Data from: New species of Karydomys (Rodentia) from the Miocene of Chios Island (Greece) and phylogenetic relationships of this rare democricetodontine genus

Karydomys is a rare and little diversified democricetodontine, of which
only six species are currently recognized. This group of rodents is first
recorded in the early Miocene (MN3) in China and spread quickly thereafter
to Kazakhstan and Greece (MN4). Karydomys reached south‐western and
central Europe by early middle Miocene times (MN5), from where it became
extinct shortly thereafter (MN6). A new species of Karydomys is here
described from the Miocene Keramia Formation of Chios Island
(north‐eastern Aegean Sea). Karydomys strati sp. nov. is characterized by
the presence of a labial spur on the anterolophule, the lack of anterior
protolophule on the M1 and by the presence of a double metalophule on the
M2. A cladistics analysis involving all the species of Karydomys and some
closely related species of Democricetodon and Cricetodon show that
Karydomys split early into two different lineages, an ‘eastern stock’,
which includes the central Asian (K. debruijni and K. dzerzhinskii) and
Greek (K. symeonidisi, K. boskosi and K. strati) species, and a ‘western
lineage’ comprising the western and central European species (K. wigharti
and K. zapfei). The evolutionary stage of Karydomys strati suggests that
the lowermost part of the Keramia Formation, usually attributed to the
middle Miocene, is older than previously thought.