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Title: A Review of the Middle American Tree Frogs of the Genus Ptychohyla

Author: William E. Duellman

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University of Kansas Publications
Museum of Natural History

---

Volume 15, No. 7, pp. 297-349, pls. 11-18, 7 figs.

  October 18, 1963  

 

 

 

A Review of the Middle American Tree Frogs
of the Genus Ptychohyla

 

 

BY

 

WILLIAM E. DUELLMAN

 

 

 

 

 

 

University of Kansas
Lawrence
1963

 

 

PRINTED BY
JEAN M. NEIBARGER, STATE PRINTER
TOPEKA, KANSAS
1963

29-6531

Probably no ecological group of hylid frogs (some Hyla plus Plectrohyla and Ptychohyla) in Middle America is so poorly known as those species that live in the cloud forests on steep mountain slopes and breed in cascading mountain streams. During the last half of the nineteenth century most of the species of hylids living in the lowlands of southern México and northern Central America were named and described. Despite the extensive collecting by Salvin and Godman, Nelson and Goldman, and the various expeditions of the Mission Scientifique, no members of the genus Ptychohyla were obtained until 1927, when in the mountains of El Salvador Ruben A. Stirton found a small tree frog that subsequently was described and named Hyla euthysanota by Kellogg (1928). Until recently frogs of this genus were known from few specimens and in the literature by nearly as many names.

Although I first collected Ptychohyla in 1956, it was not until 1960 that special efforts were made to obtain specimens of this genus. The summer of 1960 was spent in southern México and Guatemala, where every accessible stream in the cloud forests was searched for tree frogs, especially Ptychohyla and Plectrohyla. Similar, but less extensive, investigations were carried out in 1961 and 1962. The result of this field work is a rather large collection of Ptychohyla representing all of the known species, plus tape recordings of the breeding calls and tadpoles of all of the species.

Previously, I have discussed the nomenclature of one of the species (Duellman, 1960) and have described two new species (Duellman, 1961). In the latter paper I made reference to a future account (this one) that would deal with the systematics and biology of the entire genus. Although I have series of specimens, tadpoles, osteological preparations, and recordings of breeding calls, thereby having a wide array of data at my disposal, much still remains to be learned about these frogs, especially about various aspects of their life histories. Even the validity of the genus is open to question; this problem is discussed at length in the section beyond entitled "Ptychohyla as a Natural Assemblage."

I am indebted to the following persons for permitting me to examine specimens in their care: Miguel Alvarez del Toro, Museo Zoología de Tuxtla Gutierrez, México (MZTG); Charles M. Bogert and Richard G. Zweifel, American Museum of Natural History (AMNH); Doris M. Cochran, United States [Pg 302] National Museum (USNM); Norman Hartweg and Charles F. Walker, University of Michigan Museum of Zoology (UMMZ); Robert F. Inger, Chicago Natural History Museum (CNHM); Hobart M. Smith, University of Illinois Museum of Natural History (UIMNH); Heinz Wermuth, Zoologisches Museum Berlin (ZMB); and Ernest E. Williams, Museum of Comparative Zoology (MCZ). The abbreviations following names of institutions will be used throughout the text; the Museum of Natural History at the University of Kansas is abbreviated KU.

Throughout my work on these frogs I have profited from discussions with L. C. Stuart, who has made many valuable suggestions and with his characteristic generosity has placed at my disposal his extensive collections of tadpoles from Guatemala. For his aid I am indeed grateful. I am grateful to Thomas E. Moore for tapes of breeding calls of two species.

My own field work was made more enjoyable and profitable through the assistance of Dale L. Hoyt, Craig E. Nelson, Jerome B. Tulecke, and John Wellman, all of whom spent many hours in often unsuccessful attempts to collect specimens and record breeding calls of Ptychohyla. I am indebted to many residents of México, Guatemala, and El Salvador for permission to work on their land and for providing shelter, food, and guides. I am especially grateful to Mr. and Mrs. Horatio Kelly of "Colegio Linda Vista" at Pueblo Nuevo Solistahuacán, Chiapas, for a pleasant stay at their school; Jordi Juliá Z. of the Comisión del Papaloapan, Ciudad Alemán, Veracruz, for arranging for field work in northern Oaxaca in 1959; Walter Hannstein and Lothar Menzel for the use of facilities at Finca La Paz, Guatemala, in 1960; Alan Hempstead for the use of facilities at Finca Los Alpes, Guatemala in 1960 and 1961; and Julio Aguirre C. of the Instituto Tropical de Investigaciones Científicas, San Salvador, El Salvador, for providing comfortable working quarters and transportation and guides to the mountains in northern El Salvador. Without the cheerful efforts of Jorge A. Ibarra, Director of the Museo Nacional de Historia Natural in Guatemala, my field work would have been greatly restricted during politically precarious times in that country. Permits to collect in México were furnished by the late Luis Macías Arellano of the Dirección General de Caza. Each of these individuals has my profound thanks for his indispensable aid.

Field work on hylid frogs in Middle America has been supported by the National Science Foundation, Grant NSF-G9827, and this is the 9th publication on the results of study of the material from America.

During the course of this study I have examined 247 frogs that I assign to the genus Ptychohyla, plus 40 lots of tadpoles and 12 skeletal preparations. Furthermore, I have examined all of the type specimens. I have studied each of the species and subspecies in the field and have examined from seven (P. euthysanota macrotympanum) to 33 (P. spinipollex) living individuals of each species.

Measurements given in the analysis of data and in the descriptions of the species are those described by Duellman (1956). In the descriptions of living colors the capitalized names are from Ridgway (1912). All interpretations of osteological characters are based on specimens cleared in potassium hydroxide and stained with alizarin red.

[Pg 303] Recordings of the breeding calls were made with a Magnemite Portable Tape-recorder; audiospectrographs were made on a vibralyzer (Kay Electric Company) using normal pattern and wide bandwidth.

Data that are used to arrive at a systematic arrangement of the species of Ptychohyla are analyzed and discussed below for the values inherent in the analysis. These data are of some value also in the recognition of species and subspecies but if employed for that purpose the data must be used in combination with the keys and the diagnoses of the individual species and subspecies.

Each of the external morphological characters used in the systematic treatment of Ptychohyla, as well as the nature of the tongue, is discussed below.

Size and Proportions.—Comparisons of size and certain proportions are given in Table 1. Frogs of this genus are small; the largest specimen examined is a female of P. euthysanota euthysanota having a snout-vent length of 53.3 mm. The species comprising the Ptychohyla schmidtorum group are smaller; the largest specimen examined is a female of P. schmidtorum schmidtorum having a snout-vent length of 38.0 mm. An analysis of the various measurements and proportions shows few constant differences. Ptychohyla ignicolor differs from all of the other species in having the head slightly wider than long and the tympanum noticeably less than half the size of eye. Ptychohyla spinipollex has a relatively narrow interorbital distance, approximately equal to the width of the eyelid, whereas in all of the other species that distance is much more than the width of the eyelid.

Snout.—All 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.

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, [Pg 305] 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.

[Pg 306] 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.

[Pg 307] 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.

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.

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 [Pg 308] 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 from the ventral base of the quadrate; the quadratojugal does not articulate with the maxillary.

Fig. 3. Dorsal aspect of skull of Ptychohyla spinipollex (KU 68632). Arrow indicates reduced quadratojugal. × 6.

The posteromedian part of the hyoid plate is calcified; from this plate the long bony, posterior cornua (thyrohyales) extend posterolaterally.

The omosternum is calcified, widest anteriorly, and has a convex anterior edge. The calcified xiphisternum is roughly bell-shaped having short lateral processes anteriorly and a deep notch posteriorly.

The swollen thumb is supported by a dorsoventrally flattened spine that does not extrude through the skin.

Variation.—In general, the skull varies little. Usually the quadratojugal is present only as a short element attached to the quadrate, but in one specimen of P. spinipollex the quadratojugal articulates with the maxillary and forms a complete quadratojugal-maxillary arch on each side of the skull. One specimen of P. leonhardschultzei has a complete arch on one side and an incomplete arch on the other.

Only P. spinipollex has lateral processes anteriorly on the xiphisternum; in the other species the xiphisternum is deeply bell-shaped.

Ptychohyla schmidtorum and P. ignicolor have slightly longer [Pg 309] premaxillaries than the other species. The longer premaxillary is reflected in the larger number of teeth on the bone—9 to 11 (average 10) in four specimens of P. schmidtorum and 10 teeth in one P. ignicolor, as compared with 6 to 10 (average 7.9) in seven specimens of the other species. The number of maxillary teeth in the various species are: P. euthysanota euthysanota, 43; P. euthysanota macrotympanum, 38; P. leonhardschultzei, 38 and 40; P. spinipollex, 34 and 40; P. schmidtorum schmidtorum, 37 and 43; P. schmidtorum chamulae, 40 and 41; P. ignicolor, 43. The teeth on the premaxillary and anterior part of the maxillary are long, pointed, and terminally curved backwards. Posteriorly on the maxillary the teeth become progressively shorter and blunter.

Variation in number of vomerine teeth is shown in Table 1.

Tadpoles of the genus Ptychohyla are adapted to live in mountain streams. The bodies are streamlined, and the tails are long and have low fins (Figs. 4 and 5). The mouths are large and directed ventrally. Tadpoles of the two groups of species have strikingly different mouthparts.

Fig. 4. Tadpoles of the Ptychohyla euthysanota group: (A) P. euthysanota euthysanota (KU 60042), (B) P. euthysanota macrotympanum (KU 60049), (C) P. leonhardschultzei (KU 68556), and (D) P. spinipollex (KU 60053). ×2½.

Fig. 5. Tadpoles of (A) Ptychohyla schmidtorum schmidtorum (KU 60051), (B) P. schmidtorum chamulae (KU 58199), and (C) P. ignicolor (KU 71716). × 2½.

Lips of tadpoles of the Ptychohyla euthysanota group (Fig. 6 A-D) are folded laterally; there are 4⁄6 or sometimes 4⁄7 tooth-rows. A lateral "wing" projects on either side of the upper beak. The beaks have blunt, peglike serrations. Lips of tadpoles of the Ptychohyla schmidtorum group (Fig. 6 E-G) are greatly expanded and form a funnel-shaped disc; there are 3⁄3 short tooth-rows. There is no lateral projection or "wing" on either side of the upper beak. The beaks have long, pointed serrations.

Fig. 6. Mouthparts of tadpoles of Ptychohyla: (A) P. euthysanota euthysanota (KU 60042), (B) P. euthysanota macrotympanum (KU 60049), (C) P. leonhardschultzei (KU 68556), (D) P. spinipollex (KU 60053), (E) P. schmidtorum schmidtorum (KU 60051), (F) P. schmidtorum chamulae (KU 58199), and (G) P. ignicolor (KU 71716). × 10.

Variation in certain structural details and in coloration is discussed for each species and subspecies in the systematic accounts that follow. Sizes, proportions, and numbers of tooth-rows are tabulated in Table 2.

Evidence on the pattern of development of tooth-rows indicates that the inner rows develop first. A small tadpole of P. euthysanota euthysanota has six lower rows and three fully developed upper rows and only the beginning of the first (outer) upper row. A small tadpole of P. euthysanota macrotympanum has four upper rows and five lower rows. In a small tadpole of P. leonhardschultzei the three upper and four lower tooth-rows are well developed; the first upper and fifth lower rows are beginning to develop, and the sixth lower row is absent. In small tadpoles of P. spinipollex, the sixth lower row is poorly developed, and the seventh row is absent; large individuals normally have seven lower rows. A small tadpole of P. schmidtorum chamulae has 3⁄2 tooth-rows.

Breeding calls of all species and subspecies of Ptychohyla were recorded in the field. Obtaining series of calls of Ptychohyla is difficult because these frogs call mostly from vegetation along roaring mountain streams and only by locating a calling frog some distance from the water or along a quiet stretch of the stream can good recordings be obtained. For example, four individuals of [Pg 313] P. spinipollex were recorded, but only one recording was sufficiently free of background noise to be analyzed.

Analysis of breeding calls supports the division of the genus Ptychohyla into two groups of species. The call of each member of the Ptychohyla euthysanota group consists of a single long note, whereas the call of species in the Ptychohyla schmidtorum group consists of a series of short notes. Since no differences were found between the calls of subspecies of any given species, the following discussion of breeding calls pertains to species. These calls are described briefly below and at greater length in the systematic accounts farther on. Audiospectrographs of the breeding calls are shown in Plate 11, and comparisons of the characteristics of the calls are given in Table 3.

Plate 11.

P. spinipollex (Pl. 11A).—One long note is repeated at intervals of 45 seconds to four minutes and has an average dominant frequency of 4300 cycles per second.

P. euthysanota (Pl. 11B).—One long note is repeated six to nine times at intervals of 2.7 to 3.4 seconds and has an average dominant frequency of 3070 cycles per second.

P. leonhardschultzei (Pl. 11C).—One long note is repeated once after 10 to 13 seconds and has an average dominant frequency of 2750 cycles per second.

P. schmidtorum (Pl. 11D).—The complete call consists of one short series of notes alternating with two long series. Numbers of notes per series in one individual having a typical call were 5-8-8-3-9-9. The average dominant frequency of notes in the short and long series alike is 3400 cycles per second.

P. ignicolor (Pl. 11E).—The complete call consists of a short series of notes alternating with a long series. In one complete recording the numbers of notes in these series were 4-13-3-11. The notes in the short series have an average dominant frequency of 2100 cycles per second, whereas the notes in [Pg 314] the long series have an average dominant frequency of 3150 cycles per second. The four series of notes were given in one minute and 15 seconds.

The museum catalogue numbers of the specimens examined, together with the localities from which they came, are listed at the end of the account of each subspecies or monotypic species. The localities that are represented by symbols on the distribution map (Fig. 7) are in roman type; those that are not represented on the map, because overlapping of symbols would have occurred, are in italic type.

Diagnosis.—Small hylids having stream-adapted tadpoles and differing from other hylid genera in having large ventrolateral glands in breeding males.

Composition.—Five species, two of which are made up of two subspecies, arranged in two groups of species on the basis of morphological characters of adults and tadpoles and on the basis of breeding calls.

Distribution.—Moderate elevations from southern Guerrero and northern Oaxaca, México, to northern El Salvador and central Honduras.

Three species in group; adults having moderate amount of webbing between fingers, and tarsal fold; breeding males having spinous, horny, nuptial tuberosities on pollex; mouths of tadpoles having lateral folds in lips and 4⁄6 or 4⁄7 tooth-rows; breeding call consisting of one long note.

Diagnosis.—Rostral keel absent; nuptial spines in males small; interorbital region much wider than eyelid.

Plate 12 Click to View Larger.

Ptychohyla euthysanota euthysanota (Kellogg)   Hyla euthysanota Kellogg, Proc. Biol. Soc. Washington, 41:123-124, June 29, 1928 [Holotype.—USNM 73296 from Los Esemiles, Depto. Chalatenango, El Salvador; Ruben A. Stirton collector]. Mertens, Senckenbergiana, [Pg 316] 33:169-171, June 15, 1952; Abhand. Senckenbergische Naturf. Gesell., 487:29, December 1, 1952. Stuart, Proc. Biol. Soc. Washington, 67:169, August 5, 1954. Hyla rozellae Taylor, Univ. Kansas Sci. Bull., 28:78-80, pl. 9, fig. 1, May 15, 1942 [Holotype.—USNM 115039 from Salto de Agua, Chiapas, México; Hobart M. and Rozella Smith collectors]. Taylor and Smith, Proc. U. S. Natl. Mus., 95:587, June 30, 1945. Smith and Taylor, Bull. U. S. Natl. Mus., 194:86, June 17, 1948. Stuart, Proc. Biol. Soc. Washington, 67:169, August 5, 1954. Ptychohyla bogerti Taylor, Amer. Mus. Novitates, 1437:13-16, fig. 5, December 7, 1949 [Holotype.—AMNH 51847 from Río Grande, Oaxaca, México; Thomas MacDougall collector]. Stuart, Proc. Biol. Soc. Washington, 67:169, August 5, 1954. Ptychohyla euthysanota, Duellman, Univ. Kansas Publ. Mus. Nat. Hist., 13:351, April 27, 1961.

Life History.—This subspecies breeds in clear, swift mountain streams. Males call from stems and leaves of plants at the edge of, or overhanging, the streams. The breeding call consists of a soft "wraack," repeated at intervals of three to four seconds. Each note has a duration of 0.60 to 0.65 seconds and has 91 to 102 pulses per second; the dominant frequency falls between 3000 and 3200 cycles per second.

Tadpoles in various stages of development were found at Finca La Paz, Guatemala, in late July. This indicates that there is either extreme differential growth, or, more probably, an extended breeding season. A tadpole having a body length of 6.8 mm. and a total length of 19.1 mm. has a short median first upper tooth-row; lower tooth-rows 3-6 are only two-thirds as long as lower rows 1 and 2. Two recently metamorphosed young have snout-vent lengths of 14.2 and 14.8 mm.; they are colored like the adults.

Remarks.—The type specimen of Hyla euthysanota Kellogg (1928:123) is a female; therefore, when Taylor (1944) proposed the name Ptychohyla for hylids having ventrolateral glands in breeding males, he was unaware that Hyla euthysanota was a member of this group. In his description of Hyla rozellae, Taylor (1942) did not compare his specimens with Hyla euthysanota, but instead placed H. rozellae with H. loquax and H. rickardsi. The type series of H. rozellae consists of one large adult female and several metamorphosing young. Taylor (1949:16) based the description of Ptychohyla bogerti on two males and compared these specimens with P. adipoventris Taylor [= P. leonhardschultzei (Ahl)]. Thus, in a period of 22 years the females of this species were given two names and the male another. Stuart (1954:169) suggested that Hyla euthysanota and Hyla rozellae were Ptychohyla. Now that sufficient specimens are available from throughout the range it is possible to determine that the various named populations are conspecific.

Plate 13 Click to View Larger.

Ptychohyla euthysanota macrotympanum (Tanner)   Hyla macrotympanum Tanner, Great Basin Nat., 17:52-53, July 31, 1957 [Holotype.—AMNH 62141 (formerly BYU 13752) from 10 miles east of Chiapa de Corzo, Chiapas, México; Robert Bohlman collector]. Ptychohyla macrotympanum, Duellman, Univ. Kansas Publ. Mus. Nat. Hist., 13:351, April 27, 1961.

Life History.—This species breeds in clear mountain streams in mixed pine and broad-leafed forest. Males call from trees and bushes along the streams. The breeding call consists of a soft "wraack," repeated three to nine times with intervals of 2.7 to 3.4 seconds between notes. Each note has a duration of 0.60 to 0.65 second, and a rate of 92 to 100 pulses per second; the dominant frequency falls between 3000 and 3200 cycles per second (Pl. 11B). The call is indistinguishable from that of P. e. euthysanota.

[Pg 323] Tadpoles in various stages of development were found in the Río Hondo, Chiapas, on June 16, 1960. The smallest tadpole has a total length of 24.1 mm.; in this individual the sixth lower tooth row has barely started to develop. A metamorphosing frog taken at the same time has a snout-vent length of 19.8 mm., a short remnant of the tail, and the mouth and tongue developed, whereas another individual having a snout-vent length of 17.8 mm. and a tail 31.0 mm. in length still has larval teeth. Three completely metamorphosed juveniles collected by L. C. Stuart at Jacaltenango, Guatemala, on June 6 and 7, 1955, have snout-vent lengths of 16.0, 16.0, and 16.1 mm.

Remarks.—Tanner (1957:52) based the description of Hyla macrotympanum on a single female, which, of course, lacked the characters diagnostic of Ptychohyla. On the basis of general external characters Tanner suggested that Hyla macrotympanum was related to H. miotympanum, from which it differed in having a larger tympanum and a bifid subarticular tubercle beneath the fourth finger. The collection of additional females, together with males of the species, has shown that Hyla macrotympanum is a Ptychohyla.

Intergradation between Ptychohyla euthysanota and P. macrotympanum has not been demonstrated. Currently their ranges are separated by the dry valleys of the Río Grijalva and Río Cuilco. The similarity in structure of the adults and tadpoles and the indistinguishable breeding calls are the basis for considering the two populations subspecies.

Plate 14 Click to View Larger.

Ptychohyla leonhardschultzei (Ahl)   Hyla leonhard-schultzei Ahl, Zool. Anz., 106:185-186, fig. 1, April 15, 1934 [Holotype.—ZMB 34353 from Malinaltepec, Guerrero, México; Leonhard Schultze collector]. Smith and Taylor, Bull. U. S. Natl. Mus., 184:87, June 17, 1948. Hyla godmani, Ahl, Zool. Anz., 106:186, April 15, 1934. Hyla pinorum Taylor, Proc. Biol. Soc. Washington, 50:46-48, pl. 2, fig. 2, [Pg 324] April 21, 1937 [Holotype.—UIMNH 25049 from Agua del Obispo, Guerrero, México; Edward H. Taylor collector]. Smith and Taylor, Bull. U. S. Natl. Mus., 194:87, June 17, 1948. Ptychohyla adipoventris Taylor, Univ. Kansas Sci. Bull., 30:41-45, May 15, 1944 [Holotype.—UIMNH 25047 from Agua del Obispo, Guerrero, México; Edward T. Taylor collector]. Smith and Taylor, Bull. U. S. Natl. Mus., 194:91, June 17, 1948. Taylor, Amer. Mus. Novitates, 1437:16, December 7, 1949. Stuart, Proc. Biol. Soc. Washington, 67:169, August 5, 1954. Hyla milleri Shannon, Proc. U. S. Natl. Mus., 101:473-477, figs. 92b, 93a-c, May 17, 1951 [Holotype.—USNM 123700 from San Lucas Camotlán, Oaxaca, México; Walter S. Miller collector]. Ptychohyla leonhard-schultzei, Duellman, Herpetologica, 16:191-197, figs. 1-3, September 23, 1960; Univ. Kansas Publ. Mus. Nat. Hist., 13:351, April 27, 1961.

Life History.—This frog has been found along streams in cloud forests and in pine-oak forest. Males call from vegetation along the stream or from rocks in and at the edge of the stream. The call is a single, long, soft "wraack," repeated at intervals of anywhere from several seconds to three or four minutes. Each note has a duration of 0.62 to 0.95 of a second and a rate of 76 to 78 pulses per second; the dominant frequency falls between 2700 and 2800 cycles per second (Pl. 11C).

Tadpoles were found in several streams in northern Oaxaca. A tadpole having a total length of 21.1 mm. has three upper and four lower tooth-rows well developed; the fourth upper and fifth lower rows are weakly present, and the sixth lower row has not started to develop. Two metamorphosed young have snout-vent lengths of 15.2 and 15.5 mm.

Remarks.—Four specific names have been applied to this species. Ahl (1934:185) based his description of Hyla leonhardschultzei on a small, poorly preserved female. Taylor (1944:41) proposed the generic name Ptychohyla for a species (named therein as P. adipoventris) of hylid having ventrolateral glands and horn-covered nuptial spines. Obviously, Taylor was unaware that Hyla leonhardschultzei was the same species. Earlier Taylor (1937:46) described [Pg 327] Hyla pinorum. The types of all of these species came from the Pacific slopes of the Sierra del Sur in Guerrero. Examination of the types and other available specimens shows that they are representatives of a single species. The type of Hyla pinorum is an immature male having a snout-vent length of 26.7 mm. All of these specimens have the square snout and black and white flanks characteristic of Ptychohyla leonhardschultzei. Although Shannon (1951:473) based his description of Hyla milleri on a male having well-developed ventrolateral glands, he overlooked the presence of these glands in his description and discussion of relationships. The acquisition of more specimens from northern Oaxaca has shown that Hyla milleri is the same as Ptychohyla leonhardschultzei.

Plate 15 Click to View Larger.

Ptychohyla spinipollex (Schmidt)   Hyla euthysanota, Dunn and Emlen, Proc. Acad. Nat. Sci. Philadelphia, 84:25, March 22, 1932. Hyla spinipollex Schmidt, Proc. Biol. Soc. Washington, 49:45-46, May 1, 1936 [Holotype.—MCZ 21300 from the mountains behind Ceiba, Depto. Atlantidad, Honduras; Raymond E. Stadelman collector]. Stuart, Misc. Publ. Mus. Zool. Univ. Michigan, 69:32-34, figs. 5-6, June 12, 1948; Contr. Lab. Vert. Biol. Univ. Michigan, 45:22, 52, 54, 57, May, 1950; Proc. Biol. Soc. Washington, 67:169, August 5, 1954. Ptychohyla spinipollex, Stuart, Contr. Lab. Vert. Biol. Univ. Michigan, 68:48, November, 1954. Duellman, Univ. Kansas Publ. Mus. Nat. Hist., 13:351, April 27, 1961.

Life History.—At Finca Los Alpes, Guatemala, in July, 1960, and in August, 1961, calling males were found on bushes and trees along cascading mountain streams. The breeding call consists of a soft "wraack," repeated at intervals of 45 seconds to four minutes. Each note has a duration of about .46 of a second and a rate of 147 pulses per second. The dominant frequency is 4300 cycles per second (Pl. 11A).

Tadpoles have been found in cascading mountain streams. Two metamorphosed young have snout-vent lengths of 15.0 and 15.5 mm.

Remarks.—There is little doubt that all of the specimens herein referred to Ptychohyla spinipollex are conspecific. However, the three specimens from Honduras, including the type of Ptychohyla spinipollex, differ from Guatemalan specimens in lacking all dark spotting on the venter. Additional specimens from Honduras and eastern Guatemala may show that two subspecies are recognizable, in which case the nominal subspecies will be the population in Honduras.

Two species in group; adults having only vestige of web between fingers and lacking tarsal fold; pollex of breeding males lacking spinous, horny, nuptial tuberosities; mouth of tadpole greatly expanded, funnel-shaped, lacking lateral folds, and having 3⁄3 tooth-rows; breeding call consisting of series of short notes.

Plate 16 Click to View Larger.

Ptychohyla schmidtorum schmidtorum Stuart Ptychohyla schmidtorum Stuart, Proc. Biol. Soc. Washington, 67:169-172, August 5, 1954 [Holotype.—CNHM 27055 from El Porvenir (17 kilometers air-line west of San Marcos), Depto. San Marcos, Guatemala; Karl P. Schmidt collector]. Duellman, Univ. Kansas Publ. Mus. Nat. Hist., 13:351, 355, April 27, 1961.

Life History.—This species breeds in clear mountain streams where males call from vegetation along the stream. The call consists of series of short notes, three to nine notes per series, sounding like "raa-raa-raa." The duration of each note is approximately .065 of a second, and has a rate of 96 to 119 pulses per second; the dominant frequency is about 3400 cycles per second. The call is almost indistinguishable from that of Ptychohyla schmidtorum chamulae.

Tadpoles and metamorphosing young were found at Finca La Paz, Guatemala, in late July, 1960. Two young lacking tails but not having completely developed mouths have snout-vent lengths of 14.2 and 14.6 mm. L. C. Stuart collected four metamorphosing young at Finca La Paz on May 6, 1949. By May 10 the frogs were completely metamorphosed, at which time they had snout-vent lengths of 15.5 to 17.0 (average 16.1) mm.

Remarks.—There is no doubt that this frog is most closely related to Ptychohyla schmidtorum chamulae, even though the ranges of the two subspecies are separated by the interior depression of Chiapas. Since at least at Finca La Paz, Guatemala, P. s. schmidtorum occurs with P. e. euthysanota, it is surprising that the former species has not been found at more localities along the Pacific slopes [Pg 334] on northern Central America. At Finca La Paz in July, 1960, P. s. schmidtorum was more abundant than P. e. euthysanota.

Plate 17 Click to View Larger.

Ptychohyla schmidtorum chamulae Duellman Ptychohyla chamulae Duellman, Univ. Kansas Publ. Mus. Nat. Hist., 13: 354-357, pl. 25, fig. 2, April 27, 1961 [Holotype.—KU 58063 from 6.2 kilometers south of Rayón Mescalapa, Chiapas, México; William E. Duellman collector].

Life History.—Calling males were found on leaves of herbs and bushes by cascading streams in cloud forest. The call consists of series of short notes, three to nine notes per series, sounding like "raa-raa-raa." The duration of each note is .054 to .070 of a second, and has a rate of 96 to 110 pulses per second. The dominant frequency falls between 3350 and 3450 cycles per second (Pl. 11D). The call is almost indistinguishable from that of Ptychohyla schmidtorum schmidtorum.

Tadpoles were found in the cascading streams; the smallest tadpole has a total length of 17.2 mm. and has only 3⁄2 tooth-rows. At a stream 6.2 kilometers south of Rayón Mescalapa, Chiapas, metamorphosing young were found on June 16 and August 5, 1960. Each of two completely metamorphosed young has a snout-vent length of 15.7 mm. Another having a snout-vent length of 16.2 mm. has a tail stub 2 mm. long and a completely metamorphosed mouth. Two others have snout-vent lengths of 13.6 and 14.1 mm. and tail lengths of 11.5 and 8.1 mm. respectively; in these the mouth parts are incompletely metamorphosed.

Remarks.—Duellman (1961:354) described Ptychohyla chamulae [Pg 337] and stated that it probably was most closely related to P. schmidtorum. Further study has revealed additional resemblance in morphological and behavioral details. It is concluded that the two populations are more realistically treated as subspecies than as species. The geographic ranges, as now known, are disjunct. Ptychohyla schmidtorum chamulae inhabits cloud forest on the Atlantic slopes of the Chiapan Highlands, whereas P. s. schmidtorum lives in cloud forest on the Pacific slopes of the Sierra Madre in Chiapas and Guatemala. Between their known geographic ranges are the pine clad Sierra Madre and Chiapan Highlands, and intervening sub-humid Grijalva Valley.

Plate 18 Click to View Larger.

Ptychohyla ignicolor Duellman Ptychohyla ignicolor Duellman, Uni. Kansas Publ. Mus. Nat. Hist., 13:352-353, pl. 25, fig. 1, April 27, 1961 [Holotype.—UMMZ 119603 from 6 kilometers south of Vista Hermosa, Oaxaca, México; Thomas E. Moore collector].

Life History.—At Vista Hermosa, Oaxaca, males were calling on vegetation above small streams on March 30, 1959, and on June 28, 1962; males were found on vegetation overhanging a stream 6 kilometers south of Vista Hermosa on June 27 and July 3, 1962. The call consists of a series of short notes, three to thirteen notes per [Pg 340] series, sounding like "raa-raa-raa." The duration of each note is about .08 of a second and has a rate of 123 to 129 pulses per second. The dominant frequency of notes in short series is about 2100 cycles per second, whereas the dominant frequency of notes in long series is about 3150 cycles per second (Pl. 11E).

On June 28, 1962, two tadpoles of this species were found in a quiet pool in a spring-fed rivulet at Vista Hermosa, Oaxaca. Females are unknown.

Remarks.—The absence of a tarsal fold and of nuptial spines in breeding males, the nature of the breeding call, and the form of tadpole are characters that place Ptychohyla ignicolor in the P. schmidtorum-group.

The distribution of species of Ptychohyla reflects the distribution of cloud forest in southern México and northern Central America. The frogs are restricted to mountainous areas, usually at elevations higher than 1000 meters above sea level. Ptychohyla does not range to great heights in the mountains, where west of the Isthmus of Tehuantepec the mountain streams are inhabited by frogs of the Hyla bistincta group, and in Chiapas and Guatemala by species of Plectrohyla.

Frogs of the Ptychohyla euthysanota group have a greater combined geographic range than the species comprising the Ptychohyla schmidtorum group (Fig. 7). No two species in the same group are sympatric, but members of different groups are sympatric in at least parts of their ranges. Apparently P. leonhardschultzei ranges around the southern edge of the Mexican Highlands, where the species occurs on both Atlantic and Pacific slopes; as can be seen from the distribution map, there are many gaps in the known range of this species. The range of P. euthysanota euthysanota is along the Pacific slopes of the Sierra Madre in Chiapas, Guatemala, and El Salvador, whereas that of P. euthysanota macrotympanum is along the southern interior slopes of the Central Highlands of Chiapas and the Sierra de Cuchumatanes in Guatemala. Ptychohyla [Pg 341] spinipollex occurs on the wet Atlantic slopes of the Guatemalan and Honduranean Highlands; the range of the species in Honduras is poorly known.

Fig. 7. Map showing locality records for the species and subspecies of Ptychohyla.

The frogs of the Ptychohyla schmidtorum group have more restricted geographic ranges than members of the former group. Ptychohyla schmidtorum schmidtorum occurs on the Pacific slopes of the Sierra Madre in Chiapas and Guatemala, where it occurs with P. euthysanota euthysanota; P. schmidtorum chamulae is known from only two localities on the Atlantic slopes of the Central Highlands of Chiapas, where it occurs close to, but as now known not with, P. euthysanota macrotympanum. On the Atlantic slopes of the Sierra Madre Oriental in northern Oaxaca P. ignicolor occurs with P. leonhardschultzei.

In the Sierra de los Tuxtlas in southern Veracruz and in the cloud forests along the eastern slopes of the Sierra Madre Oriental northward to Nuevo León, Hyla miotympanum seems to be the ecological replacement of Ptychohyla. On the Pacific slopes north of Guerrero, México, humid forests in which there are cascading mountain streams are absent; consequently, no Ptychohyla are known from that region. In the mountains of El Salvador Ptychohyla euthysanota euthysanota occurs sympatrically with another small stream-breeding hylid, Hyla salvadorensis. To the south of Honduras the highlands diminish into the lowlands of Nicaragua, where habitat suitable for Ptychohyla apparently does not exist. In the mountains of Costa Rica and Panamá, the habitats occupied by Ptychohyla in northern Central America are filled by a variety of [Pg 342] stream-breeding Hyla, such as Hyla legleri, H. rivularis, H. rufioculis, H. alleei, and H. uranochroa.

Although members of the genus Ptychohyla occur in the southern part of the Mexican Highlands to the west of the Isthmus of Tehuantepec, the greater distribution and differentiation in the genus is in the Chiapan-Guatemalan Highlands. In this respect Ptychohyla is a counterpart of Plectrohyla.

Frogs of the genus Ptychohyla are ecologically associated with mountain streams at elevations between 650 and 2200 meters; in the geographic region where these frogs occur the vegetation between those elevations consists of cloud forest or pine-oak forest. In some places the frogs have been found in a mixture of oak and semi-deciduous scrub forest. At Vista Hermosa, Oaxaca, P. leonhardschultzei and P. ignicolor were found in cloud forest, whereas at Agua del Obispo, Guerrero, the former species was found in pine-oak forest. Ptychohyla schmidtorum is known only from cloud forest; P. euthysanota euthysanota and P. spinipollex generally are found in cloud forest, but in some places they live in pine-oak forest. Ptychohyla euthysanota macrotympanum has been found in pine-oak forest and in a mixture of oak and semi-deciduous scrub forest. With the possible exception of the members of the Ptychohyla schmidtorum group, which has been found only in cloud forest, it seems as though the type of vegetation is not the controlling factor in the ecological distribution of these frogs.

Ptychohyla has been found only where there are clear, cascading streams overhung by vegetation, on which adults and young perch at night, or even by day. The presence of these streams, in which the tadpoles live, seems to be an important factor in the distribution of Ptychohyla. As has been shown previously, the tadpoles of Ptychohyla are adapted for existence in torrential streams, where the water is cool, and the amount of oxygen is high. Clearly these tadpoles are unsuited for life in ponds or sluggish streams in the lowlands, where the temperature of the water is high, a layer of silt on the bottom is deep, and the amount of oxygen is low. The tadpoles cling to rocks on the bottom of the streams; there they move slowly across the rocks, apparently feeding on the thin covering of algae. Tadpoles were not observed on rocks having a thick covering of algae or moss. The tadpoles were observed to swim against the current in torrential streams, in which no fishes were [Pg 343] found. Therefore, it seems as though the presence of the stream-habitat for the tadpoles is a significant factor in the ecological distribution of the species of Ptychohyla.

At localities where two species of Ptychohyla occur sympatrically (P. ignicolor and P. leonhardschultzei at Vista Hermosa, Oaxaca, and P. euthysanota euthysanota and P. schmidtorum schmidtorum at Finca La Paz, Depto. San Marcos, Guatemala) effort was made to determine what, if any, ecological interspecific relationships existed. Although adults of the sympatric species were found on adjacent leaves or branches of bushes overhanging the streams at both localities, segregation at the time of breeding seems to be maintained by the notably different breeding calls in sympatric species (see discussion of breeding calls). Thus, as has been shown by Blair (1956), Fouquette (1960), and others working on a variety of pond-breeding frogs and toads, the breeding call in Ptychohyla acts as an important reproductive isolating mechanism.

At no locality were Ptychohyla and associated species of hylids found so abundantly as were species of pond-breeding hylids in the lowlands. Apparently reproductive activity is not concentrated in a short breeding season, and it is highly doubtful if the populations of these frogs are as large as those of the lowland pond-breeders. The continual humid conditions and abundance of insect food throughout the year in the cloud forest are perhaps indicative of little interspecific competition among adults of Ptychohyla and other sympatric hylids.

At Finca La Paz, Guatemala, tadpoles of two species of Ptychohyla were ecologically segregated. The tadpoles of P. euthysanota euthysanota were found in riffles in the streams, whereas those of P. schmidtorum schmidtorum were found in slower water, chiefly in small pools in the streams. At Vista Hermosa, Oaxaca, tadpoles of P. leonhardschultzei were found in riffles, and tadpoles of the sympatric P. ignicolor were found in a small pool in a stream. Similar ecological relationships were observed for several species of Costa Rican hylids. Throughout the range of Ptychohyla east of the Isthmus of Tehuantepec, members of the genus occur with species of Plectrohyla, all of which are larger than Ptychohyla, and all of which have tadpoles that live in torrential streams. Tadpoles of Ptychohyla spinipollex have been found in streams inhabited by the tadpoles of Plectrohyla guatemalensis and P. quecchi; tadpoles of Ptychohyla euthysanota euthysanota and P. schmidtorum schmidtorum [Pg 344] were found in streams inhabited by tadpoles of Plectrohyla guatemalensis, P. matudai, and P. sagorum. In some streams great numbers of tadpoles occur. The habitat is rather restricted, and the food supply is limited. Consequently, interspecific competition among the various species of hylids whose tadpoles live in the torrential streams probably is highest during the larval stage. Unfortunately, this aspect of salientian population ecology has received no intensive study.

Since the cloud forests inhabited by Ptychohyla are daily bathed in clouds and have a fairly evenly distributed rainfall throughout the year, the frogs living in these forests are active throughout the year. At least some of the species evidently have a long breeding season, for I found calling males of P. leonhardschultzei in February, March, and August, and found tadpoles in February, March, June, and August. Tadpoles of the various species have been obtained throughout much of the year, as follows: P. euthysanota euthysanota, February, March, May, and July; P. euthysanota macrotympanum, March, June, and August; P. spinipollex, February, March, April, June, July, and August; P. schmidtorum schmidtorum, March, May, June, July, and August; P. schmidtorum chamulae, June and August; P. ignicolor, June. I suspect that this temporal distribution more accurately reflects the seasonal activities of collectors than of the frogs.

Calling frogs usually are on vegetation adjacent to or overhanging streams; some calling males of P. spinipollex were on rocks in or by streams. Clasping pairs of P. euthysanota and P. schmidtorum were observed on vegetation by streams. Despite intensive search, no eggs were found. It is doubtful if Ptychohyla deposit eggs on vegetation overhanging streams, as do centrolenids and Phyllomedusa, for egg-clutches of these frogs are easily found. Possibly the eggs are laid separately on vegetation above the stream, in which case they could be overlooked easily. In streams where Ptychohyla and other hylid tadpoles occur, empty egg capsules have been found on the lee sides of rocks, but there is no way to determine which species laid the eggs.

Numbers of eggs were counted in gravid females; the largest eggs have diameters ranging from 2.5 to 3.0 mm. The smaller species, comprising the Ptychohyla schmidtorum group, have fewer eggs than do the larger species. Numbers of eggs found in females of the various species are: P. euthysanota euthysanota, 108; P. euthysanota [Pg 345] macrotympanum, 136, 160; P. leonhardschultzei, 141; P. spinipollex, 119, 134, 143; P. schmidtorum schmidtorum, 59, 61, 90; P. schmidtorum chamulae, 60, 71, 89.

Duration of the larval stage is unknown. Metamorphosing young have been found from May through August. From two to six completely metamorphosed young are available for each of the species, except for P. ignicolor of which none is available. The smallest young frog is a P. euthysanota having a snout-vent length of 14.2 mm.; the largest young frog is a P. schmidtorum schmidtorum having a snout-vent length of 17.0 mm.

The preceding data on morphology, life histories, and behavior form the basis for the following interpretation of the phylogeny of Ptychohyla. Additional data are needed to support some of the ideas discussed below; many of the data that are available for Ptychohyla are lacking for other, possibly related, hylids. The family Hylidae is composed of several hundred species, and most of the species are poorly known. Consequently, any attempt to place Ptychohyla in the over-all scheme of hylid phylogeny would be premature at this time. But, as between the five species of two species-groups here recognized as constituting the genus Ptychohyla, some estimate of relationships can be made. First, it is necessary to determine the validity of the genus itself.

As stated in the diagnosis of the genus, the only character that sets this group of species apart from other hylids is the presence of ventrolateral glands in the breeding males. To many systematists the thought of being able to identify to genus only breeding males is sufficiently disturbing to cause them to view with disfavor the recognition of the genus. Nonetheless, the question is raised: Do the five species herein placed in the genus Ptychohyla constitute a natural assemblage? If the genus is considered to be more than a category of convenience, that is to say, a group of related species having a common origin, the primary problem is to determine whether or not the five species form a phylogenetic unit.

The species of Ptychohyla are divided into two groups on the basis of external morphology, breeding calls, and tadpoles. The Ptychohyla euthysanota group seems to be a natural group composed of three species, all of which are more closely related to one another than to any other hylid. Likewise, the species comprising [Pg 346] the Ptychohyla schmidtorum group seem to represent a natural unit. If the presence of ventrolateral glands in breeding males is ignored, a student of salientian systematics might derive the Ptychohyla euthysanota group from a hylid stock containing Hyla miotympanum and Hyla mixomaculata. Likewise, Ptychohyla schmidtorum could be placed with Hyla uranochroa and related species in Costa Rica. Nonetheless, the fact remains that all of the species assigned to the genus Ptychohyla have ventrolateral glands in the breeding males; furthermore, ventrolateral glands are unknown in other hylids. If the P. schmidtorum group and the P. euthysanota group each evolved from separate hylid stocks, then the ventrolateral glands must have developed independently in both groups. That ventrolateral glands developed independently in five species of frogs in southern México and northern Central America and not in any of the other approximately 500 species of hylids in the world is untenable. It is more logical to assume that the development of the glands took place only once in a stock of hylids that gave rise to the five species herein recognized as members of the genus Ptychohyla.

The affinities of Ptychohyla apparently are not with any of the other groups that have been generically separated from Hyla. Of the daughter genera in Middle America only Plectrohyla has stream-adapted tadpoles, but these large frogs are not closely related to Ptychohyla. Stuart (1954:169) suggested that certain montane species of Hyla in lower Central America and Hyla salvadorensis in El Salvador may be related to Ptychohyla or even congeneric. I have had experience with most of these species in the field and believe that Stuart was correct in his suggestion of relationships. The species concerned are four red-eyed stream-breeding Hyla in Costa Rica—H. alleei, H. legleri, H. rufioculis, and H. uranochroa, plus Hyla salvadorensis in the mountains of El Salvador. Morphologically all of the species are similar; Hyla uranochroa, H. legleri, and H. rufioculis have a lateral white stripe that is expanded to form a spot beneath the eye, as in Ptychohyla schmidtorum. The tadpoles of Hyla rufioculis and H. uranochroa have large funnel-shaped mouths and long slender tails like those of Ptychohyla schmidtorum. Lips of the tadpoles of H. legleri and H. salvadorensis are folded laterally, in this respect resembling those of the Ptychohyla euthysanota group. I do not know the tadpoles and the breeding call of Hyla alleei. The breeding calls of Hyla rufioculis [Pg 347] and H. uranochroa consist of high melodious notes; the calls of H. legleri and H. salvadorensis consist of series of short notes that have the general characteristics of the call of Ptychohyla schmidtorum. Affinities of the genus Ptychohyla seem to me to be with the red-eyed species forming the Hyla uranochroa group in Costa Rica. All of the species in the Hyla uranochroa group have large frontoparietal fontanelles, rather small ethmoids, and small nasals that are not in contact with one another or with the ethmoid. Some species have a complete quadratojugal-maxillary arch; others do not. Assuming that the parental stock that gave rise both to the Hyla uranochroa group and to Ptychohyla was widespread in Central America at a time of cooler, more humid conditions, it is possible that with subsequent warming temperatures and seasonal rainfall in the lowlands the parental stock was restricted to the Costa Rican highlands, where the Hyla uranochroa group developed, and to the Chiapas-Guatemala highlands, where Ptychohyla evolved.

Ptychohyla schmidtorum is thought to resemble more closely the parental stock of the genus than does any other species of Ptychohyla now extant. This parental stock is discussed above in the account of the generic relationships. Ptychohyla schmidtorum has a red eye, white lateral stripe, frontoparietal fontanelle, funnel-shaped mouth in tadpoles, and lacks nuptial spines; in all of these characters it resembles members of the Hyla uranochroa group. Probably during times of glaciation during the Pleistocene, when climates in México and Central America were depressed, the Ptychohyla stock was more widespread than it is now. Subsequent elevation of climatic zones during interglacial periods would have isolated populations as they are today in regions of cloud forests. Thus, through geographic isolation populations could have differentiated and evolved into the present species. Climatic fluctuation in the Pleistocene must have been of sufficient magnitude to permit the spread of cool, moist forests containing Ptychohyla across the Isthmus of Tehuantepec into the mountains of Oaxaca.

Because of its small nuptial spines, small triangular vomers, coloration, and absence of a rostral keel, Ptychohyla euthysanota, more than any of the other species in the P. euthysanota group, resembles P. schmidtorum. At the present time P. euthysanota and P. schmidtorum are sympatric.

As I have mentioned previously, ecological segregation and [Pg 348] interspecific competition probably is highly developed in the tadpoles of Ptychohyla. If this ecological segregation resulted from intraspecific competition in a stock of Ptychohyla, possibly P. euthysanota and P. schmidtorum differentiated sympatrically in this way. Specific identity is maintained, at least in part, by different breeding calls in males.

Ptychohyla spinipollex and P. leonhardschultzei seem to be more closely related to one another than either is to P. euthysanota. Probably a stock of P. euthysanota was isolated on the Atlantic slopes of northern Central America from P. euthysanota on the southern slopes. The frogs on the Atlantic slopes differentiated and spread into the mountains of Oaxaca, where through isolation by the barrier of the Isthmus of Tehuantepec they developed into P. leonhardschultzei, while the stock on the northern slopes of Central America evolved into P. spinipollex. Subsequent to the differentiation of P. leonhardschultzei and P. spinipollex from P. euthysanota and during a time of cooler more equable climate than exists now, P. euthysanota and P. schmidtorum invaded the Central Highlands of Chiapas. Subsequent climatic changes isolated populations of each in the Central Highlands, where P. euthysanota macrotympanum and P. schmidtorum chamulae evolved. Ptychohyla ignicolor probably represents stock of P. schmidtorum that crossed the Isthmus of Tehuantepec and became isolated in Oaxaca on the western side of the isthmus.

[Pl 12]

PLATE 12

Ptychohyla euthysanota euthysanota (KU 58008). × 2.

PLATE 13

Ptychohyla euthysanota macrotympanum (KU 58049). × 2.

PLATE 14

Ptychohyla leonhardschultzei (KU 64117). × 2.

PLATE 15

Ptychohyla spinipollex (KU 58054). × 2.

PLATE 16

Ptychohyla schmidtorum schmidtorum (KU 58043). × 2.

[Pl 17]

PLATE 17

Ptychohyla schmidtorum chamulae (KU 58069). × 2.

[Pl 18]

PLATE 18

Ptychohyla ignicolor (UMMZ 119603). × 2.

Transmitted December 27, 1962.

[Pub_1]

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