Acrocanthosaurus atokensis

Overview

Acrocanthosaurus, meaning "high-spined lizard," was one of the largest predators to ever roam North America! Living approximately 116-110 million years ago during the Early Cretaceous, this massive meat-eater had a distinctive row of tall spines running down its back and was the apex predator of its ecosystem—basically the T. rex before T. rex!

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Taxonomy & Classification

• Clade: Theropoda
• Family: Carcharodontosauridae
• Diet: Carnivorous
• Locomotion: Bipedal

Acrocanthosaurus was related to giant Southern Hemisphere predators like Giganotosaurus and Carcharodontosaurus.

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Physical Characteristics

Size & Build

• Length: 11-11.5 meters (36-38 feet)
• Height: About 3.5 meters (11.5 feet) at the hip
• Weight: 4,400-6,600 kg (4.8-7.3 tons)
• Skull Length: About 1.3 meters (4.3 feet)

The High Spines

Acrocanthosaurus's most distinctive feature:

• Tall neural spines along the neck, back, and tail
• Up to 17 inches (43 cm) tall on some vertebrae!
• Created a ridge or low hump down its back
• NOT a thin sail like Spinosaurus—more of a muscular ridge

What Were the Spines For?

• Muscle attachment—extra power for the back
• Display—making it look bigger and more impressive
• Species recognition—"I'm an Acrocanthosaurus!"
• Possibly fat storage for lean times
• Could have been brightly colored

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The Ultimate Predator

Top of the Food Chain

Acrocanthosaurus was the dominant predator of its time:

• No other large predators in its ecosystem
• Hunted giant sauropods like Sauroposeidon
• Also ate large ornithopods like Tenontosaurus
• Had no natural predators as an adult

Hunting Weapons

• Large, serrated teeth for slicing flesh
• Powerful jaw muscles
• Strong arms with three huge claws
• Could use arms to grip prey while biting

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Following the Footprints

Glen Rose Trackways

Amazing evidence of Acrocanthosaurus hunting:

• Dinosaur Valley State Park in Texas
• Tracks show Acrocanthosaurus following sauropods!
• Multiple trackways preserved in rock
• Shows a predator stalking potential prey
• One of the most famous dinosaur track sites in the world

What the Tracks Tell Us

• Acrocanthosaurus could walk and run on two legs
• It actively hunted sauropods
• Tracks are about 2 feet (60 cm) long
• Shows it was a persistent hunter

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Acrocanthosaurus vs. T. rex

Feature	Acrocanthosaurus	T. rex
Length	11-11.5m	12m
Weight	4.4-6.6 tons	8-9 tons
Time	116-110 mya	68-66 mya
Arms	Long, 3 claws	Very short
Bite	Slicing	Crushing
Spines	Tall, ridge	Normal

Acrocanthosaurus was the Early Cretaceous version of T. rex—ruling before T. rex evolved!

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"Fran" - The Famous Skeleton

A Nearly Complete Fossil

• Found in McCurtain County, Oklahoma in 1990
• Named "Fran" after amateur paleontologist Fran Graffham
• About 70% complete—very rare!
• Now displayed at the North Carolina Museum of Natural Sciences
• One of the best theropod skeletons ever found

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Where It Lived

Early Cretaceous North America

Acrocanthosaurus fossils have been found in:

• Oklahoma (the famous "Fran" skeleton)
• Texas (Glen Rose tracks)
• Wyoming and Maryland
• Lived in warm, coastal plains with rivers
• Lots of prey animals available!

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The Arms Question

Strong Arms

Unlike T. rex, Acrocanthosaurus had useful arms:

• Three-fingered hands with large claws
• Arms could reach its mouth
• Strong enough to hold struggling prey
• May have helped pin down large animals
• A significant hunting advantage!

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Cool Facts

• Acrocanthosaurus was the largest predator in North America during the Early Cretaceous!
• Its footprints in Texas show it actively hunted sauropods
• The tall spines were not a sail—they were covered in thick muscle
• Unlike T. rex, it had strong, functional arms
• "Fran" the skeleton is worth millions of dollars!
• Baby Acrocanthosaurus were probably covered in fuzz or feathers
• It was named in 1950 but became famous with better fossils in the 1990s

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Acrocanthosaurus was the ruler of Early Cretaceous North America—a high-spined giant that hunted the biggest dinosaurs of its time!