Conical, calcareous tubes and worm burrows in Lower Cambrian stromatolites in eastern Newfoundland are found associated with indications of grazing activity. Cropping by early herbivores may have reduced the degree of dominance of the existing stromatolite-constructing algae, allowing diversification of new groups. Stromatolites, so plentiful in Precambrian and early Cambrian time, slowly perished and at present are limited only to specific environments. The cause of this drastic reduction was probably the activity of cropping, grazing, and burrowing animals.

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