94 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 253 paucity <strong>of</strong> the description and poor condition <strong>of</strong> the juvenile holotype, Microbatrachus pusillus cannot be identified with any known BODY FORM AND PROPORTIONS SEXUAL DIMORPHISM: Typically the sexes cannot be distinguished externally. The male subgular vocal sac is not evident except when the frog is calling. The only male external secondary sexual character, found in a some species <strong>of</strong> Austrochaperina, is a tendency for an elongation <strong>of</strong> the snout that is paler than the dorsal surface <strong>of</strong> the head. Females grow slightly larger than males. In 25 species the largest males average 90% <strong>of</strong> the SVL <strong>of</strong> the largest females, (range 81– 100%). In only one species with an adequate sample (i.e. Liophryne allisoni) are the largest male and female <strong>of</strong> equal size. HANDS AND FEET: Hands range in size from about 19% to 27% <strong>of</strong> SVL. Smaller hands appear to be associated with secretive or burrowing habits, whereas scansorial species are at the high end <strong>of</strong> the range. Relative sizes <strong>of</strong> feet in different species range more widely than do those <strong>of</strong> hands, from about 33% to 51% <strong>of</strong> SVL. As would be expected, the burrowing and litter-dwelling species fall at the lower end <strong>of</strong> the range, roughly 40% <strong>of</strong> SVL, whereas species known to be active on the forest floor have the relatively longest feet. The lengths, both relative and absolute, <strong>of</strong> the tibia and foot (and presumably other leg segments not measured) are typically similar, but some exceptions are notable. The relative finger lengths are the same in all species: 3 4 2 1. The first finger is typically long; only in Sphenophryne cornuta is it conspicuously reduced (fig. 52). The toe lengths <strong>of</strong> all species show no variation from the presumably primitive order 4 3 5 2 1, and most are webless. Only one species, Austrochaperina palmipes, has moderately webbed toes (fig. 56D), while one other, A. basipalmata, has basal webbing (fig. 56C). A slight trace <strong>of</strong> webbing appears in some A. derongo. The fingertips and toe tips may be narrow MORPHOLOGY genus and species, and that future taxonomic stability will be enhanced if the name is set aside as a nomen dubium. and rounded with no trace <strong>of</strong> expansion or <strong>of</strong> terminal grooves, or they may be broadened into adhesive organs up to more than twice the width <strong>of</strong> the penultimate phalanx and with a prominent terminal groove, or any degree in between (figs. 49, 51). Intermediate conditions include discs present on toes but not on fingers, but never the reverse, or discs on toes and longer fingers only. The adhesive pad cells <strong>of</strong> one species, Austrochaperina derongo (fig. 50), are perhaps more similar to the cuboidal cells <strong>of</strong> terrestrial Liophryne rhododactyla (Green and Simon, 1986: fig. 8) than to those <strong>of</strong> scansorial Cophixalus riparius (Green and Simon, 1986: fig. 9). Most species have discs on fingers and toes, typically with those <strong>of</strong> the toes being distinctly larger. For comparative purposes I use the discs on the third finger and fourth toe, which normally are the largest. Two species, S. cornuta and A. palmipes, have the largest finger discs. In S. cornuta the finger disc is markedly wider than the toe disc by about 1.2. The finger disc <strong>of</strong> A. palmipes is virtually the same size (relative to body size) as that <strong>of</strong> S. cornuta, but in contrast the toe disc is also large, usually almost equal to the finger disc. There is a clear correlation between the state <strong>of</strong> the digital tips and habits. The species with the largest discs (and most pronounced T-shaped terminal phalanges; see Osteology) are, so far as their habits are known, scansorial: S. cornuta climbs into shrubs or low into trees when active at night; A. basipalmata, A. palmipes, A. rivularis, and A. macrorhyncha are riparian forms with need for adaptation to traversing slick, sometimes steep rock surfaces. Those species with small to intermediate degrees <strong>of</strong> expansion are terrestrial, active on and within the leaf litter and in some cases doing limited climbing. The narrow, rounded tips seen in Oxydactyla alpestris and O. stenodactyla are associated with a burrowing mode <strong>of</strong> life. Most species have subarticular elevations
2000 ZWEIFEL: PARTITION OF <strong>SPHENOPHRYNE</strong> 95 Fig. 49. SEM photographs <strong>of</strong> tip <strong>of</strong> third finger <strong>of</strong> Oxydactyla stenodactyla AMNH A135289 in palmar (left) and end-on views. Scale line spans 400 m. Fig. 50. SEM photographs <strong>of</strong> lower surface <strong>of</strong> disc <strong>of</strong> third finger <strong>of</strong> Austrochaperina derongo AMNH A145507. Left scale line spans 20 m, right 4 m.
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