Dinosaurs are ambassadors of paleontology. Much to the frustration of scientists who study plants, invertebrates, and even fossil mammals, the word "paleontologist" is closely associated with the image of scruffy researchers digging around for dinosaur bones. Despite the popularity of dinosaurs, though, our ability to understand what they can tell us about how evolution works has been limited by the relative scarcity of skeletons. Finding a single skeleton of one species is just the very beginning of unraveling the mystery of how that creature evolved and how it fits into our understanding of ancient life.
Paleontologist John Bell Hatcher understood this. In 1901 Hatcher wrote a paper on the Jurassic dinosaurs found near Cañon City, Colorado, and he prefaced his summary with a few remarks on the study of dinosaurs:
Notwithstanding the great wealth of certain of our Mezozoic horizons in dinosaurian remains and the exceptional vigor with which the bringing together and study of dinosaur bones have been pursued for the last quarter of a century in this country by Marsh, Cope, Baur, Osborn, Williston and others, and for an even longer period, though under much less favorable conditions, by British and European paleontologists, yet we are still ignorant of the complete osteology of all but a few of the many proposed genera of dinosaurs, while of the phylogeny of the various genera and species of the different families we know absolutely nothing. This is the more remarkable considering the progress that has been made in mammalian paleontology, where in many families, as for instance the horses, camels, and titanotheres, nearly every step in their development has been traced and can be pointed out with as much precision as can the different stages in the perfection of the modern steam engine, electric motor, or other mechanical device wherein the forces of nature have been made to serve the uses of man.
Why did this disparity exist? The problem was not "a lack of interest in dinosaur remains as such," Hatcher wrote, but due to "the vastly greater difficulties encountered in bringing together sufficiently complete collections from the various localities and horizons to permit of a comparative study of the different forms from each." In other words, paleontologists had not yet systematically sampled and compared bones from particular localities to get a refined picture of how dinosaurs changed over time. The rush to obtain the biggest and best specimens, as well as the time required to exhume those bones, kept scientists from taking a closer look at the tempo and mode of dinosaur evolution. The fossil deposits in the vicinity of Cañon City seemed to have the most potential for outlining the history of dinosaurs from the Triassic through the Cretaceous, and so Hatcher reviewed them in the hopes out drawing out some clues about dinosaur evolution.
One hundred and ten years later, we know quite a bit more than Hatcher did about dinosaurs and their relationships. In the past decade, especially, a more refined picture of dinosaur evolution has emerged, though not everything has been solved. The study of dinosaurs is not restricted to the American West, but is now a worldwide endeavor, and new species are constantly adding to our understanding of dinosaur evolution. Still, there is much basic work that remains to be done in terms of understanding how individuals of dinosaur species varied from one another and investigating the natural history of particular dinosaur species. Dinosaur science has never been as lively or vibrant as it is now, but our understanding of their lives and evolution will continue to change.