Quercus macrocarpa hybrid

Chestnuts, hazelnuts and heart nuts....

Some examples of the numerous variations of chestnut and hazel nut I am propagating this year.

Castanea spp. Luther Burbank hybrid chestnuts

Quercus spp., Q. macrocarpa?

I found this unusual species of Oak the other day falling from a neighborhood tree.

The closest similar oak species I can find is Quercus macrocarpa, the Burr oak or Mossy cup oak. However Q. macrocarpa has a more hairy cup with clearly visible hairs along the cup margin. In contrast the cup of this acorn was extremely thick, hard and woody, almost like scales.

One possibility is that this is a hybrid of Q. macrocarpa and some other oak species and that this acorn is an one of many phenotypic expressions.

Quercus macrocarpa is one of the largest seeded oak species in the world and the largest in N. America. The largest is the neotropical Quercus insignia. The seed is notable for its massive size and considerably low tannin content when compared to other acorns.

Any thoughts on positive ID welcomed in Comments.