207 / 2025-04-14 22:26:06

Macrofossil Horodyskia from the terminal Ediacaran Dongpo Formation in North China

North China,Ediacaran,Dongpo Formation,Horodyskia,pyritization

Theme 3: Earth-Life Co-evolution Through Time > Session 3a: Precambrian Earth and Life Co-evolution

The Ediacaran Period represents a critical interval for the origin and evolution of macroscopic multicellular eukaryotes, which have been reported across multiple continents. However, the Ediacaran strata in the North China are highly incomplete with scarce fossil record, resulting in limited understanding on the biodiversity of the Ediacaran period in North China. The Dongpo Formation represents one of the few terminal Ediacaran sequences primarily distributed along the southern margin of the North China. But paleontological records of the Dongpo Formation remain poorly understood. In this study, abundant ‘string of beads’ macroscopic fossils have been discovered in the Dongpo Formation from two Ediacaran–Cambrian boundary sections in western Henan Province, North China. By using optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and micro-CT, our analyses find that the fossils are bead-shaped, either randomly distributed or arranged in equidistant strings, with beads in the same string being of approximately equal diameters. The beads are three dimensionally preserved in mold or pyritization, occasionally surrounded with a halo-like ring. These observations indicate that the fossils are Horodyskia. Although Horodyskia has been widely reported from the Mesoproterozoic to late Ediacaran with silicified, molded, and carbonaceous compression preservations, our study represents the first record of Horodyskia revealed in the terminal Ediacaran of North China, expanding the paleogeographic distribution of Horodyskia in the late Ediacaran. The pyritized preservation of Horodyskia from the Dongpo Formation also expands the known preservation potential of this organism.