No idea, sometimes with mixes it's so hard to tell what the parentage is. I do think that your dog's head is a bit more refined than many of the pit mixes i've seen.
Happy birthday to Momo! She looks like a happy little sweetheart. And wow - calm at a year? She is certainly a gem. I'm still waiting to see any sign of calm from my girl - who will be 3 in December. LOL