Oasis (Dinotopia Series) by Cathy Hapka
Jack and Ty are opposites. So when they travel together in a caravan across the Great Desert, there are bound to be disagreements. And when a sandstorm separates the boys from the rest of their group, the arguments get worse. Then they stumble upon a legendary oasis where they find a lost colony of small dinosaurs called Saltopus. Somehow, Jack and Ty must put aside their differences long enough to befriend the shy dinosaurs–and figure out how to help them!