Ferugliotherium

Ferugliotherium is a genus of fossil mammals from the Campanian and/or Maastrichtian (Late Cretaceous, around 70 million years ago) of Argentina in the family Ferugliotheriidae. It contains a single species, Ferugliotherium windhauseni, which was first described in 1986. Originally interpreted as a member of Multituberculata, an extinct group of small, rodent-like mammals, on the basis of a single brachydont (low-crowned) molar, it was recognized as related to the hypsodont (high-crowned) Sudamericidae after the discovery of additional material in the early 1990s. After a jaw of the sudamericid Sudamerica was described in 1999, these animals (collectively known as Gondwanatheria) were no longer considered to be multituberculates and a few fossils that were previously considered to be Ferugliotherium were assigned to unspecified multituberculates instead. Since 2005, a relationship between gondwanatheres and multituberculates has again received support. A closely related animal, Trapalcotherium, was described in 2009 on the basis of a single tooth.

About twenty teeth and a jaw fragment have been referred to Ferugliotherium, but the assignment of many of these is controversial or has been superseded. The upper and lower incisors are long and rodent-like and have enamel on only one side of the crown. A fragment of the lower jaw shows that the tooth socket of the lower incisor was very long, extending below the fourth premolar (p4). The p4 is preserved in this fragment. It is blade-shaped and resembles multituberculate p4s. However, the determination of this fossil as Ferugliotherium is in question. The identity of a few additional isolated premolars assigned to Ferugliotherium, some resembling multituberculates, is also uncertain. The first lower molariform (molar-like tooth; mf1) is known from four examples, of which two were originally identified as upper molars of a different species (Vucetichia gracilis), which is now considered a synonym of Ferugliotherium. They bear two longitudinal rows of three or four cusps and transverse crests and furrows. A single example each of the second lower (mf2) and first upper molariform (MF1) show that these teeth also had longitudinal cusp rows and transverse furrows and crests, but the mf2 had only two or perhaps three cusps per row and the MF1 had three longitudinal rows.

Although Ferugliotherium teeth are much lower-crowned than those of the Sudamericidae, they share an essentially similar pattern on the occlusal (chewing) surface of mf1 and mf2, similar incisors, backward jaw movement during chewing, and enamel with small prisms. Ferugliotherium is thought to have been a small animal, with a body mass of about 70 g (2.5 oz), and may have eaten insects and plant material. Its remains have been found in two geological formations of southern Argentina, where it is part of a mammal fauna that also includes the sudamericid Gondwanatherium, a variety of dryolestoids, and the possible triconodont Austrotriconodon.