"Determining the higher level relationships of the modern amphibian order Gymnophiona (caecilians) poses a number of methodological problems. A cladistic methodology is outlined by which the phylogenetic relationships of this group can be determined objectively. Among the possible sister groups analyzed, which include dissorophid temnospondyls, aistopods, nectrideans, lysorophoids, microsaurs, anurans and urodeles, the microsaurs of the families Gymnarthridae and Goniorhynchidae are the most plausible sister group of caecilians, based on cranial osteology. Hence, the three modern orders of amphibians, caecilians, anurans and urodeles, do not constitute a monophyletic assemblage exclusive of all other groups. Ingroup analysis indicates that the Ichthyophiidae is the most primitive living caecilian family. The cladistic analysis suggests that features of the unique jaw apparatus define two groups of caecilians which diverged, phylogenetically, early in the group's history. Morphometric analysis reveals that elements of the jaw apparatus compose a functional suite of features. Aspects of the development, function, and significance of the jaw to miniaturization of the caecilian skull are inferred from the morphometric analysis."--

One of the little known species in the danger of extinction, gymophionan amphibians, are also known as caecilians or apoda. Gymnophiona contains 154 species belonging to 34 genera and 6 families. For many years, studies on the Gymnophiona were disparate and still only a few species have been deeply studied. Fortunately, in recent years, some new wo

This book appears at a time when molecular cytogenetics is positioned to make a significant impact upon evolutionary studies, enabling problems of chromosomal structure and change to be critically assessed. It is an up-to-date and comprehensive survey of the cytogenetics of a major class of animals, including all three amphibian orders, with chapters authored by international leaders in the field.Amphibian Cytogenetics and Evolution will be of interest to classical and molecular cytogeneticists, systematicists, evolutionary biologists, herpetologists, and anyone using amphibians in genetic research. Offers the only current and comprehensive survey of amphibian cytogenetics Gives authoritative and in-depth coverage of topics of present interest Reviews general cytogenetic topics Presents new insights into evolutionary changes in chromosome structure and amphibian phylogeny and relationships including: Phylogenetic analysis of chromosome data, Current techniques of cytogenetic analysis, Examination of all three amphibian orders

Caecilians, or Gymnophiona, constitute one of the three extant orders of the Recent Amphibia and comprise about 170 named species in six families. They are the least known, major living tetrapod clade. Compared to frogs and salamanders, caecilians have an unusual skull morphology. With few exceptions, previous studies on caecilian morphology have been restricted to investigations on adult material and were usually carried out on small samples. This thesis investigates skull development in caecilians. Earlier reports of an unusually high number of individual skull ossifications in Hypogeophis rostratus are addressed and found to be erroneous. Changes in skull morphology and myology at metamorphoses are investigated in representatives of all taxa possessing free-living larvae. It is argued that caecilians are derived from gymno- or zygokrotaphic ancestors and that stegokrotaphy evolved within Recent caecilians. To investigate the influence of different life-histories, postembryonic skull development was studied in two direct-developing species. The direct-developing Boulengerula taitanus is characterized by very immature hatchlings, which is correlated with an extended period of post-hatching parental care in this species, during which juveniles feed on the modified stratum corneum of their mothers. Direct development in caecilians is characterized by ontogenetic repatterning and heterochronic shifts in certain developmental events. The ontogeny of Scolecomorphus kirkii was studied as a representative of a viviparous form. The emerging picture of available published information, together with observations presented here, suggest a previously unsuspected degree of developmental diversity among caecilians. It is further argued that caecilians are lissamphibians with temnospondyl affinities rather than closely related to lepospondyl microsaurs.