Researchers have discovered China's oldest known freshwater arthropod in Xinjiang

Nanjing, April 4 (Reporter Yang Yanci) According to the news of the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences on the 21st, the institute and Chinese and foreign researchers carried out research in the late Silurian strata in the northwest margin of the Junggar Basin in Xinjiang, China, and found a new freshwater arthropod - the Serma di Brak worm.

The study suggests that the Serma dibrak species represents the earliest known freshwater arthropods in China and the oldest terrestrial/freshwater arthropod solid fossil record outside the Lau-Russian continent. The relevant research results were published in the international paleontological journal Papers in Palaeontology.

Researchers introduced that animal landing is one of the important events in the evolution of life, and arthropods, as one of the important representatives of metazoans, lived in marine environments or sea-land transitional environments before the Silurian period.

Recently, Xu Honghe and Wang Yi, researchers of the early terrestrial plant research team of the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Liu Bingcai, graduate student, together with Associate Professor Ruiwen Zhen of China University of Geosciences (Wuhan), graduate students Yin Jiayi and Ma Juan, and Professor Gregory D. Edgecombe of the Natural History Museum in London, reported on a new freshwater arthropod in the late Silurian strata of the northwest margin of the Junggar Basin in Xinjiang, China, and the early terrestrial / The paleogeographical distribution and origin evolution of freshwater arthropods have proposed a new understanding.

Researchers collect fossils (top) and large plant fossils in the same layer (bottom). Photo courtesy of Nangusho

The cellmar dibrak fossils found in a set of strata known as the "Shemistai Formation" in the Sayr Mountains near northern Xinjiang and Buxel County. This set of formations is mainly composed of volcanic rocks and pyroclastic rocks, and has long been considered a "dumb formation".

In October 2020, researchers searched for plant fossils in the "Shemistai Formation" formation and accidentally found the fossil material. After detailed morphological studies, it was named the Serma di Brac worm after a pair of lateral spines and a slender tail spine characteristic of its body segment.

Through the lithological characteristics and paleosalinity analysis of the surrounding rock, as well as the fact that the companion organisms are only large plant fossils and spore fossils, the researchers believe that the Serma dibrak worm may have lived in mountainous river or lake environments.

The discovery of Cellmardibrak in Xinjiang extended the paleogeographic range of terrestrial/freshwater arthropods from the Laurio continent to the island arc belt in the Paleo-Asian Ocean in the Northern Hemisphere, suggesting that arthropods may have begun to migrate extensively from the sea to terrestrial or river-lake environments during the late Silurian period. (End)