Speciation and Evolution of the Pygmy Mice, Genus Baiomys

by Robert L. Packard

Comparisons.—For comparisons with B. t. allex, B. t. canutus, B. t. paulus, and B. t. fuliginatus, see accounts of those subspecies. From B. t. taylori, B. t. analogous differs as follows: sides and dorsum darker, differing most in freshly prepared specimens; dorsal surface of forefeet and hind feet darker; basal part of hairs on belly darker gray; frontal bones less constricted, causing less taper anteriorly in interorbital space; interparietal wider transversely; basioccipital more expanded laterally, narrowing more abruptly at suture between basioccipital and basisphenoid.

Remarks.—The pelage of analogous becomes paler with wear as pointed out by Osgood (1909:257). A paratype, U. S. Nat. Mus. 120260, and several specimens from 1 mi. S, 11 mi. W Zamora, Michoacán, are grayish rather than brownish-black. All of these are old adults having the terminal black parts of the hairs on the dorsum nearly worn away. Excluding such grayish individuals, B. t. analogous, like B. t. subater and B. t. fuliginatus, is uniformly brownish-black. Both analogous and fuliginatus occur in relatively high mountainous country on dark soils or pedregals, and all three of the aforementioned subspecies occur in zones of high relative humidity.

B. t. analogous intergrades with B. t. paulus (see account of that subspecies) and B. t. allex south and west of Lago de Chapala in Jalisco. Additional specimens are needed from Querétaro and San Luis Potosí in order to ascertain whether or not B. t. analogous intergrades with B. t. fuliginatus or B. t. taylori. Specimens from western Jalisco, in the past referred to B. t. analogous, are referable to B. t. allex (see account of that subspecies). Specimens obtained west of, and bordering, the Río del Naranjo in Jalisco show a mixture of characters of both B. t. allex and B. t. analogous. For example, specimens from 2 mi. N Ciudad Guzmán resemble analogous on the dorsum, whereas, on the belly, the individual hairs are white-tipped, pale gray at the base, and in over-all appearance are whitish-gray, unlike typical analogous (being like allex instead). The dorsal surface of the forefeet are sooty to light brownish (as in analogous), whereas, the hind feet are flesh-colored (as in allex). Another series of specimens from 4 mi. W León, Guanajuato, are intergrades between B. t. analogous and B. t. paulus. These specimens are grayish to brownish on the dorsum, have sooty forefeet and hind feet (more nearly as in analogous than in paulus), are grayish-white on the venter, and have a distinctly bicolored tail (resembling that of paulus more than that of analogous). When the average of cranial characters is considered, both series are best referred to analogous.

Hooper (1947:50) pointed out that specimens from the pedregal San Gerónimo, Distrito Federal, were more nearly black than topotypes and generally showed less brownish hues typical of analogous. I have examined this series and several others from this area (see Specimens examined, [p. 640]) and am convinced that these populations average darker. Actually, the dorsum is more nearly black and the venter is more buffy than in typical analogous. The hairs of these individuals average longer than in other populations of analogous. Skulls of the specimens from the pedregal are indistinguishable from those of paratypes of analogous. The populations from the Distrito Federal seem to be incipient subspecies.

Specimens examined.—Total 696, all from the Republic of México, distributed as follows: San Luis Potosí: Hacienda Capulín, 5[33]; 3.3 mi. N Tamazunchale, by-road, 2[34]; 1 mi. N Tamazunchale, 700 ft., 1[35]. Veracruz: Acultzingo, 4[29], 1[31]. Jalisco: 1 mi. S Jalostotitlán, 5700 ft., 5; 7 mi. NW Tepatitlán, 3[29]; 6 mi. N, 4 mi. E Tepatitlán, 6400 ft., 25; 2¹/₂ mi. E Tepatitlán, 6200 ft., 15; 2 mi. S, ¹/₂ mi. W Tepatitlán, 9; near Tepatitlán, 2; 5 mi. SW Arrandas, 6700 ft., 6; 2 mi. E Zapotlanejo, 23; 2¹/₂ mi. E Puente Grande (5¹/₂ mi. SW Zapotlanejo), 3; 8 mi. S Guadalajara, 10[29]; 3 mi. ENE Santa Cruz de las Flores, 9; 4 mi. NE Ocotlán, 5050 ft., 18; 13 mi. S, 9¹/₂ mi. W Guadalajara, 1; 2 mi. WNW Ocotlán, 5000 ft., 15; 13 mi. S, 15 mi. W Guadalajara, 2; Ocotlán, 5000 ft., 8[30]; 1 mi. S Ocotlán, 5000 ft., 12; 27 mi. S, 12 mi. W Guadalajara, 9; 1¹/₂ mi. N Mazatmitla, 6[29]; ¹/₂ mi. NW Mazatmitla, 4; 3 mi. WSW Mazatmitla, 4; 2 mi. N Ciudad Guzmán, 5000 ft., 18. Guanajuato: 4 mi. N, 5 mi. W León, 7000 ft., 25; 5 mi. S Salamanca, 2[29]; 5 mi. E Celaya, 6000 ft., 6; 1 mi. E Yuriria, 5725 ft., 3; Salvatierra, 5775 ft., 8; NE edge Acambaro, 6050 ft., 10; Acambaro, 3[30]. Querétaro: Tolimán, 7[30]; 6 mi. E Querétaro, 6550 ft., 37. Hidalgo: Tula, 2050 m., 1[31]. Michoacán: 2 mi. E La Palma, SE side Lago de Chapala, 7; type locality, 4000 ft., 10[30] (including the type); 9 mi. E Zamora (Camenaro), 2[29]; 1 mi. S, 11 mi. W Zamora, 5400 ft., 17; S Cuitzeo, 36[29]; Jiquilpan, 4800 ft., 15; 11 mi. W Jiquilpan, 6700 ft., 2; 1 mi. E Jiquilpan, 7; 1 mi. E Zinapecuaro, 6300 ft., 17; 4¹/₂ mi. NE Tarequato (Tarecuato), 6600 ft, 1; Tanganciguaro (Tangancicuaro), 5500 ft., 4; 2 mi. N Tarecuato, 7200 ft., 1; 2 mi. S Maravatio, 6650 ft, 6; 2 mi. SE Zacapu, 6600 ft., 11; 1 mi. N Tinquindin (Tinguindin), 6300 ft., 2; 3 mi. E Morelia, 6600 ft., 3; 11 mi. E, 2 mi. S Morelia, 1; 2 mi. SE Hidalgo (Villa Hidalgo), 6; 1¹/₂ mi. N Los Reyes, 1; E Los Reyes, 18[29]; Los Reyes, 8[30]; 3 mi. W, 1 mi. N Pátzucuaro, 6600 ft., 2; N Pátzucuaro, 2[29]; Pátzucuaro 9[31], 4[30], 4[29]; Uruapan, 1[29]; E Uruapan, 12; 2¹/₂ mi. E Uruapan (La Presca), 2[29]; 2 mi. SW Zitacuaro, 1; 1 mi. E, 6 mi. S Tacámbaro, 4000 ft., 11[37]; La Huacana, 1[30]. Mexico: Templo del Sol, Pyramídes de San Juan, [Pg 640] Teotihuacán, 8000 ft., 1; 31 km. E México City, 7500 ft., 11[36]; 17 km. E México City, 7500 ft, 1[36]; Cerro La Caldera, 11 mi. ESE México, 2350 m., 5; 4 km. ENE Tlalmanalco, 2290 m., 9; Hacienda Córdoba (Córdova), 6. Mexico, D. F.: Cerro de la Estrella, Ixtapalapa, 2450 m., 1; ³/₄ mi. S, 1 mi. E Churubusco, 2400 m., 2; 5 km. S México City, South of Cd. Universitaria, l[32]; Pedregal San Angel, 2.6 mi. S Monumento a Obregón, 2; El Pedregal, 1 km. S San Angel, 2260 m., 1; Falda SW Cerro Zacatepec, 3.9 mi. SW Monumento a Obregón, 1; 2 mi. N Tlalpan, Zacayuca, 2380 m., 5; Tlalpan (Pedregal), 2400 m., 21[31]; San Gerónimo, 37[29], 6[38]; Santa Rosa, 2700 m., 1[32]; Tlalpan, 8; ³/₄ mi. SW Las Fuentes, Tlalpan, 2450 m., 25[30]; Tepepán, 6[29]; Rancho La Noria, 1 mi. W Xochimilco, 2270 m., 4; 500 meters N Xochitepec, 2250 m., 7; 200 m. N San Mateo Xalpa (Jalpa), 2390 m., 2.

Marginal records.—San Luis Potosí: Hacienda Capulín; 1 mi. N Tamazunchale. Hidalgo: Tula, 2050 m. Mexico: Templo del Sol, Pyramídes de San Juan, Teotihuacán. Veracruz: Acultzingo. Mexico: 4 km. ENE Tlalmanalco. Mexico, D. F.: 200 m. N San Mateo Xalpa (Jalpa), 2390 m. Michoacán: 2 mi. SW Zitacuaro; 1 mi. E, 6 mi. S Tacámbaro; Uruapan. Jalisco: 2 mi. N Ciudad Guzmán; 27 mi. S, 12 mi. W Guadalajara; 13 mi. S, 15 mi. W Guadalajara; 7 mi. NW Tepatitlán; 1 mi. S Jalostotitlán, 5700 ft. Guanajuato: 4 mi. N, 5 mi. W León. Querétaro: 6 mi. E Querétaro, 6550 ft.; Tolimán.

[29] Univ. Michigan, Museum of Zoology.

[30] U. S. Nat. Museum (Biol. Surv. Coll.).

[31] Chicago Natural History Museum.