What is "praecambridium"

Praecambridium sigillum is an extinct organism that superficially resembles a segmented trilobite-like arthropod, though the majority of experts now place it within the Proarticulata. It is from the Late Precambrian of Ediacara Hills, Australia, about 555 million years ago. On average, P. sigillum had at least 5 pairs of segments, with each unit becoming progressively larger as they approach the cephalon-like head.