Researchers have found a rare, 500-million-year-old “worm-like” fossil called a palaeoscolecid, which is an uncommon fossil group in North America.
Many scientists consider the “Cambrian explosion”—which occurred about 530-540 million years ago—as the first major appearance of many of the world’s animal groups in the fossil record. Like adding pieces to a giant jigsaw puzzle, each discovery dating from this time period has added another piece to the evolutionary map of modern animals.
“This group of animals are extinct, so we don’t see them, or any modern relatives, on the planet today.”
The researchers believe the new find, from an area in western Utah, can help scientists better understand how diverse the Earth’s animals were during the Cambrian explosion.
While this fossil has the same anatomical organization as modern worms, it doesn’t exactly match with anything we see on modern Earth, says coauthor Jim Schiffbauer, an associate professor of geological sciences at the University of Missouri.
“This group of animals are extinct, so we don’t see them, or any modern relatives, on the planet today,” Schiffbauer says. “We tend to call them ‘worm-like’ because it’s hard to say that they perfectly fit with annelids, priapulids, or any other types of organism on the planet today that we would generally call a ‘worm.’ But palaeoscolecids have the same general body plan, which in the history of life has been an incredibly successful body plan.
“So, this is a pretty cool addition because it expands the number of worm-like things that we know about from 500 million years ago in…