A New Piñon Mouse (Peromyscus truei) from

Durango, Mexico

BY

ROBERT B. FINLEY, JR.

University of Kansas Publications

Museum of Natural History

Volume 5, No. 20, pp. 263-267
May 23, 1952

University of Kansas

LAWRENCE

1952

University of Kansas Publications, Museum of Natural History



Editors: E. Raymond Hall, Chairman, A. Byron Leonard,

Edward H. Taylor, Robert W. Wilson



Volume 5, No. 20, pp. 263-267

May 23, 1952

University of Kansas

Lawrence, Kansas

PRINTED BY

FERD VOILAND, JR., STATE PRINTER

TOPEKA, KANSAS

1952

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A New Piñon Mouse (Peromyscus truei) from
Durango, Mexico

BY

ROBERT B. FINLEY, JR.

The extensive collection of Mexican mammals made by Mr. J. R.
Alcorn for the University of Kansas Museum of Natural History
contains fourteen piñon mice from lava rocks eight miles northeast
of the city of Durango, Mexico. These mice are all much darker
than the piñon mice, Peromyscus truei gentilis, of adjoining areas
in Durango and Zacatecas and show a superficial resemblance to
the widespread P. t. gratus which occurs 450 miles to the southeast.
Morphological differences from P. t. gratus, as well as geographic
considerations (see remarks), make desirable the recognition of the
lava-dwelling piñon mice from Durango as a distinct subspecies.

All specimens examined of subspecies compared with the series
of piñon mice from northeast of Durango are in the University of
Kansas Museum of Natural History. Capitalized color names and
designators are of Maerz and Paul, A Dictionary of Color, McGraw
Hill Book Co., New York, 1930.

I wish to acknowledge generous financial aid from the Kansas
University Endowment Association which made possible the field
work by Mr. Alcorn in Mexico.

This heretofore unknown subspecies is characterized below and
may be known as:

Remarks.—The tail of P. t. erasmus varies greatly in color, being
either bicolor or unicolor, dark gray above and varying from white
to dark gray below. The type has the tail dark gray above grading
gradually on the sides to medium gray below. A buffy pectoral
spot or band is present in about half of the adults examined, being
most prominent in the type, which is also one of the darkest specimens
in the series. The shape of the posterior edge of the bony
palate is also variable, being convex, square, or concave; and the
dorsal branches of the premaxillaries may terminate slightly anterior
or slightly posterior to the posterior ends of the nasals. In the type
the posterior palatal margin is concave and the dorsal branches of[Pg 267]
the premaxillaries almost reach the ends of the nasals. Peromyscus
truei gratus from Distrito Federal also shows high variability in all
these characters.

Peromyscus truei erasmus is a dark race of the piñon mouse known
from the west side of a rough area of dark lavas a few miles northeast
of the city of Durango and closely surrounded by the light colored
race, P. t. gentilis, known from outside the area of lava rocks.
Specimens of erasmus from eight miles northeast of Durango are
all conspicuously darker than 11 specimens of gentilis from five
miles north of Durango and four miles west of Durango which are
typical in color for gentilis. Although erasmus more nearly resembles
in color gratus, in cranial characters and external measurements
it shows closer relationship to gentilis.

Alcorn reported (verbal communication) that the type series of
erasmus was collected on the west side of the Río de la Saucida in
hills covered with broken lava rocks, cactus, and spiny shrubs.
Some cottonwoods grow along the river, which is almost dry most
of the time. East of the river is a flat plain or valley of adobelike
soil a few miles wide beyond which extends a rough area of dark
lavas. The approximate extent of the lava plain is indicated on
World Aeronautical Chart, Lake Santiaguillo (521). The specimens
of gentilis from five miles north of Durango and four miles west of
Durango were collected on slopes of adobe soil covered with grasses,
scattered junipers and low shrubs, this habitat being the lower eastern
edge of the juniper-wooded slopes that rise westward to the
Sierra Madre Occidental.

The available facts suggest that P. t. erasmus has evolved from
P. t. gentilis by natural selection for concealing coloration on the
dark lavas northeast of Durango, México. P. t. erasmus probably
reaches its western limit close to the type locality.

Specimens examined.—Total 14, from the type locality.

Museum of Natural History, University of Kansas, Lawrence.

Transmitted January 21, 1952.

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