Fossil discovery in China signals earlier appearance of complex animals

Key Points:

• Newly discovered fossils from the Jiangchuan Biota site in southwestern China, dating between 554 and 539 million years ago, reveal complex animals existed during the late Ediacaran period, predating the Cambrian explosion by at least 4 million years.
• The fossils, preserved as two-dimensional impressions, include diverse forms such as goblet-shaped jellies, sausage-like worms with visible guts, and segmented creatures resembling Cambrian species, indicating a mix of Ediacaran and Cambrian characteristics.
• Many specimens exhibit bilateral symmetry, a trait common in modern animals, and some fossils potentially represent early deuterostomes, the group that includes vertebrates, suggesting vertebrate ancestors appeared earlier than previously believed.
• While this discovery challenges the notion that complex animal life began with the Cambrian explosion, researchers emphasize the Cambrian period still marks significant diversification and the emergence of new animal phyla like mollusks and arthropods.
• Scientists plan further studies on the fossil site’s preservation conditions and the biology and ecology of these ancient animals to better understand early animal evolution and our own ancestry.