You can start tracking them and recording their coordinates (in play) as early as Chapter 2, preferably after you have accepted Deborah MacGuiness's quest, just north of Flatneck Station. Bones are on the ground and are easily confused with common animal carcasses, which can make them difficult to find unless you look for them specifically and know where to look. There are a total of thirty dinosaur bones in Red Dead Redemption 2, such as Dream Catchers, all of which are required to validate 100% progress and are included in the collectibles category.
