Microtus (Pitymys) fatioi (Mottaz)
Fig. 26
The baculum of a single specimen (KU 67103) of M. fatioi from Zermatt, Valais, Switzerland, was examined. The baculum is immature, as evidenced by its small size, slender stalk and absence of ossified processes, therefore no characterization is included.
The baculum of another Old World species of the subgenus Pitymys, M. pyrenaicus from France, figured and described by Didier (1954:242-243), differs from all New World Pitymys examined in processing ossified lateral processes.
The status of Pitymys, as a genus or as a subgenus, is uncertain. Hall and Cockrum (1953:448) considered the North American Pitymys and Pedomys as subgenera of Microtus. They did not state specifically the basis for this point of view, but mention the fact that these two subgenera (Pitymys and Pedomys) closely resemble each other cranially. These authors did not study nor comment upon the status of the Old World Pitymys. It may be asked whether the Old World and New World Pitymys have developed as fossorial Microtus independently, or from an ancestor common to both groups and not common to any other Microtus. Matthey (1955:202) found 62 chromosomes (2N) in both the New World Pitymys pinetorum and the Old World Pitymys duodecimcostatus. This suggests, but does not prove, common ancestry.