eggshells. The eggs are thought to have been a blue-green color, because biliverdin is preserved in much greater abundance the photoporphyrin. In modern bird eggs, coloration can camouflage the eggs or help parents identify eggs, and it is correlated with more intensive parental care. Metabolism A study by Robert Eagle et al. of the University of California-Los Angeles indicates that from specimens of eggs found in Mongolia and examination of the isotopes carbon-13 and oxygen 18 found within, Oviraptorids had body temperatures that could be elevated higher than that of the surrounding environment but lower than that of birds. This is very different from the isotope ratios of sauropod dinosaurs like Brachiosaurus, which had body temperatures of up to and were fully endothermic. Feathers Oviraptorids were probably feathered, since some close relatives were found with feathers preserved (including species of Caudipteryx, Protarchaeopteryx and Similicaudipteryx). Another finding pointing to this is the discovery in Nomingia of a pygostyle, a bone that results from the fusion of the last tail vertebrae and is responsible in birds to hold a fan of feathers in the tail. Finally, the arm position of the brooding Citipati would have been far more effective if feathers were present to cover the eggs. Pathology The brooding oviraptorid specimen IGM 100/979 showed a callus and possible longitudinal groove left over from a healed fracture of the right ulna. Other oviraptorids have had pathological features reported in their phalanges but these have not been described in detail in the scientific literature. Paleoenvironment Almost all oviraptorids come from desert deposits of the Gobi Desert. Even in the late Cretaceous period, much of this area was desert, or at least very dry, habitat. In many of the localities where they are found, oviraptorids are among the most abundant dinosaurs present, second only to ankylosaurs and protoceratopsids. This is consistent with the idea that they were primarily herbivores, which tend to far outnumber carnivores in a given environment. Oviraptorids appear to have been far more abundant in arid habitats dominated mainly by small dinosaurs (such as those preserved in the Barun Goyot and Djadochta Formations) than in wetter ecosystems where large dinosaurs are common (such as the Nemegt Formation). The same pattern holds true for protoceratopsids, indicating that both groups preferred dry, desert-like habitat, and fed mainly on the types of tough, low-growing plant life that grows in arid climates. See also Timeline