Large ornamented Ediacaran microfossil
Large ornamented Ediacaran microfossils are microscopic acritarchs, usually over 100 μm in diameter, which are common in sediments of the Ediacaran period, 635 to 538.8 million years ago. They largely disappear from the Ediacaran period fossil record before 560 million years ago, roughly coeval with the origin of the Ediacara biota.
Source: Wikipedia — Large ornamented Ediacaran microfossil (CC BY-SA 4.0)