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

并且我们偶尔仍能发现鲸鱼残留着微型后肢。

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肢消失因变化。他们发现了一个使对四肢发育很重因失活重大变化，我没开玩笑，这个因叫做音猬因子。

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未成年霸王龙进行比较时候，它们后肢、尾巴和身体比例都出奇地相近。

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，因为这两种类型树懒后肢上都有三个爪子。

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

最终，它们前肢变成了鳍状肢，而它们后肢变得虚弱和多余。

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肢。

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

鸟类只用它们后肢， 它们腿，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.

与那些人类遗骸一起发现还有来自左前肢、左后肢以及各种远端骨头，这些骨头属于一只非常大太平洋海象四肢和手指脚趾部分。

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.

而且最重是， 它还拥有更大原始臀部，因此它后肢有了可以附着东西，这是成为完全四足动物重一步。

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

我们确实看到后肢肌肉质量有大约 5% 到 10% 差异。

Snake embryos, for example, sprout hind limb buds.

比如说，蛇胚胎萌发了后肢芽。

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

恐龙差异另一个主类别是后肢。

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可能性，因为它们前臂太短，后肢太长，不适挖洞动物。

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，他们将以不同姿势测试后肢，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四肢；一些看上去更像蛇而不是蜥蜴，还有一些完全失去了后腿脚趾。

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

因此，即使在这个变形标本中，也没有证据表明该动物可以将后肢置于水平面上。

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

如果你还记得话，我之前提到过，鸭嘴龙旧观认为它们几乎直立，用后肢站立。

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

但如果后肢不能做同样事情，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前后肢以及鳍状尾巴。

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肢直立。