Part 14

Table 5.--Variation in the Number of Teeth in the Species of Smilisca. (All Are Males; N = Number of Jaws, or Twice the Number of Individuals; Means Are Given in Parentheses After the Observed Ranges.)

=================+====+==============+==============+=========== Species | N | Maxillary | Premaxillary | Vomerine -----------------+----+--------------+--------------+----------- S. baudini | 20 | 49-65 (56.0) | 9-16 (13.6) | 5-9 (7.2) S. cyanosticta | 8 | 50-64 (57.9) | 10-12 (10.8) | 4-11 (7.1) S. phaeota | 20 | 50-68 (58.1) | 10-15 (12.1) | 5-9 (7.3) S. puma | 6 | 60-67 (63.6) | 11-13 (12.0) | 4-7 (5.3) S. sila | 8 | 48-60 (52.9) | 10-14 (11.3) | 5-7 (5.7) S. sordida | 12 | 39-55 (44.2) | 7-11 (9.3) | 4-6 (5.2) -----------------+----+--------------+--------------+-----------

The teeth of all species of Smilisca are spatulate and bifid. The numbers of maxillary, premaxillary, and vomerine teeth are summarized in Table 5. Smaller and presumably younger specimens of all species of Smilisca have fewer teeth than do larger specimens of the same species. This correlation between size and number of teeth does not exist as an interspecific trend within the genus; for example, the smallest species in the genus, S. puma, has the highest number of maxillary teeth. In small specimens of a given species wide gaps are present between the maxillary teeth posteriorly; in large specimens the gaps are filled by teeth, beginning anteriorly and progressing posteriorly, until the maxillary dentition is continuous.

Musculature

No extensive study of the muscular system was undertaken, but certain muscles know to be of taxonomic importance were studied.

Jaw Musculature.--Starrett (1960) pointed out the unique jaw musculature in Smilisca. In this genus M. depressor mandibulae consists of two parts, one arising from the dorsal fascia and one from the posterior arm of the squamosal. Two muscles arise from the anterior arm of the squamosal and insert on the lateral face of the mandible. Of these muscles, M. adductor mandibulae posterior subexternus lies medial to the mandibular branch of the trigeminal nerve; the other, M. adductor mandibulae externus superficialis, lies lateral to the same nerve (Fig. 9). In most other hylids the latter muscle is absent. No significant variation in the position of the muscles was noted in the various species of Smilisca, though M. adductor mandibulae originate somewhat more anteriorly in S. baudini and S. cyanosticta than in the other members of the genus, all of which have a shorter anterior arm of the squamosal that does not reach the maxillary. The two separate parts of M. depressor mandibulae are not so widely separated in members of the sordida group as in the baudini group.

Throat Musculature.--The frogs that comprise the genus Smilisca are characterized by paired subgular vocal sacs, essentially the same as those in Triprion (Duellman and Klaas, 1964). The following description is based on Smilisca baudini (Fig. 10).

M. submentalis lies in the anterior angle of the lower jaw, is thick, and consists of transverse fibers extending between the dentaries. M. submaxillaris is thin and arises from the whole of the inner surface of the lower jaw, except for the anterior angle occupied by M. submentalis. Anteriorly M. submaxillaris is broadly attached by fascia to M. hyoglossus and M. geniohyoideus, which lie dorsal to M. submaxillaris. Medially this attachment continues posteriorly for about one-half the length of the hyoglossus. Posteriorly M. submaxillaris is folded and attached to M. sternoradialis of the pectoral girdle. The vocal sacs are formed by a pair of posterolateral evaginations of M. submaxillaris; a broad connection between the pouches allows free passage of air between the pouches.

The deeper throat musculature is essentially the same as that described for Phrynohyas spilomma by Duellman (1956), except for slight differences in the place of attachment on the hyoid.

Skin

Structure

The skin of Smilisca is typical of that of most hylids in organization and structure. Smilisca sila is distinguished from other members of the genus by the presence of small wartlike protrusions and peculiar white, pustular spots on the dorsum. The wartlike structures are composed of three or four epidermal cells, which protrude from the surface of the epidermis; the structures are covered by a slightly thickened layer of keratin. The white pustules are slightly elevated above the surrounding skin. Internally they consist of aggregations of swollen, granular, pigment-cells (perhaps lipophores) lying between the epidermis and the melanophores.

Biochemical Variations

Dried skins of all species of Smilisca were sent to Jose M. Cei, Instituto Nacional de Cuyo, Mendoza, Argentina, for biochemical screening by means of the chromatographic techniques described by Erspamer and Cei (1963). The species in the baudini group have detectable amounts of penta-hydroxi-trypatamine, whereas only a trace is present in the other species. Furthermore, species in the baudini group differ from S. sila and the sordida group in lacking, or having only a trace of, tryptophan-containing polypeptides. These superficial biochemical tests support the arrangement of species as ascertained by conventional taxonomic characters.

External Morphological Characters

The features of external morphology that were studied in connection with the taxonomy of the genus Smilisca are discussed below.

Size and Proportions

The frogs of the genus Smilisca_ are medium to large tree frogs. The three species comprising the baudini group (S. baudini, cyanosticta, and phaeota) are notably larger than S. puma, sila, and sordida (Table 6). The largest specimen that we examined is a female of S. baudini having a snout-vent length of 90 mm. Smilisca puma_ is the smallest species; the largest male has a snout-vent length of 38 mm. and the largest female, 46 mm.

Table 6.--Comparison of Sizes and Certain Proportions of the Species of Smilisca. (Means in Parentheses Below Observed Ranges; Data for Males Only.)

================+====+===========+=============+===========+ | | Snout-vent|Tibia length/| Tympanum/ | Species | N | length | snout-vent | eye | ----------------+----+-----------+-------------+-----------+ | | | | | S. baudini |140 | 47.3-75.9 | 42.1-53.6 | 56.1-94.4 | | | (58.7) | (47.8) | (73.5) | | | | | | S. cyanosticta| 40 | 44.6-56.8 | 51.9-59.7 | 62.7-88.4 | | | (50.7) | (56.0) | (71.4) | | | | | | S. phaeota | 50 | 40.8-65.5 | 50.9-60.2 | 62.7-85.5 | | | (53.9) | (55.5) | (76.6) | | | | | | S. puma | 20 | 31.9-38.1 | 48.2-53.1 | 52.1-72.2 | | | (34.7) | (51.3) | (64.9) | | | | | | S. sila | 33 | 31.6-44.8 | 49.7-58.1 | 47.6-58.3 | | | (37.7) | (54.8) | (53.2) | | | | | | S. sordida | 55 | 31.9-44.6 | 50.5-57.1 | 46.5-57.1 | | | (37.9) | (53.4) | (49.1) | ----------------+----+-----------+-------------+-----------+

No outstanding differences in proportions exist between species, although certain proportions are sufficiently different in some species to warrant mention. Smilisca baudini is a more squat and stocky frog than other members of the genus; this is reflected in the somewhat shorter hind legs (Table 6). The size of the tympanum relative to that of the eye is highly variable within samples of a given species. Even so, noticeable differences in the tympanum/eye ratio are apparent. Members of the baudini group have the largest tympani, whereas S. sila and sordida have the smallest, and S. puma is intermediate (Table 6).

Shape of Snout

Although all members of the genus have rather truncate snouts, subtle differences exist among the species (Pl. 12). Smilisca sila has the shortest snout; that of S. baudini is only slightly longer. The snouts of S. cyanosticta and puma are nearly square in lateral profile, whereas those of S. phaeota and sordida are slightly inclined. The shape of the snout is relatively uniform within each species and displays no noticeable sexual dimorphism, except in S. sordida, in which there are sexual differences and geographic variation (see p. 324).

Hands and Feet

The characters of the hands and feet are among the most taxonomically important external features in Smilisca. Consistent differences exist in relative lengths of the digits, size of subarticular tubercles, size and number of supernumerary tubercles, size and shape of the inner metatarsal tubercle, and amount of webbing (Pls. 4 and 5). In the baudini group the series of species (baudini-phaeota-cyanosticta) show a progressive increase in amount of webbing in the hand and a decrease in number, and corresponding increase in size, of supernumerary tubercles. The amount of webbing in the feet of S. baudini and phaeota is about the same, but the webbing is slightly more extensive in S. cyanosticta. Smilisca puma is unique in the genus in lacking webbing in the hand; furthermore, this species is distinctive in having many large subarticular tubercles on the hand and a relatively small inner metatarsal tubercle. The two stream-inhabitants, S. sila and sordida, have shorter and stouter fingers than the other species. The webbing is most extensive in both the hands and feet of these species, which also are distinctive in having many small supernumerary tubercles on the feet.

Ontogenetic Changes

Minor ontogenetic changes in structure involve the shape of the snout, relative size of the eye, development of the tympanum, and amount of webbing in the hand. In recently metamorphosed young the snout is more rounded than in adults; the canthus and loreal concavity are not evident. Usually the tympanum is not differentiated in recently metamorphosed young, and the eye is proportionately large. The webbing in the feet is completely developed at metamorphosis, but young individuals have noticeably less webbing in the hand than do adults of the same species.

Coloration