Comments on the Taxonomic Status of Apodemus peninsulae, with Description of a New Subspecies from North China

In the past several years the United States National Museum has received a large number of mammals from central and southern Korea through the auspices of the Commission on Hemorrhagic Fever of the Armed Forces Epidemiological Board. Among these Korean collections are more than a hundred specimens of a murine rodent originally described as Micromys speciosus peninsulae by Oldfield Thomas but currently placed in the genus Apodemus . In attempting to ascertain the specific relationships of this mouse I have examined, through the generosity of Dr. David H. Johnson, Acting Curator of Mammals, most of the other Oriental specimens of the subgenus Sylvaemus in the U. S. National Museum and it is on this combined material that the following comments and description are based.
Fig. 1. Ventral views of skulls and left maxillary tooth-rows of two species of the genus Apodemus. a. Apodemus flavicollis flavicollis (Melchior), Lolland, Denmark, adult ♂, No. 141691 USNM, ×2. b. Apodemus flavicollis flavicollis (Melchior), Mauseklippe, Germany, young ♂, No. 112895 USNM, ×10. c. Apodemus peninsulae peninsulae (Thomas), Central Nat'l Forest, near Pup'yong-ni, 200 m., Korea, subadult ϓ2, No. 300650 USNM, ×10. d. Apodemus peninsulae peninsulae (Thomas), 6 mi. S Yongdongp'o, Korea, adult ♂, No. 299554 USNM, ×2.
In comparing the ventral views of skulls note especially the size and location of incisive foramina and posterior palatine foramina as well as the breadth of mesopterygoid fossae. In comparing the left maxillary tooth-rows note especially the size of M3 and the reduced posterointernal cusp on Ml in A. peninsulae .]
More recently, Ellerman (1949:32) and Ellerman and Morrison-Scott (1951:566) have arranged peninsulae as a subspecies of Apodemus flavicollis under the assumption that all the members of the subgenus Sylvaemus on the eastern Asiatic mainland are subspecies of one or another of the species of western Europe, A. flavicollis or A. sylvaticus . Ellerman (in Ellerman and Morrison-Scott, 1951:564) states: The majority of the forms I distribute in a somewhat arbitrary manner between sylvaticus , average smaller skull, and flavicollis , average larger skull; occurring together nearly throughout the Palaearctic. I feel fairly sure that there are some errors of judgment in my arrangement, and equally sure that there is no other way to define species in this very large and difficult group. I have compared the specimens of peninsulae available to me from central and southern Korea with specimens of A. f. flavicollis from Denmark, Germany and Sweden and find, although the two are similar in many ways, that peninsulae differs from flavicollis in several important characters: Mammae 1-2=6 in flavicollis , and 2-2=8 in peninsulae ; incisive foramina reaching level of alveoli of M1, or nearly so, in flavicollis , but ending conspicuously short of that level in peninsulae ; posterior palatine foramina large in flavicollis and opposite a point where M1 and M2 meet, but small in peninsulae and situated farther back on the palate, opposite M2. Moreover, peninsulae lacks the characteristic buffy throat patch of flavicollis , has a much reduced posterointernal cusp on the M1, a relatively (frequently actually) larger M3 and, on the average, a broader mesopterygoid fossa. In view of these differences, all of which appear to be constant, I consider peninsulae specifically distinct from flavicollis . Throughout its known geographic range (see below) peninsulae is evidently confined to wooded terrain, either scrub or brush types or forested areas, and the vernacular name wood mouse, therefore, seems appropriate for this species.