Cenozoic

• mammalian era, from 50 million years ago to present

59:0.65. The mam­malian era oc­cu­pies the last fifty mil­lion years. This re­cent-times era is known as the Ceno­zoic.

• mammalian era, from 50 million years ago to present

61:0.2Dur­ing this Ceno­zoic age the world’s land­scape pre­sented an at­trac­tive ap­pear­ance—rolling hills, broad val­leys, wide rivers, and great forests. Twice dur­ing this sec­tor of time the Panama isth­mus went up and down; three times the Bering Strait land bridge did the same. The an­i­mal types were both many and var­ied. The trees swarmed with birds, and the whole world was an an­i­mal par­a­dise, not­with­stand­ing the in­ces­sant strug­gle of the evolv­ing an­i­mal species for su­prem­acy.

• mammalian era, from 50 million years ago to present

61:7.19This nar­ra­tive, ex­tend­ing from the rise of mam­malian life to the re­treat of the ice and on down to his­toric times, cov­ers a span of al­most fifty mil­lion years. This is the last—the cur­rent—ge­o­logic pe­riod and is known to your re­searchers as the Ceno­zoic or re­cent-times era.