Dinosaurs

With almost nothing but fossils to study, scientists can only guess at most dinosaur behavior. For example, although T. rex is often described as a ferocious predator, scientists only know that it had a skeleton that likely supported a strong body, and it had the jaws and teeth necessary to eat large prey animals. It is possible, however, that T. rex never even attacked live animals, but instead ate only animals that were already dead. Recently, scientists think they may have found evidence that some dinosaurs were social animals, which means that they spent time together in groups. They based this idea on a fossil find in Patagonia, where the bones of six, large, carnivorous dinosaurs were found huddled together in one area. The scientists think the dinosaurs, a new species that measures 40 feet (12.2 meters) long and had sharp and bladelike teeth, may have hunted together so they could attack and kill sauropods that grew to at least twice their size. Scientists believe some dinosaurs were social because their bones suggest that they were able to make loud noises. The lambeosaurs, for instance, had sound-producing tubes inside the skull, and scientists suspect that the animals communicated with one another.

Scientists sometimes find dinosaur footprints that have been preserved over time. From these, they can learn how the animal moved. Footprints of ornithomimids, which were ostrich-like dinosaurs, show that they could run at least 25 miles (40 kilometers) an hour, while those of a 3-foot-long (9 meter) meat eater called a Megalosaurus could zip along on its hind legs at speeds of 29 miles (48 kilometers) an hour. By looking at the bones of dinosaurs, scientists can also guess their fastest running speed. A recent study of T. rex bones shows that it probably could run no faster than the much smaller ornithomomids.

Scientists have recently found many dinosaur eggs, some of them with young still inside. A group of Allosaurus eggs found in Portugal provided some clues to the way they were born. The egg shells were covered with tiny holes, called pores, and looked very much like the pore-covered eggs of current-day crocodilians. The pores allow air to flow into the eggs, so the growing babies can breathe. Based on these findings, scientists believe the female dinosaurs of this species laid their eggs in mounds of vegetation or buried them, just as the now-living crocodilians do.

One of the best places in the world to find dinosaur fossils is Mongolia. In 1993, scientists learned that it was also an excellent place to find eggs with developing babies, called embryos (EM-bree-ohs), still inside. Here, they discovered a nest containing the first embryo ever found of a meat-eating dinosaur. It was a theropod, called an oviraptorid, that looked much like an ostrich, and the embryo dated back 70 to 80 million years ago. Interestingly, they also found the skulls of two small velociraptors in the nest. Were the velociraptors there to eat the eggs, or had the mother oviraptorid brought the velociraptors to feed her babies? Scientists do not know for sure. Some even guess that the mother velociraptor may have laid her eggs in the oviraptorid nest. If the oviraptorid mother did not notice the intruders, she would raise them as her own.