语法问题

原文：Andanothermystery-someoftheseunrealisticanimals-thatsintheengravings-seemtobehalfhuman.

老师， that is in the engravings 这句话是someoftheseunrealisticanimals这句话的从句吗， 若是，为何不需要that are

And another mystery - some of these unrealistic animals - thats in the engravings - seem to be half human.

红色部分是定语从句，应为：which arein the engravings.

去掉破折号，全句的结构是：

And another mystery is that some of these unrealistic animals which are in the engravings seem to be half human.

另一个谜团是，这类雕刻上的虚假的动物好像是半人半兽。