The enigmatic Early Miocene fossorial mammal Mesoscalops montanensis shows one of the most modified humeri among terrestrial mammals. It has been suggested, on qualitative considerations, that this species has no extant homologues for humerus kinematics and that, functionally, the closest extant group is represented by Chrysochloridae. We combine here three dimensional geometric morphometrics, finite element analysis and phylogenetic comparative methods to explore the shape and mechanical stress states of Mesoscalops montanensis as well as of extant and extinct Talpidae and Chrysochloridae under realistic digging simulations. Evolutionary convergence analyses reveal that the shape of Mesoscalops montanensis represents a unique morphology in the context of fossorial mammals and that its functional performance, albeit superficially similar to that of extant Chrysochloridae, still represents a nonconvergent optimum for adaptation to digging.

Edited by Vladimir SkulachevKeywords: Ribonuclease/angiogenin inhibitor Reactive oxygen species Reactive oxygen species scavenger Mitochondria Nucleus a b s t r a c tThe data presented here show for the first time that the protein known as ''ribonuclease (RNase) inhibitor'' (RI or RNH1) is present not only in the cell cytosol, but also in mitochondria, the central organelles in cell redox homeostasis. This finding directly correlates with the reported ability of RI to protect the cell from oxidative stress, with its sensitivity to oxidation and reactivity as a reactive oxygen species scavenger. While this study was carried out we also surprisingly discovered the presence of RI in the cell nucleus. We deem that these data open new views in the investigation on the cellular role(s) of the RI.

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