Finding Bilaterians

The burrows,found in northeastern Uruguay,have details that offer hints about the appearance of the animals that made them. The slugs were less than four-tenths of an inch long and had primitive feet that they could extend into the mud to help them slide along.

The researchers dated the fossils by measuring uranium decay over time,geologically speaking: within 6 million years.

These fossils represent some behaviours that have already evolved, said Murray K. Gingras,a professor of paleontology at the University of Alberta,who reported the findings in Science.

These probably arent the oldest trace fossilsthere must be something older out there. That gives paleontologists something to do.