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Taxonomic Revision of the Cambrian Trilobite Abadiella and its Stratigraphic Significance in Gondwana

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Submitted:

31 July 2022

Posted:

02 August 2022

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Abstract
The taxonomy of trilobites Abadiella Hupé, 1953 and Parabadiella Zhang, 1966 from the lower Cambrian of Gondwana has long been a controversy. Based on newly-collected and formerly-reported materials, 94 trilobite cranidia within 21 species are selected for morphometric analyses: principal components analysis (PCA) and canonical variates analysis (CVA). The integrated morphological characters are successfully accounted for by two principal components in PCA. The further validations for the presupposed qualitative groupings are indispensable to detect and calibrate the ultimate taxonomic results in CVA. By this way, all specimens distributed in a consistent morphospace in PCA and the short distances between them demonstrate their close morphological affinity, supporting their congeneric status within Abadiella. Additionally, three morphotypes were recognized from all selected specimens and they were eventually revised and incorporated into A. bourgini Hupé, 1953, A. huoi Zhang, 1966, and A. yunnanensis Luo, 1981, through stepwise test-calibration to get a high correct rate as far as possible in CVA. From this, it is certain that A. huoi is conspecific in South Australia and South China. Its occurrence allows to correlate the Australian A. huoi Range Zone to the identical zone in South China (in platform), having an approximately consistent stratigraphic range in the two regions. In comparison with A. huoi, A. bourgini was reported from fewer localities in South China. Nevertheless, its presence in the Daguinaspis Zone of Issendalenian Stage in Morocco permits a correlation with Chinese and Australian A. huoi Zone. As an auxiliary marker for A. huoi, the occurrence of A. bourgini in Morocco, South Australia and South China reinforce the correlation potential and resolution in species-level for the Cambrian Stage 3 in Gondwana region.
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