Answer:
Because once they were very common they disappeared after the mass extinction event. ... Many geologic periods were defined by events that made natural boundary to the period.
Explanation:
Mosses go through sporophyte and gametophyte stages in their life cycle. ... However, mosses are nonvascular while ferns are vascular. Gymnosperms and angiosperms are both vascular, seed-bearing plants. However, gymnosperms release their seeds in cones (like pinecones) while angiosperms release their seeds through flowers.
Question is unclear, please re word it and i will answer it.
The lithosphere, hydrosphere,biosphere and atmosphere
(I hope this helps)
