Keep its Chin Up.

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A 2005 computer simulation found that, given the shape of its inner ear (which helps creatures keep balanced), Acrocanthosaurus habitually let the tip of its snout point 25 degrees downward rather than straight ahead.

5. The Dinosaur Might Have Stalked Maryland.

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Though far better remains are known from Oklahoma and Texas, Acrocanthosaurus-like teeth have been found in the Old Line State.

6. A Similar-Looking Dinosaur Lived in England.

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Becklespinax was 16 feet long and lived in the UK from 142 to 132 million years ago. Its name references some long spines that protruded from its vertebrae—much like the ones we see on Acrocanthosaurus. The two are widely thought to be relatives.

7. Many Footprints Have Been Attributed to Acrocanthosaurus.

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Dinosaur Valley State Park in Glen Rose, Texas is loaded with 112-million-year-old fossilized track ways, most of which were probably made by passing Acrocanthosaurus. Some especially cool prints even hint at a prehistoric battle: While exploring the area in the ‘40s, explorer Roland T. Bird noticed a set of theropod tracks running parallel to some that were left by a sauropod. At one point, the predator appears to have broken stride and taken two consecutive right steps.

Why would it do this? Maybe the carnivorous theropod had latched on to the much bigger, long-necked herbivore. But the sauropod’s tracks show no change in spacing or direction—so if this particular animal was indeed under attack, it was weirdly relaxed about it.

8. The Animal Has Proven Very Difficult to Classify.

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Acrocanthosaurus has been viewed as a close cousin of Allosaurus, a North American predator that died out long before the ridge-backed dino came along. It’s also been lumped closer to a humongous carnivore from Africa known as Carcharodontosaurus. Thankfully, the water got slightly less murky in 2011. By comparing and contrasting several anatomical features, including the brain cavity, paleontologists Drew R. Eddy and Julia A. Clarke found that while Acrocanthosaurus definitely shared a common ancestor with Allosaurus, the dinosaur really belongs to Carcharodontosaurus’ family.

9. Acrocanthosaurus Had Plenty of Dietary Options.

etee, Flickr // CC BY-SA 2.0

One hundred and twenty-five million years ago, this massive carnivore shared its range with such sauropods as Astrodon and the 60-foot-tall Sauroposideon. A beaked, long-tailed plant-eater called Tenontosaurus was also available.

10. The North Carolina State Museum of Natural Science Once Paid $3 Million for One.

North Carolina Museum of Natural Sciences, Flickr// CC BY-NC-ND 2.0

Over the past 25 years, dinosaur skeletons have gotten absurdly expensive. In 1997, the Chicago Field Museum—backed by corporate sponsors—bought Sue, a T. rex skeleton that's 90 percent complete, for $8.36 million at auction. Shortly thereafter, the North Carolina State Museum of Natural Science found itself shelling out $3 million to secure a handsome Acrocanthosaurus from southern Oklahoma.