A Review of the Middle American Tree Frogs of the Genus Ptychohyla. William Edward Duellman
species have a blunt snout. In P. leonhardschultzei and P. ignicolor the snout is nearly square in lateral profile; in P. schmidtorum the snout is slightly rounded above and below, and in the other species it is rounded above. Ptychohyla leonhardschultzei and P. spinipollex have a vertical fleshy rostral keel on the snout; in these species, because of this keel, the snout in dorsal profile is pointed. The nostrils are slightly protuberant in all species, and in P. schmidtorum the internarial region is slightly depressed.
Table 1.—Variation in Certain Characters in the Species of Ptychohyla. (Means Are in Parentheses Below the Ranges.)
| SpeciesSexNumber of specimensMaximum snout-vent lengthTibia length Snout-vent lengthTympanum EyeVomerine teethP. euthysanota euthysanota♂1738.144.4–55.0 (48.7)48.6–63.8 (56.3)4–6 (5.1)♀1553.346.5–56.6 (51.4)42.9–56.4 (51.4)6–18 (9.6)P. euthysanota macrotympanum♂538.048.8–52.0 (50.2)50.0–57.1 (54.1)0–4 (2.6)♀544.846.4–54.1 (50.2)48.7–58.9 (53.7)8–10 (9.2)P. leonhardschultzei♂1635.648.8–56.1 (51.2)48.7–61.9 (52.1)6–9 (6.5)♀341.652.3–59.5 (54.7)47.5–48.6 (48.1)7–12 (9.5)P. spinipollex♂3241.246.9–53.1 (49.0)45.0–55.2 (49.5)3–7 (4.9)♀644.646.1–50.2 (48.8)47.7–53.8 (50.4)6–10 (7.6)P. schmidtorum schmidtorum♂2532.845.3–52.4 (48.1)51.5–59.3 (54.7)5–11 (6.2)♀938.046.5–49.1 (47.7)51.3–58.3 (54.9)7–11 (8.7)P. schmidtorum chamulae♂4030.546.0–51.9 (48.2)48.2–65.6 (54.9)4–6 (4.7)♀431.848.1–52.4 (50.5)51.4–61.7 (55.7)4–9 (6.2)P. ignicolor♂1330.545.9–52.2 (49.6)37.1–47.1 (43.2)3–9 (6.1) |
Hand.—The species in the Ptychohyla euthysanota group have a vestige of web between the first and second fingers; the other fingers are about one-third webbed. Breeding males have a cluster of horny nuptial spines on the thumb. The spines are largest in P. spinipollex (Fig. 1) and vary in number from 35 to 66 (average 47.4) on each thumb. In the other species of the Ptychohyla euthysanota group the spines are smaller and usually more numerous; the numbers of spines on each thumb (means in parentheses) in members of this group are: P. euthysanota euthysanota, 44–143 (83.8); P. euthysanota macrotympanum, 40–110 (63.0); P. leonhardschultzei, 24–80 (54.7). The species in the Ptychohyla schmidtorum group have no web between the first and second fingers and only a vestige of web between the other fingers. Furthermore, these species lack nuptial spines in breeding males. Like the usual horny excrescences on the thumbs of many species of frogs, the horny spines on the thumbs of members of the Ptychohyla euthysanota group are seasonal in development.
Fig. 1. Palmar views of right hands of (A) Ptychohyla spinipollex (KU 58054) and (B) Ptychohyla schmidtorum schmidtorum (KU 58043). × 4.
Many workers have used the presence of a bifid subarticular tubercle beneath the fourth finger as a diagnostic character of certain species of hylids. Examination of the subarticular tubercles in Ptychohyla reveals considerable intraspecific variation. Bifid tubercles beneath the fourth finger are found in all species except P. ignicolor, which is known from only two specimens. In P. euthysanota euthysanota nearly 60 per cent and in P. schmidtorum schmidtorum about 90 per cent of the specimens have a bifid tubercle beneath the fourth finger on one or both hands. All specimens of P. leonhardschultzei have either a bifid or double tubercle beneath the fourth finger, and some have a bifid distal tubercle beneath the third finger.
Feet.—Members of the Ptychohyla euthysanota group have a weak tarsal fold, whereas in the species comprising the Ptychohyla schmidtorum group the tarsal fold is absent. Webbing on the foot extends to the discs of the third and fifth toes and to the base of the penultimate phalanx of the fourth toe, except in P. ignicolor, which has less webbing.
Ventrolateral Glands.—Breeding males develop thickened, pigmented glandular areas on the sides of the body. In living specimens of P. schmidtorum and P. ignicolor the glands are not readily visible, but in preservative they show as distinctive orange-colored areas. These glands are most distinct in P. euthysanota; in many specimens of this species the glands are elevated above the surrounding skin. The extent of the glands is variable (Fig. 2); probably this variability is due to different degrees of development in individual frogs rather than to interspecific differences. All Ptychohyla ignicolor and some P. schmidtorum chamulae have a small, round glandular area on the chin; to my knowledge this does not occur in the other species. Superficial examination of microscopic preparations of the glands reveals no histological differences between species. The glands occupy most of the thickened area and have narrow ducts leading to the exterior. Detailed studies of the histology will be reported elsewhere. Since the glands are developed only in breeding males, it is surmised that the glands are associated with some phase of the breeding activity.
Fig. 2. Normal extent of ventrolateral glands in (A) Ptychohyla euthysanota euthysanota (KU 58008), (B) Ptychohyla schmidtorum schmidtorum (KU 58037), and (C) Ptychohyla ignicolor (UMMZ 119603). × 21⁄4.
Tongue.—The shape of the tongue varies intraspecifically. Usually the tongue is ovoid; in some specimens it is barely notched posteriorly, whereas in others it is deeply notched, making the tongue cordiform. Deeply notched cordiform tongues are found in P. leonhardschultzei and P. schmidtorum; with the exception of these two species, some individuals of all species have emarginate tongues. Some individuals of all species have tongues that are shallowly notched posteriorly.
Color and Pattern
The dorsum in living frogs of the genus Ptychohyla is primarily yellowish or reddish brown, except in P. schmidtorum chamulae and P. ignicolor in which it is green. Usually there are some darker blotches or reticulations on the dorsum. The venter usually is white; in P. ignicolor it is yellow. The venter is spotted in all members of the Ptychohyla euthysanota group; the species, arranged from least to most spotting ventrally, are: P. euthysanota euthysanota, P. euthysanota macrotympanum, P. leonhardschultzei, and P. spinipollex. The last two species also have bold dark spots on the flanks. Ptychohyla schmidtorum lacks spots on the venter, whereas P. ignicolor has small dark flecks ventrally.
Ptychohyla euthysanota and P. schmidtorum have white stripes on the upper lips and on the flanks. All species have some form of a pale stripe above the anus and usually rather distinct white or pale stripes along the ventrolateral edges of the tarsi and forearms. There are no bright or boldly marked flash-colors (colors that are revealed only when the hind limbs are extended), except in P. ignicolor, which has bright red flash-colors in the groin and on the thighs. In life the iris varies from several different shades of bronze color to deep red in P. schmidtorum schmidtorum.
The degree of metachrosis is moderate. Usually any change of color in life consists only of change in the intensity of color. At times when the over-all coloration is darkened some markings are obscured.
Osteology
The following description of the skull, hyoid, sternum, and prepollex is based on a male specimen of P. spinipollex (KU 68632) that has been cleared and stained. The broad, flat skull (Fig. 3) has a large frontoparietal fontanelle. The ethmoid is large and has a flange laterally. The nasals are of moderate size and in broad contact with the ethmoid, but are separated from one another medially. The anterior half of the maxillary bears a thin, high flange. The anterior process of the squamosal is short and widely separated from the maxillary. The quadratojugal is a small spine-shaped element projecting anteriorly