Titanosaurs (members of the group Titanosauria) were a diverse group of sauropod dinosaurs, which included Saltasaurus and Isisaurus. When the extinction event at the end of the Cretaceous period occurred, they were the last surviving group of long necked dinosaurs. It includes some of the heaviest creatures ever to walk the earth, such as Argentinosaurus and Puertasaurus, which are estimated to have weighed up to 90 tonnes (89 long tons; 99 short tons). The group's name refers to the much earlier discovery Titanosaurus, a now dubious genus named for the mythological Titans of Ancient Greece. Together with the brachiosaurids and relatives, titanosaurs make up the larger clade Titanosauriformes.