China has found the earliest known bryozoan fossils on earth

Source: Guangming Daily

The earliest moss restoration image Data picture

【Frontiers of Science and Technology】

Xi'an, October 30 (Reporter Zhang Zhehao, correspondent Li Chen) On the evening of October 27, Beijing time, the journal Nature published in the form of a long article the latest research results of Zhang Zhiliang, a doctoral student under the guidance of Professor Zhang Zhifei of the Early Life Research Team of Northwest University - "Fossil Evidence Reveals the Cambrian Origin of the Moss Animal Phylum", announcing the discovery of the earliest known fossils of mosses (mosses) on the earth in Ba County, Zhenba County, shaanxi province.

Zhang Zhiliang is the first author of the paper, and Northwest University is the first completion and communication unit. This is the 15th paper published in Nature and Science by the Northwest University Early Life and Environment Innovation Research Team led by Academician Shu Degan.

The study further supports the "three-act Cambrian explosion" hypothesis proposed by Shu Degan's team, improves the 40 million-year construction process of Cambrian earth animal trees, and effectively connects the explosive and phased fossil evidence chains from three animal subcategories (basic animals, proto-mouth animals and post-mouth animals).

The Cambrian explosion is the most magnificent event known on Earth for the eruption of life by symmetrical animals on both sides. Between 540 million and 518 million years ago, early ancestors of almost all modern animals, including vertebrates, suddenly appeared in the oceans. But the moss phylum has lacked a solid Cambrian fossil record, so it is thought to be the product of ordician radiation.

The research team of Northwest University found millimeter-sized micro-fossilized stone in the biodestic limestone of the Xi artemisia section of the Xiaoyangba Section of the Xiaoyangba Formation in Zhenba County, Shaanxi Province, through acid etching experiments. After the research team's preliminary research, together with Glenn Brock, professor at Macquarie University in Australia and adjunct professor at Northwestern University, and cooperating with Chinese and foreign scholars such as the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences, the British Natural History Museum, and the Swedish Museum of Natural History, the research team believes that these micro-fossils are the earliest moss fossils on the earth, revealing the Cambrian origin of this category. After Bayesian and maximal minimalist branch systematic analysis of 52 features, 18 taxa and 2 outer groups, it is shown that the Cambrian bryozoan fossil Protomelission is the basal taxon of bryozoans, representing the most primitive ancestor type. The discovery pushed the origins of mosses forward by at least 50 million years.

In addition, through scanning electron microscopy (SEM and BSEM) and X-ray tomography (μ-CT) analysis, the research team believes that the modular construction of the multi-layered plasticity and complexity of the bryozoan population originated 530 million years ago, elucidating important ecological innovations during the Cambrian explosion.

Lichen mosses are tiny, with calcareous or chitinous chambers on the surface, and are typically shelled reef-building animals, usually living on other shell animals or hard-bottomed ocean surfaces. The fossil's discovery in the argillaceous limestone of southern Shaanxi suggests that Cambrian mosses are similar to later genera and are suitable for living in a clear hard-bottom environment. This reveals the reason for the lack of bryozoan fossils in the mud shale fossil pool. The study of such fossils is of great significance for understanding the evolution of the Earth's habitability and how benthic (grass-roots) animals have transformed and adapted the Earth.

"The discovery of the source of the moss phylum in the strata 530 million years ago once again perfectly supports the validity of our hypothesis of a 'three-act Cambrian explosion', or it further confirms the reliable scientific predictability of this hypothesis," Shudgan said. ”