[10]Univ. Michigan, Museum of Zoology.[11]U. S. Nat. Museum (Biol. Surv. Coll.).[12]Chicago Natural History Museum.[13]Univ. California, Mus. Vert. Zoology.Baiomys musculus nigrescens(Osgood)Peromyscus musculus nigrescensOsgood, Proc. Biol. Soc. Washington, 17:76, March 21, 1904; Elliot, Field Columb. Mus. Publ., 105(4):136, July 1, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus., 62:135, January 15, 1909; Osgood, N. Amer. Fauna, 28:259, April 17, 1909.Baiomys musculus nigrescens, Miller, Bull. U. S. Nat. Mus., 79:137, March 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318, April 29, 1924; Goodwin, Bull. Amer. Mus. Nat. Hist., 68(1):40, December 12, 1934; Ellerman, The Families and Genera of Living Rodents, 2:402, March 21, 1941; Poole and Schantz, Bull. U. S. Nat. Mus., 178:259, March 6, 1942; Hooper, Jour. Mamm., 28:50, February 15, 1947; Goldman, Smith. Miscl. Coll., 115:357, July 31, 1951; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:513, March 3, 1955; Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10, 1957; Hall and Kelson, The Mammals of North America, 2:661, March 31, 1959 (part).[Peromyscus musculus]nigrescens, Elliot, Field Columb. Mus. Publ., 95(4):176, 1904.B.[aiomys]m.[usculus]nigrescens, Goodwin, Bull. Amer. Mus. Nat. Hist., 79(2):160, May 29, 1942; Hooper, Jour. Mamm., 33:97, February 18, 1952 (part); Packard, Univ. Kansas Publs., Mus. Nat. Hist., 9:399, December 19, 1958.B.[aiomys]m.[usculus]musculus, Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10, 1957 (part).Type.—Adult female, skin and skull; No. 76827 U. S. Nat. Mus. (Biol. Surv. Coll.); Valley of Comitán, Chiapas, Republic of México, obtained on December 9, 1895, by E. W. Nelson and E. A. Goldman, original number 8719.Range.—Southern coastal region and eastern parts of Chiapas, southeastward into central and southern Guatemala, thence south into El Salvador (seeFigure 10). Zonal range: parts of Lower Austral; also occurs in parts of the arid division of the Upper Tropical Life-zone, and in parts of the arid division of the Lower Tropical Life-zone; approximates a part of the Chiapas Highlands Biotic Province of Goldman and Moore (1945:349), and parts of the Guatemalan Subregion of Smith (1949:235).Diagnosis.—Size medium to small for the species; dorsum Vandyke Brown mixed with blackish, individual hairs black-tipped with a subterminal band of Warm Buff, Neutral Gray at base; guard hairs of dorsum black distally, Neutral Gray basally; hairs on sides grayish-brown, facial region like dorsum; chin buffy-brown; vibrissae brown, ventrally some white; venter creamy-buff to grayish, individual hairs creamy-buff at tips, gray basally; in region of throat and chin, hairs tipped with Ochraceous-Buff; dorsal surface of forefeet and hind feet dull whitish gray to brownish-black; tail indistinctly bicolored, dusky above, grayish to brownish below; incisive foramina short, wide medially;[Pg 624]average and extreme external and cranial measurements of 15 adults from 6 mi. NW Tonalá, Chiapas, are as follows: total length, 107.5 (100-116); length of tail vertebrae, 41.1 (33-48); length of body, 66.1 (62-73); length of hind foot, 15.0 (14-16); length of ear, 10.9 (10-12); occipitonasal length, 18.9 (18.4-19.7); zygomatic breadth, 9.8 (9.4-10.2); postpalatal length, 6.9 (6.6-7.4); least interorbital breadth, 3.7 (3.5-3.8); length of incisive foramina, 4.4 (4.1-4.8); length of rostrum, 6.7 (6.1-7.1); breadth of braincase, 9.2 (9.0-9.4); depth of cranium, 6.9 (6.5-7.3); alveolar length of maxillary tooth-row, 3.1 (2.9-3.2); for photographs of skull, seePlate 1f, andPlate 3f.Comparisons.—For comparisons withB. m. handleyi,B. m. grisescens,B. m. musculus,B. m. pallidus, andB. m. pullus, see accounts of those subspecies.FromB. m. brunneus,B. m. nigrescensdiffers in: dorsum blackish-brown rather than reddish to ochraceous brown; face and ears brownish-black rather than brownish with tinges of ochraceous; vibrissae darker; forefeet and hind feet darker; venter with more grayish tones; dorsalmost part of zygomatic plate projects farther anteriorly; interparietal oval to diamond-shaped and narrower anteroposteriorly; zygomata narrower at anteriormost part; slightly smaller in most cranial and external measurements.FromB. m. infernatis,B. m. nigrescensdiffers in: dorsum darker; region of face and ears darker; venter buffy to gray rather than whitish-buff; vibrissae darker; forefeet and hind feet darker; tail darker above and below; incisive foramina shorter, more constricted laterally; cranium slightly smaller in most dimensions.Remarks.—Hooper (1952a:93-94) reported specimens from the coastal strip of southern Chiapas as the most intensely pigmented, whereas, specimens from central and western Chiapas were distinctly paler. Crania of specimens from the coastal region of southern Chiapas were smaller than crania from the central highlands and mountains of Chiapas. My studies essentially corroborate the findings of Hooper. The gradation of color between the pale brownpallidusto the north in Oaxaca, and the brownish-blacknigrescensto the south in Chiapas is extremely gradual. Specimens from the central and western parts of Chiapas (seeFigure 10for localities) are difficult to assign to eitherpallidusornigrescens. Equal justification exists for assignment to either subspecies. I have assigned the specimens tonigrescensbecause they are geographically closer to the type locality ofnigrescens. Specimens from Reforma, Oaxaca (assigned by Hooper, 1952a:93-94, tonigrescens), are nearly identical in size and color to paratypes ofpallidus. I assign the Reforma specimens topallidus.The darkest of all the specimens examined and assigned tonigrescensare from 1 mi. NW San Salvador and 1 mi. S Los Planes, El Salvador. The variations in color in this subspecies closely correspond to degree of relative humidity; the palest samples are from areas of low relative humidity and the darkest are from areasof high relative humidity. In view of the present state of differentiation of specimens from the southern coastal areas of Chiapas and mountainous areas of El Salvador, it would seem that populations there might be incipient subspecies.Specimens examined.—Total 319.Chiapas:17 mi. W Bochil, 1[14];15 mi. W Bochil, 1[14];14 mi. W Bochil, 1[14]; Bochil, 6[15]; Ocuilapa, 3500 ft., 5[16];5 mi. NNW Tuxtla Gutiérrez, 9;11 km. W Tuxtla Gutiérrez, 800 m., 2[15];10 km. W Tuxtla Gutiérrez, 800 m., 2[15];Tuxtla Gutiérrez, 2600 ft., 8[16], 11;Ocozocoautla, 10[15], 2[16]; 25 mi. E Comitán, Las Margaritas, 1250 m., 5[17], 24[15]; Cintalpa, 555 m., 1[14], 18[15], 3[17];Jiquilpilas, 2000 ft., 1[16]; San Bartolome, 3[16];type locality, 5700 ft., 26[16](including the type); 15 mi. SW Las Cruces, 1; Villa Flores, 600 m., 12[15];23 mi. S Comitán, 1[14];15 mi. S, 2 mi. E La Trinitaria, 4;30 mi. S Comitán, 2[14]; 35 mi. S Comitán, 1[14];3 mi. E Arriga, 1[14]; 6 mi. NW Tonalá, 19;Tonalá, 8[16];Los Amates, 1[14]; Pijijiapan, 10 m., 7[15]; Mapastepec, 45 m., 25[15], 4[17].Guatemala: Chanquejelve, 1[14];Nentón, 3000 ft., 1[16]; Jacaltenango, 5400 ft., 8[16]; La Primavera, 5[14]; 4 mi. S Guatemala City, 4700 ft., 3;5 mi. S Guatemala City, 4050 ft., 10;6 mi. S Guatemala City, 4680 ft., 1;Lake Amatitlán, 4500 ft., 13[16]; El Progresso (Distrito Santa Rosa), 3[15];2 mi. N, 1 mi. W Cuilapa, 2980 ft., 1[14];1 mi. WSW El Molino(Distrito Santa Rosa), 2;21/2mi. W, 21/4mi. N San Cristobal, 2900 ft., 1; El Zapote, 1[15].El Salvador: 1 mi. NW San Salvador, 29; 1 mi. S Los Planes, 15.Marginal Records.—Chiapas: Bochil; 25 mi. E Comitán, Las Margaritas, 1250 ft.Guatemala: Chanquejelve; La Primavera; Jacaltenango, 5400 ft.; 4 mi. S Guatemala City, 4700 ft.; El Progresso.El Salvador: 1 mi. NW San Salvador; 1 mi. S Los Planes.Guatemala: El Zapote.Chiapas: Mapastepec, 45 m.; Pijijiapan, 10 m.; 6 mi. NW Tonalá; 15 mi. SW Las Cruces; Cintalpa, 555 m.; Ocuilapa, 3500 ft.[14]American Museum of Natural History.[15]Univ. Michigan, Museum of Zoology.[16]U. S. Nat. Museum (Biol. Surv. Coll.).[17]University of Florida Collections.Baiomys musculus pallidusRussellBaiomys musculus pallidusRussell, Proc. Biol. Soc. Washington, January 29, 1952; Davis and Russell, Jour. Mamm., 35:75, February 10, 1954; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512; Hall and Kelson, The Mammals of North America, 2:662, March 31, 1959.Peromyscus musculus brunneus, Elliot, Field Columb. Mus. Publ., 115(8):203, 1907 (part).Peromyscus musculus[musculus], Osgood, N. Amer. Fauna, 28:257, April 17, 1909 (part).Baiomys musculus musculus, Miller, Bull. U. S. Nat. Mus., 79:137, December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:318, April 29, 1924 (part); Davis, Jour. Mamm., 25:394, December 12, 1944 (part); Hooper, Jour. Mamm., 28:50, February 15, 1947 (part); Goldman, Smith, Miscl. Coll., 115:336, July 31, 1951 (part); Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, 1955 (part); Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10, 1957 (part); Hall and Kelson, The Mammals of North America, 2:661, March 31, 1959 (part); Goodwin, Amer. Mus. Novitates, 1929:1, March 5, 1959.B.[aiomys]m.[usculus]musculus, Hooper, Jour. Mamm., 33:97, February 18, 1952 (part).B.[aiomys]m.[usculus]nigrescens, Hooper, Jour. Mamm., 33:97, February 18, 1952 (part).Baiomys musculus nebulosus Goodwin, Amer. Mus. Novitates, 1929, March 5, 1959.Type.—Adult female, skin and skull; No. 4501 Texas A&M Cooperative Wildlife Collection; 12 kms. NW Axochiapán, 3500 feet, Morelos, Republic of México, obtained on July 28, 1950, by W. B. Davis, original number 5112.Range.—Guerrero thence eastward into Morelos and west central Puebla along the southern edge of the Transverse Volcanic Biotic Province (Goldman and Moore, 1945:349), south into Oaxaca, seeFigure 10. Zonal range: largely Arid Lower Tropical Subzone of Goldman (1951:330). Occurs from near sea level in Oaxaca and Guerrero up to 6550 feet in Oaxaca.Diagnosis.—Size medium for the species; dorsum Buffy Brown in palest series to Olive-Brown in darkest series, individual hairs Warm Buff, Neutral Gray basally, some with black tips and a subterminal band of Warm Buff, guard hairs of dorsum black-tipped, gray basally; hairs on sides creamy-buff, gray basally; face same color as back fading to white on throat; vibrissae white-tipped, pale brown basally; venter, whitish with tinges of buff on lower throat, individual hairs having tips white to buffy-white, light gray basally; dorsal surface of forefeet and hind feet whitish to flesh-color; tail indistinctly bicolored, brownish above, grayish brown below; zygoma bowed as inB. m. grisescens; tail short; average and extreme external and cranial measurements for 17 adults from Tehuantepec, Oaxaca, are: total length, 117.3 (110-126); length of tail vertebrae, 46.9 (41-51); length of body, 70.4 (65-76); length of hind foot, 15.8 (15-16); occipitonasal length, 18.9 (18.2-20.1); zygomatic breadth, 10.1 (9.7-10.6); postpalatal length, 6.9 (6.6-7.5); least interorbital breadth, 3.8 (3.6-3.9); length of incisive foramina, 4.4 (4.2-4.7); length of rostrum, 6.7 (6.3-7.2); breadth of braincase, 9.3 (8.7-9.7); depth of cranium, 6.6 (6.4-6.8); alveolar length of maxillary tooth-row, 3.2 (3.1-3.4); for photographs of skull, seePlate 1g, andPlate 3g.Comparisons.—For comparisons withB. m. brunneusandB. m. infernatis, see accounts of those subspecies.FromB. m. musculus,B. m. pallidusdiffers in: dorsum more olive-gray and brown, less ochraceous on either side of mid-dorsal region; face below eye grayish, not buffy; sides gray with buffy overtone, not creamy with light yellow overtones; venter grayish-white rather than an olive-buff; zygomata more tapering anteriorly; maxillary part of zygoma narrower when viewed from above; external and cranial dimensions smaller.FromB. m. nigrescens,B. m. pallidusdiffers in: dorsum paler, fewer black hairs medially; face paler, less sooty; vibrissae brownish with white tips rather than black with brownish tips; venter paler; dorsal surface of forefeet and hind feet whitish to flesh-colored rather than sooty to dusky-white; tail paler; nasals slightly more attenuated; averaging slightly larger in external and cranial measurements.Remarks.—Russell (1952:21) describedpallidus, on the basis of specimens from the arid Balsas Basin, of Morelos, as pale gray dorsally. After examining the original material from Morelos, I find the dorsal color ofpallidusto be much closer to a buffy brown than a pale grayish. Even so, smaller size differentiatespallidusfrommusculus.B. m. infernatis, notB. m. pallidus, is the most pallid of all named subspecies ofB. musculus.B. m. pallidusintergrades to the northwest withB. m. musculus, to the northeast withB. m. infernatis, and to the southeast withB. m. nigrescens.According to Goodwin (1959:2),B. m. nebulosus(named on the basis of one specimen) differs fromB. m. musculus[=pallidus] from southern Oaxaca in: darker and longer pelage; larger skull; interorbital region broader and less constricted posteriorly. FromB. m. nigrescensandB. m. brunneus,B. m. nebulosusdiffers as follows: pelage longer and softer; skull larger.Study of specimens ofB. musculusfrom Oaxaca reveals considerable variation in external and cranial measurements as well as color, corresponding to that reported by Goodwin (loc. cit.). Specimens from higher altitudes average somewhat darker and larger in external and cranial size than those at lower elevations. These differences seem to be microgeographic and not of subspecific rank. Among specimens that I have studied in Oaxaca are several from different localities (KU 63052, an adult male, from 3 mi. W Miahuatlán; KU 68964, an adult male from 3 mi. W Mitla, 6000 ft.; KU 63055, an adult female from 3 mi. S Candelario, 1200 ft.) that, according to Goodwin (in. litt.) matchnebulosusin reported color, size of body and skull (except for the region of the rostrum).Two of the three specimens (KU 63052 and 63055) are the darkest of a series in which the palest are inseparable fromB. m. pallidus. Goodwin, who kindly compared the three specimens with the type ofnebulosus, mentioned (in. litt.) that the skull of the type has a slenderer rostrum. Included in the series of skulls ofB. m. pallidusfrom 3 mi. W Mitla are several adults (not seen by Goodwin) with slender rostra.B. m. nebulosusis judged to be a synonym ofB. m. pallidus.Populations of pygmy mice occurring in partially isolated areas of highland in Oaxaca seem to me to be incipient subspecies.Specimens examined.—Total 824 all from the Republic of México and distributed as follows:Puebla: 2 mi. S Atlixco, 5800 ft., 1;1 mi. SSW Tilapa, 5800 ft., 2;6 mi. SW Izucár de Matemores, 7;Piaxtla, 3900 ft., 4[18]; Acatlán, 4100 ft., 1.Morelos: 5 mi. W Tepoztlán, 6000 ft., 7[19];1 mi. W Tepoztlán, 6000 ft., 9[19];2 mi. SW Tepoztlán, 7000 ft., 1[20];Cuernvaca, 9[19];6 mi. W Yautepec, 4500 ft., 1[20];Yautepec, 12[19];3 mi. N Alpuyeca, 4000 ft., 2[20];Puente de Ixtla, 2[19];Tetecala, 4[21];2 km. S Jonacatepec, 4500 ft., 6[20];type locality, 6 (including the type).Guerrero:Yerbabuena, 1800 m., 1;Cueva de tia Juana[=1.5 km. SSW Yerbabuena], 1;Laguna Honda, 1840 m. [=1.5 km. S Yerbabuena], 3; 9 mi. SE Taxco, 3800 ft., 1[22];17 km. S Taxco, 4000 ft., 2[20];Iguala, 5[19];3.2 km. SSE Iguala, 970 m., 1; 1 km. SSE Texcaizintla, 1600 m., 2;Teloloapán, 20[19], 5[24];1 km. N Chapa, 1470 m., 6;Chapa, 1470 m., 5; El Limón, 3[18]; 21/2mi. W Mexcala, 2100 ft., 1[20];Río Balsas, 1[18]; Ayusinaha [= Ayotzinapa], 1[18];Tlapa,[Pg 628]3900 ft, 1[18];2.5 mi. S Almolonga, 5600 ft., 13[20];1 km. N Zihuatanejo, 1; Zihuatanejo Bay, 4[19];Las Gatas[=2 km. S. Zihuatanejo], 2;2 km. SSE Zihuatanejo, 9;4 mi. W Chilpancingo, 5800 ft., 3[20];Chilpancingo, 4800 ft., 14[18], 21[19], 45[21];2 mi. N Tixtla, 4400 ft., 3[20];3.2 km. S Chilpancingo, 4;Cd. Chamilpa[=12 km. ESE Chilpancingo], 5;Tlalixtaquilla, 4200 ft., 2[18];15 km. S. Chilpancingo, 4300 ft., 10[20];1 mi. SW Colotlipa, 2700 ft., 16[20];2 mi. SW Colotlipa, 2700 ft., 1[20];Achuitzotla, 2800 ft., 7[20];8 mi. SW Colotlipa, 1[20];5 mi. S Rincón, 2600 ft., 2[20];8 mi. SW Tierra Colorado, 600 ft., 1[20]; Río Aguacatillo,30 km. N Acapulco, 1000 ft., 3[20]; 5 mi. ESE Tecpán, 50 ft., 9;Ejido Viejo,12 km. NNW Acapulco, 1;2 mi. NNW Acapulco, 7; Acapulco, 3[18], 3[21]; Omentepec, 200 ft., 7[18].Oaxaca:4 mi. E Huajuapám, 5000 ft., 1; 2 mi. NW Tamazulapán, 6550 ft., 1; Yalalag, 3000 ft., 5[18];11 mi. NW Oaxaca[City], 1;Yaganiza, 3900 ft., 1[18]; Oaxaca [City], 5000 ft., 15, 7[21], 7[19], 5[24];3 mi. ESE Oaxaca[City], 30;4 mi. ESE Oaxaca[City], 5050 ft., 1;10 mi. SE Oaxaca[City], 1[22];Cerro Ocotepec, 1[23]; Tepantepec, 9[23];1 mi. E Tlacolula, 5500 ft., 53[19];3 mi. W Mitla, 11; Jalapa, El Campanario, 1[23];2 mi. SE Matalán, 5950 ft., 14;Lachiguiri, 2[23];Tres Cruces, 10[23];Agua Blanca, 11[23];San José, 1[23]; Reforma, 30[19], 7[21], 10[23], 6[24]Totolapa, 1[18];Nejapa,85 km. WNW Tehuantepec, 500 m., 12[19], 6[24];Chicapa, 2[18];Gueladu[=Jalapa], 6[23];Juchitán,Laguna Superior; Manteca, 8[23], 1[23]; San Bartolo, 3000 ft., 1[18];Ejutla, 1400 m., 21[19];El Bambita,Tequisitlán4[23];Mixtequilla, 2[23];Guiencola, 5[23];Tehuantepec, 200 ft., 26[18], 11[19];Sola de la Vega, 26[19], 3[24]; Huilotepec, 13[18], 3[23];Santa Lucia, 24[23];Cerro de Paste,Tenango, 7[23];Sta. C. Quieri, 3[23];Santa Marie Ecatepec,Zarzamora, 13[23];Rincón Bamba, 11[23];3 mi. W Miahuatlán, 5300 ft., 1;Miahuatlán, 12[19], 1[23], 6[24];San Juan Acaltepec, 5[23];Zapotitlán, 1[23];Llano Grande, 3[18]; Pinotepa, 700 ft., 2[18]; Juquila, 8[18];Arroyo,San Juan,north of Cerro Otate, 1[23]; Cerro Otate, 3[23]; 3 mi. S Candelaria, 1.Marginal records.—Morelos: 5 mi, W Tepoztlán, 6000 ft.Puebla: 2 mi. S Atlixco, 5800 ft.; Acatlán, 4100 ft.Oaxaca: 2 mi. NW Tamazulapán, 6550 ft; Tepantepec; Oaxaca [City], 5000 ft; Yalalag, 3000 ft; Jalapa, El Campanario; Reforma; Huilotepec; 3 mi. S Candelaria; Cerro Otate; Pinotepa, 700 ft.Guerrero: Acapulco; Zihuatanejo Bay; El Limón; 9 mi. SE Taxco, 3800 ft.[18]U. S. Nat. Museum (Biol. Surv. Coll.).[19]Univ. Michigan, Museum of Zoology.[20]Texas A & M, Cooperative Wildlife Research Collection.[21]Chicago Natural History Museum.[22]California Academy of Sciences.[23]American Museum of Natural History.[24]University of Florida Collections.Baiomys musculus pullusPackardBaiomys musculus pullusPackard, Univ. Kansas Publs., Mus. Nat. Hist., 9:401, December 19, 1958.Baiomys musculus grisescens, Goodwin, Bull. Amer. Mus. Nat. Hist., 79(2):161, May 29, 1942 (part); Miller and Kellogg, Bull. U. S. Nat. Mus., 205:513, March 3, 1955 (part); Hall and Kelson, The Mammals of North America, 2:661, March 31, 1959 (part).Type.—Adult female, skin and skull; No. 71605 University of Kansas Museum of Natural History; 8 mi. S Condega, Estelí, Nicaragua, obtained on July 15, 1956, by A. A. Alcorn, original number 4218.Range.—West-central Nicaragua, from Matagalpa northwest into the valley of the Río Estelí, east as far as Jinotega, seeFigure 10. Zonal range: Upper Tropical Life-zone.Diagnosis.—Size medium to small for the species; dorsum Fuscous-Black, individual hairs black-tipped with a subterminal band of Ochraceous-Buff, Neutral Gray at base; some hairs on dorsum all black to Neutral Gray at base; hair on sides Neutral Gray tinged with blackish; face blackish, becoming buffy on sides[Pg 629]of head, and white on throat; vibrissae black; tail unicolored Chaetura Black; forefeet and hind feet sooty to dusky-white; mid-ventral region of venter white, hairs white to base; in region of anus and throat, hairs white-tipped, Neutral Gray at base; average and extreme external and cranial measurements of the type and 16 paratypes are as follows: total length, 117.3 (111-121); length of tail vertebrae, 47.2 (44-50); length of body, 70.4 (66-74); length of hind foot, 15.5 (14-17); length of ear from notch, 11.9 (10-13); occipitonasal length, 19.3 (18.9-19.8); zygomatic breadth, 10.2 (9.7-10.6); postpalatal length, 7.0 (6.8-7.3); least interorbital breadth, 3.9 (3.8-4.1); length of incisive foramina, 4.3 (4.0-4.6); length of rostrum, 7.0 (6.5-7.4); breadth of braincase, 9.6 (9.3-10.0); depth of cranium, 7.0 (6.8-7.3); alveolar length of maxillary tooth-row, 3.1 (3.0-3.2); for photographs of skull, seePlate 1h, andPlate 3h.Comparisons.—FromB. m. grisescens,B. m. pullusdiffers in: dorsum and tail darker; sides and lateral parts of venter grayish instead of buffy-brown, thus forming distinct mid-ventral white stripe; average length of body and tail significantly longer, thus total length greater; maxillary tooth-row significantly shorter; slightly larger in other cranial and external dimensions.FromB. m. nigrescens,B. m. pullusdiffers in: dorsum slightly darker; face grayish, not sooty; mid-ventral white stripe (absent in most specimens ofnigrescens) present and becoming grayish laterally; tail darker, less hairy, and averaging significantly longer; smaller in most external and cranial dimensions.Remarks.—B. m. pullusresemblesB. m. nigrescensin size and color but can readily be distinguished fromnigrescensby the shorter tail.B. m. pullusintergrades withnigrescensas shown by specimens, referable toB. m. nigrescens, from 1 mi. NW San Salvador and from 1 mi. S Los Planes, El Salvador. In color of the dorsum, specimens from these localities are intermediate betweennigrescensandpullus.The mid-ventral white stripe characteristic ofpullusis present in three of 28 adults from El Salvador. Goodwin (1942:160) reported white hairs on the pectoral region of several topotypes ofB. m. grisescens. The areas of white hairs on the venter ofgrisescensoccur in approximately 10 per cent of the specimens examined, whereas inpullus, the frequency of occurrence is 90 per cent. The areas of white hairs ingrisescensare in broad patches on the pectoral region, while inpullus, a white stripe passes from the pectoral region to the inguinal region in both males and females. I know of no selective advantage that the presence of this white stripe would confer on the mice.Specimens examined.—Total 46, all fromNicaragua, and distributed as follows: Type locality, 32 (including the type);9 mi. NNW Estelí, 8;8 mi. NNW Estelí, 3; San Rafael Del Norte, 1 (Amer. Mus. Nat. Hist.);1 mi. NW Jinotega, 1; Matagalpa, 1 (Amer. Mus. Nat. Hist.).Marginal records.—Nicaragua: San Rafael Del Norte; Matagalpa; type locality.Baiomys tayloriNorthern Pygmy Mouse(Synonymy under subspecies)Type.—Hesperomys(Vesperimus)tayloriThomas, Ann. Mag. Nat. Hist., Ser. 5, 19:66, January, 1887.Range.—Southeastern Arizona and southwestern New Mexico, south into Chihuahua and Durango, just east of the Sierra Madre Occidental, thence southeast through Zacatecas, Aquascalientes, Jalisco, Querétaro, and Guanajuato; two fingerlike projections extend northward, one on the west along the coast of Sinaloa into southern Sonora, and the other on the east covering eastern San Luis Potosí, Tamaulipas, eastern Coahuila, Nuevo León, into south, southeast, and north-central Texas. Southern margin of range in central México approximates the 19th degree of latitude (seeFigure 11). Arid lower and arid upper subdivisions of the Tropical Life-zone in south; principally Lower Sonoran and Lower Austral life-zones in north.Characters for ready recognition.—Unless otherwise noted, characters are usable for the age-categories of adult and old adult. Differs fromB. musculusin: hind foot less than 16 millimeters; occipitonasal length less than 19 millimeters; zygomatic breadth less than 10 millimeters; rostrum deflected ventrally at frontoparietal suture rather than curving gradually toward anteriormost point of nasals; cingular ridges and secondary cusps on teeth reduced or absent; basihyal having entoglossal process much reduced or absent, shoulders of basihyal not protruding anteriorly, but more flattened (characteristic of all age categories); baculum having narrower shaft, knob-shaped tip, wings at base projecting laterally, baculum less than 3 millimeters long; short process of incus attenuate; muscular process of posterior crus of stapes reduced.Characters of the species.—Size small (extremes in external measurements of adults: total length, 87-123; length of tail vertebrae, 34-53; length of hind foot, 12-15; length of ear, 9-12). Upper parts pale drab or reddish-brown to almost black; underparts grayish to cream-buff.Geographic variation.—Eight subspecies are here recognized (seeFigure 11). Features that vary geographically are mostly the same as those that do so inB. musculus(seepage 609).External and cranial size is less inB. t. allex, the southernmost subspecies, and progressively more inB. t. paulus,B. t. taylori,B. t. ater,B. t. subater,B. t. fuliginatus,B. t. canutus, andB. t. analogous. Size is largest in subspecies that occur at higher altitudes. Those subspecies areB. t. analogousandB. t. fuliginatus. The correlation with Bergman's Rule is less exact inB. taylorithan inB. musculus. It is noteworthy that the smallest subspecies,B. t. allex, occurs in the area where the two species are sympatric.There is close correlation inB. taylori, as also inB. musculus, of darker pelages with zones of high relative humidity. The subspecies having dark pelages are:analogous,fuliginatus, andsubater. The two first-mentioned subspecies occur at high altitudes, andthe other,subater, occurs in the humid coastal region of Texas. The paler subspecies,taylori,canutus, andallex, occur at lower altitudes. Two subspecies that occur at relatively high altitudes,aterandpaulus, are reddish-brown. The color of pelage in these subspecies resembles the color of soil upon which they live. Blair and Blossom (1948:5) demonstrated close correlation of color of soil with color of pelage inB. t. aterby use of an Ives tint photometer.
[10]Univ. Michigan, Museum of Zoology.
[10]Univ. Michigan, Museum of Zoology.
[11]U. S. Nat. Museum (Biol. Surv. Coll.).
[11]U. S. Nat. Museum (Biol. Surv. Coll.).
[12]Chicago Natural History Museum.
[12]Chicago Natural History Museum.
[13]Univ. California, Mus. Vert. Zoology.
[13]Univ. California, Mus. Vert. Zoology.
Baiomys musculus nigrescens(Osgood)
Peromyscus musculus nigrescensOsgood, Proc. Biol. Soc. Washington, 17:76, March 21, 1904; Elliot, Field Columb. Mus. Publ., 105(4):136, July 1, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus., 62:135, January 15, 1909; Osgood, N. Amer. Fauna, 28:259, April 17, 1909.
Baiomys musculus nigrescens, Miller, Bull. U. S. Nat. Mus., 79:137, March 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318, April 29, 1924; Goodwin, Bull. Amer. Mus. Nat. Hist., 68(1):40, December 12, 1934; Ellerman, The Families and Genera of Living Rodents, 2:402, March 21, 1941; Poole and Schantz, Bull. U. S. Nat. Mus., 178:259, March 6, 1942; Hooper, Jour. Mamm., 28:50, February 15, 1947; Goldman, Smith. Miscl. Coll., 115:357, July 31, 1951; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:513, March 3, 1955; Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10, 1957; Hall and Kelson, The Mammals of North America, 2:661, March 31, 1959 (part).
[Peromyscus musculus]nigrescens, Elliot, Field Columb. Mus. Publ., 95(4):176, 1904.
B.[aiomys]m.[usculus]nigrescens, Goodwin, Bull. Amer. Mus. Nat. Hist., 79(2):160, May 29, 1942; Hooper, Jour. Mamm., 33:97, February 18, 1952 (part); Packard, Univ. Kansas Publs., Mus. Nat. Hist., 9:399, December 19, 1958.
B.[aiomys]m.[usculus]musculus, Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10, 1957 (part).
Type.—Adult female, skin and skull; No. 76827 U. S. Nat. Mus. (Biol. Surv. Coll.); Valley of Comitán, Chiapas, Republic of México, obtained on December 9, 1895, by E. W. Nelson and E. A. Goldman, original number 8719.Range.—Southern coastal region and eastern parts of Chiapas, southeastward into central and southern Guatemala, thence south into El Salvador (seeFigure 10). Zonal range: parts of Lower Austral; also occurs in parts of the arid division of the Upper Tropical Life-zone, and in parts of the arid division of the Lower Tropical Life-zone; approximates a part of the Chiapas Highlands Biotic Province of Goldman and Moore (1945:349), and parts of the Guatemalan Subregion of Smith (1949:235).Diagnosis.—Size medium to small for the species; dorsum Vandyke Brown mixed with blackish, individual hairs black-tipped with a subterminal band of Warm Buff, Neutral Gray at base; guard hairs of dorsum black distally, Neutral Gray basally; hairs on sides grayish-brown, facial region like dorsum; chin buffy-brown; vibrissae brown, ventrally some white; venter creamy-buff to grayish, individual hairs creamy-buff at tips, gray basally; in region of throat and chin, hairs tipped with Ochraceous-Buff; dorsal surface of forefeet and hind feet dull whitish gray to brownish-black; tail indistinctly bicolored, dusky above, grayish to brownish below; incisive foramina short, wide medially;[Pg 624]average and extreme external and cranial measurements of 15 adults from 6 mi. NW Tonalá, Chiapas, are as follows: total length, 107.5 (100-116); length of tail vertebrae, 41.1 (33-48); length of body, 66.1 (62-73); length of hind foot, 15.0 (14-16); length of ear, 10.9 (10-12); occipitonasal length, 18.9 (18.4-19.7); zygomatic breadth, 9.8 (9.4-10.2); postpalatal length, 6.9 (6.6-7.4); least interorbital breadth, 3.7 (3.5-3.8); length of incisive foramina, 4.4 (4.1-4.8); length of rostrum, 6.7 (6.1-7.1); breadth of braincase, 9.2 (9.0-9.4); depth of cranium, 6.9 (6.5-7.3); alveolar length of maxillary tooth-row, 3.1 (2.9-3.2); for photographs of skull, seePlate 1f, andPlate 3f.Comparisons.—For comparisons withB. m. handleyi,B. m. grisescens,B. m. musculus,B. m. pallidus, andB. m. pullus, see accounts of those subspecies.FromB. m. brunneus,B. m. nigrescensdiffers in: dorsum blackish-brown rather than reddish to ochraceous brown; face and ears brownish-black rather than brownish with tinges of ochraceous; vibrissae darker; forefeet and hind feet darker; venter with more grayish tones; dorsalmost part of zygomatic plate projects farther anteriorly; interparietal oval to diamond-shaped and narrower anteroposteriorly; zygomata narrower at anteriormost part; slightly smaller in most cranial and external measurements.FromB. m. infernatis,B. m. nigrescensdiffers in: dorsum darker; region of face and ears darker; venter buffy to gray rather than whitish-buff; vibrissae darker; forefeet and hind feet darker; tail darker above and below; incisive foramina shorter, more constricted laterally; cranium slightly smaller in most dimensions.
Type.—Adult female, skin and skull; No. 76827 U. S. Nat. Mus. (Biol. Surv. Coll.); Valley of Comitán, Chiapas, Republic of México, obtained on December 9, 1895, by E. W. Nelson and E. A. Goldman, original number 8719.
Range.—Southern coastal region and eastern parts of Chiapas, southeastward into central and southern Guatemala, thence south into El Salvador (seeFigure 10). Zonal range: parts of Lower Austral; also occurs in parts of the arid division of the Upper Tropical Life-zone, and in parts of the arid division of the Lower Tropical Life-zone; approximates a part of the Chiapas Highlands Biotic Province of Goldman and Moore (1945:349), and parts of the Guatemalan Subregion of Smith (1949:235).
Diagnosis.—Size medium to small for the species; dorsum Vandyke Brown mixed with blackish, individual hairs black-tipped with a subterminal band of Warm Buff, Neutral Gray at base; guard hairs of dorsum black distally, Neutral Gray basally; hairs on sides grayish-brown, facial region like dorsum; chin buffy-brown; vibrissae brown, ventrally some white; venter creamy-buff to grayish, individual hairs creamy-buff at tips, gray basally; in region of throat and chin, hairs tipped with Ochraceous-Buff; dorsal surface of forefeet and hind feet dull whitish gray to brownish-black; tail indistinctly bicolored, dusky above, grayish to brownish below; incisive foramina short, wide medially;[Pg 624]average and extreme external and cranial measurements of 15 adults from 6 mi. NW Tonalá, Chiapas, are as follows: total length, 107.5 (100-116); length of tail vertebrae, 41.1 (33-48); length of body, 66.1 (62-73); length of hind foot, 15.0 (14-16); length of ear, 10.9 (10-12); occipitonasal length, 18.9 (18.4-19.7); zygomatic breadth, 9.8 (9.4-10.2); postpalatal length, 6.9 (6.6-7.4); least interorbital breadth, 3.7 (3.5-3.8); length of incisive foramina, 4.4 (4.1-4.8); length of rostrum, 6.7 (6.1-7.1); breadth of braincase, 9.2 (9.0-9.4); depth of cranium, 6.9 (6.5-7.3); alveolar length of maxillary tooth-row, 3.1 (2.9-3.2); for photographs of skull, seePlate 1f, andPlate 3f.
Comparisons.—For comparisons withB. m. handleyi,B. m. grisescens,B. m. musculus,B. m. pallidus, andB. m. pullus, see accounts of those subspecies.
FromB. m. brunneus,B. m. nigrescensdiffers in: dorsum blackish-brown rather than reddish to ochraceous brown; face and ears brownish-black rather than brownish with tinges of ochraceous; vibrissae darker; forefeet and hind feet darker; venter with more grayish tones; dorsalmost part of zygomatic plate projects farther anteriorly; interparietal oval to diamond-shaped and narrower anteroposteriorly; zygomata narrower at anteriormost part; slightly smaller in most cranial and external measurements.
FromB. m. infernatis,B. m. nigrescensdiffers in: dorsum darker; region of face and ears darker; venter buffy to gray rather than whitish-buff; vibrissae darker; forefeet and hind feet darker; tail darker above and below; incisive foramina shorter, more constricted laterally; cranium slightly smaller in most dimensions.
Remarks.—Hooper (1952a:93-94) reported specimens from the coastal strip of southern Chiapas as the most intensely pigmented, whereas, specimens from central and western Chiapas were distinctly paler. Crania of specimens from the coastal region of southern Chiapas were smaller than crania from the central highlands and mountains of Chiapas. My studies essentially corroborate the findings of Hooper. The gradation of color between the pale brownpallidusto the north in Oaxaca, and the brownish-blacknigrescensto the south in Chiapas is extremely gradual. Specimens from the central and western parts of Chiapas (seeFigure 10for localities) are difficult to assign to eitherpallidusornigrescens. Equal justification exists for assignment to either subspecies. I have assigned the specimens tonigrescensbecause they are geographically closer to the type locality ofnigrescens. Specimens from Reforma, Oaxaca (assigned by Hooper, 1952a:93-94, tonigrescens), are nearly identical in size and color to paratypes ofpallidus. I assign the Reforma specimens topallidus.
The darkest of all the specimens examined and assigned tonigrescensare from 1 mi. NW San Salvador and 1 mi. S Los Planes, El Salvador. The variations in color in this subspecies closely correspond to degree of relative humidity; the palest samples are from areas of low relative humidity and the darkest are from areasof high relative humidity. In view of the present state of differentiation of specimens from the southern coastal areas of Chiapas and mountainous areas of El Salvador, it would seem that populations there might be incipient subspecies.
Specimens examined.—Total 319.Chiapas:17 mi. W Bochil, 1[14];15 mi. W Bochil, 1[14];14 mi. W Bochil, 1[14]; Bochil, 6[15]; Ocuilapa, 3500 ft., 5[16];5 mi. NNW Tuxtla Gutiérrez, 9;11 km. W Tuxtla Gutiérrez, 800 m., 2[15];10 km. W Tuxtla Gutiérrez, 800 m., 2[15];Tuxtla Gutiérrez, 2600 ft., 8[16], 11;Ocozocoautla, 10[15], 2[16]; 25 mi. E Comitán, Las Margaritas, 1250 m., 5[17], 24[15]; Cintalpa, 555 m., 1[14], 18[15], 3[17];Jiquilpilas, 2000 ft., 1[16]; San Bartolome, 3[16];type locality, 5700 ft., 26[16](including the type); 15 mi. SW Las Cruces, 1; Villa Flores, 600 m., 12[15];23 mi. S Comitán, 1[14];15 mi. S, 2 mi. E La Trinitaria, 4;30 mi. S Comitán, 2[14]; 35 mi. S Comitán, 1[14];3 mi. E Arriga, 1[14]; 6 mi. NW Tonalá, 19;Tonalá, 8[16];Los Amates, 1[14]; Pijijiapan, 10 m., 7[15]; Mapastepec, 45 m., 25[15], 4[17].Guatemala: Chanquejelve, 1[14];Nentón, 3000 ft., 1[16]; Jacaltenango, 5400 ft., 8[16]; La Primavera, 5[14]; 4 mi. S Guatemala City, 4700 ft., 3;5 mi. S Guatemala City, 4050 ft., 10;6 mi. S Guatemala City, 4680 ft., 1;Lake Amatitlán, 4500 ft., 13[16]; El Progresso (Distrito Santa Rosa), 3[15];2 mi. N, 1 mi. W Cuilapa, 2980 ft., 1[14];1 mi. WSW El Molino(Distrito Santa Rosa), 2;21/2mi. W, 21/4mi. N San Cristobal, 2900 ft., 1; El Zapote, 1[15].El Salvador: 1 mi. NW San Salvador, 29; 1 mi. S Los Planes, 15.Marginal Records.—Chiapas: Bochil; 25 mi. E Comitán, Las Margaritas, 1250 ft.Guatemala: Chanquejelve; La Primavera; Jacaltenango, 5400 ft.; 4 mi. S Guatemala City, 4700 ft.; El Progresso.El Salvador: 1 mi. NW San Salvador; 1 mi. S Los Planes.Guatemala: El Zapote.Chiapas: Mapastepec, 45 m.; Pijijiapan, 10 m.; 6 mi. NW Tonalá; 15 mi. SW Las Cruces; Cintalpa, 555 m.; Ocuilapa, 3500 ft.
Specimens examined.—Total 319.Chiapas:17 mi. W Bochil, 1[14];15 mi. W Bochil, 1[14];14 mi. W Bochil, 1[14]; Bochil, 6[15]; Ocuilapa, 3500 ft., 5[16];5 mi. NNW Tuxtla Gutiérrez, 9;11 km. W Tuxtla Gutiérrez, 800 m., 2[15];10 km. W Tuxtla Gutiérrez, 800 m., 2[15];Tuxtla Gutiérrez, 2600 ft., 8[16], 11;Ocozocoautla, 10[15], 2[16]; 25 mi. E Comitán, Las Margaritas, 1250 m., 5[17], 24[15]; Cintalpa, 555 m., 1[14], 18[15], 3[17];Jiquilpilas, 2000 ft., 1[16]; San Bartolome, 3[16];type locality, 5700 ft., 26[16](including the type); 15 mi. SW Las Cruces, 1; Villa Flores, 600 m., 12[15];23 mi. S Comitán, 1[14];15 mi. S, 2 mi. E La Trinitaria, 4;30 mi. S Comitán, 2[14]; 35 mi. S Comitán, 1[14];3 mi. E Arriga, 1[14]; 6 mi. NW Tonalá, 19;Tonalá, 8[16];Los Amates, 1[14]; Pijijiapan, 10 m., 7[15]; Mapastepec, 45 m., 25[15], 4[17].
Guatemala: Chanquejelve, 1[14];Nentón, 3000 ft., 1[16]; Jacaltenango, 5400 ft., 8[16]; La Primavera, 5[14]; 4 mi. S Guatemala City, 4700 ft., 3;5 mi. S Guatemala City, 4050 ft., 10;6 mi. S Guatemala City, 4680 ft., 1;Lake Amatitlán, 4500 ft., 13[16]; El Progresso (Distrito Santa Rosa), 3[15];2 mi. N, 1 mi. W Cuilapa, 2980 ft., 1[14];1 mi. WSW El Molino(Distrito Santa Rosa), 2;21/2mi. W, 21/4mi. N San Cristobal, 2900 ft., 1; El Zapote, 1[15].
El Salvador: 1 mi. NW San Salvador, 29; 1 mi. S Los Planes, 15.
Marginal Records.—Chiapas: Bochil; 25 mi. E Comitán, Las Margaritas, 1250 ft.Guatemala: Chanquejelve; La Primavera; Jacaltenango, 5400 ft.; 4 mi. S Guatemala City, 4700 ft.; El Progresso.El Salvador: 1 mi. NW San Salvador; 1 mi. S Los Planes.Guatemala: El Zapote.Chiapas: Mapastepec, 45 m.; Pijijiapan, 10 m.; 6 mi. NW Tonalá; 15 mi. SW Las Cruces; Cintalpa, 555 m.; Ocuilapa, 3500 ft.
[14]American Museum of Natural History.
[14]American Museum of Natural History.
[15]Univ. Michigan, Museum of Zoology.
[15]Univ. Michigan, Museum of Zoology.
[16]U. S. Nat. Museum (Biol. Surv. Coll.).
[16]U. S. Nat. Museum (Biol. Surv. Coll.).
[17]University of Florida Collections.
[17]University of Florida Collections.
Baiomys musculus pallidusRussell
Baiomys musculus pallidusRussell, Proc. Biol. Soc. Washington, January 29, 1952; Davis and Russell, Jour. Mamm., 35:75, February 10, 1954; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512; Hall and Kelson, The Mammals of North America, 2:662, March 31, 1959.
Peromyscus musculus brunneus, Elliot, Field Columb. Mus. Publ., 115(8):203, 1907 (part).
Peromyscus musculus[musculus], Osgood, N. Amer. Fauna, 28:257, April 17, 1909 (part).
Baiomys musculus musculus, Miller, Bull. U. S. Nat. Mus., 79:137, December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:318, April 29, 1924 (part); Davis, Jour. Mamm., 25:394, December 12, 1944 (part); Hooper, Jour. Mamm., 28:50, February 15, 1947 (part); Goldman, Smith, Miscl. Coll., 115:336, July 31, 1951 (part); Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, 1955 (part); Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10, 1957 (part); Hall and Kelson, The Mammals of North America, 2:661, March 31, 1959 (part); Goodwin, Amer. Mus. Novitates, 1929:1, March 5, 1959.
B.[aiomys]m.[usculus]musculus, Hooper, Jour. Mamm., 33:97, February 18, 1952 (part).
B.[aiomys]m.[usculus]nigrescens, Hooper, Jour. Mamm., 33:97, February 18, 1952 (part).
Baiomys musculus nebulosus Goodwin, Amer. Mus. Novitates, 1929, March 5, 1959.
Type.—Adult female, skin and skull; No. 4501 Texas A&M Cooperative Wildlife Collection; 12 kms. NW Axochiapán, 3500 feet, Morelos, Republic of México, obtained on July 28, 1950, by W. B. Davis, original number 5112.Range.—Guerrero thence eastward into Morelos and west central Puebla along the southern edge of the Transverse Volcanic Biotic Province (Goldman and Moore, 1945:349), south into Oaxaca, seeFigure 10. Zonal range: largely Arid Lower Tropical Subzone of Goldman (1951:330). Occurs from near sea level in Oaxaca and Guerrero up to 6550 feet in Oaxaca.Diagnosis.—Size medium for the species; dorsum Buffy Brown in palest series to Olive-Brown in darkest series, individual hairs Warm Buff, Neutral Gray basally, some with black tips and a subterminal band of Warm Buff, guard hairs of dorsum black-tipped, gray basally; hairs on sides creamy-buff, gray basally; face same color as back fading to white on throat; vibrissae white-tipped, pale brown basally; venter, whitish with tinges of buff on lower throat, individual hairs having tips white to buffy-white, light gray basally; dorsal surface of forefeet and hind feet whitish to flesh-color; tail indistinctly bicolored, brownish above, grayish brown below; zygoma bowed as inB. m. grisescens; tail short; average and extreme external and cranial measurements for 17 adults from Tehuantepec, Oaxaca, are: total length, 117.3 (110-126); length of tail vertebrae, 46.9 (41-51); length of body, 70.4 (65-76); length of hind foot, 15.8 (15-16); occipitonasal length, 18.9 (18.2-20.1); zygomatic breadth, 10.1 (9.7-10.6); postpalatal length, 6.9 (6.6-7.5); least interorbital breadth, 3.8 (3.6-3.9); length of incisive foramina, 4.4 (4.2-4.7); length of rostrum, 6.7 (6.3-7.2); breadth of braincase, 9.3 (8.7-9.7); depth of cranium, 6.6 (6.4-6.8); alveolar length of maxillary tooth-row, 3.2 (3.1-3.4); for photographs of skull, seePlate 1g, andPlate 3g.Comparisons.—For comparisons withB. m. brunneusandB. m. infernatis, see accounts of those subspecies.FromB. m. musculus,B. m. pallidusdiffers in: dorsum more olive-gray and brown, less ochraceous on either side of mid-dorsal region; face below eye grayish, not buffy; sides gray with buffy overtone, not creamy with light yellow overtones; venter grayish-white rather than an olive-buff; zygomata more tapering anteriorly; maxillary part of zygoma narrower when viewed from above; external and cranial dimensions smaller.FromB. m. nigrescens,B. m. pallidusdiffers in: dorsum paler, fewer black hairs medially; face paler, less sooty; vibrissae brownish with white tips rather than black with brownish tips; venter paler; dorsal surface of forefeet and hind feet whitish to flesh-colored rather than sooty to dusky-white; tail paler; nasals slightly more attenuated; averaging slightly larger in external and cranial measurements.
Type.—Adult female, skin and skull; No. 4501 Texas A&M Cooperative Wildlife Collection; 12 kms. NW Axochiapán, 3500 feet, Morelos, Republic of México, obtained on July 28, 1950, by W. B. Davis, original number 5112.
Range.—Guerrero thence eastward into Morelos and west central Puebla along the southern edge of the Transverse Volcanic Biotic Province (Goldman and Moore, 1945:349), south into Oaxaca, seeFigure 10. Zonal range: largely Arid Lower Tropical Subzone of Goldman (1951:330). Occurs from near sea level in Oaxaca and Guerrero up to 6550 feet in Oaxaca.
Diagnosis.—Size medium for the species; dorsum Buffy Brown in palest series to Olive-Brown in darkest series, individual hairs Warm Buff, Neutral Gray basally, some with black tips and a subterminal band of Warm Buff, guard hairs of dorsum black-tipped, gray basally; hairs on sides creamy-buff, gray basally; face same color as back fading to white on throat; vibrissae white-tipped, pale brown basally; venter, whitish with tinges of buff on lower throat, individual hairs having tips white to buffy-white, light gray basally; dorsal surface of forefeet and hind feet whitish to flesh-color; tail indistinctly bicolored, brownish above, grayish brown below; zygoma bowed as inB. m. grisescens; tail short; average and extreme external and cranial measurements for 17 adults from Tehuantepec, Oaxaca, are: total length, 117.3 (110-126); length of tail vertebrae, 46.9 (41-51); length of body, 70.4 (65-76); length of hind foot, 15.8 (15-16); occipitonasal length, 18.9 (18.2-20.1); zygomatic breadth, 10.1 (9.7-10.6); postpalatal length, 6.9 (6.6-7.5); least interorbital breadth, 3.8 (3.6-3.9); length of incisive foramina, 4.4 (4.2-4.7); length of rostrum, 6.7 (6.3-7.2); breadth of braincase, 9.3 (8.7-9.7); depth of cranium, 6.6 (6.4-6.8); alveolar length of maxillary tooth-row, 3.2 (3.1-3.4); for photographs of skull, seePlate 1g, andPlate 3g.
Comparisons.—For comparisons withB. m. brunneusandB. m. infernatis, see accounts of those subspecies.
FromB. m. musculus,B. m. pallidusdiffers in: dorsum more olive-gray and brown, less ochraceous on either side of mid-dorsal region; face below eye grayish, not buffy; sides gray with buffy overtone, not creamy with light yellow overtones; venter grayish-white rather than an olive-buff; zygomata more tapering anteriorly; maxillary part of zygoma narrower when viewed from above; external and cranial dimensions smaller.
FromB. m. nigrescens,B. m. pallidusdiffers in: dorsum paler, fewer black hairs medially; face paler, less sooty; vibrissae brownish with white tips rather than black with brownish tips; venter paler; dorsal surface of forefeet and hind feet whitish to flesh-colored rather than sooty to dusky-white; tail paler; nasals slightly more attenuated; averaging slightly larger in external and cranial measurements.
Remarks.—Russell (1952:21) describedpallidus, on the basis of specimens from the arid Balsas Basin, of Morelos, as pale gray dorsally. After examining the original material from Morelos, I find the dorsal color ofpallidusto be much closer to a buffy brown than a pale grayish. Even so, smaller size differentiatespallidusfrommusculus.B. m. infernatis, notB. m. pallidus, is the most pallid of all named subspecies ofB. musculus.
B. m. pallidusintergrades to the northwest withB. m. musculus, to the northeast withB. m. infernatis, and to the southeast withB. m. nigrescens.
According to Goodwin (1959:2),B. m. nebulosus(named on the basis of one specimen) differs fromB. m. musculus[=pallidus] from southern Oaxaca in: darker and longer pelage; larger skull; interorbital region broader and less constricted posteriorly. FromB. m. nigrescensandB. m. brunneus,B. m. nebulosusdiffers as follows: pelage longer and softer; skull larger.
Study of specimens ofB. musculusfrom Oaxaca reveals considerable variation in external and cranial measurements as well as color, corresponding to that reported by Goodwin (loc. cit.). Specimens from higher altitudes average somewhat darker and larger in external and cranial size than those at lower elevations. These differences seem to be microgeographic and not of subspecific rank. Among specimens that I have studied in Oaxaca are several from different localities (KU 63052, an adult male, from 3 mi. W Miahuatlán; KU 68964, an adult male from 3 mi. W Mitla, 6000 ft.; KU 63055, an adult female from 3 mi. S Candelario, 1200 ft.) that, according to Goodwin (in. litt.) matchnebulosusin reported color, size of body and skull (except for the region of the rostrum).
Two of the three specimens (KU 63052 and 63055) are the darkest of a series in which the palest are inseparable fromB. m. pallidus. Goodwin, who kindly compared the three specimens with the type ofnebulosus, mentioned (in. litt.) that the skull of the type has a slenderer rostrum. Included in the series of skulls ofB. m. pallidusfrom 3 mi. W Mitla are several adults (not seen by Goodwin) with slender rostra.B. m. nebulosusis judged to be a synonym ofB. m. pallidus.
Populations of pygmy mice occurring in partially isolated areas of highland in Oaxaca seem to me to be incipient subspecies.
Specimens examined.—Total 824 all from the Republic of México and distributed as follows:Puebla: 2 mi. S Atlixco, 5800 ft., 1;1 mi. SSW Tilapa, 5800 ft., 2;6 mi. SW Izucár de Matemores, 7;Piaxtla, 3900 ft., 4[18]; Acatlán, 4100 ft., 1.Morelos: 5 mi. W Tepoztlán, 6000 ft., 7[19];1 mi. W Tepoztlán, 6000 ft., 9[19];2 mi. SW Tepoztlán, 7000 ft., 1[20];Cuernvaca, 9[19];6 mi. W Yautepec, 4500 ft., 1[20];Yautepec, 12[19];3 mi. N Alpuyeca, 4000 ft., 2[20];Puente de Ixtla, 2[19];Tetecala, 4[21];2 km. S Jonacatepec, 4500 ft., 6[20];type locality, 6 (including the type).Guerrero:Yerbabuena, 1800 m., 1;Cueva de tia Juana[=1.5 km. SSW Yerbabuena], 1;Laguna Honda, 1840 m. [=1.5 km. S Yerbabuena], 3; 9 mi. SE Taxco, 3800 ft., 1[22];17 km. S Taxco, 4000 ft., 2[20];Iguala, 5[19];3.2 km. SSE Iguala, 970 m., 1; 1 km. SSE Texcaizintla, 1600 m., 2;Teloloapán, 20[19], 5[24];1 km. N Chapa, 1470 m., 6;Chapa, 1470 m., 5; El Limón, 3[18]; 21/2mi. W Mexcala, 2100 ft., 1[20];Río Balsas, 1[18]; Ayusinaha [= Ayotzinapa], 1[18];Tlapa,[Pg 628]3900 ft, 1[18];2.5 mi. S Almolonga, 5600 ft., 13[20];1 km. N Zihuatanejo, 1; Zihuatanejo Bay, 4[19];Las Gatas[=2 km. S. Zihuatanejo], 2;2 km. SSE Zihuatanejo, 9;4 mi. W Chilpancingo, 5800 ft., 3[20];Chilpancingo, 4800 ft., 14[18], 21[19], 45[21];2 mi. N Tixtla, 4400 ft., 3[20];3.2 km. S Chilpancingo, 4;Cd. Chamilpa[=12 km. ESE Chilpancingo], 5;Tlalixtaquilla, 4200 ft., 2[18];15 km. S. Chilpancingo, 4300 ft., 10[20];1 mi. SW Colotlipa, 2700 ft., 16[20];2 mi. SW Colotlipa, 2700 ft., 1[20];Achuitzotla, 2800 ft., 7[20];8 mi. SW Colotlipa, 1[20];5 mi. S Rincón, 2600 ft., 2[20];8 mi. SW Tierra Colorado, 600 ft., 1[20]; Río Aguacatillo,30 km. N Acapulco, 1000 ft., 3[20]; 5 mi. ESE Tecpán, 50 ft., 9;Ejido Viejo,12 km. NNW Acapulco, 1;2 mi. NNW Acapulco, 7; Acapulco, 3[18], 3[21]; Omentepec, 200 ft., 7[18].Oaxaca:4 mi. E Huajuapám, 5000 ft., 1; 2 mi. NW Tamazulapán, 6550 ft., 1; Yalalag, 3000 ft., 5[18];11 mi. NW Oaxaca[City], 1;Yaganiza, 3900 ft., 1[18]; Oaxaca [City], 5000 ft., 15, 7[21], 7[19], 5[24];3 mi. ESE Oaxaca[City], 30;4 mi. ESE Oaxaca[City], 5050 ft., 1;10 mi. SE Oaxaca[City], 1[22];Cerro Ocotepec, 1[23]; Tepantepec, 9[23];1 mi. E Tlacolula, 5500 ft., 53[19];3 mi. W Mitla, 11; Jalapa, El Campanario, 1[23];2 mi. SE Matalán, 5950 ft., 14;Lachiguiri, 2[23];Tres Cruces, 10[23];Agua Blanca, 11[23];San José, 1[23]; Reforma, 30[19], 7[21], 10[23], 6[24]Totolapa, 1[18];Nejapa,85 km. WNW Tehuantepec, 500 m., 12[19], 6[24];Chicapa, 2[18];Gueladu[=Jalapa], 6[23];Juchitán,Laguna Superior; Manteca, 8[23], 1[23]; San Bartolo, 3000 ft., 1[18];Ejutla, 1400 m., 21[19];El Bambita,Tequisitlán4[23];Mixtequilla, 2[23];Guiencola, 5[23];Tehuantepec, 200 ft., 26[18], 11[19];Sola de la Vega, 26[19], 3[24]; Huilotepec, 13[18], 3[23];Santa Lucia, 24[23];Cerro de Paste,Tenango, 7[23];Sta. C. Quieri, 3[23];Santa Marie Ecatepec,Zarzamora, 13[23];Rincón Bamba, 11[23];3 mi. W Miahuatlán, 5300 ft., 1;Miahuatlán, 12[19], 1[23], 6[24];San Juan Acaltepec, 5[23];Zapotitlán, 1[23];Llano Grande, 3[18]; Pinotepa, 700 ft., 2[18]; Juquila, 8[18];Arroyo,San Juan,north of Cerro Otate, 1[23]; Cerro Otate, 3[23]; 3 mi. S Candelaria, 1.Marginal records.—Morelos: 5 mi, W Tepoztlán, 6000 ft.Puebla: 2 mi. S Atlixco, 5800 ft.; Acatlán, 4100 ft.Oaxaca: 2 mi. NW Tamazulapán, 6550 ft; Tepantepec; Oaxaca [City], 5000 ft; Yalalag, 3000 ft; Jalapa, El Campanario; Reforma; Huilotepec; 3 mi. S Candelaria; Cerro Otate; Pinotepa, 700 ft.Guerrero: Acapulco; Zihuatanejo Bay; El Limón; 9 mi. SE Taxco, 3800 ft.
Specimens examined.—Total 824 all from the Republic of México and distributed as follows:Puebla: 2 mi. S Atlixco, 5800 ft., 1;1 mi. SSW Tilapa, 5800 ft., 2;6 mi. SW Izucár de Matemores, 7;Piaxtla, 3900 ft., 4[18]; Acatlán, 4100 ft., 1.Morelos: 5 mi. W Tepoztlán, 6000 ft., 7[19];1 mi. W Tepoztlán, 6000 ft., 9[19];2 mi. SW Tepoztlán, 7000 ft., 1[20];Cuernvaca, 9[19];6 mi. W Yautepec, 4500 ft., 1[20];Yautepec, 12[19];3 mi. N Alpuyeca, 4000 ft., 2[20];Puente de Ixtla, 2[19];Tetecala, 4[21];2 km. S Jonacatepec, 4500 ft., 6[20];type locality, 6 (including the type).Guerrero:Yerbabuena, 1800 m., 1;Cueva de tia Juana[=1.5 km. SSW Yerbabuena], 1;Laguna Honda, 1840 m. [=1.5 km. S Yerbabuena], 3; 9 mi. SE Taxco, 3800 ft., 1[22];17 km. S Taxco, 4000 ft., 2[20];Iguala, 5[19];3.2 km. SSE Iguala, 970 m., 1; 1 km. SSE Texcaizintla, 1600 m., 2;Teloloapán, 20[19], 5[24];1 km. N Chapa, 1470 m., 6;Chapa, 1470 m., 5; El Limón, 3[18]; 21/2mi. W Mexcala, 2100 ft., 1[20];Río Balsas, 1[18]; Ayusinaha [= Ayotzinapa], 1[18];Tlapa,[Pg 628]3900 ft, 1[18];2.5 mi. S Almolonga, 5600 ft., 13[20];1 km. N Zihuatanejo, 1; Zihuatanejo Bay, 4[19];Las Gatas[=2 km. S. Zihuatanejo], 2;2 km. SSE Zihuatanejo, 9;4 mi. W Chilpancingo, 5800 ft., 3[20];Chilpancingo, 4800 ft., 14[18], 21[19], 45[21];2 mi. N Tixtla, 4400 ft., 3[20];3.2 km. S Chilpancingo, 4;Cd. Chamilpa[=12 km. ESE Chilpancingo], 5;Tlalixtaquilla, 4200 ft., 2[18];15 km. S. Chilpancingo, 4300 ft., 10[20];1 mi. SW Colotlipa, 2700 ft., 16[20];2 mi. SW Colotlipa, 2700 ft., 1[20];Achuitzotla, 2800 ft., 7[20];8 mi. SW Colotlipa, 1[20];5 mi. S Rincón, 2600 ft., 2[20];8 mi. SW Tierra Colorado, 600 ft., 1[20]; Río Aguacatillo,30 km. N Acapulco, 1000 ft., 3[20]; 5 mi. ESE Tecpán, 50 ft., 9;Ejido Viejo,12 km. NNW Acapulco, 1;2 mi. NNW Acapulco, 7; Acapulco, 3[18], 3[21]; Omentepec, 200 ft., 7[18].Oaxaca:4 mi. E Huajuapám, 5000 ft., 1; 2 mi. NW Tamazulapán, 6550 ft., 1; Yalalag, 3000 ft., 5[18];11 mi. NW Oaxaca[City], 1;Yaganiza, 3900 ft., 1[18]; Oaxaca [City], 5000 ft., 15, 7[21], 7[19], 5[24];3 mi. ESE Oaxaca[City], 30;4 mi. ESE Oaxaca[City], 5050 ft., 1;10 mi. SE Oaxaca[City], 1[22];Cerro Ocotepec, 1[23]; Tepantepec, 9[23];1 mi. E Tlacolula, 5500 ft., 53[19];3 mi. W Mitla, 11; Jalapa, El Campanario, 1[23];2 mi. SE Matalán, 5950 ft., 14;Lachiguiri, 2[23];Tres Cruces, 10[23];Agua Blanca, 11[23];San José, 1[23]; Reforma, 30[19], 7[21], 10[23], 6[24]Totolapa, 1[18];Nejapa,85 km. WNW Tehuantepec, 500 m., 12[19], 6[24];Chicapa, 2[18];Gueladu[=Jalapa], 6[23];Juchitán,Laguna Superior; Manteca, 8[23], 1[23]; San Bartolo, 3000 ft., 1[18];Ejutla, 1400 m., 21[19];El Bambita,Tequisitlán4[23];Mixtequilla, 2[23];Guiencola, 5[23];Tehuantepec, 200 ft., 26[18], 11[19];Sola de la Vega, 26[19], 3[24]; Huilotepec, 13[18], 3[23];Santa Lucia, 24[23];Cerro de Paste,Tenango, 7[23];Sta. C. Quieri, 3[23];Santa Marie Ecatepec,Zarzamora, 13[23];Rincón Bamba, 11[23];3 mi. W Miahuatlán, 5300 ft., 1;Miahuatlán, 12[19], 1[23], 6[24];San Juan Acaltepec, 5[23];Zapotitlán, 1[23];Llano Grande, 3[18]; Pinotepa, 700 ft., 2[18]; Juquila, 8[18];Arroyo,San Juan,north of Cerro Otate, 1[23]; Cerro Otate, 3[23]; 3 mi. S Candelaria, 1.
Marginal records.—Morelos: 5 mi, W Tepoztlán, 6000 ft.Puebla: 2 mi. S Atlixco, 5800 ft.; Acatlán, 4100 ft.Oaxaca: 2 mi. NW Tamazulapán, 6550 ft; Tepantepec; Oaxaca [City], 5000 ft; Yalalag, 3000 ft; Jalapa, El Campanario; Reforma; Huilotepec; 3 mi. S Candelaria; Cerro Otate; Pinotepa, 700 ft.Guerrero: Acapulco; Zihuatanejo Bay; El Limón; 9 mi. SE Taxco, 3800 ft.
[18]U. S. Nat. Museum (Biol. Surv. Coll.).
[18]U. S. Nat. Museum (Biol. Surv. Coll.).
[19]Univ. Michigan, Museum of Zoology.
[19]Univ. Michigan, Museum of Zoology.
[20]Texas A & M, Cooperative Wildlife Research Collection.
[20]Texas A & M, Cooperative Wildlife Research Collection.
[21]Chicago Natural History Museum.
[21]Chicago Natural History Museum.
[22]California Academy of Sciences.
[22]California Academy of Sciences.
[23]American Museum of Natural History.
[23]American Museum of Natural History.
[24]University of Florida Collections.
[24]University of Florida Collections.
Baiomys musculus pullusPackard
Baiomys musculus pullusPackard, Univ. Kansas Publs., Mus. Nat. Hist., 9:401, December 19, 1958.
Baiomys musculus grisescens, Goodwin, Bull. Amer. Mus. Nat. Hist., 79(2):161, May 29, 1942 (part); Miller and Kellogg, Bull. U. S. Nat. Mus., 205:513, March 3, 1955 (part); Hall and Kelson, The Mammals of North America, 2:661, March 31, 1959 (part).
Type.—Adult female, skin and skull; No. 71605 University of Kansas Museum of Natural History; 8 mi. S Condega, Estelí, Nicaragua, obtained on July 15, 1956, by A. A. Alcorn, original number 4218.Range.—West-central Nicaragua, from Matagalpa northwest into the valley of the Río Estelí, east as far as Jinotega, seeFigure 10. Zonal range: Upper Tropical Life-zone.Diagnosis.—Size medium to small for the species; dorsum Fuscous-Black, individual hairs black-tipped with a subterminal band of Ochraceous-Buff, Neutral Gray at base; some hairs on dorsum all black to Neutral Gray at base; hair on sides Neutral Gray tinged with blackish; face blackish, becoming buffy on sides[Pg 629]of head, and white on throat; vibrissae black; tail unicolored Chaetura Black; forefeet and hind feet sooty to dusky-white; mid-ventral region of venter white, hairs white to base; in region of anus and throat, hairs white-tipped, Neutral Gray at base; average and extreme external and cranial measurements of the type and 16 paratypes are as follows: total length, 117.3 (111-121); length of tail vertebrae, 47.2 (44-50); length of body, 70.4 (66-74); length of hind foot, 15.5 (14-17); length of ear from notch, 11.9 (10-13); occipitonasal length, 19.3 (18.9-19.8); zygomatic breadth, 10.2 (9.7-10.6); postpalatal length, 7.0 (6.8-7.3); least interorbital breadth, 3.9 (3.8-4.1); length of incisive foramina, 4.3 (4.0-4.6); length of rostrum, 7.0 (6.5-7.4); breadth of braincase, 9.6 (9.3-10.0); depth of cranium, 7.0 (6.8-7.3); alveolar length of maxillary tooth-row, 3.1 (3.0-3.2); for photographs of skull, seePlate 1h, andPlate 3h.Comparisons.—FromB. m. grisescens,B. m. pullusdiffers in: dorsum and tail darker; sides and lateral parts of venter grayish instead of buffy-brown, thus forming distinct mid-ventral white stripe; average length of body and tail significantly longer, thus total length greater; maxillary tooth-row significantly shorter; slightly larger in other cranial and external dimensions.FromB. m. nigrescens,B. m. pullusdiffers in: dorsum slightly darker; face grayish, not sooty; mid-ventral white stripe (absent in most specimens ofnigrescens) present and becoming grayish laterally; tail darker, less hairy, and averaging significantly longer; smaller in most external and cranial dimensions.
Type.—Adult female, skin and skull; No. 71605 University of Kansas Museum of Natural History; 8 mi. S Condega, Estelí, Nicaragua, obtained on July 15, 1956, by A. A. Alcorn, original number 4218.
Range.—West-central Nicaragua, from Matagalpa northwest into the valley of the Río Estelí, east as far as Jinotega, seeFigure 10. Zonal range: Upper Tropical Life-zone.
Diagnosis.—Size medium to small for the species; dorsum Fuscous-Black, individual hairs black-tipped with a subterminal band of Ochraceous-Buff, Neutral Gray at base; some hairs on dorsum all black to Neutral Gray at base; hair on sides Neutral Gray tinged with blackish; face blackish, becoming buffy on sides[Pg 629]of head, and white on throat; vibrissae black; tail unicolored Chaetura Black; forefeet and hind feet sooty to dusky-white; mid-ventral region of venter white, hairs white to base; in region of anus and throat, hairs white-tipped, Neutral Gray at base; average and extreme external and cranial measurements of the type and 16 paratypes are as follows: total length, 117.3 (111-121); length of tail vertebrae, 47.2 (44-50); length of body, 70.4 (66-74); length of hind foot, 15.5 (14-17); length of ear from notch, 11.9 (10-13); occipitonasal length, 19.3 (18.9-19.8); zygomatic breadth, 10.2 (9.7-10.6); postpalatal length, 7.0 (6.8-7.3); least interorbital breadth, 3.9 (3.8-4.1); length of incisive foramina, 4.3 (4.0-4.6); length of rostrum, 7.0 (6.5-7.4); breadth of braincase, 9.6 (9.3-10.0); depth of cranium, 7.0 (6.8-7.3); alveolar length of maxillary tooth-row, 3.1 (3.0-3.2); for photographs of skull, seePlate 1h, andPlate 3h.
Comparisons.—FromB. m. grisescens,B. m. pullusdiffers in: dorsum and tail darker; sides and lateral parts of venter grayish instead of buffy-brown, thus forming distinct mid-ventral white stripe; average length of body and tail significantly longer, thus total length greater; maxillary tooth-row significantly shorter; slightly larger in other cranial and external dimensions.
FromB. m. nigrescens,B. m. pullusdiffers in: dorsum slightly darker; face grayish, not sooty; mid-ventral white stripe (absent in most specimens ofnigrescens) present and becoming grayish laterally; tail darker, less hairy, and averaging significantly longer; smaller in most external and cranial dimensions.
Remarks.—B. m. pullusresemblesB. m. nigrescensin size and color but can readily be distinguished fromnigrescensby the shorter tail.B. m. pullusintergrades withnigrescensas shown by specimens, referable toB. m. nigrescens, from 1 mi. NW San Salvador and from 1 mi. S Los Planes, El Salvador. In color of the dorsum, specimens from these localities are intermediate betweennigrescensandpullus.
The mid-ventral white stripe characteristic ofpullusis present in three of 28 adults from El Salvador. Goodwin (1942:160) reported white hairs on the pectoral region of several topotypes ofB. m. grisescens. The areas of white hairs on the venter ofgrisescensoccur in approximately 10 per cent of the specimens examined, whereas inpullus, the frequency of occurrence is 90 per cent. The areas of white hairs ingrisescensare in broad patches on the pectoral region, while inpullus, a white stripe passes from the pectoral region to the inguinal region in both males and females. I know of no selective advantage that the presence of this white stripe would confer on the mice.
Specimens examined.—Total 46, all fromNicaragua, and distributed as follows: Type locality, 32 (including the type);9 mi. NNW Estelí, 8;8 mi. NNW Estelí, 3; San Rafael Del Norte, 1 (Amer. Mus. Nat. Hist.);1 mi. NW Jinotega, 1; Matagalpa, 1 (Amer. Mus. Nat. Hist.).Marginal records.—Nicaragua: San Rafael Del Norte; Matagalpa; type locality.
Specimens examined.—Total 46, all fromNicaragua, and distributed as follows: Type locality, 32 (including the type);9 mi. NNW Estelí, 8;8 mi. NNW Estelí, 3; San Rafael Del Norte, 1 (Amer. Mus. Nat. Hist.);1 mi. NW Jinotega, 1; Matagalpa, 1 (Amer. Mus. Nat. Hist.).
Marginal records.—Nicaragua: San Rafael Del Norte; Matagalpa; type locality.
Baiomys tayloriNorthern Pygmy Mouse(Synonymy under subspecies)
Type.—Hesperomys(Vesperimus)tayloriThomas, Ann. Mag. Nat. Hist., Ser. 5, 19:66, January, 1887.Range.—Southeastern Arizona and southwestern New Mexico, south into Chihuahua and Durango, just east of the Sierra Madre Occidental, thence southeast through Zacatecas, Aquascalientes, Jalisco, Querétaro, and Guanajuato; two fingerlike projections extend northward, one on the west along the coast of Sinaloa into southern Sonora, and the other on the east covering eastern San Luis Potosí, Tamaulipas, eastern Coahuila, Nuevo León, into south, southeast, and north-central Texas. Southern margin of range in central México approximates the 19th degree of latitude (seeFigure 11). Arid lower and arid upper subdivisions of the Tropical Life-zone in south; principally Lower Sonoran and Lower Austral life-zones in north.Characters for ready recognition.—Unless otherwise noted, characters are usable for the age-categories of adult and old adult. Differs fromB. musculusin: hind foot less than 16 millimeters; occipitonasal length less than 19 millimeters; zygomatic breadth less than 10 millimeters; rostrum deflected ventrally at frontoparietal suture rather than curving gradually toward anteriormost point of nasals; cingular ridges and secondary cusps on teeth reduced or absent; basihyal having entoglossal process much reduced or absent, shoulders of basihyal not protruding anteriorly, but more flattened (characteristic of all age categories); baculum having narrower shaft, knob-shaped tip, wings at base projecting laterally, baculum less than 3 millimeters long; short process of incus attenuate; muscular process of posterior crus of stapes reduced.Characters of the species.—Size small (extremes in external measurements of adults: total length, 87-123; length of tail vertebrae, 34-53; length of hind foot, 12-15; length of ear, 9-12). Upper parts pale drab or reddish-brown to almost black; underparts grayish to cream-buff.
Type.—Hesperomys(Vesperimus)tayloriThomas, Ann. Mag. Nat. Hist., Ser. 5, 19:66, January, 1887.
Range.—Southeastern Arizona and southwestern New Mexico, south into Chihuahua and Durango, just east of the Sierra Madre Occidental, thence southeast through Zacatecas, Aquascalientes, Jalisco, Querétaro, and Guanajuato; two fingerlike projections extend northward, one on the west along the coast of Sinaloa into southern Sonora, and the other on the east covering eastern San Luis Potosí, Tamaulipas, eastern Coahuila, Nuevo León, into south, southeast, and north-central Texas. Southern margin of range in central México approximates the 19th degree of latitude (seeFigure 11). Arid lower and arid upper subdivisions of the Tropical Life-zone in south; principally Lower Sonoran and Lower Austral life-zones in north.
Characters for ready recognition.—Unless otherwise noted, characters are usable for the age-categories of adult and old adult. Differs fromB. musculusin: hind foot less than 16 millimeters; occipitonasal length less than 19 millimeters; zygomatic breadth less than 10 millimeters; rostrum deflected ventrally at frontoparietal suture rather than curving gradually toward anteriormost point of nasals; cingular ridges and secondary cusps on teeth reduced or absent; basihyal having entoglossal process much reduced or absent, shoulders of basihyal not protruding anteriorly, but more flattened (characteristic of all age categories); baculum having narrower shaft, knob-shaped tip, wings at base projecting laterally, baculum less than 3 millimeters long; short process of incus attenuate; muscular process of posterior crus of stapes reduced.
Characters of the species.—Size small (extremes in external measurements of adults: total length, 87-123; length of tail vertebrae, 34-53; length of hind foot, 12-15; length of ear, 9-12). Upper parts pale drab or reddish-brown to almost black; underparts grayish to cream-buff.
Geographic variation.—Eight subspecies are here recognized (seeFigure 11). Features that vary geographically are mostly the same as those that do so inB. musculus(seepage 609).
External and cranial size is less inB. t. allex, the southernmost subspecies, and progressively more inB. t. paulus,B. t. taylori,B. t. ater,B. t. subater,B. t. fuliginatus,B. t. canutus, andB. t. analogous. Size is largest in subspecies that occur at higher altitudes. Those subspecies areB. t. analogousandB. t. fuliginatus. The correlation with Bergman's Rule is less exact inB. taylorithan inB. musculus. It is noteworthy that the smallest subspecies,B. t. allex, occurs in the area where the two species are sympatric.
There is close correlation inB. taylori, as also inB. musculus, of darker pelages with zones of high relative humidity. The subspecies having dark pelages are:analogous,fuliginatus, andsubater. The two first-mentioned subspecies occur at high altitudes, andthe other,subater, occurs in the humid coastal region of Texas. The paler subspecies,taylori,canutus, andallex, occur at lower altitudes. Two subspecies that occur at relatively high altitudes,aterandpaulus, are reddish-brown. The color of pelage in these subspecies resembles the color of soil upon which they live. Blair and Blossom (1948:5) demonstrated close correlation of color of soil with color of pelage inB. t. aterby use of an Ives tint photometer.