You can find this material in Sandy Plains, in any master rank quest, both for monster quests and when starting an expedition. But we recommend you opt for the expeditions.
In Sandy Plains, you will also be able to get additional collection points from Piles of Bones. But keep in mind that you will not always get it from each of these harvest points, we recommend you take the Palamute to search quickly and when you leave, you can come back when you need more of this material.
In this way we come to the end of this guide on where to find the Eroded Elder Skeleton in Monster Hunter Rise Sunbreak, so now that we are done, we hope this information has been very helpful, so that you can obtain this material quickly.