中国科学院南京地质古生物研究所机构知识库

Heliolitine tabulate corals are extremely rare in pre-Katian (Upper Ordovician) rocks worldwide, hindering the understanding of their origin and early evolution. Here, we systematically study new heliolitine material from the upper member (Sandbian) of the Huadan Formation in the Yunnan-Sichuan border area, Southwest China, which includes Protaraea ningnanensis, Plasmoporella kiaeri, Worm-sipora sp. and Heliolites spinosus. The findings indicate that Protaraea and Heliolites are ancestral forms of coccoserids and typical tubu-lar heliolitines, respectively, and that the absence of trabecular septa is probably a primitive feature of plasmoporellids. The refined Ordovician stratigraphy of this area implies that the coccoserid Protaraea ningnanensis Lin, 1965 from the lower member (late Darriwil-ian) of the Huadan Formation is the earliest known heliolitine, which further indicates that all heliolitines might have evolved from Pro-taraea. The comparison of Protaraea with other early tabulate corals also suggests an independent heliolitine origin from auloporinids and sarcinulinids. (c) 2022 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights reserved.