'Oldest fossils of animal gut found'

Researchers have unearthed the oldest fossilised remains of animal digestive tract, dated to be 550 million years old, in the Nevada desert in the US -- a finding that sheds light on the early history of life on the Earth.

According to the researchers, including those from the University of Missouri in the US, ocean life forms that existed more than half a billion years ago mostly had simple body structures, unlike any creature which lives today.

They said beginning about 540 million years ago, the body structures of animals in the ocean changed dramatically.

This period, called the Cambrian Explosion, is widely considered by scientists to be the key point in history of life on the planet when the ancestors of many animal groups we know today emerged, according to the researchers behind the current study.

During the Cambrian Explosion, the ancestors of many modern-day animals, such as primitive crustaceans and worms, appeared, noted the study, published in the journal Nature Communications.

However, scientists did not know how these communities of prehistoric animals were related, until now.

The scientists believe they can possibly find how these ancestral creatures were connected by studying the currently unearthed tubular digestive tract fossils, which offers clues on the internal anatomical structures of the animals of this time.

"Not only are these structures the oldest guts yet discovered, but they also help to resolve the long-debated evolutionary positioning of this important fossil group," said Jim Schiffbauer, study co-author from the University of Missouri.

"These fossils fit within a very recognizable group of organisms -- the cloudinids -- that scientists use to identify the last 10 to 15 million years of the Ediacaran Period, or the period of time just before the Cambrian Explosion. We can now say that their anatomical structure appears much more worm-like than coral-like," Schiffbauer said.

As part of the current study, the researchers used an X-ray-based analysis technique called micro-CT imaging, and created a digital 3D image of the fossil.

The method allowed the scientists to view the fossil structure's internal contents, the study noted.

"With CT imaging, we can quickly assess key internal features and then analyze the entire fossil without potentially damaging it," said study co-author Tara Selly from the University of Missouri.