Based on the Argentinosaurus bones they found and information about related dinosaurs, scientists made a hypothesis, or best guess, about what a complete Argentinosaurus skeleton looked like. The Argentinosaurus skull was not found, but scientists knew what the skulls of related dinosaurs looked like. They also knew about how big the skull should be based on the size of the other bones. The scientists gave this information to artists, and the artists made models of the missing bones.