One of the problems for the paleontology of this period is that almost all the rocks from it have been eroded away - the great unconformity. It has been specula

One of the problems for the paleontology of this period is that almost all the rocks from it have been eroded away - the great unconformity. It has been speculatively attributed to erosion during Snowball Earth, which preceded the Cambrian explosion, though it seems the story is becoming more complicated. https://www.atlasobscura.com/articles/great-unconformity-geology-mystery https://www.atlasobscura.com/articles/great-unconformity-geo...