Remains of an ancient dragon god.
Can be found on land.
Tap occasionally for a unearthed skeleton. Every 10 minutes additional Unearthed Skeleton will be generated, stuck up to 6 unearthed skeletons(1 hour from "empty" ancient dragon skull until "full" with 6 enearthed skeletons).
Can be harvested for unearthed skeletons or treasure chests. Doing so will diminish the skull each time until it's gone.