Middle American Frogs of the Hyla microcephala Group Part 3

Nat. Hist., 86:416, August 22, 1946.

_Diagnosis._--Dark brown lateral stripe, if present, usually extending only to insertion of forearm, never posteriorly to sacral region; white line above brown stripe absent or faint; dorsal pattern weak, usually consisting of irregular dashes or interconnected lines; interorbital dark mark present; shanks having weakly defined transverse bars.

_Description and variation._--In the majority of specimens (70%) the lateral dark stripe extends from the nostril to the eye and thence above the tympanum to a point above the insertion of the arm; in 17 per cent the stripe extends to the mid-flank, whereas in 13 per cent the stripe is absent. A narrow and faint white line is present on the canthus in some specimens, but no distinct white stripe is present above the lateral dark line posterior to the eye. An interorbital bar and transverse marks on the shanks are invariably present. The dorsal markings are variable, but in most specimens (92%) consist of either an X- or )(-shaped mark in the scapular region; in the other specimens the markings are irregular short lines or absent. Approximately equal numbers of specimens have a transverse bar, chevron, or broken lines in the sacral region, whereas about eight per cent of the specimens lack markings in the sacral region.

When active at night, individuals are pale yellowish tan with faint brown dorsal markings. By day they are tan with more distinct brown markings (Pl. 14). The thighs are pale yellow; the belly is white. The iris is pale creamy tan with brown flecks. In breeding males the vocal sac is yellow.

_Tadpoles._--Tadpoles of this species have been found in an extensive gra.s.sy pond at Puerto Viejo, Costa Rica. The following description is based on KU 104099, a specimen in development stage 36 (Gosner, 1960).

Total length, 21.0 mm.; body length, 6.7 mm.; body slightly wider than deep, snout pointed; nostrils large, directed anteriorly, situated near end of snout; eyes small, situated dorsolaterally, directed laterally; spiracle sinistral, located just posteroventral to eye; a.n.a.l tube dextral. Tail xiphicercal; caudal musculature moderately deep, extending far beyond posterior edge of fins; fins deepest at about midlength; dorsal fin extending onto body, slightly deeper than caudal musculature; ventral fin slightly shallower than musculature.

Mouth small, terminal, lacking teeth and fringing papillae, but having finely serrate beaks. In preservative top of head olive-tan with brown flecks; dark stripe from snout through eye to posterior edge of body; belly white, flecked with brown anteriorly; tail creamy tan with grayish brown blotches. In life, dorsum of body reddish tan mottled with darker brown; lateral stripe dark brown; belly white, mottled with brown and black; caudal musculature heavily pigmented with grayish tan; posterior tip of tail marked with dark gray; caudal fins heavily blotched with grayish tan; iris orange-tan peripherally, red centrally (Pl. 15).

_Remarks._--This species has been confused with _Hyla microcephala underwoodi_ by many workers. Dunn (1931, 1933, 1934) and Breder (1946) referred Panamanian specimens of _H. phlebodes_ to _H. underwoodi_; likewise, Gaige, Hartweg, and Stuart (1937) made the same error. Cole and Barbour (1906) and Kellog (1932) used the name _H. phlebodes_ for Mexican specimens of _H. microcephala underwoodi_. The similarity in color pattern of _H. microcephala underwoodi_ and _H. phlebodes_ easily accounts for the misapplication of names. Although both species have nearly identical dorsal color patterns, that of _H. microcephala underwoodi_ usually is bolder. Furthermore, in that species a narrow white line usually is present above the well-defined lateral dark stripe, whereas the lateral dark stripe is short and posterior to the eye is not bordered above by a white line in _H. phlebodes_.

The type locality "San Carlos, Costa Rica" given by Stejneger (1906:817) apparently refers to a region, the Llanuras de San Carlos, in the northern part of Alajuela Province, Costa Rica.

[Ill.u.s.tration: Fig. 3. Map showing locality records for _Hyla phlebodes_.]

_Distribution._--_Hyla phlebodes_ inhabits humid tropical forests from southeastern Nicaragua southeastward on the Caribbean slopes and lowlands to the Ca.n.a.l Zone in Panama, thence eastward in the Chucunaque Basin of eastern Panama and onto the Pacific lowlands of Colombia (Fig. 3). The species also reaches the Pacific slopes in the Arenal Depression in northwestern Costa Rica and in the Panamanian isthmus, where it occurs in humid forests on the Pacific slope of El Valle and Cerro La Campana. Mostly the species is found at low elevations, but it occurs at 600 meters at Turrialba and at 700 meters at Finca San Bosco in Costa Rica.

_Specimens examined._--410, as follows: +Nicaragua+: Zelaya: Isla Grande del Maiz, MCZ 14848; Rio Mico, El Recrero, UMMZ 79720 (6).

+Costa Rica+: Alajuela: 12.4 km. N Florencia, MVZ 76108-10, USC 2628; *Las Playuelas, 11 km. S Los Chiles, USC 7216; Los Chiles, USC 7217, 7219; 3 km. NE Muelle de Arenal, USC 2644 (2); *"San Carlos," USNM 29970. Cartago: Chitaria, KU 103690; *1.6 km. E Rio Reventazon Bridge, east of Turrialba, UMMZ 119978 (2); *Tunnel Camp, near Peralta, KU 32456, 32458-69, 41098 (skeleton); Turrialba, FMNH 101794, 103188-9, KU 25725-9, 32439-48, 41095-7 (skeletons), 64797-827, 68300-2 (skeletons), 68403 (eggs), 68404 (tadpoles), MCZ 29224-5, 29310-2, UMMZ 119979 (6), USC 31, 256 (2), 458 (2), 580, 594, 599 (7), 7074 (2), USNM 29933. Guanacaste: Arenal, USC 6254; *Finca San Bosco, USC 62724, 6276 (3), Guayabo de Bagaces, USC 7022 (3), 7023; *Laguna Arenal, USC 6262 (4); 3 km. NE Tilaran, USC 524; *5 km. NE Tilaran, USC 6269; *6 km. NE Tilaran, UMMZ 122653 (6), S-2680 (skeleton), USC 523 (8).

Heredia: Puerto Viejo, KU 64828-63, 68303-7 (skeletons), 68405-6 (tadpoles), 104099-100 (tadpoles); *1.5 km. N Puerto Viejo, KU 64871; *1 km. S Puerto Viejo, KU 86432-40; *4.2 km. W Puerto Viejo, KU 64864-5; *5.9 km. W Puerto Viejo, KU 64866-70; *7.5 km. W Puerto Viejo, KU 86431. Limon: Batan, UMMZ 119980 (2); La Castilla, ANSP 23707; Puerto +Limon+, KU 32449-55.

+Panama+: Bocas del Toro: 3.2 km. NW Almirante, KU 96026; Cayo de Agua, KU 96027-31; Fish Creek, KU 96032-4. Ca.n.a.l Zone: Barro Colorado Island, AMNH 69790, ANSP 23244-50; FMNH 13380, 22972-4; Juan Mina, AMNH 55429, UU 3899; *8.6-13.8 km. N Miraflores Locks, TNHC 23439, 23477, 23484-8, 23491, 23494-9, 23501-2, 23504-8, 23510-17, 23519-30, 23532-8, 23541-54, 23561. *Rio Chagres, AMNH 55431-4; Rio Cocoli, 3.5 km. N Miraflores Locks, TNHC 23461, 23489-90, 23493, 23500, 23503, 23509, 23518, 23531, 23539-40; *Summit, ANSP 23361, KU 97788; *Three Rivers Plantation, SU 2130. Cocle: El Valle de Anton, AMNH 55435, 69786-9, ANSP 23506-9. Colon: Achiote, KU 77215-78; Ciricito, CAS 71499-500, 71505-6. Darien: Rio Canclon at Rio Chucunaque, UMMZ 126733; Rio Chucunaque, near Yavisa, AMNH 51783. Panama: Cero La Campana, FMNH 67847-50.

+Colombia+: Choco: Andagoya, FMNH 81856; Boca de Raspadura, AMNH 13570-8.

+Hyla sartori+ Smith

_Hyla underwoodi_ (in part), Smith and Taylor, Bull. U. S. Natl.

Mus., 194:85, June 17, 1948.

_Hyla microcephala sartori_ Smith, Herpetologica, 7:186, December 31, 1951 [Holotype.--UIMNH 20934 from 1 mile north of Organos, south of El Treinte, Guerrero, Mexico; H. M. Smith and E. H. Taylor collectors]. Duellman, Univ. Kansas Publ., Mus. Nat.

Hist., 15:124, December 20, 1961. Porter, Herpetologica, 18:168, October 17, 1962. Davis and Dixon, Herpetologica, 20:230, January 25, 1965. Duellman, Univ. Kansas Publ. Mus. Nat. Hist., 15:652, December 30, 1965.

_Diagnosis._--Dorsum tan with broad dark brown chevrons or transverse bars; shanks marked with two or three broad transverse bars; dorsolateral stripes absent.

_Description and variation._--No noticeable geographic variation is apparent in either structural features or coloration in this species.

All specimens lack a dorsolateral dark stripe and white line, although a dark line is present on the canthus and dissipates in the loreal region. A broad interorbital brown bar is present in all specimens.

The color pattern on the dorsum invariably consists of a broad, dark, chevron-shaped mark in the scapular region and a broad dark chevron or transverse bar in the sacral region. The shanks invariably have two or three dark brown transverse bars.

When active at night individuals are yellowish tan above with chocolate brown markings (Pl. 14). The belly is white, and the thighs are pale yellowish tan. The iris is dark bronze-color. In breeding males the vocal sac is yellow. By day some individuals were observed to change to creamy gray with distinct darker markings.

_Remarks._--Although tadpoles of this species have not been found, observations on the breeding sites indicate that the tadpoles probably develop in ponds. Except for calling males observed around a pool in a stream-bed 11.8 kilometers west-northwest of Tierra Colorada, Guerrero, all breeding congregations have been found at temporary ponds.

Smith (1951:186) named _Hyla sartori_ as a subspecies of _Hyla microcephala_. This subspecific relations.h.i.+p seemed reasonable until a.n.a.lysis of the mating calls showed that the call of _H. sartori_ is more nearly like that of _H. phlebodes_ than that of _H. microcephala_.

The broad hiatus separating the ranges of _H. microcephala_ and _H.

sartori_ is additional evidence for considering _H. sartori_ as a distinct species.

[Ill.u.s.tration: Fig. 4. Map showing locality records for _Hyla sartori_.]

_Distribution._--_Hyla sartori_ occurs in mesophytic forests to elevations of about 300 meters on the Pacific slopes of southern Mexico from southwestern Jalisco to south-central Oaxaca (Fig. 4). The lack of specimens from Colima and Michoacan probably reflects inadequate collecting instead of the absence of the species there. On the basis of available habitat the species would be expected to occur in Nayarit, but extensive collecting there has failed to reveal its presence. The semi-arid Plains of Tehuantepec apparently limit the distribution to the east.

_Specimens examined._--190, as follows: +Mexico+: Guerrero: 5 km. E Acapulco, AMNH 54611-2; 23.2 km. N Acapulco, UIMNH 26404-7; Colonia Buenas Aires, 23 km. E Tecpan de Galeana, UMMZ 119223 (7); *El Limoncito, FMNH 75785, 100390-402, 104631, 104633, UMMZ 117250, USNM 134266; El Treinte, FMNH 100403, UIMNH 20935-7; Laguna Coyuca, AMNH 59686; La Venta, MCZ 29635; *Morjonares, UIMNH 26392-402; 1.6 km.

N Organos, FMNH 100404-5, UIMNH 20933-4; 19.2 km. S Petaquillas, UIMNH 26408; 6.1 km. E. Tecpan de Galeana, TNHC 23396-408; *11.2 km.

N Tierra Colorada, UIMNH 26403; 11.8 km. WNW Tierra Colorada, UMMZ 119225 (51), S-2677-9 (skeletons); Zacualpan, UMMZ 119224 (6). Jalisco: 6.4 km. NE La Resolana, KU 67853-69; 24 km NE La Resolana, KU 67870-3.

Oaxaca: 3 km. N Pochutla, KU 57539; 13.4 km. N Pochutla, UMMZ 123495 (40).

CRANIAL OSTEOLOGY

The frogs of the _Hyla microcephala_ group have a minimal amount of cranial ossification as compared to more generalized hylid skulls, such as _Smilisca_ (Duellman and Trueb, 1966). In the _Hyla microcephala_ group the sphenethmoid is small and short, and a large frontoparietal fontanelle is present. The quadratojugal exists only as a small spur and is not in contact with the maxillary. The prootics are poorly developed. The anterior and posterior arms of the squamosal are short; the anterior arm extends no more than one-fourth of the distance to the maxillary, and the posterior arm does not have a bony connection with the prootic. The nasal lacks a maxillary process, and the medial ramus of the pterygoid lacks a bony connection to the prootic.

Teeth are absent on the parasphenoid and palatines, but present on the maxillaries, premaxillaries, and prevomers. The teeth are simple, pointed, and slightly curved. Although the number of teeth varies (Table 3), no consistent differences between the species are apparent.

Table 3.--Variation in the Number of Teeth in the Species of the Hyla Microcephala Group. (N=Number of Jaws, or Twice the Number of Individuals; Means are Given in Parentheses After the Observed Ranges).

========================+====+=============+==============+========== Species | N | Maxillary | Premaxillary | Prevomer ------------------------+----+-------------+--------------+---------- _H. microcephala_ | 32 | 31-47(37.8) | 4-13(8.9) | 2-4(3.2) | | | | _H. phlebodes_ | 10 | 38-45(40.1) | 8-13(10.3) | 2-5(3.9) | | | | _H. robertmertensi_ | 6 | 23-43(32.8) | 7-12(10.5) | 2-3(2.7) | | | | _H. sartori_ | 6 | 27-43(38.2) | 9-10(9.3) | 3-4(3.7) ------------------------+----+-------------+--------------+----------

[Ill.u.s.tration: PLATE 13 Upper figure, _Hyla microcephala microcephala_ (KU 64593); middle figure, _H. microcephala underwoodi_ (KU 64565); lower figure, _H. microcephala underwoodi_ (UMMZ 115247).

All approximately 3.]

[Ill.u.s.tration: PLATE 14 Upper figure, _Hyla robertmertensi_ (UMMZ 115243); middle figure, _H. phlebodes_ (KU 64798); lower figure, _H. sartori_ (UMMZ 119225). All approximately 3.]

[Ill.u.s.tration: PLATE 15 Tadpoles of _Hyla microcephala_ group: upper figure, _H. m.

microcephala_ (KU 104097); lower figure, _H. phlebodes_ (KU 104099). Both 4.]

[Ill.u.s.tration: PLATE 16 Audiospectrograms and sections of mating calls of _Hyla microcephala_ group: (a) _H. m. microcephala_ (KU Tape No. 19); (b) _H. robertmertensi_ (KU Tape No. 41); (c) _H. phlebodes_ (KU Tape No. 6); (d) _H. sartori_ (KU Tape No. 190).]