I believe that, under the rules in place in 2015, you could either
a. assume ownership of the IRA, or
b. keep it as an inherited IRA.
You had to the end of the year, or possible April 15 of the following year, to make that decision. However, once making the decision, you can't change it. If you have an inherited IRA ("John Smith as beneficiary for Mary Smith") then it is an inherited IRA forever and it can't be mixed with regular IRA funds that you own in your own name.
On reading the 2016 version of publication 590-B, it is not clear to me whether the decision is revokable or not. Some factors that might help us help you are,
a. have you made contributions to the inherited IRA?
b. have you been taking RMDs from the inherited IRA following the rules for inherited IRAs?
One thing you can definitely do is rollover the inherited IRA from one bank to an inherited IRA at another bank or broker. If this is done by direct trustee- to trustee transfer, I don't think you get a 1099-R, and even if you do, it's not a taxable event.
I don't know if, at this point 10 years later, you can assume ownership and combine the funds with your own non-inherited IRAs. I'm going to wait for the top expert to comment.
@dmertz
