I bet it's caused by uneven moisture. I have no idea what your weather has been like. But here, if we had dry weather for a while, and then A LOT of rain, I would not be surprised to see such a thing. But it is more common with melons than with squash.

Perhaps this shape of squash is more susceptible to such conditions.
George
Tahlequah, OK

I don't know if it is characteristic of the wheel shaped squash but I have not had any problems with them. I have planted Long Island Cheese, Sweet Meat, Mrs Amerson's, and Rumbo in the past 5 years

This year I am planting Amish Pie, Potimarron, Sibley, Guatamala Blue, Uncle Dave's Dakota, Warsaw Buff Pie Pumpkin, Greek Sweet Red, Canada Crookneck, Mrs Amerson's, Futtsu, and Seminole and the only problem I have seen was 2 CC split the length of their neck.

Canada Crookneck

Thanks for the responses guys. I think maybe I'll scale back the watering a little and see how that goes.
Festus, how do you like the eating quality of the "Long Island Cheese" squash. Amy Goldman in her book said to do anything with it except eat it. But I don't necessarily buy that.

I did not even try the Long Island Cheese because of what Amy Goldman said in her book. I guess I should have tried them as one person's poison is another person's cup of tea. She also said that Iran was no good to eat but I have always wanted to plant that one if only for decorative purposes. I had plenty of squash that year anyway as I had planted Lakota, Sweet Meat, and Butternut.

I have not tried any I have listed this year but I am having a bumper crop. There is probably 200 squash out there.

Sigh... I just checked the last two large Sweet Meats in my squash patch. Both have major cracks. They're in the compost now. There are plenty of baseball sized fruits coming along, but they won't make anything useful in time. I had high hopes for Sweet Meat. It was supposed to be a Northwest favorite. In fairness I have to say that about half of the Marina Chioggias also split. But that one plant is gonna give me 5 impressively large specimens. Next year, I think I'll go with Bananas and Butternuts. And maybe a Warty Red Thing thrown in for laughs.