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Summary

  • 1
    Apart from their elongation, the skulls of pygopods are gecko-like in general form and in the elements present. Cranial morphology supports the views of gecko-pygopod affinities which have been expressed by McDowell & Bogert (1954) and Underwood (1957).
  • 2
    Of the various pygopod genera, the skull of Pygopus is the least modified, while that of Delma is very similar to it.
  • 3
    The most extreme elongation of the pre-optic and post-optic regions of the skull occurs in Lialis. In Aprasia, differential elongation of dorsal and ventral regions of the skull anteriorly results in the mouth being ventral instead of terminal.
  • 4
    Pletholax is the only known genus amongst pygopods and Australian geckos in which the frontals are not fused, and is further characterized by the fact that certain bones of the head overlap.
  • 5
    Lialis is unique among pygopods in lacking a jugal.
  • 6
    Aprasia invariably lacks maxillary teeth. Furthermore, premaxillary teeth are lacking in juveniles of this genus, and also in adult females except those of A. striolata.
  • 7
    As in Australian geckos, only a single splinter-like temporal bone may be recognized between the parietal and quadrate.
  • 8
    The hyobranchial apparatus is extremely gecko-like in form.
  • 9
    The reduced, U-shaped pectoral girdle of Aprasia is re-interpreted. It is suggested that the elements present are the two cartilaginous suprascapulae, the two bony clavicles, and a median piece representing the clavicular symphysis.
  • 10
    The pectoral girdle of Pletholax gracilis is unique amongst known pygopods and Australian geckos in the presence of a bony interclavicle.
  • 11
    The three elements of the pelvic girdle, namely the pubis, ischium and ilium, are invariably present. However, different pygopod genera show various stages of hind limb reduction, from Pygopus in which even four digits of the foot are present, to Aprasia, in which only one bone, the femur, is present in the hind limb rudiment.
  • 12
    The morphological distinctiveness of various pygopod genera is discussed in terms of heterochrony. Differences between adult species and genera, though genetically based, are subsequently related to the time of embryonic appearance of certain structures as compared with neighbouring structures, and to their varying rates of development.