Enigmas Overturned by Chinese Fossils

Article excerpt

With the help of a new fossil discovered in China, paleontologists are starting to make sense out of some of the most problematic and bizarre animals known in Earth's history. Several of these strangers from 530 million years ago -- previously viewed as failed evolutionary experiments, with no counterparts in the modern world -- now appeear to fit into an existing animal phylum.

The newly found caterpillar-like animal is among the latest prizes to emerge from an extraordinary set of fossil beds in the Chengjiang area of southwestern China. The dozens of species discovered so far within these rich formations are painting a picture of life in the early Cambrian period, which began just after the evolutionary "big bang" that gave birth to almost all the major groups of modern multicellular animals.

For decades, paleontologists have labored to understand the Cambrian's odd-ball creatures, which don't fit readily into existing animal phyla. Using the new, as-yet-unnamed Chinese fossil as a guidepost, two researchers now suggest that some of the most enigmatic of these animals belong to the phylum Onychophora, which in the modern world includes the velvet worms of the tropics. Lars Ramskold of the Swedish Museum of Natural History in Stockholm and Hou Xian-guang of the Nanjing Institute of Geology and Paleontology in China describe their findings and conclusions in the May 16 NATURE.

The newly discovered animal "makes the Cambrian bestiary look a lot less bizarre than it used to," says Stefan Bengtson, a specialist in Cambrian fossils at Uppsala University in Sweden.

The keystone fossil has a segmented body stretching 5 to 6 centimeters in length, with 11 pairs of ballonish legs that end in two-pronged claws. Onychophorans share these same features, leading Ramskold and Hou to group the new fossil with the existing phylum. In the modern world, onychophorans live on land, mainly in the moist litter of tropical forests. Bengtson describes them as looking like a cross between a centipede and the Michelin Man.

To make the onychophoran connection, Ramskold and Hou have stretched the boundaries of the phylum. …