请教OG阅读里的一句话
是OG阅读第一篇:9 v( u7 Q8 m O& z' a
小马过河-新托福专业备考社区; I3 D& Z2 |$ P, z8 x
Missing until recently were fossils clearly intermediate, or transitional, between land mammals and cetaceans.
$ ], a' M/ |& p) f: q% x4 d* R lTOEFL,IBT,托福,新托福,机经,小马过河,留学,美国,海外小马过河1 N3 {- \( _: y" ?' v' K
这句话什么意思啊, 结构该怎么看,谢谢