Chinese scientists reported their research and classification of the "walking-cactus" fossil in the February 25, 2011, issue of Nature and at this site.
The "walking-cactus" fossil (Diania cactiformis) is 520 million years old. The fossil was originally discovered in Chengjiang, southwest China's Yunnan Province, in 2006 and has been studied for the last five years.
The specimen is six centimeters long and has ten pairs of jointed legs. The legs of the fossil are partially jointed with a proboscis in the rear that was protected by projecting jointed limbs.
This fossil has been determined to be a link between arthropods (lobsters, insects, etc.) and worms.
Paleontologists from Northwest University in Xi'an, capital of northwest China's Shaanxi Province, have determined the "walking-cactus" belongs to the Lobopodia group of animals. The Lobopodia were worms with legs.
The "walking-cactus" is believed to be the missing link between worms and arthropods. The development of jointed limbs was the evolutionary leap that worms needed to make in order to acquire the agility and speed that arthropods posses according to Dr. Liu Jianni.
A representation of the most likely appearance of the walking-cactus" fossil (Diania cactiformis) can be seen at this site.
Paper
"An armored Cambrian lobopodian from China with arthropod-like appendages,"
Principal Author
Dr. Liu Jianni
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