118．Missing until recently were fossils clearly intermediate，or transitional，between land mammals and cetaceans．

(倒装句)

到最近为止，一直缺乏连接陆地哺乳动物和鲸目动物的明显的中间或过渡化石。

分句1：Missing until recently were fossilsclearly intermediate

分句2：or transitional

分句3：between land mammals and cetaceans

1和2并列

1、2和3嵌套