No description available.

No description available.

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.

Thesis (Ph. D.)--University of Chicago, 1908. / "Reprinted from the Journal of geology, vol. XVII, no. 1, Jan.-Feb., 1909." Includes bibliographical references.

The importance of fossils to phylogenetic reconstruction is well established. However, analyses of fossil data sets are confounded by problems related to the incomplete nature of the specimens. Taxa that are incompletely known are problematic because of the uncertainty of their placement within a tree, leading to a proliferation of most parsimonious solutions because of wild card behavior. Problematic taxa are commonly deleted based on a priori criteria of completeness. Paradoxically, a taxon's problematic behavior is tree dependent, and levels of completeness are not necessarily associated with problematic behavior. Exclusion of taxa based on completeness eliminates real character conflict and, by not allowing incomplete taxa to determine tree topology, the phylogenetic hypothesis is diminished. / A method is proposed to allow optimization of taxonomic inclusion and tree stability. It identifies and removes taxa causing multiple most parsimonious solutions, producing a more stable topology, called the phylogenetic trunk. This method is used in an analysis of the Paleozoic Lepospondyli. A single most parsimonious tree, or trunk, was found after removal of one taxon identified as being problematic. The 38 trees found one additional step from this primary trunk are reduced to two by removal of one additional taxon. These trunks are compared to the trees found by excluding taxa with various degrees of completeness. Effects of incomplete taxa are explored by comparison with the stable tree. Correlated characters associated with limblessness are discussed regarding the assumption of character independence. Inclusion of intermediate taxa is found to be the single best method for breaking down long branches.

No description available.

Thesis (Ph.D.) -- La Trobe University, 2006. / "A thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy, Dept. of Zoology, School of Life Sciences, La Trobe University". Research. Includes bibliographical references (p. 445-481). Also available via the World Wide Web.

No description available.

No description available.

The Lysorophia is an order of small, but extremely elongate and tiny-limbed aquatic lepospondyl amphibians existing from the Middle Pennsylvanian through the Lower Permian, primarily in North America. The order comprises one family, Cocytinidae, with three recognized species: Brachydectes newberryi (=Cocytinus gyrinoides), B. elongatus (=Lysorophus tricarinatus, partim) and Pleuroptyx clavatus. Other named species are considered Lysorophia, incertae sedis. Lysorophoids are distinguished by their fenestrated skulls, anteriorly sloping suspensoria, short mandibles (each bearing a lateral mandibular fenestra) and by extensive, well-ossified hyobranchial skeletons. Presacral vertebrae are holospondylous and number between 69 (B. newberryi) and 97 (B. elongatus). Neural arch halves are sutured at their midlines and to their centra. Aspects of lysorophoid anatomy, including the hyobranchial skeleton, suggest that the lysorophoids are neotenic. / While closely similar to one another, lysorophoid species are highly derived relative to other Paleozoic amphibians. They are most closely related to microsaurs, principally through the morphology of the craniovertebral articulation.