University of Kansas Publications
Museum of Natural History
A New Subspecies of Wood Rat
(Neotoma) from Northeastern Mexico
BY
TICUL ALVAREZ
[141]
A New Subspecies of Wood Rat
(Neotoma) from Northeastern Mexico
BY
TICUL ALVAREZ
The White-throated woodrat, Neotoma albigula, has been known
previously from the Mexican state of Tamaulipas by only eight individuals
reported by Goldman (N. Amer. Fauna, 31:37, October
19, 1910), which were assigned to Neotoma albigula leucodon (type
locality, city of San Luis Potosí, México). Additional specimens
from southwestern Tamaulipas, obtained in recent years by representatives
of the Museum of Natural History, along with specimens
from parts of Nuevo León and Coahuila, represent an unnamed
subspecies, which is named and described as follows:
Neotoma albigula subsolana new subspecies
Type.—Male, adult, skin and skull, No. 56950, Museum of Natural History,
The University of Kansas, from Miquihuana, 6400 ft., Tamaulipas; obtained
on July 20, 1953, by Gerd H. Heinrich, original number 7553B.
Geographic distribution.—Sierra Madre Oriental from southeastern Coahuila
to southwestern Tamaulipas.
Diagnosis.—Over-all size small for species (see measurements), but tail,
maxillary tooth-row and incisive foramina relatively long; upper parts dark
(individual hairs banded subterminally with cinnamon and tipped with grayish,
yielding an over-all color of grayish brown); lips gray, especially anteriorly
and medially; alveoli of incisors narrow (4.8-5.2); posterior branch of premaxilla
extending only slightly behind nasals; rostrum short; braincase broad;
mastoid breadth averaging 51.1 (47.8-52.7) per cent of basilar length.
Comparisons.—Neotoma albigula subsolana, differs from topotypes of N. a.
leucodon, the subspecies geographically adjacent to the southwest, as follows:
size smaller, especially length of palatal bridge (6.9-8.1 instead of 8.2-9.6), alveolar
length of maxillary tooth-row (8.3-8.9 instead of 8.8-9.7), and greatest
length of auditory bulla (7.3-7.9 instead of 8.2-8.9); mastoid breadth relatively
greater, 51.1 (47.8-52.7) instead of 47.0 (45.5-49.1) per cent of basilar
length; posterior process of premaxilla extending only slightly beyond posterior
border of nasals; auditory bulla conspicuously smaller; upper parts darker, especially
middorsally; over-all color grayish instead of ochraceous or yellowish;
lips gray instead of nearly white.
Neotoma albigula subsolana differs from N. a. albigula, geographically adjacent
to the northwest (specimens from Pima County, Arizona) as follows:
size averaging slightly larger, except length of nasals; mastoid breadth averaging
18.8 (17.9-20.2) instead of 17.9 (17.7-18.2), its ratio to basilar length
therefore greater, 51.1 (47.8-52.7) instead of 49.4 (47.9-50.0); zygomatic[142]
arches expanded posteriorly instead of nearly parallel as in albigula; interparietal
longer and narrower; mesopterygoid fossa broader; auditory bulla
slightly smaller; upper parts distinctly darker.
Remarks.—N. a. subsolana is characterized by the combination of
small size, dark color, small auditory bulla and relatively broad
braincase. Typical specimens have been collected only at higher
elevations in the Sierra Madre Oriental where no other species of
Neotoma is known to occur.
Intergradation between N. a. subsolana and N. a. leucodon occurs
at lower elevations on the west side of the Sierra Madre Oriental
as shown by specimens from nine miles southwest of Tula, Tamaulipas,
and Sierra Guadalupe, Coahuila, from which places some
specimens are paler than others, approaching leucodon in color, and
are slightly larger than typical subsolana. Specimens assigned to
leucodon from vicinity of Presa Guadalupe and from 1 to 6 kilometers
south of Matehuala, San Luis Potosí, are typical of that subspecies
in measurements but are darker than topotypes.
N. a. subsolana intergrades with N. a. albigula in southeastern
Coahuila (specimens from 6 to 9 miles east of Hermanas and from
Panuco) where some individuals average paler and smaller than
topotypes of subsolana and some have skulls that combine characters
of subsolana and albigula. These specimens, which were referred
to N. a. leucodon by Baker (Univ. Kansas Publ., Mus. Nat.
Hist., 9:281-282, June 15, 1956), are assigned to subsolana on the
basis of relatively dark upperparts and broad mesopterygoid fossa
(narrow in only one specimen).
On geographic grounds, specimens not studied by me from Municipio
de Galeana, Nuevo León (Koestner, Great Basin Nat., 2:13,
1941), and those from Jaumave, Tamaulipas (Goldman, N. Amer.
Fauna, 31:37, October 19, 1910), probably are referable to N. a.
subsolana.
The subspecific name subsolana (Latin adjective for eastern) is
proposed for this woodrat because of its eastern geographic occurrence.
Measurements.—Average and extreme measurements of nine topotypes (6
males and 3 females) are as follows: total length, 338 (315-370); length
of tail-vertebrae, 157 (130-182); length of hind foot, 35 (33-37); length of
ear from notch, 31 (29-34); basilar length, 36.5 (34.7-39.2); zygomatic
breadth, 23.9 (22.5-25.0); interorbital constriction, 5.5 (5.7-6.2); length of
nasals, 15.5 (15.2-16.5); length of incisive foramina, 9.4 (8.8-10.1); length
of palatal bridge, 7.7 (6.9-8.1); alveolar length of maxillary tooth-row, 8.7
(8.3-8.9); length of auditory bulla, 7.6 (7.3-7.9); mastoid breadth, 18.7
(17.9-20.2).
[143]
Specimens examined.—A total of 124 (all from Mus. Nat. Hist., Univ. Kansas)
from: COAHUILA: 6 mi. E Hermanas, 1; 9 mi. E Hermanas, 1; Panuco,
3000 ft., 4; 1 mi. S, 4 mi. W Bella Unión, 7000 ft., 3; 3 mi. S, 3 mi. E Bella
Unión, 6750 ft., 1; 6 mi. E, 4 mi. S Saltillo, 7500 ft., 5; 7 mi. S, 4 mi. E Bella
Unión, 7200 ft., 3; 14 mi. W, 1 mi. N San Antonio de las Alazanas, 6500 ft., 2;
12 mi. S, 2 mi. E Arteaga, 7500 ft., 5; north slope Sierra Guadalupe, 10 mi. S,
5 mi. W General Cepeda, 6500 ft., 26; 7 mi. S, 1 mi. E Gómez Farías, 6500 ft.,
3; 8 mi. N La Ventura, 5500 ft., 1. NUEVO LEON: Iturbide, Sierra Madre
Oriental, 5000 ft., 10; Laguna, 1; 9 mi. S Aramberri, 3900 ft., 3; 1 mi. W
Doctor Arroyo, 5800 ft., 4. TAMAULIPAS: Miquihuana, 6400 ft., 22; Joya
Verde, 35 km. SW Cd. Victoria (on Jaumave Road), 3800 ft., 2; Nicolás, 56
km. NW Tula, 5500 ft., 10; Tajada, 23 mi. NW Tula, 5200 ft., 2; 9 mi. SW
Tula, 3900 ft., 15.
Comparative material.—N. a. albigula, 10 specimens (all KU) from: ARIZONA:
4 mi. S, 5 mi. E Continental, 4; 7 mi. E Tucson, 2500 ft., 1; 30 mi. S
Tucson, 1; 14 mi. S, 3 mi. E Continental, 1; Sta. Catalina Mts., south slope
Molino basin, 4200 ft., 2; Santa Rita Mts., northwest slope, near Sta. Rita
Range, 4300 ft., 1.
N. a. leucodon, 46 specimens (in Mus. Nat. Hist., Univ. Kansas, unless
otherwise noted) from: SAN LUIS POTOSI: 6 km. S Matehuala, 13 (LSU);
1 km. S Matehuala, 2 (LSU); 7 km. W Presa de Guadalupe, 5 (LSU); Presa
de Guadalupe, 4 (LSU); 8 mi. SW Ramos, 6700 ft., 3; 10 mi. NE San Luis Potosí,
6000 ft., 2; San Luis Potosí, 9 (USNM); Hda. La Parada, 8 (USNM).
I am grateful to Prof. E. Raymond Hall and Mr. J. Knox Jones, Jr., for permission
to examine critical specimens and for helpful suggestions. I am grateful
also to Dr. George H. Lowery, Jr., of the Louisiana State University (LSU)
and to Dr. David H. Johnson and Dr. Richard H. Manville of the United
States National Museum (USNM) for the loan of specimens. Gerd H. Heinrich
(in 1953) and Percy L. Clifton (in 1961) collected for the Museum of
Natural History the Tamaulipan specimens herein reported. Fieldwork was
supported by the Kansas University Endowment Association. Laboratory
phases of the study were made when the author was a half-time Research Assistant
supported by grant No. 56 G 103 from the National Science Foundation.
Transmitted February 21, 1962.
29-2891
Comments on "A New Species of Wood Rat (Neotoma) from Northeastern Mexico" :