SCIENCE LAB SCENICS : LEGGY ANCESTORS

One thing we know about Earth's earliest insects : They had limbs to spare. Erik Tihelka's first glimpse one of the world's oldest insects came from an outdated Russian textbook he bought on eBay.

In it, a small line drawing of a fossil, labeled an early crustacean that had lived 324 million years ago, caught his eye.

'' The more I looked, the more intrigued I got,'' said Mr. Tihelka, a doctoral student in paleontology at Cambridge University in England.

For a fossil described as a crustacean, it seemed to have an awful lot of insectlike traits. Overall, it looked a lot like a modern silverfish. But there was one big difference :

While modern insects have six legs, this one had 24.

The early origins of insects are shrouded in mystery. The fossil unearthed in Texas and stored at the San Diego Natural History Museum, could be a breakthrough.

In a study published in Nature, Mr. Tilhelka's team proposes that his discovery is one of the oldest insect fossils ever found.

Genetic analyses have shown that insects' closest relatives are crustaceans, but they split off into their own group and moved onto land.

Very little is known about this transition, because insects and their fellow six-legged arthropods are missing from the fossil record from roughly 385 to 322 million years ago, a period known as the  ''hexapod gap.''

The insect-resembling fossil in Mr. Tihelka's textbook was just inside that gap.

This Master Publishing continues to Part [2]. !WOW! thanks Kate Golem Biewski.