University of Kansas Publications

Museum of Natural History



Volume 9, No. 18, pp. 513-518, 1 map

January 14, 1960

Conspecificity of two pocket mice,

Perognathus goldmani and P. artus

BY



E. RAYMOND HALL AND MARILYN BAILEY OGILVIE



University of Kansas

Lawrence

1960

University of Kansas Publications, Museum of Natural History



Editors: E. Raymond Hall, Chairman, Henry S. Fitch,

Robert W. Wilson





Volume 9, No. 18, pp. 513-518, 1 map

Published January 14, 1960





University of Kansas

Lawrence, Kansas





PRINTED IN

THE STATE PRINTING PLANT

TOPEKA, KANSAS

1960



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[Pg 515]

Conspecificity of two pocket mice,

Perognathus goldmani and P. artus

BY



E. RAYMOND HALL AND MARILYN BAILEY OGILVIE

Perognathus goldmani Osgood and Perognathus artus Osgood
from southern Sonora, northern Sinaloa and adjoining parts of
Chihuahua and Durango, are two named kinds of the Perognathus
intermedius group of pocket mice, of the subgenus Chaetodipus.
Until now the two kinds have been treated in the literature as two
species. In both goldmani and artus the upper parts are Ochraceous-Buff
(capitalized color terms after Ridgway, Color Standards and
Color Nomenclature, Washington, D. C., 1912) having a strong
admixture of black. The lateral line is Ochraceous-Buff, and the
underparts are white. P. goldmani is larger than P. artus (see
measurements beyond) and has more inflated tympanic bullae and
a relatively narrower (transverse to long axis of skull) interparietal
bone.

Specimens from a transect of southeastern Sonora show intergradation
between Perognathus goldmani and P. artus. From
northwest to southeast the specimens are as follows: one mile east
of Buena Vista, on Río Yaqui Reservoir, 1000 feet (2 specimens,
K. U.); Alamos, 1200 feet (7, U. S. B. S.); four and a half miles
southeast of Alamos, 1000 feet (5, K. U.); nine miles southeast
Alamos, 1000 feet (5, K. U.). The specimens (P. goldmani) from
Río Yaqui Reservoir are largest. Those from nine miles southeast
of Alamos (P. artus) are smallest. Those from Alamos proper are
P. goldmani. Those from four and a half miles southeast of Alamos
(80051-80055 K. U. collected by Robert L. Packard and here referred
to goldmani) include two as large as goldmani from Alamos,
one as small as artus from nine miles southeast of Alamos, and two
that are intermediate in size. Features other than size, considered
geographically, also suggest intergradation.

Six specimens (61409-61413, 61415 K. U. collected by J. R.
Alcorn), including five adults (permanent fourth premolar of full
height and having cusps worn but not so much as to make a lake
of dentine), from four miles north of Terrero, Sinaloa, also seem
to be intergrades between Perognathus goldmani and Perognathus
artus. As compared with adults of P. goldmani from 10 miles north-northwest
of Los Mochis, Sinaloa, and P. artus from one mile south[Pg 516]
of Pericos, Sinaloa, the specimens from four miles north of Terrero
are almost exactly intermediate in length of hind foot, width of
interparietal, and width of tympanic bullae. Intermediacy is shown
also in total length of animal (slightly nearer that of artus) and
length of tympanic bullae (slightly nearer that of goldmani). In
lack of inflation laterally of the mastoidal bullae the specimens
agree with artus. In occipitonasal length and mastoidal breadth
the specimens from four miles north of Terrero average even larger
than goldmani from 10 miles north-northwest of Los Mochis but
not so large as specimens of goldmani from the type locality, which
is still farther north. The uninflated mastoidal bullae "tip the
balance" slightly in favor of artus
to which the specimens from
four miles north of Terrero are
here referred. The degree of
inflation of the mastoidal bullae
elsewhere varies geographically.
For example, the mastoidal bullae
of the 25 specimens of goldmani
from two and a half miles
north of El Fuerte, Sinaloa, are
intermediate in size as between
those of goldmani and artus.

Map 1. Geographic distribution of
Perognathus goldmani. The black dots
are known localities of occurrence.


1. P. g. artus


2. P. g. goldmani

The morphological intermediacy
of the specimens from four
and a half miles southeast of
Alamos and of those from four
miles north of Terrero, along
with the geographic intermediacy
of the two localities where
the specimens were obtained
constitute basis for arranging
artus as a subspecies of goldmani
that has one page of priority.

Perognathus goldmani goldmani Osgood

Perognathus goldmani artus Osgood

Remarks.—Considerable individual variation has been noted in
each of several populations of Perognathus goldmani artus. For
example, in 14 adults from Culiacán, Sinaloa, the variation is 25.0
to 27.9 in occipitonasal length and in mastoidal breadth is 12.6 to
14.0. Ten specimens (83122-83131 Univ. Mich.) labeled as from
Carimechi, Río Mayo, Chi[huahua], were recorded by Burt and
Hooper (Occas. Papers Mus. Zool., Univ. Michigan, 430:6, May 27,
1941) as from "near Carimechi." They identified the two largest
(83130 and 83131) as Perognathus goldmani and the others as
Perognathus artus. These identifications were reasonable in the
light of knowledge available in 1941, but in the light of information
presently available from the now more abundant material it is clear
that all 10 of the specimens are P. g. artus. Examination (by Hall)
of the specimens reveals that the differences relied upon by Burt
and Hooper to differentiate the two species are well within the
range of individual variation. For example, the variation (5.3 to
5.6 mm.) in width of the supraoccipital is less than in each of some
other series of specimens of equal age of P. g. artus from other
localities.

Also, there is geographic variation in the mice here assigned to
the subspecies P. g. artus; skulls are smaller in the northern part of
the geographic range and become gradually larger toward the south.
In five adults from the northern part (Batopilas 3, and 26 mi. NE
Choix 2) the mean of 12.6 of the mastoidal breadth of the skull is
significantly smaller than the corresponding mean of 13.3 in 21
adults from the southern part (32 mi. SSE Culiacán 14, and El
Dorado 7). The pelage of individuals from one and a half miles
southwest of Tocuina is notably dark both above and below; the
venter is dusky rather than white. We suppose that the darker[Pg 518]
color is a response to a dark-colored substrate—lava and soils derived
from dark lava.

We have not seen any specimens that are intergrades between
P. goldmani and Perognathus intermedius (subspecies intermedius
or lithophilus), nor between P. goldmani and Perognathus nelsoni
(subspecies nelsoni or canescens), nor between P. intermedius and
P. nelsoni. Collecting and studying specimens from geographically
appropriate places to test for intergradation between these three
species would be worthwhile as a means of improving our knowledge
of the taxonomy of these mice.

Transmitted October 1, 1959.

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