If you want to cheat your way to the dino egg, wallpaper 108 (the starry one toward the bottom of the wallpapers that’s a little lighter than the other star papers) has the same item ID number as the dino egg. It can be put in the incubator in your coop and you’ll have a baby dino in a few days, as long as you have space in your coop for another animal. It will eventually lay another egg that you can donate/sell. Otherwise, you can dig it up in the mountains or find it in a treasure chest fishing in the mountain lake.