And occasionally we still find whales with the vestiges of tiny hind limbs.

并且我们偶尔仍能现鲸鱼残留着微型后。

This study aimed to pinpoint the genetic changes that led to hind limb loss, and discovered a drastic change that inactivated a gene essential for limb development called, and I'm not joking, Sonic hedgehog or Shh.

这项研究旨在找到导致后消失的基因变化。他们现了一个使对四很重要的基因失活的重大变化，我没开玩笑，这个基因叫做音猬因子。

When we compare a Nanotyrannus verses a sub adult Tyrannosaurus Rex of about the same size, they're going to be extraordinarily similar in terms of their hind limbs, their tail and their body proportions.

当我们把一头矮暴龙和一头大小相当的未成年霸王龙进行比较的时候，它们的后、尾巴和身体的比例都出奇地相近。

Now, this can be a little confusing because both types have three claws on their hind limbs.

现在，这可能有混乱，因为这两种型树懒的后上都有三个爪子。

Eventually, their front limbs became flippers and their hind limbs became weak and unnecessary.

最终，它们的前变成了鳍状，而它们的后变得虚弱和多余。

However, according to a 2006 study, they didn't completely lose their hind limbs until about 1 million years later, or 34 millions years ago.

然而，根据2006年的一项研究，它们直到大约100万年后，也就是3400万年前才完全失去了后。

Birds only use their hind limbs, their legs, for walking on the ground.

只用它们的后， 它们的腿，在地上行走。

Alongside those human remains were bones from the left forelimb, left hind limb, and various distal bones, the sort of fingers and toes of both sides of a very large Pacific walrus.

与那些人遗骸一起现的还有来自左前、左后以及各种远端骨头，这些骨头属于一只非常大的太平洋海象的四和手指脚趾部分。

And most importantly, it also had bigger primitive hips, so its hind limbs had something to anchor on to, an important step in becoming a fully four-legged animal.

而且最重要的是， 它还拥有更大的原始臀部，因此它的后有了可以附着的东西，这是成为完全四足动物的重要一步。

And we did see about a 5 to 10 percent difference in the weights of the hind limbs in terms of muscle mass.

我们确实看到后的肌肉质量有大约 5% 到 10% 的差异。

Snake embryos, for example, sprout hind limb buds.

比如说，蛇的胚胎萌了后芽。

Another major category in differences in dinosaurs is in the hind limbs.

恐龙差异的另一个主要别是后。

Paleontologists have ruled out burrowing, though, because their forearms were too short and their hind limbs were too long for a burrower.

不过，古生物学家排除了挖洞的可能性，因为它们的前臂太短，后太长，不适合挖洞动物。

Assuming that Microraptor was a glider, they'll test the hind limbs in different postures to see what, if anything, works best.

假设小盗龙是滑翔机，他们将以不同的姿势测试后，看看哪种姿势效果最好。

Many of these have minuscule limbs; some look more like snakes than lizards and a few have completely lost the toes on their hind limbs.

这些蜥蜴大部分有极小的四；一些看上去更像蛇而不是蜥蜴，还有一些完全失去了后腿的脚趾。

So even in this deformed specimen, there is no evidence that the animal could put the hind limb in a horizontal plane.

因此，即使在这个变形的标本中，也没有证据表明该动物可以将后置于水平面上。

If you remember, I mentioned earlier, that the old view of hadrosaurs had them standing almost upright, on their hind limbs.

如果你还记得的话，我之前提到过，鸭嘴龙的旧观认为它们几乎直立，用后站立。

But if the hind limbs couldn't do the same thing, what did they do?

但如果后不能做同样的事情，它们会做什么呢？

To adapt to an aquatic lifestyle, Ichthyosaurs evolved paddle like front and hind limbs as well as a fin tail.

为了适应水生生活方式，鱼龙进化出了像桨一样的前后以及鳍状尾巴。

Early on it was thought that Hadrosaurus stood straight up on their hind limbs using their tails for support.

早期人们认为鸭嘴龙用尾巴支撑后直立。