Wildflowers: Some Prunus?

Prunus virginiana has perfect round fruits unlike this. This might be an escapee, but it is growing high in the mountains - 2.8 km and about 10 miles from the city. But with birds anything is possible... Is it Prunus at all?
Thanks

 

Not sure what it is, but that persistent basal calyx doesn't look like a Prunus at all to me.

 

Prunus serotina produces a persistent calyx.

 

Thank you, Michael and Ron! The problem is that Prunus serotina like most of Prunus species have perfectly round (spherical, to be exact) fruits, even when they are unripe. This one. however, looks elongated and flattened at the calyx. I looked at most of photos for Prunus and could not find even close shape.

 

I run into a dead end on Prunus as well -- used USDA's PLANTS database to view all of the species that occur in Utah, and all fruits (as far as I could tell) are spherical-globose.

 

Might be an aberration, perhaps even resulting from infestation. Were there similar plants nearby, with the same fruit shape?

 

No, it was standalone small tree high in the mountains - above the belt of shrub oaks.

 

Well, memory is not the most reliable instrument. Especially, when you shoot about 400 photos every weekend (on the principle of American westerns: shoot first and ask later), it is diffucult to memorize all details. So I went up there (about 1 km rise) to look for details. And it appears to be not a tree, but rather a shrub. And not a solitary plant but rather a solitary spot of multiple stems surrounding the fir tree which probably saves them from the killing sun. And the fruits were never juicy. They are hard as nuts. I crack opened some of them and they are empty. It might be an aberration after all.

 

Still not ringing a bell with me but you might find it in books or web pages on the wild plants of your region.