Wales discovers ‘mini-world’ under the sea 460 million years ago

Recently, in the Middle Ordovician strata of Wales, England, an international joint scientific team discovered a specific buried fossil repository with a large number of exquisite soft body fossils, which is called the “mini-world” of the seabed because most organisms are small, providing a new perspective for early animal miniaturization research. The findings were published May 1 in Nature Ecology & Evolution.

Fossils are important direct evidence for the study of the history of the earth and the evolution of organisms, especially the biota with preserved soft bodies, providing an unparalleled window into the morphology and ecological community characteristics of early organisms, which is also known as the “specific buried fossil library”.

In 1909, in the Middle Cambrian Burgess Shale in British Columbia in southwestern Canada, American paleontologist Walcott discovered such fossil biota, called the “Burgess Shale” fauna. Historically, such well-preserved “Burgess Shale” fossil repositories have been generally limited to the Cambrian period, and are rarely found in the newer Ordovician formations.

This time, Joseph P. Botting, a foreign scientist at the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences (hereinafter referred to as the Nanjing Institute of Paleontology), associate researcher Ma Junye and researcher Zhang Yuandong formed an international scientific research team, and they discovered the “Burgess Shale” specific buried fossil repository – Castle Bank fauna is located in the Castle Beach quarry in central Wales, England.

Ma Junye told China Science News that the area was located in the Avalonia continental plate during the Ordovician period, in the temperate region of the southern hemisphere. The upper part of the biota is composed mainly of penstone mudstone, with volcanic ash layers and thicker tuff interbedded. Studies of penstone biostratigraphy show that the age of the Castle Beach biota is the Middle Ordovician Da Revel period, which is about 462 million years ago.

It is understood that more than 170 species of organisms have been found in the Castle Beach biota, covering sponges, spiny cell animals, echinoderms, chordates, arthropods, molluscs, star worms, trolling animals, bryozoans, link animals, brachiopods and other animal phyla. Among them, sponges are the most abundant, about 40 species. Many fossils preserve soft tissues such as the digestive and nervous systems such as the eyes, optic nerve and brain. In addition, most organisms in this biota are small, about 1~5 mm long. “Small size also makes fossil collection and research difficult.” Ma Junye told China Science News.

Comparing with published early Ordovician “Burgess Shale” fauna, such as the Fezouata biota in Morocco and the Afon Gam biota in Wales, the study found that the Castle Beach fauna has a high biodiversity in terms of both overall and soft-bodied organisms. At the same time, the Castle Beach fauna includes both typical groups of Cambrian biota, such as predatory organisms such as Obabin sea scorpion arthropods, and rich Paleozoic filter-feeding new types, such as brachiopods, penstones and bryozoans.

Therefore, the Castle Beach fauna not only provides a new perspective on the evolution of marine fauna from Cambrian biota to Paleozoic biota, but also reveals a new stage of the transformation of marine ecological balance system from Cambrian predator-dominated to Paleozoic filter-feeding dominated type. (Source: Shen Chunlei, China Science News)

Related paper information:

Castle Beach biome reconstruction map Drawn by Yang Dinghua

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