Ferugliotherium is a genus of fossil mammals in the family Ferugliotheriidae from the Campanian and/or Maastrichtian period (Late Cretaceous; around 70 million years ago) of Argentina.
Although originally interpreted on the basis of a single brachydont (low-crowned) molar as a member of Multituberculata, an extinct group of small, rodent-like mammals, it was recognized as related to the hypsodont (high-crowned) Sudamericidae following the discovery of additional material in the early 1990s.
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.
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 and a variety of dryolestoids.
Ferugliotherium windhauseni was named in 1986 by Argentinean paleontologist José Bonaparte on the basis of a single second lower molar (m2) from the Late Cretaceous Los Alamitos Formation of Argentina.
[3] Bonaparte created a new family, Ferugliotheriidae, for the new species and tentatively assigned it to Multituberculata, an extinct group of mammals that was diverse during the late Cretaceous, mostly in the northern continents (Laurasia).
[2] In 1990, Bonaparte described Vucetichia gracilis on the basis of what he interpreted as two upper molars of a relative of Gondwanatherium within the order Gondwanatheria, a small mammalian group that was at the time known only from Argentinean fossils and thought to be related to xenarthrans as part of a now-discarded group called Paratheria.
[6] Two years later, Krause, Bonaparte, and Zofia Kielan-Jaworowska described additional material of Ferugliotherium (which they tentatively placed in the multituberculate suborder Plagiaulacoidea) and suggested that the supposed upper molars of Vucetichia were in fact heavily worn first lower molariforms (mf1) of Ferugliotherium.
[1] In the same year, he and Bonaparte argued once again that Ferugliotherium, Gondwanatherium, and Sudamerica formed a closely related group of multituberculates, which they called the superfamily Gondwanatherioidea.
[9] On the basis of the morphological features of the jaw fragment, they argued that gondwanatherians were not closely related to any other multituberculate group, and consequently placed them in a suborder of their own, Gondwanatheria.
Because some of this jaw's features were thought to be incompatible with a multituberculate identity, they regarded gondwanatheres (including Ferugliotherium) as Mammalia incertae sedis.
[11] However, in 2009 Yamila Gurovich and Robin Beck argued in favor of a close relationship between gondwanatheres (including Ferugliotherium) and multituberculates.
[14] Kielan-Jaworowska and colleagues described a p4 from the La Colonia Formation (Late Cretaceous of Argentina) as a new multituberculate genus, Argentodites, in 2007,[15] but Gurovich and Beck noted close similarities between this p4 and the p4 in the possible jaw fragment of Ferugliotherium and suggested that it represented Ferugliotherium or a closely related species.
702A–D are recognizable as upper incisors because they have a less acute angle at the tip and are less laterally compressed, more curved, and elliptical in cross section.
[35] Incisors of Ferugliotherium and Gondwanatherium are similar in overall shape and share a restricted band of enamel—a feature otherwise seen only in multituberculates among Mesozoic mammals.
[37] MACN Pv-RN 975, a fragment of the mandible (lower jaw) preserving one premolar, was discovered in 1991 and tentatively identified as Ferugliotherium by Kielan-Jaworowska and Bonaparte in 1996, but this assignment remains controversial.
[39] The premolar is 4.8 mm long and bears eight faint ridges on both the labial (towards the lips) and lingual (towards the tongue) sides.
[40] By its size, the number of ridges, and apparently greater length than height, it differs from all known multituberculate first, second, and third lower premolars, indicating that it is a p4.
[49] Gurovich, Guillermo Rougier, and colleagues, on the other hand, maintain that the dentary is referable to Ferugliotherium and that the p4s of Argentodites and MACN Pv-RN 975 are very similar.
[53] Gurovich and Beck attributed the difference in shape between the MACN Pv-RN 975 and Argentodites p4s to the extensive wear of the former, and suggested that the two are similar enough that they probably represent at least closely related species.
[60] However, as with the dentary MACN Pv-RN 975, the two upper premolars were excluded from Ferugliotherium and identified as multituberculates by Kielan-Jaworowska and colleagues after the discovery of the jaw of Sudamerica.
[73] On the other hand, overall patterns of cusps and ridges are essentially similar among Ferugliotherium, Gondwanatherium, and Sudamerica, indicating that the three are closely related.
[75] LACM 149371, an enigmatic tooth from the Paleogene of Santa Rosa, Peru, may represent an upper molar of an animal related to Ferugliotherium.
[78] The Los Alamitos Formation is located in southeastern Río Negro Province, in the vicinity of the town of Cona Niyeu[80] and was probably deposited in a marshy environment.
[81] In 1983, it yielded the first Mesozoic mammal to be found in Argentina, Mesungulatum houssayi,[82] and since then, the mammalian fauna has expanded to 14 species.
[84] Other fossils found in the Los Alamitos Formation include fish, frogs, turtles, madtsoiid snakes, dinosaurs such as Secernosaurus, gastropods, and other invertebrates.
[85] The La Colonia Formation outcrops in north-central Chubut Province, and the mammalian fossils come from the Mirasol Chico valley.
The formation includes fluvial (river), deep-sea, and near-shore deposits, and the mammalian fauna probably comes from an estuary, tidal flat, or coastal plain.
[88] The high-crowned sudamericids were probably herbivores, but the lower-crowned Ferugliotherium was more probably an insectivore or omnivore, like similar multituberculates such as Mesodma, which is thought to have eaten insects, other arthropods, seeds, and/or nuts.