''Xianguangia'' is a soft-bodied

sea anemone Sea anemones ( ) are a group of predation, predatory marine invertebrates constituting the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemone ...

-like fossil animal from the

Chengjiang Biota The Maotianshan Shales () are a series of Early Cambrian sedimentary deposits in the Chiungchussu Formation or Heilinpu Formation, famous for their '' Konservat Lagerstätten'', deposits known for the exceptional preservation of fossilized orga ...

of China.

Description

''Xianguangia sinica'' has a cylindrical body with a whorl of nearly 16 tentacles around the oral disc, similar to the modern anthozoans. The tentacles are feather-like with dense pinnules on both sides of the axis which would have been well adapted to filter feeding. A bowl-shaped attachment disc at the basal part might commonly have been buried in the sediment to allow its sedentary strategy on the sea floor. The body above the pedal disc is broad and cylindrical and may correspond to the internal gastrovascular cavity. It displays several distinct longitudinal grooves and ridges on the surface, indicating possible

mesenteries In human anatomy, the mesentery is an organ that attaches the intestines to the posterior abdominal wall, consisting of a double fold of the peritoneum. It helps (among other functions) in storing fat and allowing blood vessels, lymphatics, a ...

. However, its phylogenetic affinity has long been questioned; it has even been alleged to be related to members of the

Ediacara biota The Ediacaran (; formerly Vendian) biota is a taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period (). These were enigmatic tubular and frond-shaped, mostly sessile, organis ...

. Studies from the late 2010s onwards argued that it was likely to be member of the stem-group of

Ctenophora Ctenophora (; : ctenophore ) is a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming (commonly referred to as "combs"), and they are ...

(comb jellies), related to taxa like ''

Dinomischus ''Dinomischus ''is an extinct genus of stalked filter-feeding animals within the Cambrian period, with specimens known from the Burgess Shale and the Maotianshan Shales. While long of uncertain affinities, recent studies have suggested it to be a ...

'' and ''

Siphusauctum ''Siphusauctum'' is an extinct genus of filter-feeding animals that lived during the Middle Cambrian about 510 million years ago. Description ''Siphusauctum'' was a sessile animal that was attached to the substrate by a holdfast. It had a tul ...

.'' The fossils, found in Yunnan province, China, were initially described as three distinct species, ', ', and ', and then assembled into one proposed species, ', in 2017. The animal was polyp-like, its gastric cavity divided by septa; it had a second body cavity in its holdfast, and densely-plumed feather-like tentacles, implying that it was a

suspension feeder Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a spec ...

. Early cnidarians were probably also benthic suspension feeders, unlike later mainly

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

y cnidarians.

References

Enigmatic prehistoric animal genera Fossil taxa described in 1991 Cambrian genus extinctions {{cambrian-animal-stub