Bava Kamma 78: Non-Kosher Animals Crossbreeding, Halacha and Stealing

The Gemara continues to question the meaning of "an ox or a sheep".  In their search to understand whether or not this refers to diverse kinds, the rabbis question which animals can mate with other animals.  They understand that oxen cannot mate with sheep, but which other animals might be indicated?  One of their more interesting conversations is about kosher and non-kosher animals cohabiting.  Could we benefit from such an animal?  The rabbis note that all kosher animals belong to one order - our notes teach us that these are known as artiodactyla.  There are some non-kosher animals (pigs, camels) that belong to this group as well, but generally crossbreeding kosher and non-kosher animals is impossible. 

There are many conversations in the Talmud about the koy, which is thought to be either the result of cross-breeding or its own species.  The key is mentioned here as well.

A new Mishna teaches us that if one sells a stolen animal but the animal was not slaughtered according to halacha, or if the thief kept even one one-hundredth of the sold animals for himself, he only has to pay the twofold payment.  The four or fivefold payments do not apply.

The Gemara suggests that thrives might sell most of a sheep, for example, but keep part of its fleece.  A person might steal and sell an animal that is damaged, though, and this would allow for the four or fivefold payments.  Further, a person might sell a stolen animal together with a partner.  This creates difficulties as well.  Perhaps the thief 'withholds' information about the slaughter from his partner, causing the partner to be exempt from liability.  

The rabbis end our daf using the example of a pregnant woman to better explain the concept of 'withholding'.  If a fetus is in fact considered to be part of the woman herself, like her thigh, then she is not withholding the fetus.   Or, because the fetus will eventually detach from her body, is she withholding?