Of all placental mammals, handicaps are the tiniest in comparison to their mother.

在所有胎盘哺乳动物中，与母亲相比，残疾是最小的。

This is our best guess at what the first placental mammal looked like.

这是对第一种胎生哺乳动物外貌的最好猜想了。

Paraceratherium was a placental mammal, like us, meaning that it gestated its young inside its body.

Paraceratherium 是一种胎盘哺乳动物，就像我们一样，这意味着它在体内孕育了幼崽。

The researchers suggested that the ancestors of placental mammals that lived with the dinosaurs were small, insectivorous, and nocturnal.

研究人员认为，与恐龙一起生活的胎盘哺乳动物的祖先体型小、食虫且夜间活动。

But finally, around 160 million years ago in the Late Jurassic Period, the ancestors of placental mammals and marsupials appeared.

但最终， 大约在 1.6 亿年前的侏罗纪晚期，胎盘哺乳动物和有袋动物的祖先出现了。

This includes a number of the placental mammals that are thought to have originated on the supercontinent Laurasia during the Late Cretaceous Period.

这包括许多被认为起源于白垩纪晚期超大陆劳亚大陆的胎盘哺乳动物。

These subtle 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).

这些小动物不属于今天地球上的三个主要哺乳动物群体——胎盘哺乳动物(像我们)、单孔目哺乳动物(像鸭嘴兽)和有袋哺乳动物(像考拉和袋鼠)。

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）。