Hydrodynamic Simulation Of The Early Cambrian Microscopic Sedentary Medusozoans From The Kuanchuanpu Biota

Deciphering the relationship between morphology and function is an important part for reconstructing the lifestyle of paleontology,and is of great significance for their paleoecology study.However,due to factors such as incomplete preservation and lack of comparable extant analogues,the study of functional morphology is often speculative and lacking of quantitative analysis.Thanks to the rapid advancement of the paleontological digitization,computational fluid dynamics(CFD)enables the visualization and quantitative analysis of extinct species in three dimensions,and therefore has great potential to test these hypotheses.The medusozoan cnidarians were an important part of the early Cambrian marine ecosystem in South China,and their study is of great significance for the further understanding of the origin and evolution of metazoa.The Kuanchuanpu biota(ca.535 Ma)in the early Cambrian(Fortunian stage)in southern Shaanxi was abundant in phosphatized small shell fossils(SSFs),including microscopic medusozoans exhibiting diverse radial symmetrical patterns,and the preservation quality has laid a solid foundation for this research.CFD analysis is conducted to analyze the functional performance and lifestyle of the medusozoans,quantitative studies are carried out under different scenarios.The results reveal that:(1)Ambient velocity is an important factor for tidal life of benthic medusozoans.In a certain range(0.1–0.4 m/s),the increase of flow velocity can facilitate the feeding efficiency and is beneficial to the growth of benthic medusozoans;(2)Under the same ambient fluid condition,the biradial symmetry of Hexaconularia sichuanensis is more adapted than the tetraradial symmetry of Quadrapyrgites quadratacris.It indicates that on the millimeter-scale,medusozoans with diverse radial symmetries can also produce obvious hydrodynamic differences;(3)Compared with solitary life,Anabarites trisulcatus living gregariously shows a smaller drag coefficient and lower stress at the basal part,accordingly more conducive for survival in tidal life,the results confirm previous hypothesis about the gregarious lifestyle of Anabarites trisulcatus.The simulation provides a preliminary quantitative analysis of the relationship between microscopic sedentary medusozoans and their living environments.It has significant reference value for the reconstruction of paleontological lifestyle and paleoecology research.CFD is a promising tool that provide new insights for the study of Cambrian SSFs.