Mystery Mushroom

I've been watching what I assume is a mushroom that appeared three days ago in our front yard. Initially it was soft and spongy to the touch and now has hardened. It's approx. 2 inches (5 cm) in diameter and is transversed by primitive golden colored filigree. My ID app suggests that it's of the Class 'Agaricomycetes', but you certainly couldn't prove that by me. What I don't know about Fungi would fill volumes!  Be Well! :)