Model by Tyler Keillor, Lauren Conroy, and Erin Fitzgerald. Science

Spinosaurus vs. Alligator on Nova

Basic Stats

Name: Spinosaurus aegyptiacus
"Spine reptile from Egypt"

Age: Approximately 95 million years old

Length: 50 feet (15.2 meters)

Weight: 7.5 tons

Habitat: Rivers and banks

Diet: Fish and other aquatic animals

Location: North Africa

Semiaquatic Adaptations

  • Small nostrils located in the middle of the skull. The small size and placement of the nostrils farther back on the skull allowed Spinosaurus to breathe when part of its head was in water.
  • Neurovascular openings at the end of the snout. Similar openings on crocodile and alligator snouts contain pressure receptors that enable them to sense movement in water. It’s likely these openings served a comparable function in Spinosaurus.
  • Giant, slanted teeth that interlocked at the front of the snout. The conical shape and location of the teeth were well-suited for catching fish.
  • A long neck and trunk that shifted the dinosaur’s center of mass forward. This made walking on two legs on land nearly impossible, but facilitated movement in water.
  • Powerful forelimbs with curved, blade-like claws. These claws were ideal for hooking or slicing slippery prey.
  • A small pelvis and short hind legs with muscular thighs. As in the earliest whales, these adaptations were for paddling in water and differ markedly from other predatory dinosaurs that used two legs to move on land.
  • Particularly dense bones lacking the marrow cavities typical to predatory dinosaurs. Similar adaptations, which enable buoyancy control, are seen in modern aquatic animals like king penguins.
  • Strong, long-boned feet and long, flat claws. Unlike other predators, Spinosaurus had feet similar to some shorebirds that stand on or move across soft surfaces rather than perch. In fact, Spinosaurus may have had webbed feet for walking on soft mud or paddling.
  • Loosely connected bones in the dinosaur’s tail. These bones enabled its tail to bend in a wave-like fashion, similar to tails that help propel some bony fish.
  • Enormous dorsal spines covered in skin that created a gigantic “sail” on the dinosaur’s back. The tall, thin, blade-shaped spines were anchored by muscles and composed of dense bone with few blood vessels. This suggests the sail was meant for display and not to trap heat or store fat. The sail would have been visible even when the animal entered the water.


Science: Semiaquatic adaptations in a giant predatory dinosaur. 

National Geographic: Scientists Report First Semiaquatic Dinosaur, Spinosaurus

UChicago News: Massive hunter prowled water’s edge

National Geographic: Giant Spinosaurus Was Bigger Than T. Rex—And First Dinosaur Known to Swim

National Geographic: Mister Big (From October 2014 issue)

The New York Times: A Lost-and-Found Nomad Helps Solve the Mystery of a Swimming Dinosaur

Chicago TribuneSpinosaurus aegyptiacus revealed to be first semiaquatic dinosaur

The Washington Post: The Hunt for Spinosaurus

New York Post: Giant water-living dinosaur unveiled

PBS The Rundown: A dinosaur fit for land and water

BBC News: Spinosaurus fossil: 'Giant swimming dinosaur' unearthed

The Courier News: Spinosaurus skull comes to life at Elgin company.

University of Chicago: HIRO Assists with CT Scans of the Newly Discovered Spinosaurus