Spinosaurus (meaning "spine lizard") was one of the largest theropod dinosaurs during the Late Cretaceous period, about 99 to 93.5 million years ago.

This genus was known first from Egyptian remains discovered in 1912 and described by German paleontologist Ernst Stromer in 1915. The original remains were destroyed in World War II, but additional material has come to light in the early 21st century.

Spinosaurus is believed to have primarily fed on large fish. This is based on its elongated skull, spear-like teeth, location of the nostrils on the snout, and its habitat along the North African coast.

It has been suggested that the dorsal sail of Spinosaurus was analogous to the dorsal fins of sailfish (the fastest marine animal on Earth) and served a similar hydrodynamic purpose. Like sailfish, they may also have used their sail to herd schools of fish into a "bait ball".

Based on extrapolations from skull measurements, a 2005 study in the Journal of Vertebrate Paleontology estimated Spinosaurus was 52 to 59 feet long (16 to 18 m)--making it the largest carnivorous dinosaur of all time, larger than Tyrannosaurus and Giganotosaurus.

Estimates of Spinosaurus' weight vary considerably but it is believed to have weighed as much as 20 tons--the equivalent of 3 African elephants!

According to current estimates, Spinosaurus with its spine included stood approximately 18 feet tall. That's the average height of a giraffe.

Spinosaurus anatomy exhibits another feature that may have a modern analogy: its long tail resembles that of the thresher shark, which is used to slap the water to herd and stun shoals of fish before devouring them.

Unlike other theropods, the hallux (or fourth toe) of Spinosaurus touched the ground, and the phalanges of the toe bones were unusually long and well-built. At their ends were shallow claws that had flat bottoms. This type of foot morphology is also seen in shorebirds, indicating that Spinosaurus feet evolved for walking across unstable substrates such as sand or mud and that they may have been webbed.

Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. If the sail contained abundant blood vessels, Spinosaurus may have used its large surface area to absorb heat. This would imply that the animal was only partly warm-blooded and lived in climates where night-time temperatures were low and the sky usually not cloudy. It is also possible that the sail was used to radiate excess heat from the body, rather than to collect it.