The first saltasaurid to be discovered was Alamosaurus, found by paleontologist Charles Gilmore in Utah in 1922. The next species would not be described until Opisthocoelicaudia was named by Magdalena Borsuk-Bialynicka from a postcranial material in Mongolia in 1977. In 1980, Jose Bonaparte and Jaime Powell discovered Saltasaurus in Argentina. This was the first sauropod to be discovered with armor and proved that sauropods had thrived in Cretaceous South America. Paul Sereno eventually recognized a cladistic relationship between Opisthocoelicauda and Saltasaurus to create the family Saltasauridae. Classification The group is defined by the characteristics shared by all with the two best-known members, Saltasaurus and Opisthocoelicaudia. Paleontologists J Wilson and P Upchurch defined the Saltasauridae in 2003 as the least inclusive clade containing Opisthocoelicaudia skarzynskii, and Saltasaurus loricatus, their most recent common ancestor, and all that species’ descendants. Taxonomy This taxonomy is based on those of González Riga et al. (2009) and Curry Rogers & Wilson (2005). Family Saltasauridae Unclear Subfamilies Petrobrasaurus puestohernandezi Trigonosaurus pricei Subfamily Opisthocoelicaudiinae Alamosaurus sanjuanensis Borealosaurus wimani Opisthocoelicaudia skarzynskii Subfamily Saltasaurinae Bonatitan reigi Microcoelus patagonicus Neuquensaurus australis Neuquensaurus robustus Rocasaurus muniozi Saltasaurus loricatus Phylogeny The family is then further divided into two subfamilies. Wilson and Upchurch defined Saltasaurinae in 2003 as the least-inclusive clade containing Saltasaurus but not Opisthocoelicaudia. The same paleontologists defined Opisthocoelicaudiinae as the inverse: the least-inclusive clade containing Opisthocoelicaudia but not Saltasaurus. Some species, due to the incompleteness of their skeletons, cannot yet be placed in either subfamily. Paleobiology Geographic range Many fragmentary saltasaurids have been discovered since 1980, placing members of the family in territories as widely dispersed as today's Australia, Madagascar, and France, in addition to their earlier-known residencies in North and South America. Like the other titanosaurs, the saltasaurids where a widespread, successful group that colonized all continents in the Cretaceous. Feeding habits Like all titanosaurs, the saltasaurids possessed small, peg-like teeth that were not usable for chewing. Coproliths from an unidentified titanosaur found in India suggest a diet of conifers, cycads, and early species of grasses. Unable to chew and probably lacking gastroliths, sauropods survived by retaining plant matter in their stomachs for long periods of time, fermenting it to extract as many resources as possible. Their long necks allowed them to graze over a large area while standing, reducing energy use. Osteoderms The osteoderms of Saltasaurus consisted of numerous, large bony plates embedded in the dorsal skin, each surrounded