I'm hoping someone could help me find a book from my childhood. The protagonist is a young boy who gets given a video game that accidentally allows him to travel back to a time when dinosaurs are alive. He bonds in particular with a mother-child pair of Diplodocus (or another sauropod species) and it ends with him trying to save them from a volcanic eruption. During the venture, the mother Diplodocus uses her tail as a bridge over lava, getting burned in the process. Back in the present, he goes to a museum and finds the fossilised skeletons of the pair, and he knows it is the mother because of the char marks on her tail bones.
I have been trawling google for this with no success whatsover, so I hope someone here can help!