The Devonian Period closes with another decline and mass extinction. Again, 50 percent of species vanish world-wide, the major losses taken this time by ocean life. Basic biota body blueprints remain conservative.
Note the "bottom-heavy" trend in evolution: new lineages generate remarkable diversity when they first appear, but settle to a limited number of body plans in what paleontologist Stephen Gould calls, "early experimentation and later standardization."
It takes 30 million years for biodiversity to recover fully from this mass extinction.