University of Kansas Publications

Museum of Natural History



Volume 7, No. 15, pp. 619-624, 2 figs. in text


June 10, 1955

The Pigmy Woodrat, Neotoma goldmani,

Its Distribution and Systematic Position

BY

DENNIS G. RAINEY AND ROLLIN H. BAKER

University of Kansas

Lawrence

1955

University of Kansas Publications, Museum of Natural History



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

Robert W. Wilson



Vol. 7, No. 15, pp. 619-624

Published June 10, 1955




University of Kansas

Lawrence, Kansas

PRINTED BY

FERD VOILAND. JR., STATE PRINTER

TOPEKA, KANSAS

1955



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The Pigmy Woodrat, Neotoma goldmani,

Its Distribution and Systematic Position

By

Dennis G. Rainey and Rollin H. Baker

The pigmy woodrat, Neotoma goldmani Merriam, the smallest
known member of the genus, inhabits rocky areas in the elevated
desert regions of the northern part of the Mexican Plateau (Mesa
del Norte). Goldman (N. Amer. Fauna, 31:82, October 10, 1910)
had for study ten specimens from two localities in Coahuila. Since
his report, Dalquest (Louisiana State Univ. Studies, Biol. Sci. Ser.
No. 1:162, December 28, 1953) extended the known distribution
of this species approximately 225 miles southward into San Luis
Potosí, where he reported animals from five localities. Field
workers from the Museum of Natural History at the University of
Kansas recently have taken goldmani in the Mexican states of
Chihuahua, Coahuila, Durango, Zacatecas and San Luis Potosí, and
now we can define, with greater accuracy, the geographic range
of this species (see fig. 1 and list of specimens examined).

Goldman (loc. cit.), relying chiefly on external appearance,
placed goldmani in the desertorum group, now known as the
lepida group (Goldman, Jour. Mamm., 13:67, February 9, 1932).
Blossom (Occ. Papers Mus. Zool., Univ. Michigan, 315:3, May 29,
1935) thought that goldmani might be a subspecies of lepida but
that intergradation between the two had not been demonstrated.
Our newly acquired material, instead of confirming the opinions of
Goldman and Blossom, shows that goldmani is more closely related
to Neotoma albigula.

Externally goldmani resembles Neotoma lepida (examples from
California, Utah, and Colorado) in having long, silky pelage;
ochraceous buffy coloring, especially along sides; and underparts
basally plumbeous except for a small throat patch where the hairs
are entirely white in some individuals. In albigula this patch of
white hairs usually is much larger and more conspicuous. Cranially,
instead of resembling the lepida group (including Neotoma
stephensi), goldmani looks more nearly like a miniature albigula
(specimens of albigula from Coahuila). The auditory bullae, in
relation to the length of the skull, are of comparable size in goldmani
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and albigula whereas those of the lepida group are proportionately
much larger. Moreover, the posterior margin of the palatal
bridge is concave in goldmani and albigula instead of truncate
as in the lepida group. Neotoma goldmani differs from both albigula
and lepida in: ascending branches of premaxillaries broader
posteriorly; supraorbital ridges less pronounced; rostrum less massive;
interparietal broader in relation to width of cranium; interorbital
space, relative to length of skull, wider; and upper molar
teeth broader in relation to their length.

Figure 1. Distribution of the pigmy woodrat, Neotoma goldmani. Solid
circles represent specimens examined; hollow circles represent others reported
but not examined.

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The baculum of goldmani, when compared with bacula and
with figures of these bones in Burt and Barkalow (Jour. Mamm.,
23:291 and 293, August 13, 1942) of species representing the floridana,
lepida, albigula, mexicana, fuscipes, and cinerea groups, was
found to resemble most closely the baculum of albigula in general
proportions (ratio of length to lateral diameter of base) and in
having a distinct knob at the distal end. The baculum of goldmani
differs slightly from that of albigula in having a less downwardly
curved shaft and in having a less pronounced median dorsal depression
at the proximal end. Although goldmani bears some
external resemblance to lepida, the cranial characters mentioned
above and the size and shape of the baculum show that goldmani
is best arranged as a member of the albigula group.

Figure 2. Dorsal, end (proximal),
and lateral views of the baculum of Neotoma goldmani, adult, No. 40758
KU, × 5.

Measurements (in millimeters) of the mature baculum (fig. 2,
No. 40758 KU) are: total length, 6.2; lateral diameter of base, 2.6;
dorso-ventral diameter of base, 1.4; lateral diameter of the shaft
near the middle of the bone, 0.6. Except for being smaller, the
bacula of the younger goldmani are like the mature ones.

Assistance with field work is acknowledged from the Kansas
University Endowment Association and the National Science Foundation.
The figures were drawn by Victor Hogg. Bacula were
prepared for study following the method outlined by White (Jour.
Mamm., 32:125, February 15, 1951).

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