华南埃迪卡拉纪瓮会生物群两类优势底栖宏体藻类对比研究及生态复原OA

Following the"snowball event",the Ediacaran macroalgae of South China,including the Wenghui Biota from northeastern Guizhou,have garnered global attention.The Ediacaran Biota is characterized by a predominance of benthic macroalgae,with Gesinella and Baculiphyca emerging as the dominant taxa.Their carbonaceous compressions are preserved within the black shales of the upper Doushantuo Formation(595±5.3 Ma)on the Yangtze platform.Although superficially similar in the field due to a shared basic structure(a holdfast and an unbranching thallus),Gesinella and Baculiphyca possess distinct morphological characteristics.Gesinella typically has an oval or oblong thallus with a rounded distal end.Its short,rod-like stipe transitions smoothly into the upper lamina and is 10 to 20 times narrower than the lamina's maximum width.The thallus surface features numerous,regularly arranged branching or unbranching filamentous structures,suggesting a potentially sac-like morphology.Additionally,the stipe is preserved as a three-dimensional cylinder with noticeable folds,which may have reinforced this structure.The holdfast is generally composed of a cone-shaped rhizome with numerous filamentous rhizoids,functioning as a crucial anchoring organ that secures the sac-like body within seafloor sediments while allowing it to suspend in the water column.In contrast,the thallus of Baculiphyca is generally a long,rod-like structure,often broken and lacking a preserved upper lamina.Its surface shows no filamentous or other decorative structures.The stipe is mostly preserved as a cylindrical form,and numerous filamentous rhizoids grow above the rhizome with thickened carbonaceous ridges.This study presents a statistical analysis of 108 Gesinella and 103 Baculiphyca specimens from the black carbonaceous shales of the Doushantuo Formation in northeastern Guizhou.For the first time,the ontogenetic development of both taxa has been categorized into three distinct growth stages:juvenile,adult,and senescent phases.Gesinella and Baculiphyca are common in these shales,frequently forming dense fossil layers.The specimens frequently exhibit well-preserved holdfasts or rhizoids,with complete holdfast-thallus associations preserved within single bedding planes,suggesting in situ or parautochthonous burial conditions.Moreover,numerous specimens display evidence of bending and fragmentation,while others exhibit preferential orientation,indicating deposition in a marine environment with moderate hydrodynamic energy.These taphonomic and sedimentological features suggest that Gesinella and Baculiphyca inhabited a shallow,low-energy marine environment characterized by warm waters,euphotic conditions,normal salinity,and moderate oxygenation levels.