FerugliotheriumBonaparte, the first known multituberculate from South America

Abstract

Ferugliotherium windhauseni Bonaparte 1986a, the only known species of the Ferugliotheriidae, is the first multituberculate recognized from South America. It is known from the previously described holotype ml and 12 additional isolated teeth (m1, M1, and, tentatively, three lower incisors, one lower premolar, four upper incisors, and two upper premolars), which we describe here. All of the specimens were discovered in the Campanian Los Alamitos Formation of Argentina at one locality, Estancia Los Alamitos. Two other teeth, a purported lower premolar and a large lower incisor, both from the same locality and both previously referred to F. windhauseni, probably do not belong to that taxon. The lower premolar is unidentifiable and the lower incisor is probably referable to Gondwanatherium patagonicum. We regard two worn specimens previously identified as upper molars and comprising the hypodigm of Vucetichia gracilis Bonaparte, 1990 as probable mis of F. windhauseni. Vucetichia, previously assigned to the Gondwanatheriidae, is therefore probably a junior synonym of Ferugliotherium but formal synonymy is deferred pending the recovery of more nearly complete m1s of Ferugliotherium and/or less worn molars of Vucetichia. The gross dental morphology of the new specimens and the inferred pattern of jaw movement help to confirm the multituberculate affinities of F. windhauseni. The Ferugliotheriidae is more derived than the Haramiyoidea and Paulchoffatoidea but probably still retained more than two lower premolars and generally low cusp formulae on m 1 and M 1; these characteristics indicate that a cimolodont grade of organization had not been attained. The family, tentatively assigned to the Plagiaulacoidea, is considered a derived member of that group, possibly most closely related to an undescribed genus from the Upper Jurassic Morrison Formation. In other characters (e.g., presence of fully restricted band of enamel on central incisors, development of lingual row of cusps on M1, large size of m1 relative to m2), ferugliotheriids resemble either taeniolabidoids or ptilodontoids, or both. The Ferugliotheriidae differ from all other known multituberculates in possessing prominent transverse ridges and furrows on the molars. This unique mosaic of attributes indicates a significant interval of isolation from Laurasian populations.