Hallidaya

These Ediacaran organisms thrived by living in low-energy inner shelf, in the wave- and current-agitated shoreface, and in the high-energy distributary systems.

[3] During the Belomorian of the Late Ediacaran other organisms who lived on the ocean floor diversified their appearances through frondomorphs, tribrachiomorphs, and bilateralomorphs.

Hallidaya became extinct in the Kotlinian (550-540 Ma) of the Late Ediacaran after there was an increase of migration to high-energy areas by burrowing animals.

These Ediacaran organisms were progressively outcompeted by bilaterians who anchored into the microbial mat of the ocean floor with their basal bulbs and possibly evolved a symbiosis with photoautotrophic or chemoautophrophic microorganisms.

[2] [4] There were also Ediacara fan-shaped sets of paired scratches found from the Eidacara Member of the Rawnsley Quartzite in South Australia, Kimberichnus teruzzii.

Their co-occurrence and systematic feeding traces in the Ediacara biota record supports the theory that bilaterians existed globally before the Cambrian explosion.

Ediacaran fossil Hallidaya brueri from the Ediacara Member of the Rawnsley Quartzite in Crisp Gorge, Flinder Ranges, South Australia (Retallack 2018) [ 6 ]