Large ornamented Ediacaran microfossils (LOEMs) are microscopic acritarchs, usually over 100 μm in diameter, which are common in sediments of the Ediacaran period, 635 to 541 million years ago. They largely disappear from the Ediacaran fossil record before 560 million years ago, roughly coeval with the origin of the Ediacara biota. They differ from Palaeozoic microfossils in many respects; they are larger, often have internal contents, have a differently-constructed cell wall, and differ in shape.