On the evening of October 27, Beijing time, nature magazine published the latest results of doctoral student Zhang Zhiliang and others under the guidance of Professor Zhang Zhifei of the Early Life Research Team of Northwest University in the form of "Article", "Fossil Evidence Reveals the Cambrian Origin of the Moss Animal Phylum", announcing the discovery of the earliest known fossil of moss (moss) on the earth in Zhenba County, shaanxi province . https://www.nature.com/articles/s41586-021-04033-w)。
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 Northwestern 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 ShuDegan's team, perfects the construction process of cambrian earth animal trees that lasted 40 million years, and effectively connects the explosive and phased fossil evidence chains of three animal subcategories (basic animals, protozoa 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. 540-518 million years ago, early ancestor representatives 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 preliminary research of the research group, together with Glenn Brock, a professor at Macquarie University in Australia and an adjunct professor at Northwestern University, and cooperating with international 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, it is believed that these micro-fossils are the earliest bryozoic 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. This discovery pushes the origin of bryozoans forward by at least 50 million years.
In addition, through scanning electron microscopy (SEM and BSEM) and X-ray tomography (μ-CT) analysis, Zhang Zhiliang et al. believe that the multi-layered plasticity and complexity of the moss population originated 530 million years ago, elucidating important ecological innovations during the Cambrian explosion.
Bryozoans 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 is remarkable and requires young people to have a solid foundation and a tenacious spirit of exploration," Shudgan said. At the same time, this event once again perfectly supports the validity of our "three-act Cambrian explosion" hypothesis, or it further confirms that this hypothesis has reliable scientific predictability. ”