Field studies on hylid frogs in southern México and northern Central America have resulted in the collection of numerous specimens of Ptychohyla, a genus of hylid frogs heretofore poorly represented in museum collections. Experience with the living frogs in their natural habitats has been helpful in defining the species and in formulating ideas concerning their relationships.
Taylor (1944) proposed the generic name Ptychohyla for a new species of frog, Ptychohyla adipoventris [= Ptychohyla leonhard-schultzei (Ahl)—fide Duellman, 1960] from Agua del Obispo, Guerrero. Taylor defined the genus as having large ventrolateral glands and horny nuptial spines in males. Stuart (1954:169) discussed the generic characters and pointed out that both the ventrolateral glands and horny nuptial spines were seasonal in their development, being found only in breeding males. Stuart then went on to describe Ptychohyla schmidtorum, a species characterized by the absence of horny nuptial spines in breeding males. My investigations of these frogs have revealed the presence of two groups of species. In both groups breeding males have large ventrolateral glands, but the two groups are easily separated by four characters. The first group contains, among others, Ptychohyla leonhard-schultzei, euthysanota, spinipollex, and another species in the Mesa Central of Chiapas to which I tentatively apply the name Ptychohyla macrotympanum (Tanner), 1957. This group of species is characterized by horny nuptial spines in breeding males, presence of a tarsal fold, a call consisting of a single long note, and tadpoles having lips not greatly expanded. The second group, as recognized here, is characterized by the absence of horny nuptial spines in breeding males, lack of a tarsal fold, a call consisting of a series of short notes, and tadpoles having greatly expanded lips. In this group belong Ptychohyla schmidtorum and the two species described below.
Only the descriptions of the new species are given in this paper; detailed comparisons, descriptions of osteological features, analyses of calls, and discussions of relationships are reserved for a forthcoming review of the entire genus.
In the spring of 1959, collections of amphibians and reptiles were made in the cloud forests on the northern slopes of the Sierra Madre Oriental in northern Oaxaca. Among the hylids found, two specimens of a heretofore unnamed species of Ptychohyla have brilliant red flash-colors on the groin and thighs; in allusion to these fiery colors I propose that this species be named:
Ptychohyla ignicolor new species
(Plate 25, [Fig. 1])
Holotype.—University of Michigan Museum of Zoology No. 119603, from a stream 6 kilometers south of Vista Hermosa, Oaxaca, México (1865 meters); obtained on March 31, 1959, by Thomas E. Moore. Original Number WED 14159.
Paratype.—UMMZ 119602 from Vista Hermosa, Oaxaca (1500 meters); obtained on March 30, 1959, by William E. Duellman.
Diagnosis.—A species of the schmidtorum-group of Ptychohyla differing from other known members of the group in having the diameter of the tympanum less than one-half the diameter of the eye, no white spot below the eye, no lateral light stripe, bright green dorsum in life and red flash-colors on groin and thighs.
Description of Holotype.—Adult male having a snout-vent length of 30.0 mm.; tibia length, 14.6 mm.; tibia length/snout-vent length, 48.7 per cent; foot length (measured from proximal edge of inner metatarsal tubercle to tip of longest toe), 12.3 mm.; head length, 9.2 mm.; head length/snout-vent length, 32.3 per cent; head width, 9.3 mm.; head width/snout-vent length, 31.0 per cent; diameter of eye, 3.2 mm.; diameter of tympanum, 1.3 mm.; tympanum/eye, 40.6 per cent. Snout in lateral profile square, in dorsal profile obtusely rounded; canthus pronounced; loreal region slightly concave; lips moderately flaring; top of head flat; nostrils protuberant; internarial distance, 2.8 mm.; interorbital distance, 3.3 mm., much broader than width of eyelid, 2.8 mm. A heavy dermal fold from posterior corner of eye above tympanum to insertion of forelimb, covering upper edge of tympanum; tympanum elliptical, its greatest diameter equal to its distance from eye. Forearm robust with a distinct fold on wrist; pollex moderately enlarged without nuptial spines; second and fourth fingers equal in length; subarticular tubercles round; none is bifid; disc of third finger slightly larger than tympanum; no web between first and second fingers; vestige of web between other fingers. Heels overlap when hind limbs adpressed; tibiotarsal articulation extends to anterior corner of eye; no tarsal fold; inner metatarsal tubercle large, flat, and elliptical; outer metatarsal tubercle near inner one and triangular; subarticular tubercles round; length of digits from shortest to longest 1-2-5-3-4; toes about one-half webbed; discs smaller on toes than on fingers. Anal opening directed posteriorly at upper level of thighs; no anal flap; pair of large tubercles below anal opening; small tubercles ventral and lateral to these. Skin of dorsum and ventral surfaces of limbs smooth, that of throat and belly granular. Ventrolateral glands noticeably thickened, extending from axilla nearly to groin and only narrowly separated medially on chest. Skin of anterior part of chin thickened and glandular. Tongue cordiform, shallowly notched behind and only slightly free posteriorly; vomerine teeth 0-3, situated on rounded elevations between somewhat larger, round inner nares; openings to vocal sac large, one situated along posterior margin of each mandibular ramus.