(1)哺乳類の増加と巨大化
(2)1千3百万年前から2百年前まで
(3)造山運動
(4)気候の冷却
(5)more and larger mammals
さらに詳しく
(1)輪郭が明快なこと
(2)clarity of outline; "exercise had given his muscles superior definition"