Echidnacaris briggsi is an extinct species of radiodont known from the Cambrian Stage 4 aged Emu Bay Shale of Australia.

[3] The first few segments of the appendages were substantially taller than they were wide, with podomeres 2-12 bearing long, slender posteriorly curving endites/ventral spines which bore numerous small auxiliary spines.

[4][5][6] Like other tamisiocaridids, it is suggested to have been a suspension feeder, using its frontal appendages to capture small prey.

Isolated eyes attributed to the species suggest that they were not stalked, but instead were adhered directly to the head, and surrounded by sclerotised structures.

The individual lenses were large, with some exceeding 335 μm in diameter, which was possibly an adaptation to seeing in low-light waters.