And the situation is very different with other four-legged animals, tetrapods.

这种情况与其它四足物有非常大的不同。

Whatcheeria was an early tetrapod, as the first land animals with backbones were known.

瓦切螈是一种期的四足物，作为第一批有脊椎的陆地物而为人所知。

Today three early tetrapods are known and none has five digits.

今天，已经知道期有三种四足物，但没有一种跟数字5有关系。

The dog is the most knowing and clever of all four-footed animals.

四足物当中，狗是最善解人意、最聪明的物。

There were bipeds, tripeds and quadrupeds.

有两足、三足和四足物。

The four-legged animal is believed to have been just 10 centimeters tall and about 40 centimeters long.

据信，这种四足物只有10厘米高，约40厘米长。

This was the missing link between bony fishes and tetrapods, including human beings, so this was a fantastic expectation.

这是硬骨鱼和包括人类在内的四足物之间缺失的一环，所以对我们来说这种期待很奇妙。

Unlike many early tetrapods, bones of Whatcheeria have been discovered from different points in the animal's life.

与期四足物不同的是，人们发现了瓦切螈不同生命阶段的骨骼。

Bears are quadrupeds, meaning they walk on four legs, but they are able to stand up on their hind legs.

熊是四足物，用四条腿走路，但他们也能用后脚站立。

Pachyrhinosaurus though was a more compact quadrupedal kind of animal, a more sturdy build than what we see in Albertosaurus.

肿鼻角龙是一种更结实的四足物，比阿尔伯特龙身体更加粗壮。

Your few four-legged ancestors, the tetrapods, struggled in tropical river plains.

你的少数四足祖先， 四足物，在热带河流平原上挣扎。

I’m using “cow” to mean “four-legged farm animal that moos”.

我用“牛” 来表示“会哞叫的四足农场物” 。

But it also had tetrapod like legs.

但它也拥有类似四足物的腿。

It was a term of derision for two-legged as well as four-legged animals.

它是对两足物和四足物的蔑称。

And he came up with one called The Four-Legged Zoo.

他构思出了一个名为《四足物园》的节目。

But, the earliest tetrapods were all carnivorous predators.

但是，最的四足物都是肉食性 捕食者。

But the bigger news was a major change among the tetrapods.

但更大的消息是 四足物发生了重大变化。

These arid wastelands would’ve been uninhabitable for early tetrapods, but not for the amniotes.

这些干旱的荒地 对于期的四足物来说是不适宜居住的，但对于羊膜物来说却不是。

What’s clear is that these tetrapods were walking on all fours, not paddling or flopping.

很明显，这些四足物是四足行走，而不是划桨或翻滚。

One of the earliest of these new creatures was a tetrapod named Acanthostega.

这些新生物中最的一种 是一种名为棘螈的四足物。