Identification: Strange mushroom

We found this mushroom, early this spring, growing on a Ponderosa Pine. The pictures were taken in the span of about 2 weeks. It looks like a puffball of some kind but I never saw one growing on a pine before.

 

I've seen slimemold (myxomycete) spore masses come apart like this, but from the bark appearance this looks too big for any slime mold fruiting body I've heard of. What diameter is this?

 

It was about 10 cm long by 6 cm wide.

 

Thanks for the hint Frog. I made some more research and found out that it is a slime mold, Reticularia lycoperdon (Enteridium lycoperdon). It can grow to 15 cm, irregular shape and grows on pines.

 

Very cool! I had no idea the spore mass could be that large! Thanks for sharing the ID on this.