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The new micromammal site of Beydere 3 represents a typical Anatolian MN3 fauna in the high diversification and abundance of Eumyarion. Notably, two Eumyarion species are new; combined, they make up almost half of the assemblage. While Eumyarion beyderensis sp. nov. shows simple morphology in upper molars, Eumyarion aegeaniensis sp. nov. shows a more complex lophs pattern. In addition, Beydere 3 yielded nine species of rodents and an ochotonid: the hamsters Cricetodon kasapligili, Mirrabella crenulata, Megacricetodon hellenicus, Democricetodon doukasi, Vallaris zappai and Eumyarion sp., the dormice Glirulus ekremi and Glis sp., the beaver Steneofiber eseri, the squirrel Palaeosciurus fissurae and Ochotonidae indet. The fauna is significant in that it represents the first common occurrence of Megacricetodon in Anatolia. Eumyarion and Megacricetodon are both dominant groups which may indicate a signal of environmental change, but still closer to wet conditions. This, in combination with the new species of Eumyarion, suggests that Beydere 3 represents a time slice which was previously not recorded in Anatolia. Radiometric dating of ashes overlying the section indicates that the age of the locality is older than 18.21 (± 0.19) Ma. [ABSTRACT FROM AUTHOR]

Equations estimating body mass were used to depict a near 5-million-year history of size change in pocket gophers and cotton rats from the Meade Basin of southwestern Kansas. Although phyletic size decrease was noted in Sigmodon minor and Geomys minor and size increase in Geomys quinni, no long-term intra-basin size trends were observed. Immediately following the Huckleberry Ridge ash-fall at 2.11 Ma, the small Pliocene cotton rat S. minor became extinct, a large cotton rat entered the basin, two gophers became extinct, and two new ones entered the basin. Assuming the same rodent contingent at the Short Haul locality as at the Aries A site, between deposition of the Borchers and Short Haul assemblages, minimally about 0.12 million years, 40% of the Meade Basin rodent fauna turned over and Microtus dispersed into North America across Beringia. Geochemical environmental proxy data did not identify significant climatic events in the Borchers Badlands Pleistocene sequence; consequently it is possible that a super-eruption from the Yellowstone caldera was at least partly responsible for size shifts in cotton rats and pocket gophers and significant modifications to the Meade Basin rodent community. [ABSTRACT FROM AUTHOR]

Establishing an evolutionary timeline is fundamental for tackling a great variety of topics in evolutionary biology, including the reconstruction of patterns of historical biogeography, coevolution, and diversification. However, the tree of life is pruned by extinction and molecular data cannot be gathered for extinct lineages. Until recently methodological challenges have prevented the application of tip-dating Bayesian approaches in morphology-based fossil-only data sets. Herein, we present a morphological data set for a group of cricetid rodents to which we apply an array of methods fairly new in paleontology that can be used by paleontologists for the analysis of entirely extinct clades. We compare the tree topologies obtained by traditional parsimony, time-calibrated, and noncalibrated Bayesian inference phylogenetic approaches and calculate stratigraphic congruence indices for each. Bayesian tip-dated clock methods outperform parsimony in the case of our data set, which includes highly homoplastic morphological characters. Regardless, all three topologies support the monophyly of Megacricetodontinae, Democricetodontinae, and Cricetodontinae. Dispersal and speciation events inferred through Bayesian Binary Markov chain Monte Carlo and biodiversity analyses provide evidence for a correlation between biogeographic events, climatic changes, and diversification in cricetids. [Bayesian tip-dating; Cricetidae; Miocene; morphological clock; paleobiodiversity; paleobiogeography; paleoecology; parsimony; STRAP.] [ABSTRACT FROM AUTHOR]