emerald-of-the-eight:

Researchers first discovered the pancake-shaped creatures — a group known as Dickinsonia — in the late 1940s. The species were among the most common residents of the world’s oceans 558 million years ago, during the Ediacaran period. Whereas most living things during that time ranged in size from microscopic to a few millimetres long, some Dickinsonia grew up to 1.4 metres in length.

The creatures’ large size has puzzled scientists because Dickinsonia lived tens of millions of years before the Cambrian explosion, the period 541 million years ago when living things became bigger and most major animal groups emerged. Scientists have since debated whether Dickinsonia were primitive animals, giant single-celled organisms called protists, bacterial colonies or something else entirely.

The latest study attempts to end that debate by analysing chemical biomarkers preserved in a unique set of Dickinsonia fossils from Russia, rather than by examining the ancient species’ body characteristics.

World’s first animal was a pancake-shaped prehistoric ocean dweller