A wild guess: the acorn-cup of Quercus ithaburensis subsp. macrolepis?? For anyone who doesn't know this Mediterranean oak, the seed receptacle, or cup of the acorn, is a remarkable thing, with excrescences that eventually harden into something that makes it look like a wooden model of a sea anemone. I have planted a few seedlings in the unwatered part of our hot Greek garden, in the shade of a stone bench, in the hope that at least one will survive, to give shade in its turn to people on the bench - not me alas, as I'll be long gone by then!