The Pigmy Woodrat, Neotoma goldmani, Its Distribution and Systematic Position by Rainey, Dennis G.

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_ 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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