Evolution of the brachiosaur in a book

When I was a kid, a book told me that the brachiosaur stood with keeping his neck perpendicularly. However, recently I noticed that a new book shows the neck of brachiosaur is horizontal rather than vertical. Although the dinosaurs are creatures more than 100 million years ago, why the characteristics of them change among twenty years? Moreover, the velociraptor has feathers now, whereas he didn’t have them twenty years ago. These changes may be considered to be a result of the improvement of the techniques for examinations. The paleontology of dinosaur may be the clearest example of the development of science. But actually, we have no idea whether it is truly called as the development. However the technologies develop, we will not be able to know the true shapes of dinosaurs before we make a time machine. Twenty years later, the tyrannosaurus may fly in the sky.