Cambrian "feathered anemone" to solve the evolutionary history of spiny animals

Cambrian Chinese pre-light anemone three-dimensional restoration model (Courtesy photo: Li Zhaozhen, Ou Qiang)

The joint research team of China University of Geosciences (Beijing), Northwest University and Kassel University in Germany, based on the new discovery of the morphological details of the "Chinese Pre-light Anemone" of the Chengjiang biota, revealed an extinct somatic configuration and restored the early evolution trajectory of spiny animals, which became another important achievement in the field of early life research. In the early morning of August 2, Beijing time, the results were published in the Journal of the Academy of Sciences of the United States of America (PNAS).

Common corals, anemones, hydras, jellyfish and other creatures belong to the spiny cell. Its phylum has more than 10,000 species, most of which are marine carnivores, and has a very important ecological position in the modern ocean through the paralyzing of thorn cells and the killing of small organisms on the surface of the tentacles. Some of the spiny animals are also known as the most famous in the world, such as the Australian tank jellyfish as the most toxic animal, the lion-maned jellyfish as the longest known individual (greater than 36 meters), and the lighthouse jellyfish is considered to be probably the longest-lived animal. Located at the root of Earth's "animal lineage tree", ternitos are essential for studying the origin and early evolution of the entire animal kingdom. Because of this, the early fossil record of spiny animals has attracted much attention from the academic community.

Ou Qiang, a researcher at the Early Life Evolution Laboratory of China University of Geosciences (Beijing) and the first corresponding author of the paper, told the reporter of China Science Daily that through the study of multiple fossil specimens of Chinese pre-light anemones in the early Cambrian Chengjiang biota (about 520 million years ago), they found "exciting morphological characteristics" - complex pinnate tentacles, with alternate branches on both sides of the tentacles, and dense cilia on both sides of the branches; digestive circulation cavity with diaphragm and single opening Holders with independent inner cavities and basement depressions, radiation symmetrical systems, etc. These features indicate an extinct animal body configuration.

Based on the new traits of the Chinese precocious anemone, the researchers analyzed its phylogenetic status by Bayesian inference and concluded that the Chinese preluminous anemone represents a backbone taxon of the Phylum Australoquis and is the Cambrian precursor of this phylum.

Ou Qiang said that this conclusion has important indicative significance for the morphology and ecological evolutionary history of spiny animals. First of all, from the body shape and separate digestive cavity of the Chinese pre-light anemone, it is speculated that the ancestral type of the spiny pod is the hydra type rather than the jellyfish type, which supports the "hydra hypothesis" of modern molecular biology. Second, the feeding strategies of Archaeopteryx and their modern descendants may be very different.

"Most of the modern spiny animals are predatory, poisoning and preying on small prey by touching the stinging cells that touch the surface of the face; the tentacles of the Chinese anemone have alternate branches and dense cilia, which are very similar to the tentacle structures of modern ciliated filter-eating animals such as dracuna, terriers, rod wallworms, etc., so the preluminous anemone is not a fierce meat eater similar to modern anemones, but a gentle and harmless filter eater - filtering suspended food particles in the sea through feathery tentacles." Ou Qiang said.

The researchers speculate that pinnate filter-feeding tentacles may be primitive traits, while predatory tentacles with spiny filamentous sacs are derivative features. In addition, the unique combination of traits of the Chinese preluminous anemone increased the morphological differentiation of the whole population of echinozoans.

The research was supported by the New Century Talent Support Program, the National Natural Science Foundation of China, and the Humboldt Foundation in Germany.