The bones of tiny dinosaurs have rarely been preserved, either because they were simply too fragile or because predators often ate the young, leaving few remains. Some researchers think that dinosaurs, like birds, grew extremely fast, so babies reached their adult sizes quickly. It's difficult to determine the dietary habits of animals that have been dead for tens of millions of years, but in this case there is a piece of unusually good evidence. The bones of a small lizard were found near the stomach of an Oviraptor philoceratops , and as lizards make up the diets of a number of birds, it's likely that it was this birdlike dinosaur's last meal. Recently discovered dinosaur fossils, including many seen in this exhibition, reveal that many of these bird characteristics were present in theropod dinosaurs long before birds evolved.
Birds have hollow, lightweight bones, ideal for flight-but poor for fossilization.
The fragile bones break quickly after a bird dies, and they are preserved as fossils only under extraordinary circumstances. Most people recognize mammals as warm-blooded animals that produce milk for their young, and scientists further classify mammals using additional features. Like their ancient relatives, all living mammals have three middle ear bones. Modern mammals also have hair or fur on their bodies, and when well-developed teeth are present, they are differentiated into incisors, canines, premolars and molars.