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Spinosaurus aegyptiacus ("Egyptian spine lizard") is a theropod dinosaur species from the Albian to early Cenomanian stages of the Cretaceous period, about 95 to 93 million years ago. Its distinctions include being the longest of all meat-eating dinosaurs, rivaling even Tyrannosaurus rex (at somewhere between 12 to 20 metres (40 and 60 feet) long, 4.8 to 6 metres (16 to 20 feet) tall, and 4.5 to 6 tons, having large bones extending from the vertebrae up to 1.8 m long. These spines most likely had skin or a membrane stretching between them, forming a sail-like structure. Spinosaurus provides the name of a family of dinosaurs, the Spinosauridae, of which other members include Angaturama (probably synonymous with Irritator), Baryonyx, Irritator, Suchomimus, and Siamosaurus.

Much mystery surrounds the nature of this animal. First of all, although it has been well-known to dinosaur enthusiasts because of its unusual features, even before it was popularized by its role as main antagonist in Jurassic Park III, it is mostly known through remains that have been destroyed, aside from a few more recently discovered teeth. Unpublished jaw and skull material suggest that it may have had one of the longest skulls of any carnivorous dinosaur. Originally found in the Baharija Valley of Egypt in 1912, it was named by German paleontologist Ernst Stromer in 1915. Some of the fossils were damaged during transport back to the Munich Museum in Germany, and the remaining bones were completely lost due to Allied bombing in 1944.

Aside from its sail, notable characteristics of Spinosaurus include:

• A long, narrow snout similar to other Spinosaurids, and like them filled with conical teeth.
• A slender build.
• One enlarged, hook-like claw on each of its front limbs, perhaps for catching fish.
• Relatively short legs and long arms, leading some paleontologists to suggest it may have been quadrupedal, rather than strictly bipedal (though it was undoubtedly capable of at least facultative bipedality).

Much of this is speculation based on Baryonyx and other Spinosaurids, as no limb material has ever been attributed to Spinosaurus.

Scientists disagree whether Spinosaurus was a cursorial predator (like Tyrannosaurus rex) or a fisher, sitting lazily by riverbanks and snatching up helpless prey as they swam by. In Jurassic Park III, it is portrayed as a lethal and dangerous killer, even winning a battle with a Tyrannosaurus, but such Hollwood movie battles are little more than pure fantasy. Tyrannosaurus and Spinosaurus lived on seperate continents and were seperated by at least 30 milion years of evolution. A formidable large theropod that lived in the same time and place as Spinosaurus was Carcharodontosaurus, a huge allosauroid of Cretaceous Northen Africa, who possibly did come into conflict with Spinosaurus due, probably because of prey or territory. Spinosaurus, as noted above, was more lightly built than other large theropods, including Tyranosaurus and Carcharodontosaurus, and its elongated jaws, conical teeth and raised nostrils suggest it may have largely eaten fish or fed on carrion. Spinosaurus was likely a more generalized and oportunistic predator, possibly a Cretaceous equivalent of large grizzly bears, being biased toward fishing, though it undoubtedly took many kinds of small to medium sized prey in general. Such prey would include fish, small crocodilians, lizards, and for small and young examples, mammals, birds, and pterosaurs.

The purpose of its sail is unclear, but its very interesting that other dinosaurs of the same time and area, namely the ornithopod Ouranosaurus and the sauropod Rebbachisaurus, developed a similar structure of their dorosal vertebrae. The sail is possible analogous (not homologous) to that of the Permian mammal-like reptile, Dimetrodon, who lived before the dinosaurs even appeared, strongly points in the direction of parallel evolution.

Though we can only guess true nature of such odd structures, scientists have proposed several hypothessis about use of these sails:

• Heat regulator. If the sail was vascular, the animal could have used it to heat itself up when sunrise took place, by turning the sail at a 90 degree angle to the rising sun. This would imply that the animal was only partly warm-blooded at best and lived in climates where nighttime temperatures were cool or low and the sky usually not cloudy. It is thought that Spinosaurus and Ouranosaurus both lived in or at the margins of an earlier version of the Sahara Desert, which would explain this. However, a more likely explanation was that the sail was in fact used to radiate excess heat from the body, rather than to collect it. Large animals, due to the relatively small ratio of surface area of their body compared to the overall volume (Haldane's principle), face far greater problem of loosing excess heat at higher temperatures than gaining it at lower. Vascular sails of these dinosaurus added conisderably to the skin area of the body with minimum increase of volume; furthermore, if the sail was turned away from the sun, or positioned at a 90 degree angle towards a cooling wind, the animal would quite effectivly cool itself in the warm climate of Cretaceous Africa.
• Matting aid. Elaborate body structures of many modern-day animals usually serve to attract members of opposite sex during matting. It is quite possible sails of these dinosaurus were used for courtship, in a way similar to peacock's tail. If this was so, one could suspect the sails were lively colored, but this is a pure guesswork.
• Intimidating device. The sail was possibly used to intimidate rivals or frighten enemies, making animal look bigger than it is. The dinosaur could display its sail as a final warning signal before it would resort to open attack, like modern-day rattlesnakes use their tail.

Finaly, since things in nature rarely develop for a singular reason, it is quite possible that the sail combined all these functions, acting normaly as a heat regulator, becoming a courting aid during the mating season, and, on ocassions, turning into an intimidating device when an animal was feeling threathened.

External links

• "Spinosaurus". DinoData.

• Cretaceous dinosaurs
• Spinosaurids
• Jurassic Park species