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Mortality curves of extinct rodents can be reconstructed by using relative wear calculated from the amount of dentine exposed. MicroCT scanning of molars of the extinct Eomyid genus Ligerimys shows that this Wear Index increases gradually with wear; this means that wear classes can serve as a proxy for age and can therefore be used to reconstruct mortality curves. We reconstructed mortality curves of three species of Ligerimys from the late early Miocene of Spain. These curves show a similar trend, with decreasing numbers of molars as the amount of wear in each class increases. The curves show remarkable similarities to those of the wood mouse Apodemus. This suggests that Ligerimys was, like Apodemus, at the fast end of the fast-slow continuum, in other words r-selected, though not as extreme as some other rodents. [ABSTRACT FROM AUTHOR]

We describe cranial and mandibular remains of three undescribed individuals of the giant mustelid Megalictis ferox Matthew, 1907 from the latest Arikareean (Ar4), Early Miocene mammal fauna of Nebraska, and Wyoming (USA) housed at the American Museum of Natural History (New York, USA). Our phylogenetic hypothesis indicates that Ar4 specimens assigned to M. ferox constitute a monophyletic group. We assign three additional species previously referred to Paroligobunis to Megalictis: M. simplicidens, M. frazieri, and “M.” petersoni. The node containing these four species of Megalictis and Oligobunis forms the Oligobuninae. We test the hypothesis that Oligobuninae (Megalictis and Oligobunis) is a stem mustelid taxon. Our results indicate that the Oligobuninae form the sister clade to the crown extant mustelids. Based on the cranium, M. ferox is a jaguar-size mustelid and the largest terrestrial mustelid known to have existed. This new material also sheds light on a new ecomorphological interpretation of M. ferox as a bone-crushing durophage (similar to hyenas), rather than a cat-like hypercarnivore, as had been previously described. The relative large size of M. ferox, together with a stout rostrum and mandible made it one of the more powerful predators of the Early Miocene of the Great Plains of North America. [ABSTRACT FROM AUTHOR]

Deep-time perspectives in macroecology are essential with regard to understanding the impact of climate forcing on faunal communities. Using late Miocene rodent faunas (12 to 5 Ma) from two different biogeographical provinces from southwestern Europe, we asked whether the waxing and waning of faunas with dissimilar ecological affinities tracked climate in different ways. The latest middle Miocene featured a fauna dominated by dormice with forest and mixed-habitat affinities. This group declined towards the Upper Miocene. Rodent taxa with the highest values of richness at the beginning of the Upper Miocene are generalists in the southern province and specialists of forested habitats in the northern province. Finally, we identified a third, increasingly significant group of rodents linked to open landscapes towards the end of the Miocene. These three broad ecological groups showed differential responses to a complex set of interconnected circumstances, including the biogeographic structure of the study area and climatic changes throughout time. [ABSTRACT FROM AUTHOR]

A new species of Cricetodontini (Cricetidae, Rodentia, Mammalia), Cricetodon nievei sp. nov. from the Toril section (Toril 3A, Toril 3B, Toril 2) and Las Planas 5H is described. All this sites belong to the local biozone G3 (late Aragonian, late middle Miocene) from the Calatayud-Daroca Basin (Zaragoza, Spain). The new species displays a mosaic pattern consisting in a combination of primitive and derived characters: the upper molars have a basal Cricetodon-like pattern - short and not complete ectolophs -, whereas the lower molars share several derived features with the older representatives of Hispanomys - absence of metalophulid II. The generic assignation of the new taxon is further discussed and it is compared with all the species of Cricetodon and Hispanomys described until date. This mosaic evolutionary pattern of dental characters is also recognized in other species of Cricetodontini from Europe during the late Aragonian, although involving different combination of morphological characters. At this time, the diversity of the tribe increases, including species with complex morphology and higher intraspecific variability than the older representatives. The new species proposed here is morphologically close to Cricetodontini recorded outside the Calatayud-Daroca Basin, especially C. albanensis and H. decedens from France. Finally, the palaeoecological context of the new species is discussed; the stratigraphical distribution of Cricetodon nievei sp. nov. coevals changes in the faunal assemblages which are possibly related to an increase of humidity detected in the Calatayud-Daroca Basin. [ABSTRACT FROM AUTHOR]

Murine rodents represent a highly diverse group, which displays great ecological versatility. In the present paper we analyse the relationship between dental morphology, on one hand, using geometric morphometrics based upon the outline of first upper molar and the dietary preference of extant murine genera, on the other. This ecomorphological study of extant murine rodents demonstrates that dietary groups can be distinguished with the use of a quantitative geometric morphometric approach based on first upper molar outline. A discriminant analysis of the geometric morphometric variables of the first upper molars enables us to infer the dietary preferences of extinct murine genera from the Iberian Peninsula. Most of the extinct genera were omnivore; only Stephanomys showed a pattern of dental morphology alike that of the herbivore genera. [ABSTRACT FROM AUTHOR]

Material of Hispanomys (Rodentia, Cricetodontinae) is described from various localities at Batallones (MN10) (Madrid, Spain). All of it belongs to a single species, which differs from the other known species of the genus and a new taxon, , is created for it. The samples from the various localities show differences interpreted as being the result of slight age disparities amongst the different sites. Although they were previously thought to be coeval, Batallones 10 is probably older than Batallones 1, which is possibly older than Batallones 3. Hispanomys moralesi sp. nov. is characterized by several morphological features such as the lack of cingula and mesolophs, the presence of well-developed ectolophs, four- or five-rooted M1, short or absent mesolophids, and reduced and simplified M3. Hispanomys moralesi sp. nov. is a relatively derived species, the evolutionary stage of which is comparable to those of other members of the genus from the Upper Vallesian. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, , 725-747. [ABSTRACT FROM AUTHOR]

A new genus of Gliridae, Simplomys gen. nov. is proposed. It contains glirids with a simplified dental pattern from the European Early and Middle Miocene. Simplomys gen. nov. includes several species originally described as Pseudodryomys such as Simplomys simplicidens, Simplomys robustus, Simplomys julii, and Simplomys aljaphi. In addition, a new species, Simplomys meulenorum sp. nov., is proposed from the Spanish Miocene. The species of this genus share not only a very reduced and simplified dental morphology, but also unique dental proportions that clearly separate them from any other genera of Gliridae. Simplomys gen. nov. is recorded in most of the fossil faunas from the Early and Middle Miocene of the Iberian Peninsula, and shows the maximum diversity in this area during Mammal Neogene Zones MN 3 and MN 4. The genus has been also recorded in other European countries such as France, Germany, and Switzerland, conferring to this very characteristic taxon an important role for biochronological correlations within the European continent. [ABSTRACT FROM AUTHOR]