Acrocanthosaurus was a large meat-eating dinosaur that lived in North America during the Early Cretaceous Period, about 115 to 105 million years ago. Its name means high-spined lizard because of the tall neural spines that rose from its neck, back, and hips. These spines formed a long ridge along the body, making its silhouette very different from many other theropods.
Studying Acrocanthosaurus helps paleontologists understand predator roles before later giants like Tyrannosaurus appeared.
Key Facts
- Acrocanthosaurus lived about 115 to 105 million years ago during the Early Cretaceous Period.
- Estimated adult length was about 11 to 12 meters, with a mass of roughly 5,000 to 6,000 kg.
- The tall neural spines were extensions of vertebrae, not separate plates or armor.
- Speed can be estimated from trackways using v = d/t when distance and time are known.
- Weight comparison formula: percent difference = (measured difference / reference value) x 100.
- As a theropod, Acrocanthosaurus had a bipedal stance, sharp teeth, grasping forelimbs, and a carnivorous diet.
Vocabulary
- Theropod
- A group of mostly meat-eating dinosaurs that walked on two legs and includes Acrocanthosaurus, Allosaurus, and Tyrannosaurus.
- Neural spine
- A bony projection that extends upward from a vertebra and can support muscles, ligaments, or display structures.
- Fossil
- Preserved evidence of ancient life, such as bones, teeth, footprints, or impressions in rock.
- Trackway
- A sequence of fossil footprints that records how an animal moved across a surface.
- Cretaceous Period
- A geologic period from about 145 to 66 million years ago when many dinosaur groups diversified.
Common Mistakes to Avoid
- Calling the back ridge a sail like Spinosaurus, because Acrocanthosaurus had shorter, thicker neural spines that likely supported muscles or a low ridge rather than a tall sail.
- Assuming all large theropods were close relatives of Tyrannosaurus, because Acrocanthosaurus belonged to a different lineage called carcharodontosaurians.
- Treating fossil size estimates as exact measurements, because body mass and length are reconstructed from incomplete bones and comparisons with related species.
- Ignoring the time period, because Acrocanthosaurus lived millions of years before Tyrannosaurus and did not share the same ecosystems.
Practice Questions
- 1 An Acrocanthosaurus is estimated to be 11.5 m long. If a museum scale model is built at 1:25 scale, how long should the model be in meters?
- 2 A fossil trackway shows footprints spaced 2.8 m apart over 10 steps. If the dinosaur covered those 10 step intervals in 8 seconds, what was its average speed in m/s?
- 3 Explain why the tall neural-spine ridge of Acrocanthosaurus might affect how paleontologists interpret its muscles, posture, or display behavior.