Large ornamented Ediacaran microfossil

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Large ornamented Ediacaran microfossils are microscopic

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.[1]

Affinity

The affinity of large ornamented Ediacaran microfossils is a matter of current research.

Like the resting cysts of some animals, these microfossils have three layers in their cell walls.[1] If large ornamented Ediacaran microfossils represent animal resting stages, this would be consistent with frequent periods of oceanic anoxia in the Ediacaran period, which disappear in the Cambrian period.[1]

They are much larger than any known dinoflagellate, and dinoflagellate biomarkers are absent in the Ediacaran period.[1]

Green alga-related spores and cysts are generally differently or un-ornamented, and an order of magnitude smaller in diameter.[1]

Role of spines

In the Ediacaran period, predatory (cell-ingesting) organisms were just evolving.[2] It has been suggested that the spines evolved as a defence to predation,[3] although this argument loses weight if predation began earlier.[1] Further, many predators are unaffected by spines, with the cyst alone providing sufficient protection from digestion.[1]

References