A New Species of Frog (Genus Tomodactylus) from Western Mexico

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Title: A New Species of Frog (Genus Tomodactylus) from Western Mexico
Author: Webb, Robert G.
Language: English
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*** Start of this LibraryBlog Digital Book "A New Species of Frog (Genus Tomodactylus) from Western Mexico" ***

UNIVERSITY OF KANSAS PUBLICATIONS
MUSEUM OF NATURAL HISTORY

Volume 15, No. 3, pp. 175-181, 1 fig.
March 7, 1962

A New Species of Frog (Genus Tomodactylus)
from Western México

ROBERT G. WEBB

UNIVERSITY OF KANSAS
LAWRENCE
1962

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
Theodore H. Eaton, Jr.

Volume 15, No. 3, pp. 175-181, 1 fig.
Published March 7, 1962

UNIVERSITY OF KANSAS
Lawrence, Kansas

PRINTED BY
JEAN M. NEIBARGER, STATE PRINTER
TOPEKA, KANSAS
1962

29-1923

A New Species of Frog (Genus Tomodactylus)
from Western México.

ROBERT G. WEBB

Thirteen specimens of frogs collected in the summers of 1960 and 1961
in the Mexican states of Durango and Sinaloa represent a heretofore
unnamed species. The specimens have been deposited in the Museum of
Natural History of the University of Kansas (KU) and in the Museum of
Michigan State University (MSU). The species may be named and
described as follows:

Tomodactylus saxatilis new species

_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.

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.

_Habitat._--The three records of occurrence for _Tomodactylus
saxatilis_ are in a mixed boreal-tropical habitat, which is
transitional between a pine-oak forest at higher elevations and a
tropical deciduous forest at lower elevations. The mixed
boreal-tropical habitat is most conspicuous at elevations between
approximately 7800 and 5500 feet on southerly exposed slopes of
barrancas and arroyos of the dissected plateau of the Sierra Madre
Occidental. The mixed boreal-tropical habitat occurs for approximately
30 miles along the paved highway (Mexican Highway 40) between Cd.
Durango, Durango, and Mazatlán, Sinaloa. The records of occurrence in
those states that are along this highway are separated by 14.5 miles
(_via_ road).

[Illustration: FIG. 1. _Tomodactylus saxatilis_ new species,
adult male, KU 63326, holotype (× 2), dorsal view.]

The terrain consists of occasional level areas, but is mostly of steep
hillsides. Dominant trees are large oaks and pines; a characteristic
pine is the sad or drooping-needle pine, locally called "pino triste."
The vegetational cover is usually open, including grasses, small oaks
and pines, broad-leaved shrubs and herbs, prickly pears, magueys,
thorny acacias, bracken fern, and epiphytes in trees. Ferns occur in
moist protected places, and orchids are occasional, sometimes in
trees.

Outcrops of rock, boulder-strewn areas, and occasional rock slides
(talus) also characterize the terrain. _Tomodactylus saxatilis _seems
to be restricted to rocky habitats. The individuals collected were
detected when they called at night from within crevices of rocks or
from exposed perches on rocks and boulders; some calling frogs were
out of reach on steep rock walls. The call is a single, loud, high
peep.

_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.

_Remarks._--The characteristics delimiting the genera _Tomodactylus_
and _Syrrhophus_ are not agreed upon by all workers (see discussions
by Firschein, 1954:50; Langebartel and Shannon, 1956:164; and Dixon,
1957:383). I have referred _saxatilis_ to the genus _Tomodactylus_ on
the basis of a lumbar gland, which was considered a distinguishing
character for the genus by Smith and Taylor (1948:46) and Langebartel
and Shannon (1956:165). Lumbar glands are longer than broad, at least
one third the distance from axilla to groin, lateral and usually high,
and often conspicuous and protuberant. The elevation or flatness of
the lumbar glands seems to be due to individual variation; living
specimens in the field had conspicuous and protuberant, or
non-elevated, indistinct lumbar glands. Lumbar glands are not to be
confused with inguinal glands, which are roundish, often yellowish,
sometimes diffuse, lateral but low, often inconspicuous, and usually
not protuberant. Inguinal glands occur in the genus _Microbatrachylus_
and in some species of _Eleutherodactylus_, and have been described as
flat, or low, or small, or indistinct for most species of
_Syrrhophus_.

For financial assistance with field work I am grateful to Rollin H.
Baker, and those individuals who administer the Michigan State
University Development Fund and the Bache Fund of the National Academy
of Sciences (Grant No. 463). I am grateful also to J. Keever Greer,
Donald F. Switzenberg, and Rudolph A. Scheibner for aid in the field,
to Edward H. Taylor, James R. Dixon, and William E. Duellman for
profitable discussions, and to Thomas Sweringen for figure 1. The
specific name alludes to the habitat (Latin, _saxatilis_ = found among
rocks).

LITERATURE CITED

DIXON, J. R.
1957. Geographic variation and distribution of the genus
Tomodactylus in Mexico. Texas Journ. Sci., 9(4):379-409,
5 figs., 1 map, December.

DUELLMAN, W. E., and DIXON, J. R.
1959. A new frog of the genus _Tomodactylus_ from Michoacan,
Mexico. Texas Journ. Sci., 11(1):78-82, 1 fig., 1 table,
March.

FIRSCHEIN, I. L.
1954. Definition of some little-understood members of the
leptodactylid genus _Syrrhophus_, with a description of
a new species. Copeia, 1954, 1:48-58, February 19.

LANGEBARTEL, D. A., and SHANNON, F. A.
1956. A new frog (_Syrrhophus_) from the Sinaloan lowlands of
Mexico. Herpetologica, 12(3):163-165, 2 figs., September 1.

SMITH, H. M., and TAYLOR, E. H.
1948. An annotated checklist and key to the Amphibia of Mexico.
Bull. U. S. Nat. Mus., No. 194, pp. iv + 118.

TAYLOR, E. H.
1940. Herpetological miscellany. Univ. Kansas Sci. Bull.,
26(15):489-571, 10 pls., 7 figs., November 15.

29-1923

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