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Spinosaurus: The Largest Carnivorous Dinosaur

Spinosaurus was the biggest of all the carnivorous dinosaurs, larger than Tyrannosaurus and Giganotosaurus. It lived during the middle of the Cretaceous Period about 112 million to 97 million years ago, roaming the swamps of North Africa.

Two Spinosaurus species have been named based on the region where they were discovered: Spinosaurus aegyptiacus (Egyptian spine lizard) and Spinosaurus maroccanus (Moroccan spine lizard).

Artwork by Scott Hartman reveals the bone structure of Spinosaurus.
Artwork by Scott Hartman reveals the bone structure of Spinosaurus.
Credit: © Scott Hartman / All rights reserved

Spinosaurus means "spine lizard," an appropriate descriptor, as the dinosaur had very long spines growing on its back to form what is referred to as a "sail." The spines were more than 10 times the diameter of the vertebrae structures from which they extended and were slightly longer front to back at the base than higher up.

The distinctive spines were about 5.4 feet (1.65 m) long and were likely to have been connected by skin. Because the spines were connected by tissue, the structure may also have been more of a large hump than a sail, according to German paleontologist Ernst Stromer.

There has been much scientific debate regarding the evolution and purpose of the Spinosaurus' sail. It is possible that the sail served multiple purposes, including regulating body temperature by absorbing heat, and attracting mates. Because of its size, the Spinosaurus did not have many predators, but the sail could have been used to ward off enemies, as the dinosaur appeared to be twice its size when the sail was fully extended. Paleontologists theorize that the sails were brightly colored, much like the fins of some modern-day reptiles.

The dinosaur's upper spine was fairly flexible and its vertebrae had ball-and-socket joints, so it was likely able to arch its back to a point and may have been able to spread the sail when threatened or looking to attract a mate.

The Spinosaurus' sail was unusual, although other dinosaurs — including the Ouranosaurus, which lived a few million years earlier in the same general region as Spinosaurus, and the South American Amargasaurus — might have developed similar structures emanating from their vertebrae.

More gigantic than Giganotosaurus

Spinosaurus weighed an estimated 7 to 23 tons (6,350 to 20,870 kg), outweighing Giganotosaurus by half a ton and T. rex by about a ton. Its length ranged from 41 feet to 59 feet (12.6 m to 18 m).

It is believed that Spinosaurus walked on two muscular legs most of the time, although it may have moved on all fours at times based on the length of its arms and fossil tracks. Spinosaurus may have been able to run 12 mph to 15 mph (19 kph to 24 kph), making it relatively fast for its size.

Spinosaurus had a long and narrow snout at the end of its skull. It had six or seven needle-like teeth on each side of the very front of the upper jaw and another twelve behind them. There were a few large teeth at the end of its snout. While its jaw was powerful, none of the teeth were serrated, making it unlikely that it could have used them to tear into tough prey. This gives credence to the theory that it mostly survived on fish and carcasses.

A small crest above its eyes was thought to provide a shield from the sun, or perhaps provide the dinosaur the ability to glance at its prey without being spotted.

spinosaurus
Spinosaurus lived during the late Cretaceous Period.
Credit: Joe Tucciarone

What did Spinosaurus eat?

Spinosaurus is thought to have survived primarily on fish and scientists believe its eating habits resembled that of modern-day crocodiles. There is evidence that it lived on both land and sea.

The only direct substantiation that Spinosaurus ate fish was a juvenile discovered with fish scales and bones in its stomach. There is also evidence that it preyed on other small herbivore dinosaurs and scavenged.

Spinosaurus lived in Egypt and Morocco. There is speculation that the Sahara is rich with Spinosaurus fossils, but the harsh environment makes them difficult to unearth.

Fossil discoveries

Very few Spinosaurus fossils have been discovered and no complete remains have been found. The first Spinosaurus partial skeleton was unearthed in 1912 by Richard Markgraf in the Bahariya Formation of western Egypt.

These original remains, which were described and named by Ernst Stromer in 1915, were destroyed in Allied bombing raids on Munich, Germany, during World War II. It is only due to Stromer's meticulous notes, including detailed descriptions and sketches, that much of the scant knowledge surrounding this dinosaur has been retained.

In 2011, a neck vertebra from a dinosaur with a snout resembling that of a crocodile — believed to be a Spinosaurus — was found in Australia, showing that the creature had a much wider range than scientists had previously thought possible.

— Kim Ann Zimmermann, LiveScience Contributor

Learn about the prominent back sail, bones, habitat and other secrets of Spinosaurus.
Learn about the prominent back sail, bones, habitat and other secrets of Spinosaurus.
Credit: Ross Toro, Livescience contributor

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