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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]

El Cerro de los Batallones is one of the most important fossil sites of the Miocene. The quantity and preservation of its fossil remains have allowed us to describe many new mammal species. One of these is Hispanomys moralesi, a derived species of the Tribe Cricetodontini, a wide group of rodents with great importance in the faunal assemblage during the Miocene. Unlike most fossil micromammals in this fossil site, we have obtained skull remains that preserve never recorded anatomical structures in this time interval. Due to the fragility of the material, it could only be studied in detail using X-ray micro-computed tomography (µ-CT Scan). With this technique, we obtained three-dimensional models of 12 skulls of Hispanomys moralesi, in which different osteological parts have been described. In this way, we compared the morphological variation of the skull with other fossil cricetids and concluded that Batallones' species is an opisthodont rodent, with a relatively elongated rostrum, a robust base of zygomatic arches and big-sized tooth rows. Opisthodont incisor characterises omnivore and herbivore diets in rodents. Therefore, these new findings of Hispanomys moralesi could allow us to describe the dietary affinities of this extinct species. [ABSTRACT FROM AUTHOR]

The material of Rotundomys (Rodentia, Cricetinae) from the Late Miocene fossiliferous complex of Cerro de los Batallones (Madrid, Spain) is described and compared with all species currently placed in the genera Rotundomys and Cricetulodon. Both the morphology and size variation encompassed in the collection of specimens from Batallones suggest they belong to a single taxon different from the other known species of these genera. A new species Rotundomys intimus sp. nov. is, therefore, named for it. A cladistic analysis, which is the first ever published concernig these taxa, has been conducted to clear up the phylogenetic position of the new species. Our results suggest that Rotundomys intimus sp. nov. inserts between R. mundi and R. sabatieri as a relatively primitive taxon inside the clade Rotundomys. The new taxon is more derived than R. mundi in having a transversal connection between the metalophulid and the anterolophulid on some m1 but more primitive than R. sabatieri and the most evolved species of Rotundomys (R. montisrotuni +R.bressanus) in its less developed lophodonty showing distinct cusps, shallower valleys, and the presence of a subdivided anteroloph on the M1. The species of Cricetulodon do not form a monophyletic group. As a member of Rotundomys, Rotundomys intimus sp. nov. is more derived than all of these taxa in its greater lophodonty and the complete loss of the anterior protolophule, mesolophs, and mesolophids. [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 species of Gliridae (Rodentia, Mammalia), Microdyromys remmerti, sp. nov., from the Aragonian type area in the Calatayud-Montalban basin (Miocene, Spain) is described. This species is characterized by combining a relatively large size and a moderately complicated to very complicated and irregular dental morphology. It has a wide and continuous range of morphological variation with intermediate forms filling all the range. In the studied localities, M. remmerti, sp. nov., displays a general increase in the complexity of the dental pattern through time, showing a unique pattern of addition of extra ridges in the lower molars. Comparisons with morphologically similar species are discussed; a taxonomical and nomenclatorial issue regarding two named species of the genus is clarified. The combination of the morphometrical features that characterize M. remmerti, sp. nov., have never been found in any other glirid material outside the Calatayud-Montalban basin, thus reinforcing the idea of the endemic character of the Gliridae faunas from the Iberian Miocene. Microdyromys koenigswaldi is proposed as most probable ancestor of M. remmerti, sp. nov. The divergent evolution of the latter species is discussed in its paleoecological context. The functional consequences of this morphological divergence could be related also with the opening of new ecological niches during the middle Aragonian (Middle Miocene). [ABSTRACT FROM AUTHOR]

The Pontils fossil site (middle Eocene, Ebro Basin, Spain) includes several vertebrate-bearing levels situated in a sequence recording a continental to marine transition. Although the locality has been known since the 1980s and scarce mammal remains have been already documented, an intensive sampling has not been developed until now. This work presents the first results of the recent field campaigns carried out at this site. Seven levels have yielded significant vertebrate remains, revealing a diverse assemblage which includes chondrichthyans, actinopterygians, amphibians, crocodilians, squamates, metatherians, eulipotyphlans, apatotherians, chiropterans, rodents, artiodactyls, perissodactyls, and primates, besides other non-vertebrate fossils. The Pontils assemblage indicates a mangrove swamp environment with warm and humid conditions and increasing marine influence towards the top of the sequence. Among mammals, primates are particularly diverse, including abundant remains of a minuscule, still undetermined omomyiform, and scarce teeth of Pseudoloris, Necrolemur, and an undetermined anchomomyin. The occurrence of larger benthic foraminifera allows the assignment of Pontils to Shallow Benthic Zone 17 (Bartonian), solving the debate about the age of the locality, previously assigned either to the Bartonian or the Lutetian. These data, together with previous magnetostratigraphic analyses, allow correlation to chrons C18r or C18n.1r, constraining the age of Pontils to between 39.58 and 41 Ma. Therefore, the Pontils site represents a new reference section for the correlation of marine and continental biostratigraphy during the middle Eocene. [ABSTRACT FROM AUTHOR]

Abstract: Vallesian (early Late Miocene) strata from the recently introduced Cañada section (province of Zaragoza, east Central Spain) have yielded fairly large insectivore assemblages. These show that, after the generally dry Aragonian, the Vallesian gave rise to more humid conditions that were favourable to insectivores, both in number of taxa, and in overall number of specimens. The assemblage of Cañada 8 (Biozone H) is dominated by shrews, whereas the assemblage of Cañada 10 (uppermost Biozone H) contains the oldest record of Desmanella in the area. This seems to signify a bioevent in which after millions of years of absence, talpids return to the area. In addition to the Vallesian assemblages, a small Turolian insectivore fauna has been recovered. On the basis of the rodents, Cañada 12 was assigned to Biozone L, and the insectivore assemblage is very similar to the assemblages from the Teruel basin of that zone. This implies that the discovery of Postpalerinaceus in Cañada 12 is the youngest published record of this large spiny hedgehog. [Copyright &y& Elsevier]

The age structures of two successive rodent communities are studied on the basis of a rich record from well-dated Miocene sections (17-10 Ma) in north-central Spain. Community age is defined as the mean of the residence times of the community members at the time of the locality age. Community ages are negatively correlated with the numbers of community members. These members are divided into residents (with continuous membership times > or =1.54 million years) and transients (with membership times <1.54 million years). During episodes of species loss, there is a preferential disappearance of transients while residents are retained, a pattern referred to as the "seniority rule." The residents define the studied communities. They are associated with early successional stages of vegetation, and transients are associated with later stages. Under stable conditions, early arrivals in succession are "transient" and replaced by competitive later arrivals. The reversed roles of transients and residents in the studied fossil record are explained by assuming high degrees of disturbance. We view the system within the context of nonequilibrium metapopulation theory, in which competitively superior species become transients because of their dependence on ephemeral late successional habitats.