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SaltasaurusSaltasaurus was a small sauropod of the late Cretaceous, characterized by a diplodocid-type head (with blunt teeth only in the back of the mouth) and was the first discovered with small bony plates embedded in its skin. The bony plates (osteoderms) have since been found in other titanosaurids, and a crest of scutes have also been discovered running down the back of diplodocids. When the plates of a saltosaur were originally found independently of skeletal remains, they were assumed to be from an ankylosaurian, whose plates they resemble. Changing perceptions In the Cretaceous period, sauropod dinosaurs in North America were losing the survival game to duck-billed dinosaurs, such as Edmontosaurus. However, like modern Australia, South America was an island continent and life evolved rather differently there. Specifically, the duck-billed dinosaurs never gained a foothold and so sauropods, specifically the titanosaurids, continued on their own path of evolution. (See also: allopatric speciation.) Saltasaurus (which means "lizard from Salta") was one such highly-evolved sauropod, and lived 70 to 65 million years ago. When it was first discovered in 1980, it forced palaeontologists to reconsider many of their assumptions about what was and what was not a sauropod because Saltasaurus, although clearly a sauropod, had armour plating. Previously, it had been assumed that size alone was sufficient defence for the massive sauropods. However, a Saltasaurus was discovered with covered with bony knobs 10 to 12 centimetres (4 to 5 inches) in diameter. Since then, palaeontologists have investigated the possibility that other sauropods also had armour; for example, the Argentinian Laplatasaurus. Fact summary Saltasaurus was first described by José Bonaparte and Jaime E. Powell in 1980, and has an estimated length of 12 metres (39 feet) and a mass of 7 tonnes (8 tons). Like all sauropods, Saltasaurus was purely herbivorous, and it could rear up on its hind legs to reach higher branches. The name "Saltasaurus" is taken from the region of north-west Argentina where the first fossils were recovered, and other fossils have since been found in Uruguay. There is currently only one known species of Saltasaurus, S. loricatus. S. robustus is no longer considered a distinct species, and S. australis is now considered to be a separate genus, the Neuquensaurus. The fossils of Saltasaurus include vertebrae, limb bones and several jaw bones — plus various pieces of armour. Some of these plates appear to have spikes as well, but there is not enough evidence available to be sure. The word "Saltasaurus" is occasionally spelled "Saltosaurus", even by palaeontologists. The Saltasaurus is also confused with the Saltopus because of the similarity between their names, though the two species are unlike one another. Eggs? A large titanosaur nesting ground was discovered in 1997 by Luis Chiappe and his team near Auca Mahuevot, in Patagonia, Argentina. The small eggs, about 11 to 12 centimetres (4 to 5 inches) in diameter, contained fossiled embryos, complete with skin impressions (though there was no indication of feathers or dermal spines). These eggs have may have belonged to Saltasaurus. Apparently several hundred females dug holes, laid their eggs, and then buried them under dirt and vegetation. This gives evidence of herd behavior, which along with their armor, may have been a defence against large predators like the Abelisaurus. Further reading - Walking on Eggs: The Astonishing Discovery of Thousands of Dinosaur Eggs in the Badlands of Patagonia, by Luis Chiappe and Lowell Dingus. June 19, 2001, Scribner. ISBN 0743212118.
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