Mustela frenata latirostra Hall
Long-tailed Weasel
Plates [1], [22], [23], [24], [34], [35] and 36
Mustela frenata latirostra Hall, Carnegie Instit. Washington Publ. 473:96, November 20, 1936.
Putorius xanthogenys, Baird, Mamm. N. Amer., p. 176, 1858 (part); Stephens, California mammals, p. 246, 1906; Merriam, N. Amer. Fauna, 11:25, June 30, 1896 (part).
Putorius (Gale) brasilianus frenatus, Coues, Fur-bearing animals, p. 142 (part).
Mustela xanthogenys xanthogenys, Miller, U. S. Nat. Mus. Bull., 79:99, December 31, 1912; Grinnell, Univ. California Publ. Zoöl., 40:102, September 26, 1933.
Mustela arizonensis, Grinnell and Swarth, Univ. California Publ. Zoöl. 10, 376, October 31, 1913.
Type.—Male, adult, skull and skin; no. 3257, Mus. Vert. Zoöl.; San Diego, San Diego County, California; May 20, 1907; obtained by Frank X. Holzner.
Right M1 is missing and the part of the jaw bearing this tooth is broken away. With this exception the skull is complete and unbroken and the teeth are all present and entire. The skin is fairly well made and in good condition except that it is slightly soiled.
Range.—Altitudinally sea level to 8000 feet (Tahquitz Valley, San Jacinto Mountains); Sonoran and Transition life-zones of coast and mountains west of Mohave and Imperial deserts of southern California from Point Conception and Cuyama Valley southward at least to Mexican boundary. See figures [29] and [30] on pages 221 and 314.
Characters for ready recognition.—Differs from M. f. nigriauris by having postorbital breadth of adult males and females, more, rather than less, than width of basioccipital measured from medial margin of one foramen lacerum posterior to its opposite; from M. f. pulchra by having tympanic bulla longer than rostrum (orbitonasal length) and by near (l) Antique Brown rather than near (16 j) Buckthorn Brown to near (h) Yellow Ocher color of upper parts.
Description.—Size.—Male: Six adults and subadults from San Diego yield average and extreme measurements as follows: Total length, 439 (428-449); length of tail, 153 (142-160); length of hind foot, 45 (40-47). Corresponding measurements for a series of eight adult males from the vicinity of Los Angeles are: 416 (394-428); 158 (151-166); 44 (40-47). In the series from San Diego the tail averages 54 per cent as long as head and body. In the series from Los Angeles the average is 61 per cent. Length of hind foot in each series, less than basal length. The type specimen measures, 435, 142, 42.
Female: No. 5070, adult, from San Diego, measures 367, 141, 38. Nos. 22 and 6748 from Santa Ysabel, measure: 359, 380; 130, 140; 39, 35. No. 7194 from Jamacha measures, 358, 125, 35. Three adult females from Los Angeles yield the following: Total length, 373, 345, 368; length of tail, 150, 122, 134; length of hind foot,—, 41, 41. In no. 5070 the tail is 62 per cent as long as the head and body and in the three from Los Angeles it averages 60 (55-67) per cent. Length of hind foot, in each case, less than basal length.
The average differences in external measurements of the two sexes as shown by the six males from San Diego and the four females from San Diego County are: Total length, 73; length of tail, 19; length of hind foot, 8. Corresponding differences shown by the eight males and three females from Los Angeles are: 54, 23, 3.
Externals.—Longest facial vibrissae brownish, like dark color of head and extending beyond ear; carpal vibrissae mostly color of underparts and extending to apical pad of fifth digit; hairiness of foot-soles slightly more than shown in figure [20].
Color.—Spot between eyes, band confluent with color of underparts on each side of head extending anterodorsally anterior to ear, and posterior third of each upper lip tinged with color of underparts or, less often, white; chin and lower lips white; remainder of sides and top of head posteriorly to near line connecting posterior margins of ears, blackish; inside of pinna of ear, and sometimes outside of pinna, blackish; dark spot posterior to each angle of mouth present on each side in three-fourths of specimens; tip of tail black; remainder of upper parts near (l) Antique Brown, and with more yellow than tone 3 of Raw Umber of Oberthür and Dauthenay, pl. 301. Underparts Ochraceous-Buff to Warm Buff and in some specimens from Los Angeles and Ventura counties Ochraceous-Orange, especially in young and juveniles. Color of underparts extends distally on posterior sides of forelegs over toes onto antipalmar faces of feet and wrists and on medial sides of hind limbs over antiplantar faces of toes. Least width of color of underparts averaging, in 15 adult and subadult males from San Diego County, 54 (35-75) per cent of greatest width of color of upper parts. Black tip of tail in same series of males averaging 54.5 (46-60) mm. long. Thus averaging longer than hind foot and 35 per cent of length of tail-vertebrae.
Skull and teeth.—Male (based on 6 adults from San Diego County). See measurements and plates [22]-[24]. As described in M. f. nigriauris except that: Weight (4 specimens), 3.9 (3.8-4.0) grams; basilar length 43.8 (41.9-47.0); postorbital breadth more than width of basioccipital measured from medial margin of one foramen lacerum posterior to its opposite; interorbital breadth not less than distance between foramen opticum and anterior margin of tympanic bulla; anterior margin of tympanic bulla as far posterior to foramen ovale as width of 2 to 2-1/2 (including I3) upper incisors; length of tympanic bulla more than length of lower molar and premolar tooth-row and longer than rostrum; anterior margin of masseteric fossa below m2.
Female (based on 4 adults from San Diego County): See measurements. As described in M. f. nigriauris except that: Weight, 2.6 (2.2-2.8) grams; basilar length, 40.0 and 40.1; postorbital breadth more than width of basioccipital measured from medial margin of one foramen lacerum posterior to its opposite; length of tympanic bulla more than length of rostrum.
The skull of the female averages 34 per cent lighter than that of the average male.
The skull of the male of latirostra, compared with that of nigriauris, is by weight, more than one-fourth lighter, has a lesser basilar length, a lesser mastoid breadth, a lesser zygomatic breadth and a narrower M1. In these features no overlap has been observed between adults from the general vicinities of the type localities of the two forms. In adult males of latirostra the postorbital breadth, with one exception, is more than the combined length of P4 and P3 whereas the reverse is true in adult males of nigriauris. Both males and females of latirostra have a generally smaller skull with relatively broader interorbital and postorbital parts and the tympanic bullae are relatively larger, rounder and more inflated.
Compared with the skull of the male of pulchra that of latirostra is, by weight, more than one-fourth lighter, has a lesser basilar and orbitonasal length, lesser zygomatic and mastoid breadth and a more nearly flat braincase. In these features no overlap has been observed between adults from the general vicinities of the type localities of the two subspecies. Also, in latirostra the tympanic bulla is longer than the rostrum whereas the opposite is true in pulchra. The skull of latirostra is generally smaller and relatively, on the average, has the preorbital part of the skull deeper and broader with longer tooth-rows, although with shorter rostrum, while the zygomatic and mastoid breadths are less. Study of skulls of subadult females of pulchra indicate that females of latirostra and pulchra differ in the same fashion as do males.
Remarks.—This subspecies long has gone by the name M. xanthogenys and the type locality was generally supposed to be in the vicinity of San Diego. This supposition seems to have originated with Merriam's (1896:25) statement that the type locality was "Southern California, probably vicinity of San Diego." Nevertheless, as set forth in the account of M. f. xanthogenys the type specimen concerned now is thought to have come from much farther north.
Although 76 Recent specimens are available from southern California, additional adults are needed to understand the geographic variation there. M. f. latirostra may be a composite—made up of more than one geographic race. Specimens from San Diego County differ so much in relative length of the tail that at one stage in the present study it was thought that a difference in this respect existed between the coastal animals and those from farther inland. Material received later did not wholly substantiate this view and because of the uniformly small size of all of the skulls from that county, the animals were later regarded as of the same subspecies. Eventually, even this supposed common feature proved to be inconstant for an adult male from Jamacha, no. 7098, of the San Diego Society of Natural History, and another adult male from San Marcos, no. 8869, collection of Ralph Ellis, were later examined and found to have skulls as large as those of average-sized, adult males of nigriauris.