Palaeontologia africana
Permanent URI for this communityhttps://wiredspace.wits.ac.za/handle/10539/13253
ISSN (print): 0078-8554
ISSN (electronic): 2410-4418
For queries regarding content of Palaeontologia africana collections please contact Jonah Choiniere by email : jonah.choiniere@wits.ac.za or Tel : 011 717 6684
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Item Preliminary phylogenetic analysis and stratigraphc congruence of the dicynodont anomodonts (Synapsida: Therapsida)(Bernard Price Institute for Palaeontological Research, 2001) Angielczyk, Kenneth DA preliminary phylogenetic analysis of 20 well-known dicynodont taxa was conducted using modern cladistic methods. Many past phylogenetic hypotheses were corroborated, but others conflict with the results of this analysis. Most notably, Diictodon, Robertia, and Pristerodon are reconstructed in more basal positions than previously suggested, whereas Endothiodon and Chelydontops occupy a more crown ward position. These findings are consistent with novel evolutionary scenarios for characters such as the presence of postcanine teeth and anterior palatal ridges. The Relative Completeness Index and Gap Excess Ratio were used to examine the degree of fit between the most parsimonious cladograms of this study and the stratigraphic record of the dicynodonts. Although the results of this analysis suggest that the preferred cladogram is relatively consistent with stratigraphy, the presence of some ghost ranges and ghost lineages imply that the fossil record of dicynodonts is not as complete as is sometimes stated. These findings are important because there is a long tradition of intensive collecting in regions where dicynodont fossils are common; sections of several dicynodont lineages may not be preserved in these areas.Item Character state transformations and the fit of phylogenies to the fossil record(Bernard Price Institute for Palaeontological Research, 2002) Angielczyk, Kenneth DThere is only one true history of life, and the biostratigraphic record and the phylogenetic relationships of organisms provide the most important information regarding this history. Ideally, the historical signal preserved in each of the data sets should be the same, and several methods have been proposed to compare the fit of phylogenies to the fossil record. All of these techniques use stratigraphic data associated with taxa, but our ability to recognize taxa and reconstruct their phylogenetic relationships ultimately is based on patterns of character state distributions that we observe. This raises the question of whether character states can be used to measure the fit of a phylogeny to the fossil record. Here I argue that we can, if the order of appearance of character states is considered. Optimization of character states on a phylogeny results in a predicted order of appearance of character states; derived states must arise after basal states. This order can be compared to that predicted by the fossil record. Although a number of factors can affect the frequency at which derived character states are sampled before basal states in the fossil record, conflicts between the two data sets should be relatively rare. Phylogenies that imply a large number of character state transformations that are inconsistent with the fossil record may need to be reconsidered before the fossil record is criticized.