North American Jumping Mice (Genus Zapus)

Name: North American Jumping Mice (Genus Zapus)
Author: Krutzsch, Philip H. (Philip Henry)

Krutzsch, Philip H. (Philip Henry)

Zapus

A comparison of coefficients of variation (see table 3) for cranial
measurements between populations of like age and sex for the species _Z.
hudsonius_, _Z. princeps_, and _Z. trinotatus_ shows that variation of
approximately the same degree is recorded in corresponding elements in
all species; that is to say, structures which are most variable
individually in _Z. princeps_ are also most variable in _Z. trinotatus_
and _Z. hudsonius_.

Individual variation in the occlusal pattern of the molariform teeth is
slight. In several specimens, however, the re-entrant fold is absent
from the lingual surface of M1. Teeth in addition to the normal number
were recorded for five specimens. In all instances they are in the upper
dentition and usually at the posterior end of the maxillary tooth-row.
In each of four specimens (KU No. 34852, KU No. 32852, MVZ No. 52105,
all _Z. princeps_, and USBS No. 22921, _Z. hudsonius_), there is only a
single additional tooth. One individual (USBS No. 264388, _Z. princeps_)
possessed two extra molars, one in each maxillary tooth-row. The extra
teeth vary in size from those which are only slightly smaller than the
adjacent normal molars to those which are simple, peglike structures. In
four of the five animals the extra teeth are posterior to the normal M3;
in the fifth (MVZ No. 52105) the added tooth is anteriormedial to M3.

    TABLE 3.--Coefficients of Variation for Dimensions of Corresponding
       Parts of the Skull of Three Species of Zapus. The Specimens of
       Zapus hudsonius are from Menominee and Keweenaw counties, Michigan,
       the Zapus princeps are from the Vicinity of Encampment, Wyoming,
       and the Zapus trinotatus from Huntingdon, British Columbia.

  ==============================+=============+============+==============
                                |   _Z. h._   |   _Z. p._  |    _Z. t._
              Species           | _hudsonius_ | _princeps_ | _trinotatus_
  ------------------------------+-------------+------------+--------------
  No. examined                  |      52     |     46     |      19
                                |             |            |
  Mastoid width                 |     2.85    |    1.98    |     2.21
                                |             |            |
  Occipitonasal length          |     2.64    |    1.37    |     1.20
                                |             |            |
  Incisors to postpalatal notch |     3.02    |    2.56    |     2.56
                                |             |            |
  Interorbital constriction     |     2.75    |    3.66    |     3.22
                                |             |            |
  Zygomatic breadth             |     2.74    |    2.54    |     1.94
                                |             |            |
  Maxillary tooth-row           |     4.50    |    4.44    |     3.82
  ------------------------------+-------------+------------+--------------

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North American Jumping Mice (Genus Zapus)

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