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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

25-7820




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_ 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.

[Illustration: FIGURE 1. Distribution of the pigmy woodrat,
_Neotoma goldmani_. Solid circles represent specimens
examined; hollow circles represent others reported but not
examined.]

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.

[Illustration: 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).

_Specimens examined._ - Total, 15, all in the Museum of
Natural History at the University of Kansas. Localities
within any one state are arranged from north to south.
_Chihuahua_: Sierra Almagre, 6000 ft., 12 mi. S Jaco, 1.
_Coahuila_: 17 mi. N and 8 mi. W Saltillo, 5200 ft., 2; 3 mi.
SE Torreón, 3800 ft., 7. _Durango_: 1 mi. SSE Mapimí, 4100
ft., 1; 4 mi. WSW Lerdo, 3800 ft., 1; 5 mi. SE Lerdo, 3800
ft., 1. _Zacatecas_: Conception del Oro, 7680 ft., 1. _San
Luis Potosí_: 10 mi. NE San Luis Potosí, 6000 ft., 1.

_Other records._ - _Coahuila_: Jaral; Saltillo (Goldman,
1910:82). _San Luis Potosí_: Cerro Peñon Blanco; Ventura;
Santa Teresa; city of San Luis Potosí (Dalquest, _loc.
cit._).

_Transmitted February 8, 1955._


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Online LibraryRollin H. (Rollin Harold) BakerThe Pigmy Woodrat, Neotoma goldmani, Its Distribution and Systematic Position → online text (page 1 of 1)