SPHENOPHRYNE - American Museum of Natural History

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106 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 253 Fig. 63. Left premaxillae of Oxydactyla, Austrochaperina, and Liophryne in ventral view. Scale lines represent 1 mm unless otherwise indicated. A. O. stenodactyla, AMNH A92800. B. O. alpestris, AMNH A65299. C. O. coggeri, AMNH A140874. D. A. brevipes, AMNH A130527. E. L. allisoni, BPBM 9631. F. L. rhododactyla, BPBM 9793 (scale 2 mm). G. S. dentata, UPNG 2641. H. L. schlaginhaufeni, AMNH A78183. L. schlaginhaufeni), such similarities should not be given too much emphasis. However, note that variation among species and genera in degree of lateral expansion is greater than Burton (1986: 425) had recognized in the Genyophryninae. SQUAMOSAL: The zygomatic ramus of the squamosal varies relatively little in length, being longest in Oxydactyla alpestris and O. stenodactyla and somewhat shorter in most other species, especially Sphenophryne cornuta (figs. 66–68). The extent of the otic ramus is more variable. It may be so short as to be scarcely evident, or an elongate arm extending medially almost as far as the medial end of the columella, or some stage in between. Two small species, Austrochaperina gracilipes (Zweifel, 1985b: fig. 45) and A. novaebritanniae, show minimal development, whereas maximum elongation occurs in both a relatively small species (A. brevipes, fig. 67C) and several larger ones: A. palmipes, L. dentata, L. rhododactyla (fig. 68B), and L. schlaginhaufeni. The remaining species for which material is available show intermediate stages not readily quantified: A. basipalmata, A. blumi, A. derongo, A. fryi, A. pluvialis, A. rivularis (fig. 68A), A. robusta (short, Zweifel, 1985b: fig. 45), L. allisoni (relatively long, fig. 68C), O. alpestris (rather short), O. coggeri (fig. 67B), O. stenodactyla (short, fig. 67A), and S. cornuta (fig. 66). HYOID APPARATUS: If the variation seen in hyoids of the species studied has any systematic significance, elucidation of this must await availability of a suite of specimens that will make both individual and specific variation better known. However, there may be implications on a higher systematic level. None of the specimens examined has a parahyoid bone, which, so far as is known, is unique in the Microhylidae to the monotypic South American genus Adelastes (Zweifel, 1986: fig. 4). Some mineralization of the cartilaginous hyoid plate is present in
2000 ZWEIFEL: PARTITION OF SPHENOPHRYNE 107 Fig. 64. Left premaxillae of Austrochaperina and Sphenophryne in ventral view. Scale lines indicate 1 mm unless otherwise stated. A. A. gracilipes, AMNH A90407 (scale 0.5 mm). B. A. novaebritanniae, AMNH A88569 (scale 0.5 mm). C. A. blumi, UPNG 9559. D. S. cornuta, AMNH A92804. E. A. basipalmata, AMNH A129495. F. A. rivularis, AMNH A88445. G. A. palmipes, AMNH A92807. H. A. derongo, AMNH A145507. most species examined here, but the degree is variable. To some extent this variation may be specific: six specimens of Austrochaperina derongo all show mineralization, whereas among four Oxydactyla stenodactyla that can be scored, three lack mineralization and one has slight mineralization. There is conspicuous variation in the anterolateral and posterolateral processes of the hyoid plate. The former may be absent (fig. 69C) to very well developed (Zweifel, 1985b: fig. 50E) or some intermediate form (figs. 69A, B; Zweifel, 1985:, figs. 50A–D). The posterolateral processes are less variable (see figures cited). I direct attention to an anatomical feature of the microhylid hyoid that has been largely ignored in the literature. Trewavas (1933: 519) described ‘‘a median ventral thickening of the cartilage between the origins of the postero-medial processes, and often a midventral ridge in front of this’’ in species of Dyscophinae, Genyophryninae, Microhylinae, and Scaphiophryninae. She referred to those species possessing this morphology as the ‘‘Gastrophryne-group’’ and stated that in this and some other respects they ‘‘contrast sharply with other firmisternal families.’’ The feature was found lacking in Breviceps and Hemisus. These last two genera have been variously considered as microhylids or Hemisus has been referred to its own family. Most recently, Blommers-Schlösser (1993) has removed the Brevicipitinae from the Microhylidae and placed it with the Hemisotinae in the Hemisotidae. One worker to take notice of this feature was Roux (1944, fig. 9), who described and illustrated a ‘‘ventro-median anteriorly directed process . . . . between the origins of the thyroid processes [bony posteromedial processes of Duellman and Trueb, 1986]’’ of Gastrophryne carolinensis. DeSáand Trueb (1991: 316, fig. 2) illustrated the hyoid of a South American microhyline, Hamptophryne boliviana, and described this structure as a ‘‘small bony projection.’’ What appears to be the same process is shown in an illustration
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SPHENOPHRYNE - American Museum of Natural History

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