You mainly get these berries on Jungle Ferns and if you are able to get 5 then you can craft Narcotics in the Mortar And Pastle, Thanks For Reading :D

Tip: if your struggling to tame a pteradon or any creatures who stay unconscious for a few seconds then you can make some Narcotics and feed them to keep its torpor up, which keeps it unconscious for longer periods of tame depending on the amount you feed the creature, great for starters who are trying to tame Pteradons!