Two New Meadow Mice from Michoacán Mexico

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                  Two New Meadow Mice from Michoacan
                                Mexico

                                  BY

                           E. RAYMOND HALL


                  University of Kansas Publications
                      Museum of Natural History

            Volume 1, No. 21, pp. 423-427, 6 figs. in text
                          December 24, 1948


                         University of Kansas
                               LAWRENCE
                                 1948




     UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

 Editors: E. Raymond Hall, Chairman, A. Byron Leonard, Edward H. Taylor

            Volume 1, No. 21, pp. 423-427, 6 figs. in text
                          December 24, 1948


                         UNIVERSITY OF KANSAS
                           Lawrence, Kansas


                              PRINTED BY
                   FERD VOILAND, JR., STATE PRINTER
                            TOPEKA, KANSAS
                                 1948

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              Two New Meadow Mice from Michoacan, Mexico

                                  By

                           E. RAYMOND HALL


In preparing a list of kinds of mammals of which specimens have been
saved from the Mexican state of Michoacan, two heretofore unrecognized
subspecies of the Mexican meadow mouse, _Microtus mexicanus_, have been
found. Names for these and descriptions are given below.


             #Microtus mexicanus fundatus# new subspecies

    _Type._--Male, adult, skin and skull; No. 100637, Univ.
    California Mus. Vert. Zool.; 3-1/2 mi. S Patzcuaro, 7,900 ft.,
    Michoacan, Mexico; March 9, 1943; obtained by E. R. Hall,
    original no. 5882.

    _Range._--Known only from the vicinity of the type locality.

    _Diagnosis._--Size large (see measurements); color brown
    overlain with cinnamon; nasals expanded distally with
    premaxillary borders concave laterally; posterior border of
    orbit inclined posterolaterally; preorbital region and
    interparietal region depressed; incisive foramina narrow;
    zygomatic arches parallel; tympanic bullae much inflated.

    _Comparisons._--Among named subspecies of _Microtus mexicanus_,
    _M. m. fundatus_ most closely resembles _M. m. mexicanus_ but
    differs as follows: Larger in all parts measured; pelage with
    slightly less buffy color and with the buffy color that is
    present of a slightly lighter tint; posterior two-thirds of
    premaxillary border of each nasal concave rather than straight;
    posterior border of orbit forming more acute angle with sagittal
    plane of posterior part of skull; superior outline of nasals
    straight rather than depressed in posterior part; tympanic
    bullae more inflated both in vertical and horizontal planes.

    From _M. c. salvus_, the subspecies next to the westward,
    _fundatus_ differs as follows: Averaging larger in all parts
    measured; less reddish on upper parts; underparts with more
    reddish color but the reddish of lighter tint; perineal region
    buffy instead of plumbeous; nasals with premaxillary borders
    laterally concave rather than straight; superior outline of
    skull with nasal segment sloping anteroventrally and
    interparietal segment sloping posteroventrally rather than
    straight; posterior margin of orbit inclined posterolaterally
    thus forming an acute angle, instead of a right angle, with
    sagittal plane of braincase; zygomatic arches parallel rather
    than bowed outward; incisive foramina narrower; tympanic bullae
    more inflated in vertical plane.

    Relying on Bailey's (N. Amer. Fauna, 17:55, 1900) description of
    _Microtus fulviventer_, _fundatus_ differs in much larger
    tympanic bullae.

_Remarks._--The series of 59 specimens includes individuals of several
ages of both sexes. This has been a great advantage in making
comparisons with individuals of geographically adjoining subspecies
since individuals of the same age and sex could be compared. When the
skulls are laid top-side down on a flat surface the occiput is much
higher than in _salvus_.

Our specimens, taken in the dry season, were trapped mostly in runways
beneath a dense growth of grass underneath a rail fence.

    _Specimens examined._--Total, 59, distributed, with respect to
    the town of Patzcuaro, as follows: 3-1/2 mi. S, 7,900 ft., 9;
    4 mi. S, 7,800 ft., 16; 5 mi. S, 7,800 ft., 26; 9 mi. SE, 8,000
    ft., 8.

    [Illustration: FIGS. 1-6. Skulls of the type specimens of two
    subspecies of _Microtus mexicanus_. XI.
      FIGS. 1-3. _Microtus mexicanus fundatus._
      FIGS. 4-6. _Microtus mexicanus salvus._]


#Microtus mexicanus salvus# new subspecies

    _Type._--Female, adult, skin and skull; No. 52099, Chicago
    Natural History Museum; Mount Tancitaro, 11,400 ft., Michoacan,
    Mexico; July 19, 1941; obtained by F. C. Wonder, original No.
    1163.

    _Range._--Known only from Mount Tancitaro at elevations of 7,800
    to 11,400 feet.

    _Diagnosis._--Size medium (see measurements); color brown
    overlain with cinnamon; premaxillary borders of nasals straight;
    superior outline of skull nearly straight; posterior margin of
    orbit at right angle with long axis of skull; zygomatic arches
    bowed outward; incisive foramina wide; tympanic bullae small.

    _Comparisons._--From topotypes of its nearest relative,
    _Microtus mexicanus phaeus_ Merriam, _salvus_ differs as
    follows: Tail shorter; pelage with slightly more buffy (reddish)
    pigment which, nevertheless, is of a lighter tint; premaxillary
    borders of nasals straight rather than concave; superior outline
    of skull more nearly straight (less convex); inferior border of
    rostrum more nearly straight (less concave distally); palatal
    fossae uniformly shallower.

    Comparison with _M. m. fundatus_ is made in the account of that
    subspecies.

_Remarks._--The degree of difference between _M. m. salvus_ and _M. m.
fundatus_ exceeds that between _M. m. salvus_ and _M. m. phaeus_ or that
between _M. m. fundatus_ and _M. m. mexicanus_.

    _Specimens examined._--Total, 14, from Mount Tancitaro,
    Michoacan, distributed, according to elevation above sea level,
    as follows: 11,400 feet, 8; 11,000 ft., 2; 7,800 ft., 1; no
    elevation recorded, 8.

    _Measurements of the two subspecies._--Average and extreme
    measurements of ten adult males of _M. m. fundatus_ and eight
    adult males of _M. m. salvus_, are, respectively, as follows:
    Total length, 147 (135-158), 141 (134-146); length of tail, 33.4
    (30-39), 29.6 (25-32); length of hind foot, 21.1 (20-22), 20.0
    (18-21); condylobasal length, 27.7 (27.0-29.0), 25.9
    (25.5-26.2); occipitonasal length, 27.5 (26.8-28.5), 25.7
    (25.3-26.0); length of nasals, 8.0 (7.7-8.4), 7.5 (6.9-8.1);
    zygomatic breadth, 16.4 (15.9-17.2), 15.0 (14.6-15.3);
    interorbital breadth, 3.7 (3.5-3.9), 3.5 (3.3-3.6); mastoid
    breadth, 12.7 (12.2-13.2), 11.7 (11.7-11.7); alveolar length of
    upper molar series, 7.0 (6.8-7.3), 6.7 (6.5-6.9); width of
    rostrum, 5.7 (5.1-5.9), 5.3 (5.3-5.3); palatilar length, 13.3
    (12.7-14.3), 12.6 (11.9-12.9). Of _M. m. salvus_ only two
    specimens yield data for the first, second, sixth and eighth
    cranial measurements named above.

For the loan of comparative material I am grateful to Dr. Hartley H. T.
Jackson and Mr. Stanley P. Young of the Biological Surveys Collection in
the United States National Museum, Messrs. Karl P. Schmidt and Collin C.
Sanborn of the Chicago Natural History Museum, and for assistance with
the field work to the John Simon Guggenheim Memorial Foundation and to
Miss Annie M. Alexander.

  _Transmitted June 1, 1948._


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