Saltasaurus

Saltasaurus (which means "lizard from Salta") is a genus of sauropod dinosaur of the Late Cretaceous Period. Relatively small among sauropods, though still massive by human standards, it was characterized by a diplodocid-like 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 (a form of armour called osteoderms) have since been found in other titanosaurids, and a crest of scutes has 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.

The word "Saltasaurus" is occasionally spelled "Saltosaurus", even by palaeontologists. Saltasaurus may also be confused with Saltopus, because of the similarity between their names, although the two genera are quite unlike each other. Saltasaurus is also to be distinguished from Saltoposuchus.

Fact summary

Saltasaurus was first described by José Bonaparte and Jaime E. Powell, in 1980 and had an estimated length of 12  metres (39  feet) and a mass of 7  tonnes (8  tons). Like all sauropods, Saltasaurus was herbivorous, and its name is derived from the region of north-west Argentina, where the first fossils were recovered. Other fossils have since been found in Uruguay.

There is currently only one known species of Saltasaurus, S. loricatus, as S. australis is now considered to belong to a separate genus, 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 certain.

Changing perceptions

In the Cretaceous Period, sauropods in North America were no longer the dominant group of herbivorous dinosaurs, with the duck-billed dinosaurs, such as Edmontosaurus becoming the most abundant. However, on other landmasses such as South America and Africa (which were island continents much like modern Australia) sauropods, in particular the titanosaurs continued to be the dominant herbivores. (See also: allopatric speciation.)

Saltasaurus was one such titanosaur sauropod, and lived 70 to 65  million years ago. When it was first discovered, in 1980, it forced palaeontologists to reconsider some assumptions about sauropods as Saltasaurus possessed crocodile-like armour (osteoderms) 10 to 12  centimetres (4 to 5  in) in diameter. Previously, it had been assumed that size alone was sufficient defence for the massive sauropods. Since then, palaeontologists have investigated the possibility that other sauropods may also have had armour; for example, the Argentinian Laplatasaurus.

Eggs

A large titanosaur nesting ground was discovered in 1997, by Luis Chiappe and his team, near Auca Mahuevo, in Patagonia, Argentina. The small eggs, about 11 to 12 centimetres (4 to 5 inches) in diameter, contained fossilised embryos, complete with skin impressions (although there was no indication of feathers or dermal spines). These eggs 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 behaviour, which, along with their armour, may have been a defence against large predators like the Abelisaurus.