Superfamily Gondwanatherioidea: a previously unrecognized radiation of multituberculate mammals in South America.

Multituberculates were the longest-lived order of the Class Mammalia and, during the Mesozoic and early Cenozoic, were among the most diverse and abundant representatives of the class. However, until the recent discovery of two Cretaceous teeth, one from South America and one from Africa, they were known only from northern continents. Additional material of the South American form Ferugliotherium has confirmed its multituberculate affinities and indicates that it may be a derived member of the Suborder Plagiaulacoidea. New specimens provide evidence that two other South American forms, Gondwanatherium and Sudamerica, are also multituberculates and that they are closely related to Ferugliotherium. Gondwanatherium and Sudamerica, each possessing highly specialized hypsodont molars, were previously thought to be the earliest known representatives of the Edentata, to be involved in the origin of edentates, or to represent a previously unknown higher taxon of mammals. However, there are detailed similarities in gross dental morphology, enamel microstructure, and inferred direction of jaw movement among Ferugliotherium, Gondwanatherium, and Sudamerica. All three genera are here regarded as representatives of a highly derived, endemic radiation of South American multituberculates and are allocated to the superfamily Gondwanatherioidea. Multituberculates were therefore more common elements of Late Cretaceous and early Paleocene mammalian faunas of South America than previously recognized.