NEW YORK — A bizarre-looking fossil worm that's been a puzzle for scientists has given up a secret: Researchers now know which end is which.
The giveaway was finding evidence of eyes and teeth in the black traces of carbon the creature left behind in ancient rock.
The worm, called Hallucigenia sparsa (huh-loo-sih-JEE'-nee-uh SPAHR'-suh), lived 508 million years ago. It was up to 2 inches long. It had legs, and spiky spines sticking out of its back.
Until the 1990s, scientists thought those spines were legs. So their view of the animal was upside-down. Some researchers also falsely identified a head at what turned out to be the tail end.
Researchers in England and Canada report their new results in a paper released Wednesday by the journal Nature.