The name monotreme means one hole referring to the single orifice they use for reproduction, excretion, and egg-laying.

单孔目这个词指一个孔，指的是一个用于生育、排泄，和下蛋的孔。

And these ancient egg-layers probably reproduced a lot like today's monotremes do.

这些古老的卵层可能像今天的单孔类一样繁殖。

As a monotreme, she's part of the most ancient lineage of mammals alive today.

作为单孔类动物，她是当今最古老的哺乳动物谱系的一部分。

The three modern mammal groups -- the placentals, marsupials and monotremes -- all made it.

三个现代哺乳动物群——胎盘 动物、有袋动物和单孔动物——都成功了。

There were once hundreds of monotreme species, but there are only five left: four species of echidnas and the duck-billed platypus.

曾经有好几百种单孔目哺乳动物，现在仅存5种：4种针鼹和鸭嘴兽。

And we think monotremes have been doing it more or less that way this whole time.

我们认为单孔类动物一直以来或多或少都是这样做的。

Well, there's the platypus, an egg-laying monotreme with venomous spurs.

嗯，有鸭嘴兽，一种产卵的单孔动物，有毒刺。

Another idea is that therians followed a path similar to the monotremes, where eggs were retained in the mother's body for longer and longer periods of time.

另一个想法是， therians 遵循类似于单孔类动物的路径，卵子在母亲体内的保留时间越来越长。

For crown group mammals, our most recent common ancestor is the one shared by placentals like us, marsupials like the kangaroo, and the monotremes like the platypus.

对于冠群哺乳动物，我们最近的共同祖先是像我们这样的胎盘动物、袋鼠这样的有袋动物和鸭嘴兽这样的单孔类动物共有的祖先。

These little creatures didn't belong to any of the three main mammal groups on the planet today—which are the placental mammals (like us), monotremes (like the platypus) and marsupials (like koalas and kangaroos).

这些小动物不属于当今地球上三个主要哺乳动物群中的任何一个——胎盘哺乳动物（如我们）、单孔类动物（如鸭嘴兽）和有袋动物（如考拉和袋鼠）。