史前哺乳动物的身体结构: hair,fur,tooth,head,jaw,horn,armor,antler, pouch 史前哺乳动物的行为动作: feed,hide,fight,eat,crush,hunt,escape 史前哺乳动物的外貌特征: small,tiny, huge,large,long,saber-liketooth, strong, giant, fierce, sharp tooth, heavy, furry 与史前哺乳动物的生活习性有关的词: earth,land,milk,meat-eatingplant-eating, ocean, ice age give birth to sb./sth.生孩子，产仔 die out 灭绝 millionsof数百万的 be full of...充满...... not...anymore 不再...... with 复合结构作原因状语: But with all the big dinosaurs gone,mammals didn't have to hide anymore. 时间状语从句: Fish swam away fast when this huge hunter wasnearby. 定语从句: The hornless rhino was the biggest mammal that hasever lived on land. 比较状语从句: Giant kangaroos were much bigger than today'skangaroos. 定语从句: Manatees are mammals that live in the water. 比较状语从句: That's as long as two kids'bikes lined up endtoend. 被动语态:Amanatee baby is called a calf 动名词短语作主语: Swallowing trash can hurt manatees 结果状语从句: Fishing line can get tangled around manatees sothey can't swim.