I planted several butternut squash from seed. They came up, grew prolifically as squash vines do, and started producing squashes. I didn't pay much attention until a week or so ago when I happened to see a dark green squash in amonst the butternuts. Thought for a second it was a zucchini under the butternut vine. ( I did not have zucchini in this garden). Attached are pics of the squash (there are 3) with some of my butternuts to give you a sense of the size of these squashes. Anyone, know what kind of squash this is? I thought maybe a seed go mixed up in the butternut seeds I bought. I went on line and I can't find a squash like this. Any thoughts??