SPHENOPHRYNE - American Museum of Natural History

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96 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 253 Fig. 51. SEM photographs of tip of third finger of Austrochaperina palmipes AMNH A60178 in palmar (left) and end-on views. Scale line spans 800 m. that are low, rounded, and inconspicuous, sometimes virtually absent, with none deserving the common appellation ‘‘subarticular tubercle.’’ This group include scansorial, litter-dwelling, and burrowing forms. The six species of Liophryne have subarticular ele- Fig. 52. Lower surfaces of foot and hand of Sphenophryne cornuta, AMNH A130546. Scale bar marked in 1-mm intervals. vations of a more angular, protruding nature (fig. 54A–E; similis identical to rhododactyla). Elevations on the palms and soles are inconspicuous in all species. The inner metatarsal elevation is usually elongate and rounded, and there is no outer metatarsal elevation. None of the Australopapuan microhylids possesses a prominent, compressed outer metatarsal tubercle such as is seen in some genera of microhylids in all other parts of the world inhabited by the family. Presumably the scant development of the tubercle is related to head-first as opposed to feet-first burrowing (Menzies and Tyler, 1977). PHARYNGEAL FOLDS: The presence of one to (rarely) three smooth, lobate or serrate transverse folds or ridges across the palate just anterior to the pharynx is common to most genera and species of microhylids and is ‘‘almost diagnostic of the group’’ Parker (1934: 6). The exceptions that lack folds are three genera of the Melanobatrachinae (of Madagascar, Parker, 1934) and four genera of Cophylinae (also of Madagascar, where two genera have folds; Parker, 1934). This feature remains undescribed for three cophyline genera of Madagascar. Given the frequency of lack of folds in microhylids of Madagascar, it is curious that the only literature reference to lack of folds in a species of microhylid
2000 ZWEIFEL: PARTITION OF SPHENOPHRYNE 97 Fig. 53. Lower surfaces of feet and hands of Oxydactyla and Austrochaperina. A. O. stenodactyla, AMNH A66046. B. O. alpestris, AMNH A76584. C. O. brevicrus, AMNH A43761. D. O. coggeri, AMNH A140871. E. O. crassa, AMNH A57424. F. A. kosarek, MZB 3561. Scale bars marked in 1mm intervals. elsewhere is for the North American Gastrophryne carolinensis, for which Roux (1944: 12) stated that folds ‘‘are entirely absent.’’ Parker included Gastrophryne within Microhyla, which he characterized as having folds. A specimen of G. carolinensis that I examined has a short fold that does not protrude and could easily be overlooked. A specimen of the presumably related Hypopachus variolosus has a single protruding, smooth fold. As the genyophrynine frogs possess pharyngeal folds and thus conform to the mode for the Microhylidae, I see no utility for the folds at the systematic level of the present work. However, as the structures have not been illustrated in detail, I present SEM photographs (figs. 58, 59) of those of Liophryne rhododactyla, which species is typical of many species in having a smooth anterior fold and a longer, denticulate posterior one. The denticulate structures are not, as might be supposed, soft and flexible, but are quite firm. As they point posteriorly, they could serve to interfere with movement out of the mouth by soft-bodied prey such as earthworms. However, the role of a lesser, smooth fold is not subject to such facile explanation. EYES: All species that I have seen in life and, insofar as can be told from preserved specimens, all Australopapuan microhylids have pupils with horizontal orientation when contracted. Relative eye size among the species studied here ranges in mean EY/SVL from 0.092 to 0.141. There is a tendency for small eyes to be associated with cryptic habits (e.g., O. stenodactyla, mean 0.093) and large eyes with surface activity (L. dentata, 0.141), but the correlation is not strong. EARS: The ears of some of the species studied are of moderate size with the annulus externally well defined and with the covering skin smooth and distinct from the surround-
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SPHENOPHRYNE - American Museum of Natural History

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