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| Sunday, 6 November 2005 |
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Junior Observer |  |
| News Business Features Editorial
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When dinosaurs ruled the world... Pterosaurs dominated the skies...
"Were they birds, or weren't they?"That is a question raised by experts in the field. However, fossil remains prove that prehistoric skies were teeming with life. Different kinds of prehistoric animals had mastery in the art of flying. When dinosaurs took over the land, they took to the air and dominated the skies for 166 million years. The first such creatures were called 'Pterosaurs' meaning 'winged lizards'. They are believed to have evolved from prehistoric gliding lizards who used skin flaps attached to their sides to glide distances up to about 13 metres. They lived during the Mesozoic period, 250 to 65 million years ago. Pterosaurs evolved in many sizes - from that of a size of a crow to the size of an adult human male. Quetzalcoatlus, the largest pterosaurs had a wing span of over 12 metres - the size of a small airplane. Some had tails, others crests - both helping in keeping their balance. Their beaks were of different sizes and shapes, depending on their food patterns. They had different kinds of decorative crests. But all had skeletons of thin, hollow, lightweight bones. Each skin wing was fixed to the long bones of an arm and a fourth finger. Both wings curved back to the hind legs.
Pterosaurs evolved into two groups. One with long tails and teeth is called Ramphorhynchoids or 'prow-beaks'. Using their long tails as rudders they flew about with their rather short, broad wings. Fossil remains of prow-beaks suggest that their bodies had a covering of fur. This had made scientists think that they must have been warm-blooded and would have had muscle power to flap their wings. The other group of Pterosaurs are called Pterodactyloid or 'winged fingers'. They had long wings, little or no tail and toothless beaks.
Recent fossil findings of pterosaurs in central Argentina had revealed that they had nested in large colonies, laid soft leathery crocodile-like eggs, offered parental care to their young, and were very active predators with eagle-like eyes and precision in catching their prey. Around the height of pterosaurs' domain, about 150 million years ago evolved another group of winged creatures, the 'Archaeopteryx' or 'ancient wing' believed to have come from a hen-sized, three clawed dinosaur. Fossil findings at West Germany show that they were very large, had backward pointing toes for perching; backward pointing hip girdle bones and feathered wings much like the modern birds. However, these creatures had bony tails, beaks with reptile-like teeth and claws along their wings. Prehistoric birds also evolved in many sizes and shapes. Fossil remains found in South America had revealed a predatory bird type called terrorbirds who grew up to three metres and could have run at a speed of 70 kilometres per hour. Diatrymia, another ancient bird who was two metres tall, had been an ostrich-like creature with a horse-like skull and a hooked beak. While Hesperornis had been a two metre tall flightless sea-bird, Ichthyornis had been a small bird which looked like a sea-gull, but with a beak full of teeth. *** Did pterosaurs fly or glide?
Many pterosaurs had muscles that were too weak to flap their large wings. Therefore, scientists believe that they would have glided on rising thermal current. However, they steered well. By sweeping low, they could have seized their prey in their long beak-shaped jaws. Some believe that they must have been warm blooded and would have had energy to fly instead of simply gliding. Recent fossil findings in Argentina and China support this theory and say they would have the ability to catch their prey in flight and flap back in to the air with the weight in their beaks. **** What did pterosaurs eat? Most fed on fish while some snapped up insects, experts say. Pterosaustro with a long sieve like bottom jaw, may have filtered tiny animals from the water. Dzungaripterus with a pincer like beak could prise shellfish from rocks. Dimorphodon's strong jaws enabled it to hold its catch in a vice-like grip. Scientists believe that pterosaurs could have preyed on small lizards and dinosaurs as well. Furthermore, pterosaurs on the ground would have become prey for large and strong dinosaurs. Pterosaurs walked in an awkward manner on land, due to their weak short legs and were easy prey. Fossil findings had revealed pterosaurs beaks in dinosaur stomachs. **** How did the early birds fly? Due to its enormous size, scientists believe that Archaeopteryx may have had difficulty in launching itself to flight. Some think that Archaeopteryx would have spread its wings like nets to help it capture prey and later would have learned to leap off the ground. An 'Archaeopteryx's feathered wings could survive damage that would have clipped a petrosaur's fragile skin wings. But most experts think that the first birds would have clawed their way up tree trunks and simply used their wings for gliding down again. Whatever method they employed to learn how to fly, by the end of the dinosaur age, the birds had mastered the art of flying. |
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