中国科学院南京地质古生物研究所机构知识库

Naotic dissepiments are special structures of rugose corals, characterized by a column of distally arched plates at peripheral parts of thick septa or within the cystozone. In this study, naotic-dissepimented colonial rugose corals Gyanyimaphyllum crassiseptatum and Ipciphyllum naoticum and their associated microfacies were documented from the Late Permian Gyanyima section in Tibet, southwestern China. The morphology of the Gyanyima naotic-dissepimented corals is cerioid massive forms or fasciculate forms with connected individuals, with broken skeletons. Between coral colonies and/or skeletons, the interspaces are occupied by highly fragmented bioclasts and sparry calcite. These biotic and sedimentary characteristics suggest that the Gyanyima naotic-dissepimented corals could have developed in high water-energy environments above fair-weather wave-base. This implies that the development of naotic dissepiments was probably related to an enhanced hydrodynamic force. According to a review on the Permian naotic-dissepimented rugose corals in China, they are mainly composed of massive colonial forms with a few fasciculate colonial and solitary forms. Current available data indicate that they could occur in bioclastic grainstones and oncoid limestones with eroded skeletons, which also support a conclusion that naotic dissepiments formed in turbulent environments. Based on the ontogenic studies on naotic-dissepimented rugose corals, naotic dissepiments occur sporadically in the neanic stage and are well developed but not permanently and uniformly in adult stage. Furthermore, different species in the same genus have different degrees of development of naotic dissepiments, which might imply that naotic dissepiments are not suitable to be an important taxonomic character in higher than species level.