Famennian (Late Devonian) bryozoans from western Junggar, Xinjiang, NW China: morphological specificities and palaeoenvironmental implications
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Abstract:
This paper focuses on the morphology and palaeoecology of the latest Devonian bryozoans from western Junggar, northwestern China. Studied bryozoan materials, which contain diverse taxa of orders Cryptostomata, Fenestrata, Trepostomata, and Cysto porata, are based on museum specimens collected from the Hongguleleng and Tielieketi formations. Dominant cryptostome bryozoans possess characteristic delicately branched colonies with central axis or mesotheca, as well as bifoliate colonies. Specifically, these cryptostome bryozoans have thickened walls in exozone, strong bending of autozooecia chambers, abundant metazooecia or tectizooecia, and aktinotostyles and/or acanthostyles. Different combinations of heterozooecia, styles, forms of autozooecial chambers in colonies and different growth habits resulted in the successful evolution of the bryozoans from Xinjiang. In the lower member of the Hongguleleng Formation and the lower part of the Tielieketi Formation, three bryozoan associations, i.e., bryozoan association No. 1 (Ba1), No. 2 (Ba2), and No. 3 (Ba3) are proposed, indicating changes of environments from foreshore to offshore. Among them, the branched-bifoliate-reticulate colonies that lived in nearshore show higher abundance and diversity.