Latest progress in graptolitic phylogeny studies——Cladistic analysis of Ashgillian Dicellograptus

FENG Hongzhen 已出版文章查询
FENG Hongzhen
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1State Key Laboratory for Research of Mineral Deposits Nanjing University Nanjing 210093 China

The graptolites studied here were collected from the Ashgillian Wufeng Formation in Wuning County, Jiangxi Province, which included 9 species of Dicellograptus, 2 species of Tangyagraptus and 1 species of Dicranograptus . The polarity and states of 8 selected characters are analyzed based on the morphological features and stratigraphic sequences of the 12 species and a parsimonious cladogram is reconstructed by using the monothetic method proposed by Camin and Sokal. A phyloneny tree of evolutionary significance formed by adding a time-axis to the cladogram indicates that the Ashgillian Dicellograptus in the investigated area includes two independent evolutionary lineages starting to diverge as early as in the Caradocian and, within the main lineage composed of the dicellograptids with square or subsquare basal portion, two clades represented respectively by Dicellograptus complexus and D. turgidus mark the highest stage of the Ashgillian dicellograptid evolution.

语种: 英文   

关键词cladistics graptolites the Ashgillian age.

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