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Previously known only from isolated teeth and lower jaw fragments recovered from the Cretaceous and Palaeogene of the Southern Hemisphere, the Gondwanatheria constitute the most poorly known of all major mammaliaform radiations. Here we report the discovery of the first skull material of a gondwanatherian, a complete and well-preserved cranium from Upper Cretaceous strata in Madagascar that we assign to a new genus and species. Phylogenetic analysis strongly supports its placement within Gondwanatheria, which are recognized as monophyletic and closely related to multituberculates, an evolutionarily successful clade of Mesozoic mammals known almost exclusively from the Northern Hemisphere. The new taxon is the largest known mammaliaform from the Mesozoic of Gondwana. Its craniofacial anatomy reveals that it was herbivorous, large-eyed and agile, with well-developed high-frequency hearing and a keen sense of smell. The cranium exhibits a mosaic of primitive and derived features, the disparity of which is extreme and probably reflective of a long evolutionary history in geographic isolation. The gondwanatherians were mammals known only from teeth and some jaw fragments that lived in the southern continents alongside dinosaurs; here the entire cranium of a bizarre and badger-sized fossil mammal from the Cretaceous of Madagascar shows that gondwanatherians were related to the better-known multituberculates, a long-lived and successful group of now-extinct rodent-like mammals. Anatomy of a Gondwana mammal The gondwanatheres were mammals that lived the southern continents alongside the dinosaurs during the Late Cretaceous and early Paleocene. Known only from a few teeth and some jaw fragments, their appearance and evolutionary relationships remained obscure. The entire skull of a bizarre and badger-sized fossil mammal from the Cretaceous of Madagascar changes all that. Although almost certainly highly derived — as one would expect from a member of the unique endemic island fauna of Madagascar at that time — Vintana is clearly a gondwanathere. The anatomy of the herbivorous, large-eyed and agile creature shows that gondwanatheres were related to the better-known multituberculates, a long-lived and successful group of (now also extinct) rodent-like mammals.

The mammalian fossil record is largely composed of isolated teeth and tooth-bearing elements. In vertebrate microfossil assemblages with closely related, co-occurring species of mammals, it can be difficult to identify isolated teeth to species level because morphological differences among species may be slight and based on a single tooth position. Here we investigate the utility of the allegedly diagnostic lower fourth premolar (p4) for species-level identification in the genus Mesodma (Multituberculata, Neoplagiaulacidae). We conducted linear and geometric morphometrics on 86 p4s representing four Cretaceous-Paleogene (K-Pg) species of Mesodma that are common in deposits of the western interior of North America. Although Mesodma has been extensively discussed in the literature, these four species overlap considerably in p4 size and shape, making species-level identifications challenging. Using linear measurements, landmarks, and semilandmarks, we quantified p4 size and shape to understand morphological variation across the genus and uncover practical sources of morphological differentiation among the species represented here. Our results indicate (1) size is more important than shape for identifying p4s of Mesodma species; p4 shape varies across the genus, but cannot be used alone to identify isolated p4s to species; (2) M. garfieldensis and M. thompsoni cannot be distinguished from each other using p4 size or shape; we therefore subsume M. garfieldensis within M. thompsoni ; and (3) M. formosa increased in size across the K-Pg boundary. In light of these results, we recommend that taxonomic diagnoses relying on isolated teeth incorporate quantitative analyses of morphology whenever possible to increase the accuracy of species-level identifications and paleofaunal studies that employ them.

A new mammal fauna from the earliest Eocene of Le Clot (Corbières, Southern France) is described. Some taxa identified there, such as Corbarimys hottingeri and Paschatherium plaziati , allow a correlation with the previously described Corbières fauna of Fordones. Moreover, the presence at Le Clot of Lessnessina praecipuus , which is defined in Palette (Provence, Southern France) allows correlating both localities. All three of these localities are referred to the MP7 reference level, even if a direct correlation with the type locality of MP7 (Dormaal, Belgium) is not ascertained. A Southern Europe biochronological sequence is proposed for the beginning of the Eocene: Silveirinha, Fordones/Palette/Le Clot, Rians/Fournes. The diagnosis of a new species of a neoplagiaulacid multituberculate (? Ectypodus riansensis nov. sp.) is proposed. From a compilation of data concerning the earliest Eocene faunas from both Northern Europe and Southern Europe, we conclude that two faunas corresponding to two distinct palaeobiogeographical provinces existed in Western Europe. This faunal disparity, probably related to climatic differences, makes correlations particularly difficult between the two provinces.

Gondwanatheria is a group of extinct mammals known from the Cretaceous and Paleogene of Gondwana. Resolution of the phylogenetic affinities of gondwanatherians has proven problematical, with the group currently considered Mammalia incertae sedis . We briefly review the morphology of known gondwanatherians, and argue that isolated upper premolars and a partial dentary preserving a blade-like p4 originally referred to the ferugliotheriid gondwanatherian Ferugliotherium windhauseni but subsequently identified as Multituberculata incertae sedis do indeed belong to F. windhauseni . We also suggest that the recently described ?cimolodontan multituberculate Argentodites coloniensis , based on an isolated lower premolar, may in fact be an unworn p4 of Ferugliotherium or a closely related taxon. We present the first phylogenetic analyses to include gondwanatherians, using maximum parsimony and Bayesian methods. Both methods place Ferugliotherium and sudamericid gondwanatherians in a clade with cimolodontan and “plagiaulacidan” multituberculates, although relationships within this clade are largely unresolved. The Gondwanatheria + Multituberculata clade supported here may reflect the convergent evolution of similar dental features, but it is the best supported hypothesis based on currently available data. However, denser sampling of multituberculate taxa and the discovery of more complete gondwanatherian fossils will be required to clarify the precise relationship between gondwanatherians and multituberculates, specifically to determine whether or not gondwanatherians are members of Multituberculata. We hypothesize that the anterior molariforms of sudamericid gondwanatherians evolved from blade-like precursors similar to the p4 of Ferugliotherium , possibly in response to the appearance of grasses in Gondwana during the Cretaceous.

A new species multituberculate lumpsucker Eumicrotremus multituberculatus from the western part of the Aleutian Islands of the Bering Sea is described. The absence of tubes of the anterior nostrils and the presence of very short tubes of the posterior nostrils, numerous and very small conical bone plaques on the head and the trunk (15–17 in the circumpectoral row) without the central large spine on the plaque top distinguish the new species from other species of the genus Eumicrotremus . The new species is also differed by the terminal shape of mouth, equal length of jaws and smaller size of eye from the close species E. asperrimus and E. phrynoides . The sizes of pre-spawning females of E. multituberculatus are much less, than those of E. asperrimus . E. multituberculatus also differs from E. phrynoides by the presence of three to four rows of bone plaques on the throat and the presence of bone plaques on the rays of the first dorsal fin, and from E. asperrimus —by a dark peritoneum.