Complete specimens were found in Lower Cambrian strata of the White Mountains of California.

One much earlier form called Arkarua has been hypothesized to be an ancestral echinoderm because of its fivefold symmetry, though it appears to lack stereoms and a mouth.

Helicoplacus is thought to have been a suspension feeder living at moderate depths in highly oxygenated water with strong enough currents to ensure a steady food supply.

The helically spiraling rows of plates radiating from the base, which in life probably was anchored in the muddy substrate.

[2][1] The Poleta Formation is correlated with the as-yet unratified Cambrian Stage 3 (Series 2), giving it a provisional date of ~516 million years ago.