A New Species of Frog (Genus Tomodactylus)

from Western México

Holotype.—KU 63326 (Fig. 1); obtained eight miles west of El Palmito,
Sinaloa, approximately 6100 feet, on 23 June 1961; original field number,
2354 of Robert G. Webb.

Paratypes.—A total of 12 specimens: KU 63327-33, same data as holotype,
23-25 June 1961; MSU 4085-88, two miles north of Pueblo Nuevo, Durango,
approximately 6000 feet elevation, 24 July 1960; MSU 4089, one half mile
west of Revolcaderos, Durango, approximately 6600 feet, 29 July 1961.

Diagnosis.—A species of Tomodactylus possessing the following combination
of characters: (1) tips of two outer fingers truncate, about twice width
of narrowest part of digit; (2) tympanum small, less than one half diameter
of eye; (3) ventral surfaces smooth; (4) contrasting marbled pattern on back
and top of head, and (5) venter whitish, lacking dark marks.

Description of holotype.—Adult male; snout-vent length, 31.5 (measurements
are in millimeters and were taken by means of dial calipers reading to
one tenth of a millimeter); width of head, 11.2; length of head, 10.3; horizontal
diameter of eye, 3.1, and of tympanum, 1.2; distance from eye to nostril, 3.8;
internarial width, 2.9; interorbital width, 4.1; width of eyelid, 2.5; lumbar
gland (left side), 7.0 x 2.6; distance from axilla to groin, 15.2; tibial length,
12.7; length of foot, 13.1.

Head slightly wider than body; tip of snout rounded, slightly truncate;
canthus rounded; tympanum small, less than one half diameter of eye; tympanum
having posterior margin ill-defined, separated from eye by distance
about equal to diameter of tympanum; diameter of eye slightly less than distance
from eye to nostril; width of eyelid about two thirds interorbital width;
paratoid gland indistinct; lumbar glands high, separated from insertion of leg
by about one millimeter; back and sides of body having low, scarcely elevated
pustules; top of head, limbs and venter smooth; few low, whitish pustules
below and behind tympanum, and low on sides of body; posterior surface of
thighs and anal region pustulate; one pair of whitish postanal spots; ventral
disc attached near insertion of legs, lacking conspicuous transverse fold; skin
loose on throat, chest and abdomen.

[Pg 178]
Digits not webbed; tips of two outer fingers truncate, having terminal
transverse grooves, about twice width of narrowest part of digit; digits of
first and second fingers slightly expanded; fingers from shortest to longest,
1-2-4-3, first only slightly shorter than second; three palmar tubercles; inner
palmar tubercle about one third size of large median tubercle; outer tubercle
about one tenth size of large median tubercle; four supernumerary palmar
tubercles; tips of toes slightly wider than narrowest part of digits; toes from
shortest to longest, 1-2-5-3-4, second only slightly shorter than fifth; inner
metatarsal tubercle about four times size of small outer metatarsal tubercle;
supernumerary tubercles on foot small; no tarsal fold; heels touching when
tibiae adpressed to thighs; tibiotarsal articulation reaching eye when leg
adpressed to side of body.

Contrasting marbled pattern on back and top of head; contrasting, mostly
barred, pattern on limbs; ventral surfaces whitish, lacking dark marks, but
having minute dark peppering; marbling of dorsal surfaces blackish and
whitish in preservative.

Vomerine teeth lacking; internal choanae lateral, partly concealed by
maxillaries; tongue smooth, elongate, shallowly notched distally, free for about
half its length; vocal sac median; internal vocal slits large and near angle of jaw.

Variation.—Twelve males closely resemble the holotype. Two specimens
from Pueblo Nuevo are soft and not well preserved. The ranges of variation
(means in parentheses) for the 13 males comprising the type series are: snout-vent
length, 25.5-31.5 (27.9); width of head, 9.7-11.2 (10.5); diameter of
eye, 2.9-3.6 (3.2); horizontal diameter of tympanum, 1.1-1.8 (1.4); length
of tibia, 11.1-13.1 (12.1); length of foot, 11.0-13.1 (12.1).

The pale ground color of the marbled pattern in most specimens is least
extensive on the back and arms, but most extensive on the legs. The lumbar
glands are slightly elevated and conspicuous, and in KU 63328 are extremely
protuberant, or (KU 63330) evident on left side but flattened and indistinct
on right side. The back is rough having low, scarcely elevated pustules, but
becomes less rough anteriorly and most of the top of head is smooth. The
three specimens from Pueblo Nuevo, Durango, differ slightly from the other
specimens examined in lacking pairs of postanal white spots, and in having
smooth backs (slightly pustulate in MSU 4088). The tibiotarsal articulation
fails to reach the eye in KU 63330. The small inner palmar tubercle is
continuous with the large median tubercle on the right hand of KU 63330, and
lacking on both hands of KU 63329 and on the left hand of KU 63328. The
tip of the tongue is entire in some specimens and in others has an irregular
margin.

Coloration of living specimens.—Marbled pattern on back and top of head
of dark brown to blackish on yellowish-gold; pattern slightly less contrasting
on limbs than on back, consisting of brown to grayish on pale yellow; side
of head and body grayish sometimes having pale yellow to whitish spots;
iris blackish having fine reticulation of yellowish to greenish-gold; venter dirty
white.

Comparisons.—Dixon (1957) recognized six species of Tomodactylus
(nitidus, dilatus, albolabris, angustidigitorum, fuscus and grandis) in his
revision of the genus. Another species (rufescens) was subsequently described
by Duellman and Dixon (1959). Tomodactylus saxatilis differs from all the
species named immediately above by the combination of characters given in
the diagnosis. Tomodactylus saxatilis differs from nitidus, angustidigitorum
and grandis in having the tips of the two outer fingers widened and truncate;
saxatilis differs from dilatus, albolabris, fuscus and rufescens in having a smooth
venter (not pustulate), a contrasting pale and dark marbled pattern on the
back, and a lack of "flash" colors on the femora.

Tomodactylus saxatilis, having lumbar glands, also resembles three species
referred to the genus Syrrhophus. Tomodactylus macrotympanum was described
by Taylor (1940:496, 497) as having a large, moderately distinct
lumbar gland; the species was referred to the genus Syrrhophus by Dixon
(op. cit.:384). According to Firschein (1954:55), Syrrhophus smithi and
S. petrophilus have elongate lumbar glands shaped like those in Tomodactylus.
Tomodactylus saxatilis resembles macrotympanum, smithi and petrophilus
more than it does other species; all four attain large maximal sizes, and have
lumbar glands, mostly smooth ventral surfaces, three palmar tubercles (sometimes
absent in saxatilis), and usually contrasting dorsal patterns (reduced to
flecks and spots in all species except saxatilis). Tomodactylus saxatilis differs
from macrotympanum in having an extensive marbled dorsal pattern and a
small tympanum, and differs from smithi and petrophilus in having a marbled
dorsal pattern and the tips of the outer two fingers widened and truncate.
Tomodactylus saxatilis differs from all other named species of Syrrhophus in
having conspicuous lumbar glands and in lacking inguinal glands.