Are you two married and going through a divorce? If you aren't, then I dont think the law has any bearing on who gets what.. Your animals are your animals and his are his. If you want to get the law involved, then I would imagine you do need to show proof of ownership.

If you cant prove you own them.. Take the animals that are YOURS, and move them some place safe. Tell him you rehomed them because you were having a hard time dealing with them and the situation (or something, whatever you want to make up).

Ask him if he wants you to rehome the other animals (you will take care of doing this) or if he wants to keep them. If you go with the "rehoming" route, and ask him if you can keep "his" animals, its going to look suspicious.

That is what I would do. But with my BF and I, whenever we get an animal together, we talk about what would happen if we split up. Its a sad conversation to have, but we both know the animals would be well cared for. And he knows that all the reptiles are mine anyway :/

I also can't say this is good legal advice, I'm sorry. I would suggest talking to an attorney or something if you're really worried.