OK. I now know a lot more about the plants of the Jurassic period than I did before. This hardly makes me a paleobotanist, but it’s good enough for a minicomic.
Common flora of the Jurassic period included tree ferns, cycads, horsetails, club mosses and regular ferns. Proper trees were limited to conifers (pine trees and such) and gingkos. Flowering plants did not develop until very late in the Jurassic, so fruit of any kind would not have been in the actual brontosaurus diet. Yes, a gingko has “fruit”, but those are technically just really thick seeds and not full on fruit like a pineapple or a banana. They also smell horrible and probably taste worse, and while I’m sure a brontosaurus would eat them they would hardly constitute a treat for the poor beast.
So, really, if you were going to give a brontosaurus a period correct snack, you would probably have to offer him a pine cone or some pine nuts. I think these particular dinosaurs, being accustomed to the occasional visit to our timeline, may have cultivated a taste for something sweeter, like apples. Or root beer.
So I’m going with the apple, and assuming that something with a head as big as a brontosaurus’s and at least some teeth (even if they are the peg-like teeth of something that lived on pine branches and gingko leaves) would be able to chew it up pretty effectively. Or at least bite it a time or two to get at the juice and let the rocks in its gizzard take care of the rest of it.
Man, how many pine needles would something that big have to eat to keep going? The brontosaurus is an amazing creature.