Fig. 10. Ventral view of throat musculature in an adult male Smilisca baudini (Superficial musculature on left, deep musculature on right); A. C. anterior cornua of hyoid; Gen. L., geniohyoideus lateralis; Gen. M., geniohyoideus medialis; Hyo., hyoglossus; Omo., omosternum; Pet., petrohyoideus; S., submentalis; Sm., submaxillaris; St., sternohyoideus; V. S., vocal sac. KU 64220, × 2.5.
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.
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.
Dried skins of all species of Smilisca were sent to José 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.