The base of the Silurian is set at a major extinction event when 60% of marine species were wiped out.. 
 wọ́n gbé àwọn tọkọtaya náà jáde lórí abala àkọ́kọ́ ti ìwé ìròhìn Attitude èyí tí ó jáde ní oṣù Kejìlá ọdún 2007.. 