A systematic description of new macrofossil material from the upper Ediacaran Miaohe Member in South China

Abstract

The upper Ediacaran Miaohe Member (∼551 Ma) in South China contains exceptionally preserved macroscopic carbonaceous compression fossils that provide a crucial view of the marine ecosystem shortly before the Cambrian explosion. However, these fossils were previously known only from one locality near the Miaohe Village on the northern bank of the Yangtze River. It was puzzling that equivalent strata a short distance away contained no fossils, raising questions about the environmental, ecological and taphonomic restriction of these fossils. Here, we describe macroscopic fossils from the Miaohe Member at three new localities to the north and north-west of Miaohe Village. These fossils are taxonomically similar to those from Miaohe Village, and include mostly benthic multicellular algae, a few putative metazoans and several morphologically simple problematic taxa. Twenty-seven species are described, including one new genus (Maxiphyton gen. nov.) and six new species (Baculiphyca brevistipitata sp. nov., Doushantuophyton? laticladus sp. nov., Enteromorphites magnus sp. nov., Konglingiphyton? laterale sp. nov., Maxiphyton stipitatum sp. nov. and Sinocylindra linearis sp. nov.). Insofar as the new localities represent shallower palaeoenvironments than Miaohe Village in the late Ediacaran, the new fossils expand the palaeoenvironmental distribution of macrofossils in the Miaohe Member. Most of the new fossils are preserved as carbonaceous compressions through kerogenization, but pyritization and aluminosilicification also played an important role. This confirms the taphonomic model that there is a continuous preservational gradient among kerogenization, pyritization and aluminosilicification. This taphonomic window provides a glimpse of the late Ediacaran marine ecosystem and complements the cast-mould preservation that accounts for the much-celebrated Ediacara-type soft-bodied macrofossils.