Looks like some kind of winter squash; could be crossed with pumpkin.  I've found that volunteer squash usually are delicious, no matter what they've crossed with. Oftentimes volunteers do better than what I plant. We had a volunteer this spring that gave us some very nice acorn-type squash that was very good!

I was thinking maybe a pumpkin mix also, just by looking at it.  I love the bamboo trellis, and I sure wish I had lots and lots of bamboo.  I am not sure how many squash you have, or how big they will get, but when I was first looking up trellising cantaloupes, it said to place the young melon in a stocking and tie the stalking to the trellis.  The stocking then grows (stretches) with the growth of the melon.  Maybe this could work for you, or give you an idea....  good luck.  Would like to see it as it progresses.   

There are several winter squash that look about like that. If it's mostly circular, then it's probably some pumpkin variety (I've grown some just like that), if it's about the size of a football and elongated, it's possible it's a vegetable spaghetti squash. I'm sure there are tons of other options as well though.