SPHENOPHRYNE - American Museum of Natural History

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122 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 253 guttata recorded about an hour apart have notes with somewhat different structure. In one, 30 notes have pulses of essentially uniform length (fig. 80B). Among 30 notes of the second call, 16 have the terminal pulse abruptly longer (fig. 79C), 3 resemble notes in the first call, and 11 show a more gradual increase in pulse length. One call of A. rivularis has two sorts of pulse structure: 27 of 40 notes have the initial pulse much the longest (figs. 79B, 80C), whereas in 13 notes the pulses are more nearly equal in length. In a single call of A. derongo the notes (14 of 16) start with short pulses, then change to distinctly longer ones (fig. 80A); in only two notes are the pulses about equal in length. The notes of A. macrorhyncha begin with a short pulse and, after a brief pause, continue with longer, tightly spaced pulses. Variation in pulsation in these and other species deserves attention when more recordings are available. INTERGENERIC AND INTRAGENERIC RELATIONSHIPS Burton (1986) put forth a solid argument for monophyly of the Asterophryinae, but (p. 443) stated that ‘‘The monophyly of the Genyophryninae has not been demonstrated. Nor has its paraphyly.’’ Phylogenetic analysis of the subfamilies of Microhylidae that might affirm the status of the Genyophryninae has not been accomplished. However, the close relationship of the Genyophryninae and Asterophryinae is strongly supported by a shared derived character—direct embryonic development. This reproductive mode is indicated in all species of the two subfamilies for which adult female specimens are available. Not only is the presence of large, unpigmented, heavily yolked ova in specimens sufficient evidence, but no tadpole of the characteristic microhylid sort has been found in New Guinea. Some compression of the life-cycle is seen occasionally in other subfamilies of Microhylidae (e.g., nonfeeding tadpoles), but direct development is uncommon elsewhere in the Microhylidae. I am aware of only one example, the South American microhyline Myersiella microps (Izecksohn and Jim, 1971). In view of the independent attainment of direct development in several other families of Anura and the lack of any other apparent apomorphies linking this South American form with the Australopapuan genera, I consider the similarity an instance of homoplasy. Whereas the Genyophryninae and Asterophryinae may be considered as closest relatives, with the Asterophryinae the more derived, I have no evidence to indicate where the nearest relationship between the Geny- ophryninae and non-asterophryine microhylids may lie. Direct development in the genera Austrochaperina, Liophryne, Oxydactyla, and Sphenophryne (as well as in the Asterophryinae) is a derived character with respect to the situation in the vast majority of microhylids, but the four genera are more primitive in other respects. This is most evident in the pectoral girdle, which in all has a nearly complete complement of ventral elements, lacking only the omosternum. A complete girdle, including the omosternum (cartilaginous in all but Dyscophus of Madagascar, small or vestigial in some), is present in several genera, mostly of Madagascar, but with southern India (Melanobatrachus), Africa (Parhoplophryne), and South America (Otophryne) also represented. A girdle with the single apomorphy of loss of the omosternum is also geographically widespread, including (in addition to the Australopapuan genera treated here) southeast Asia (Chaperina), North and Central America (Hypopachus), and South America (Dermatonotus and Stereocyclops). Most of the Madagascar microhylids possess well-developed maxillary and vomerine teeth, certainly a primitive character. Vestigial(?) teeth or toothlike structures occur sporadically in the four Australopapuan genera, but not regularly enough to establish any one genus as more primitive. As an aside, I note that the dentition, pectoral girdle structure, and lack of pharyngeal folds in many microhylids of Madagascar marks this fauna as the most primitive of the Microhylidae. The monotypic Sphenophryne is the most
2000 ZWEIFEL: PARTITION OF SPHENOPHRYNE 123 derived form in the four genera, with its reduced first finger, enlarged digital discs, broad sacral diapophyses, and short braincase. None of the more advanced genyophrynine genera is likely to be directly related to Sphenophryne. Liophryne too does not appear to relate well to other genyophrynines. The long legs, large eyes, and subarticular elevations of these mostly surface-active species are not found in other genyophrynines, although the less typical L. allisoni could be a link with Austrochaperina. Oxydactyla, adapted for living cryptically in leaf litter or grass tussocks, could be derived by way of terrestrial Austrochaperina, with A. brevipes being perhaps closest morphologically to Oxydactyla. Given the specializations of the other three genera, Austrochaperina, apart from those species with adaptations for semiaquatic life, is the most generalized and perhaps the most primitive of the genyophrynine genera. I find, however, no satisfactory way of relating Austrochaperina to microhylids outside of the Australopapuan region. Such an investigation is well beyond the scope of this work. Note, however, similarities between certain Austrochaperina and another genyophrynine genus, Copiula (see following). RELATIONSHIPS WITHIN AUSTROCHAPERINA The 23 species of Austrochaperina may be arranged by body size in two groups. One, composed of relatively small frogs (maximum adult size range 21–35 mm SVL), includes the New Guinean species adamantina, aquilonia, blumi, brevipes, gracilipes, kosarek, mehelyi, novaebritanniae, parkeri, polysticta, and yelaensis, as well as the four Australian endemics, two of which are the largest species in the group. The eight species of the other group are larger (38–52 mm)—archboldi, basipalmata, derongo, guttata, hooglandi, macrorhyncha, palmipes, and rivularis. I shall refer informally to the first group as the Small group, and to the others as the Large group. Three of the five Australian members of the Small group dwell in rainforest leaf litter. The sibling species A. adelphe (Australian) and A. gracilipes (common to Australia and New Guinea) are apparent exceptions, living in seasonally dry environments and sometimes calling from sites slightly above the substratum. Only two of the New Guinean species, brevipes and novaebritanniae, are confirmed as leaf-litter inhabitants, but the morphology of the others suggests that habit. An attempt to infer relationships within the Small group is frustrated by paucity of material—four of the New Guinean species are known from only one specimen each, another from two, and the unique specimen of another was destroyed. Second, the leaf-litter habitat preference evokes no distinctive adaptations such as the long hind legs, large eyes, and subarticular elevations of surfaceactive Liophryne, the enlarged finger discs of scansorial Sphenophryne, the short hind legs and pointed toe-tips of burrowing Oxydactyla, or the large digital discs and toe-webbing of riparian Austrochaperina. The Small group is essentially what remains when the slightly better characterized Large group is removed. The Australian species (including gracilipes) have some claim to monophyletic distinction within the Small group. They are the only Austrochaperina with unpulsed, multinote advertisement calls (Zweifel, 1985b, but the calls of many New Guinean species of both groups are yet unknown), and Mahony et al. (1992) cited karyological evidence for monophyly. No New Guinean endemics of the Small group have been karyotyped, while all five Australian species have the presumably primitive 2N 26. Two of the Australian species, at maximum sizes of 33 and 35 mm SVL, are the largest species of the Small group; the largest New Guinean species attains 31 mm. Five of the eight Large group species are riparian along small watercourses, a habitat preference unknown among other Australopapuan microhylids. A. palmipes and A. basipalmata have toe webbing (slight in the latter). These, together with A. macrorhyncha and A. rivularis, have relatively large finger and toe discs; in palmipes the finger discs may be broader than those of the toes, a condition not seen elsewhere in Austrochaperina (table 3). I consider this disc development as an adaptation to wet, slippery, rocky riparian conditions. A. derongo, with relatively small-
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SPHENOPHRYNE - American Museum of Natural History

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