Thursday, March 24, 2011

A New Early Cambrian Hemichordate

Image: D. Siveter, Oxford Univ.
A new 525-million-year-old pterobranch hemichordate fossil belongs to a group of tentacle-bearing creatures which lived inside hard tubes. Previously only the tubes have been seen in detail but this new specimen clearly shows the soft parts of the body including tentacles for feeding.

Galeaplumosus abilus means 'feathered helmet from beyond the clouds', referring to both the creature's shape and its location – 'Yunnan' literally translates as 'south of the clouds'.

Pterobranch hemichordates which are related to starfish and sea urchins but also show some characteristics that offer clues to the evolution of the earliest vertebrates. About 30 species of pterobranch are known to exist today although 380-490 million years ago a group of these animals called graptolites were common across the prehistoric oceans.

Pterobranches are creatures which secrete a substance that builds up into a hard tube around their soft body. Tentacles extend from the top of the tube to catch plankton. Although less than 4cm in length, the new fossil is beautifully preserved and minute details can be seen including 36 tiny tentacles along one feathery arm. link