Reuters reports:

A worm-like creature smaller than a grain of rice that burrowed on the sea floor in search of meals like dead organic matter about 555 million years ago may be the evolutionary forerunner of most animals living today – including people.

Scientists on Monday announced the discovery in the Australian outback of fossils of this creature, named Ikaria wariootia, that represents one of the most important primordial animals ever found.

It appears to be the earliest-known member of the vast animal group called bilaterians – organisms with two symmetrical sides, a front and back, with a mouth and an anus and a gut connecting them to process food, said paleontologist and study lead author Scott Evans of the Smithsonian Institution’s National Museum of Natural History in Washington.

The advent of such a body plan during the Ediacaran Period was a pivotal moment in life’s evolution on Earth, paving the way for more advanced bilaterians such as fish, amphibians, reptiles, birds, mammals, starfish, mollusks, insects and more. The few non-bilaterian animals include sponges, corals, sea anemones and jellyfish.

Up to a quarter of an inch (6 mm) long, Ikaria had a worm-like appearance, though one end was larger than the other. Its discovery underscores the humble evolutionary beginnings of this large segment of the animal kingdom, humankind included, the researchers said. [Continue reading…]