SYSTEMATIC ACCOUNT
The availability of additional material and the new information pertaining to osteology permit an amplification of Gaige's (1926) description.
Genus Allophryne Gaige
Allophryne Gaige, Occas. Papers Mus. Zool., Univ. Michigan, 176:1, Oct. 14, 1926. Crawford, Annals Carnegie Mus., 21(1):29, 32, Nov. 14, 1931. Noble, The biology of the amphibia. McGraw-Hill, p. 510, 1931. Ruthven, Herpetologica, 1:3, July 11, 1936. Gallardo, Papéis Avulsos, 17:79, Jan. 1, 1965.
Type species.—Allophryne ruthveni Gaige.
Diagnosis and definition.—A genus of diminutive frogs; vomers, maxillae, and premaxillae edentate; skin of head strongly anchored to connective tissue on cranium; prepollical spine absent in males; disk of third finger larger than tympanum, smaller than eye; no humeral hook in either sex; ilia extending anteriorly beyond sacral expansions; adults attaining snout-vent length of 31 mm.; male having darkened external subgular vocal sac; skin of dorsum pustulate.
Allophryne ruthveni Gaige
Allophryne ruthveni Gaige, Occas. Papers Mus. Zool., Univ. Michigan, 176:1-3, pl. I, Oct. 14, 1926. Crawford, Annals Carnegie Mus., 21(1):32, Nov. 14, 1931. Ruthven, Herpetologica, 1:3, July 11, 1936. Barbour and Loveridge, Bull. Mus. Comp. Zool., 96(2):64, Feb., 1946. Peters, Occas. Papers Mus. Zool., Univ. Michigan, 539:10, Sept. 19, 1952.
Holotype.—University of Michigan Museum of Zoology 63419, adult female, from Tukeit Hill, below Kaiteur Falls, Equibo District, British Guiana; obtained in May, 1924, by E. N. Clarke.
Diagnosis.—Fingers free; toes two-thirds webbed; no supernumerary tubercles on soles or palms; no tarsal fold; elongate anal sheath, anal opening on lower surface of thighs; head broad, interorbital space 2.5 times width of upper eyelid; snout subacuminate in dorsal profile, strongly sloping in lateral profile; tympanum visible in males, concealed in females; venter areolate.
External Morphology.—([Fig. 1]) Additional features not mentioned in diagnoses: Head wider than long, about as wide as body; supratympanic fold present; canthus rostralis rounded, loreal region slightly concave, nearly vertical; nostril at tip of snout; pupil horizontal; no teeth on maxillary, premaxillary, or vomer; tongue small, round, thick, not notched behind, free posteriorly for one-sixth of length; choanae large, only partly visible from directly below; males having darkened subgular vocal sac; vocal slits present in male.
Axillary membrane lacking or but slightly developed; no tubercles or ridge under forearm; two palmar tubercles; subarticular tubercles small, simple, round, flattened; tips of fingers slightly expanded, T-shaped, with prominent transverse groove; first finger shorter than second (stated as longer than second in diagnosis by Gaige, 1926:2); folds extending laterally from anus for a short distance, then downward to venter of thighs; no appendage on heel, no inner or outer tarsal folds or tubercles; inner metatarsal tubercle oval, about twice as long as wide; outer metatarsal tubercle nearly absent; no supernumerary tubercle on sole; subarticular tubercles on foot small, round, simple, and diffuse; toes T-shaped, slightly wider than digit; toes about two-thirds webbed ([Fig. 1d]).
Skin of venter coarsely areolate; skin of flanks, throat, chest, undersurfaces of arms, tibia, tarsi, dorsal surfaces of thighs, tarsi, hands, and feet smooth; skin of dorsal surfaces of tibia, forearm, back, and top and sides of head having large horny pustules (sharply spinous in male).
Fig. 1. Allophryne ruthveni, male (KU 69890); (a) Dorsum.
(b) Thenar view of right hand. (c) Lateral profile of head.
(d) Plantar view of right foot. × 3.5.
Color.—Dorsum gray with irregular network of black lines and elongate blotches; flanks and labial region black with large white ocelli; dorsal surfaces of limbs gray, marked as follows: two large, elongate white spots on each thigh, concealed white spot on base of upper arm, black-edged gray transverse bars on forearms and shanks, white spot on each knee and elbow; ventral surfaces pale gray; black-edged white spot on ventral surface of thigh on each side of anal opening; chin and throat dark gray with white spots; vocal sac in male black ([Fig. 1]a and c).
Gaige (1926) briefly described the color, which conforms to the above in all particulars. The paratype (MCZ 11790) has lost the gray color after 40 years in preservation; now (1966) the ground-color is cream-brown, and the dorsal spotting, noted by Gaige as being black, is now brown.
The spots on the feet, tarsi, knees, thighs, flanks and upper arm are white in preservative, but in life possibly were red or yellow. These colors usually fade to white in preservative. Red or yellow spots are common aposematic colors in frogs.
Variation.—Eight measurements were taken on each specimen and four ratios were computed; these are summarized in [Table 1]. Gaige's illustration of the holotype shows that it has a greatly reduced pattern, whereas the paratype and three of the other five known specimens have relatively large and numerous spots. The male (KU 69890) and one female (AMNH 70108) have a reduced pattern intermediate between that of the holotype and the four other specimens.
TABLE I.—Variation in Measurements and Proportions of Allophryne ruthveni. (Ranges in parentheses below means.)
| Character | Male (1) | Females (5) |
| Snout-vent (in mm.) | 20.6 | 23.6 (18.4-31.0)[A] |
| Tibia/snout-vent | 0.43 | 0.43 (0.41-0.47) |
| Tympanum/head width | 0.12 | 0.15 (0.14-0.16) |
| Eyelid/interorbital space | 0.55 | 0.53 (0.49-0.56) |
| Tympanum/eye length | 0.40 | 0.46 (0.42-0.50) |
[A]Holotype is reported to be 31 mm. snout-vent length (Gaige, 1926). The largest measured by us was 26.2 mm. snout-vent.
The dorsal spinules are most pronounced and extensive on the male ([Fig. 1]) and less so in all other specimens examined. The illustration of the holotype suggests that it has equally prominent, but fewer, spinules (Gaige, 1926).
The holotype, a gravid female, is the largest known specimen (31 mm., snout-vent length). Another gravid female (AMNH 70108) has a snout-vent length of 26.2 mm.
Distribution.—All known specimens have been found in the foothills of the northeastern face of the Guiana Massif in British Guiana.