Sea creature’s soft side

This beautifully preserved 525-million-year-old fossil is barely 4 cm in length, but minute details can be seen including 36 tiny tentacles along one feathery arm.

Discovered in Yunnan Province in China, the new fossil belongs to an important group of primitive sea creatures that used the tentacles for feeding.

The creatures secreted a substance that built up into a hard tube around their soft body, with the tentacles extending from the top of the tube to catch plankton.

Previously only the tubes have been seen in detail but this new fossil clearly shows the soft parts of the body.

‘Amazingly, it has exceptionally preserved soft tissues – including arms and tentacles used for feeding – giving unrivalled insight into the ancient biology of the group,' says Professor David Siveter of the University of Leicester’s Department of Geology, who led the research.

The fossil was discovered by a team from Yunnan University in China, the University of Leicester and included Derek Siveter from the Department of Earth Sciences at Oxford. Details are published in the journal Current Biology and the study was funded by the Royal Society and the National Natural Foundation of China.

The fossil belongs to a group called pterobranch hemichordates which are related to starfish and sea urchins.

About 30 species of pterobranch are known to exist today, but 380-490 million years ago a group of these animals, called graptolites, were common across the prehistoric oceans. Pterobranches also show some characteristics that offer clues to the evolution of the earliest vertebrates.