As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by several million years.. 
Ó ń ṣiṣẹ́ báyì gẹ́gẹ́ bíi Olùkọ́ni ti ara rẹ̀.Ìgbésí ayé rẹ̀ ní oṣù kẹjọ ọdún 2005, wọ́n kẹ̀kẹ́ rẹ̀ ninu ìwé ìròyìn The Sun gẹ́gẹ́ bíi ọ̀rẹ́kùnrin ọlọ́jọ́-pípẹ́ tíí ọmọ ẹgbẹ́ WestLife, Mark Freehily.. 