Abstract

Ochotonidae and Leporidae are two living families belonging to the Order Lagomorpha, an ancient group of mammals originating in the Paleogene of Asia. Those families diversified in the Oligocene and Miocene. More primitive stem lagomorphs inhabited Asia during a time of tropical environmental conditions. A Mid-Cenozoic change towards more continental and arid climate in parallel with Antarctic glaciation resulted in significant reorganisation of paleoenvironmental and climatic conditions in Asia and involved the opening of terrestrial connections between Asia, Europe, and North America, allowing faunal exchanges. This promoted diversification and speciation of lagomorphs in the northern continents. Pronounced lagomorph turnover is documented for Central Mongolia, with new data obtained for the Baikalian region as well as adjacent areas. The earliest lagomorphs were represented by archaic stem genera including paleolagids. These were successively replaced by modern Ochotonidae and Leporidae that flourished during the Miocene and Pliocene. The diversity and abundance of ochotonids and leporids decreased during the Pleistocene and of ochotonids, only the pika genus Ochotona survived to the present.

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Abstract

For two hundred years the status of rodent suborders has been unstable. What are the natural groupings of extant rodent families? The formal recognition of rodent suborders has remained challenging and consensus has been elusive. Classically conceived rodent suborders are widely viewed as artificial, but no universally accepted classification has emerged to reflect the major features of rodent evolution. Over the last two decades molecular studies have established that extant rodents comprise three monophyletic clades. We review the molecular basis for these groups and recognize them as taxonomic units: Suborder Ctenohystrica HUCHON et al., 2000, Suborder Supramyomorpha D’ELÍA et al., 2019, and a group of families clustered with Sciuridae. The latter differs from Sciuromorpha as traditionally conceived because the suborder includes Aplodontiidae but excludes Castoridae. We review morphological character complexes that are distributed broadly within these three clades, name the third group Eusciurida, new suborder, and find this three-fold division of extant Rodentia to reflect well the major features of rodent phylogeny. That some morphological features do not characterize all families within suborders, or are not unique to individual suborders, indicates major parallel innovations and reversals in rodent evolution. These incongruent morphologies invite future study.

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