SPHENOPHRYNE - American Museum of Natural History

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108 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 253 Fig. 65. Outline drawings of left vomers of Oxydactyla, Liophryne, Austrochaperina, and Sphenophryne in ventral aspect; scale lines marked in mm. Curved line at right of each figure marks the lingual border of the maxillary shelf. A. O. stenodactyla, AMNH A92800. B. O. alpestris, AMNH A65299. C. O. coggeri, AMS R22822. D. A. brevipes, AMNH A130527. E. L. allisoni, BPBM 9631. F. L. rhododactyla, BPBM 9793. G. L. dentata, UPNG 2641. H. L. schlaginhaufeni, AMNH A78183. I. A. gracilipes, AMNH A90407. J. A. novaebritanniae, AMNH A88569. K. A. blumi, UPNG 9559. L. A. derongo, AMNH A145507. M. A. basipalmata, AMNH A129495. N. A. rivularis, AMNH A84445. O. A. palmipes, AMNH A92805. P. S. cornuta, AMNH A92803. of a New Guinean species, Aphantophryne sabini, and hinted at (by denser stippling) in another, Cophixalus verecundus, but was not discussed (Zweifel and Parker, 1989: fig. 5). In his study of the Microhylidae, Parker (1934) did not deal with the hyoid, but only referred to Trewavas’ monograph, which was in press at the time of his writing. A coathooklike process is present in all the species I examined for this study, although it earlier eluded me (not shown in Zweifel, 1985b: figs. 50A–D). It nestles in the space between the proximal ends of the posteromedial processes, whose ends appear to have slight socketlike concavities. In most specimens it is clear and takes up little cartilage stain so that stained cartilage dorsal to it shows through and commonly has been illustrated as a flat plane of cartilage. In specimens stained only for bone, the process is even more easily overlooked. However, occasionally it is heavily mineralized, and then it is conspicuous in alizarin-stained specimens. This is especially true of my specimen
2000 ZWEIFEL: PARTITION OF SPHENOPHRYNE 109 Fig. 66. Dorsal (upper) and ventral views of skull of Sphenophryne cornuta, AMNH A92804; scale bar measures 5 mm. of Liophryne allisoni (fig. 70). Although ventromedial thickening of the hyoid and the protruding process evidently are not pertinent at the level of specific and generic inquiry here, this morphology may prove to be an apomorphic state for the Microhylidae. APPENDAGES TERMINAL PHALANGES: The tips of the bones may bear T-shaped expansions whose span is more than twice the width of the base of the bone, or at the other extreme the tip may be bluntly rounded with only a slight subterminal constriction, its width less than that of the base. The relative breadths of the fleshy terminal disc and that of the phalangeal ‘‘T’’ are closely correlated. The terminal discs are discussed further under Body Form and Proportions. The terminal phalanx of the third finger, which generally shows the greatest expansion of any of the hand’s digits, illustrates the range of variation (fig. 71). Among specimens of 20 species (one examined by dissection), the span of the tip relative to the length of the phalanx or to the width of its base falls into one of three discrete groups: (1) tip span/length of 0.24 and 0.32 in Oxydactyla alpestris and O. stenodactyla (species with narrow, discless fingers); (2) of 0.54–0.82 in 13 species known or suspected to be litter-dwelling or surface active species; and (3) of 1.09–1.36 in five species of scansorial (Sphenophryne cornuta), riparian (Austrochaperina palmipes, A. rivularis, A. derongo, and A. basipalmata) habits. AXIAL SKELETON PRESACRAL VERTEBRAE: There are invariably eight nonimbricate presacrals, as described for the Australian species (Zweifel, 1985b: 355). Variations in the transverse processes include relative lengths and angular orientation among vertebrae. For example, I find relatively long processes on vertebrae 2– 4 and a strong anterior orientation to those on vertebrae 7 and 8 in Austrochaperina derongo, A. rivularis, A. pluvialis, and A. palmipes, whereas in Oxydactyla stenodactyla the processes are more similar in length and more nearly at a right angle to the column. Morphologies of the other species do not indicate that a classification of discrete types is possible. SACRAL VERTEBRAE: The sacral vertebrae are slightly to moderately expanded in most species discussed here, more so in one or two (figs. 72, 73). As an index of expansion I use the ratio of broadest diapophyseal measurement (anterior–posterior) to the span between ends of left and right diapophyses, excluding terminal cartilaginous extensions; a larger number implies broader diapophyses. Among 37 specimens of 19 species, including three Australian endemics, this ratio
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SPHENOPHRYNE - American Museum of Natural History

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