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Family Ascaphidae
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Family Ascaphidae Ascaphus montanus Mittleman and Myers, 1949 Rocky Mountain Tailed Frog ETYMOLOGY montanus: from the Latin montanus meaning ‘belonging to a mountain.’ NOMENCLATURE Synonyms: Ascaphus truei montanus Nearly all information pertaining to this species has been published under the name Ascaphus truei. IDENTIFICATION Adults. Dorsal coloration is light tan, reddish brown, medium to dark brown, or deep blackish brown with a tinge of green. Light spots may be present dorsally, but some individuals are uniformly unpatterned. Undersides are grayish white, yellowish white, or pinkish. Faint black bands may be evident from the shoulder through the eye and nostril to the upper jaw in some populations, whereas others have a light area that extends across the head, anterior to the eyes. A light mid-dorsal line may or may not be present. There is no tympanum. The eyes are large, and the pupils are oval to elliptical and vertical. Black spots may be present on the sides, back, and upper portions of the limbs, giving the species a rugose appearance. Male secondary sex characteristics (spines within the cloaca, horny black nuptial pads on front limbs and chest, rim of warts on the chin, engorged tail) are evident only during certain times of the year (Metter, 1964a; Black and Black, 1968). Minor variation in hind foot width, the extent of webbing between toes, head width, and internasal distance may be observed among populations (Metter, 1964a). Although they cannot be observed directly, Ascaphus have short ribs, unlike all our other frogs. The most striking feature of the tailed frogs is the possession of the “tail,” really a copulatory organ that is an extension of the cloaca and is found only in males. The tail is controlled by two unique muscles, the pyriformis and the caudalipuboischiotibiales, which allow it to be turned forward for insertion into the female’s cloaca. Sperm is transferred along the surface of the tail allowing internal fertilization in the fast flowing water currents of turbulent northwestern streams. Because of the tail, determination of sex is possible immediately after transformation, although maturity may not be attained for an additional 4–5 yrs. Females are larger than males. In Oregon, males were 22.1–36.2 mm SUL (mean 30.3 mm) and females 22.3–45.1 mm SUL (mean 30.9 mm) from mainstream habitats, whereas males were 22–34.2 mm SUL (mean 26.3 mm) and females 22.2–36.2 mm SUL (mean 26.3 mm) from small tributary streams (Landreth and Ferguson, 1967). In Montana, sexually mature males were 40–52 mm SUL and females 44–56 mm SUL (Daugherty and Sheldon, 1982a). Larvae. Larvae are easily identified by their large sucker-like mouth. At hatching, larvae are dark but with a large amount of yolk. Normal larval coloration is slate gray to black or occasionally reddish brown. The dorsum and sides of the tail are patterned variably with light and dark markings. Tadpoles usually have a small cream or white spot at the terminus of the tail, but occasionally the spot may be large or even absent. Franz (1971) noted larvae from Mineral County, Montana, that had reduced pigmentation on the body and tail, giving a very mottled appearance; such tadpoles also had large orange tail spots. 2 ASCAPHIDAE (2003), Werner et al. (2004), Jones et al. (2005), and Matsuda et al. (2006). FOSSIL RECORD No fossils are known. SYSTEMATICS AND GEOGRAPHIC VARIATION The genus Ascaphus comprises the monotypic basal lineage of all anurans and retains many primitive morphological characters (Ford and Cannatella, 1993). The diploid chromosome number is 46, and Ascaphus has the largest number of chromosomes of all diploid anurans (Green et al., 1980). Mittleman and Myers (1949) found small, but what they considered noteworthy, morphological variation among Ascaphus populations in the coastal Pacific Northwest, Rocky Mountains, and northern California. They divided the species into subspecies based on these differences (truei, montanus, californicus). Ascaphus truei and A. montanus are now considered distinct species, but recognition of A. t. californicus is not justified based on molecular data. Using a randomly ampli fied polymorphic DNA (RAPD) survey, Ritland et al. (2000) noted the uniqueness of inland populations but did not at that time recommend species recognition. Ascaphus montanus is distinctive, based on analyses of mitochondrial DNA (Nielson et al., 2001), skin peptides (Conlon et al., 2007b), allozymes (Daugherty, 1979), and morphology (Mittleman and Myers, 1949; Pauken and Metter, 1971; but see Metter, 1967). This species has been isolated from its...