‘Relationships between dinosaurs’ examines the techniques used to study the geneaology, or evolutionary history, of dinosaurs. The primary technique is cladistics—or phylogenetic systematics—that generates branching diagrams of relationship known as cladograms. Dinosaurs have been split into two main clades: the Saurischia (‘lizard-hipped’) and Ornithischia (‘bird-hipped’). Has the dynamic (tectonic) Earth influenced the overall pattern of the evolution of life, including the dinosaurs? The fragmentation of Pangaea during the Jurassic and Cretaceous Periods resulted in isolation of Triassic dinosaur populations. With passing time, these populations evolved independently in response to changes stimulated by changing latitude, longitude, and prevailing climatic conditions.