Abstract
The strange biota of Neoproterozoic sea bottoms become more understandable if we assume that otherwise soft sediments were sealed by firm and erosion-resistant biomats. This allowed "mat encrusters" (vendobionts; trilobozoan and other sponges) to get attached to sandy bottoms, and molluscan "mat scratchers" to scrape off an algal film, as if they were living on rocks. Minute conical "mat stickers" (Cloudina) probably required a sticky substrate to become stabilized in upright position. Horizontal burrows are interpreted as the works of worm-like "undermat miners." Only the latter lifestyle appears to go back to the Mesoproterozoic; the others emerged in Vendian times and virtually disappeared when matgrounds became restricted to hostile environments in the wake of the Cambrian ecological revolution.
