Chinese and German scholars trace the early evolutionary history of spiny animals

WASHINGTON, July 31 (Xinhua) -- Chinese and German researchers have recently reported that by studying fossil specimens of Chinese prelude anemones, they have discovered a special body configuration of this paleontology, restoring the early evolutionary trajectory of spiny cells.

The Phylum Echinostris is one of the most primitive multicellular fauna, including corals, anemones, hydras, jellyfish, etc., occupying an important position in modern marine ecosystems. Located at the base of the "phylogenetic tree" of Earth's animals, echinozoa is of great significance for studying the origin and evolution of higher fauna, but their early evolutionary history is little known.

A joint research team from China University of Geosciences (Beijing), Northwestern University and Kassel University in Germany published a paper in the latest issue of the Proceedings of the National Academy of Sciences published on July 31 that based on a study of 85 new fossil specimens of the Chengjiang animal fossil group in Yunnan, they found a series of morphological details of the Chinese anemone, confirming that it belongs to an early branch of the basal taxon of spiny animals, which is the basis of modern spiny animals in 5. The Cambrian "forerunner" 200 million years ago.

Ou Qiang, an associate professor at the China University of Geosciences (Beijing), who was in charge of the study, told Xinhua that this Cambrian animal resembles a "sea anemone with a feathered feather in its head", with a circle of feathered tentacles around its mouth, a cylindrical trunk with a raised longitudinal ridge, a smooth surface and a sucker-like base fixator at the bottom, and a more obvious circular depression between the trunk and the retainer. When the animal is alive, its retainer is partially inserted into the silt of the seabed, and the bowl-like depression at the bottom of the retainer can wrap the sediment and act as a "ballast stone".

The researchers also found that the Chinese anemone also has a digestive circulation cavity with a diaphragm. These previously unknown morphological features suggest that the ancestral type of the spiny pleurate was hydra rather than jellyfish.

In addition, the feeding strategies of prehistoric spiny and modern spiny cells may be very different. Modern spiny animals are mostly predatory, poisoning and preying on small prey through densely packed spine-celled, flexible, non-branching tentacles; however, the pinnate tentacles densely packed with cilia of the anemone are very similar to the tentacle structures of modern link animals such as terrestrial gills, dragons, and ciliated filter-feeding animals such as hemizophores rod wallworms and cephalopods.

Ou Qiang et al. deduced from this that the Chinese anemone was "not a ferocious meat eater similar to modern anemones, but a gentle and harmless filter eater", filtering suspended food particles in the sea through pinnate tentacles. They speculated that pinnate filter-feeding tentacles may be primitive traits, while predatory tentacles with prickly cells are derivative features.

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

Located in Chengjiang County, Yuxi City, Yunnan Province, the Chengjiang Fauna Fossil Group is the most distributed, well-preserved and most abundant early Cambrian paleontological fossil group on Earth, and was inscribed on the World Heritage List in 2012. The Chinese anemone is one of the iconic species of the Chengjiang Fauna Fossil Group, discovered and named in 1991, and scholars have debated its pedigree status since then.