Pouches are a peculiarity of marsupials.是什么意思？

Pouches are a peculiarity of marsupials.

腹袋是有袋动物的特色.

pouches

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例句
There were pouches under the eyes, the skin sagged from the cheekbones.
眼眶下面有皱纹,双颊的皮肉松弛.

are

vi. （用于第二人称单复数现在时，第一、三人称复数现在时）是；n. 公亩（等于100平方米）；

例句
We are scared to abandon ourselves to our feelings in case we seem weak or out of control.
我们不敢放纵自己的情感，以免显得太过软弱或缺乏自制。

peculiarity

n. 特性，特质，怪癖，奇形怪状；

例句
Joe's other peculiarity was that he was constantly munching hard candy.
乔还有一个怪癖，就是喜欢不停地嚼硬糖。

of

prep. 关于，属于…的，由…制成；aux. 助动词 [非标准用语、方言] =have [主用于虚拟语气]；

例句
He did have a real knowledge of the country...
他对该国的确知之甚多。

marsupials

有袋类；

例句
...arboreal marsupials which resemble monkeys.
和猴类相似的树栖有袋动物