It’s been a long week, looking at…this!
Give me your guesses!
We had a great guess, a walnut with the meat missing. Close, but this is my namesake tree, the Mockernut Hickory, Carya tomentosa. You humans may not see it quite this way–this nut has been chewed open by me, Hickory Squirrel. (see my mighty tooth marks?) When they fall from the tree, the nut is covered in a thick covering that splits four ways, releasing the hard nut inside.
Which they are doing right now! Look for a tree with 5 to 9 leaflets arranged like in the photo below, and you will find hickory nuts.