Characteristics of Pterosaurs
The extinct flying reptiles called pterosaurs were the second group of animals (after insects) to evolve flight. Most pterosaurs were about the size of modern seagulls. A few were as small as sparrows, but some of the later species were the largest flying animals that have ever lived. In 1817 Theodore Von Soemmerring published the first description of a pterosaur fossil, and thinking that it was that of an unusual bat species, he drew his reconstruction with a very batlike posture and wing. His early reconstruction of a pterosaur has haunted the public and scientific perception of pterosaurs ever since. Soemmerring’s reconstruction is understandable given that he was the first to try to describe a pterosaur, that few naturalists of the time accepted the idea of major groups of extinct animals, and that both pterosaurs’ and bats’ wings consist of a membrane supported by enormously elongated finger bones. Soemmerring showed his pterosaur with the laterally directed legs and reoriented feet of bats and with the wing membrane stretching from the arm and finger along the sides of the body and legs all the way to the ankle. The reconstruction also included a membrane stretching between the legs, similar to that in bats. Even though other scientists developed less batlike descriptions of pterosaurs in the late 1800s, the popular literature, and even some scientific literature, continued to describe pterosaurs as batlike into the 1980s.
Bats perch by hanging upside down from tree limbs and roofs of caves. Though many are surprisingly agile climbers, bats are generally awkward when crawling on level surfaces. Did pterosaurs also hang upside down and avoid landing on the ground? Until recently, some paleontologists thought they did, but most scientists now agree that pterosaurs got around on the ground reasonably well. What is still uncertain is whether pterosaurs walked on all fours or just on their hindlegs. Pterosaurs’ ancestors were bipedal (two-footed) and used their tails to balance their forward-tilted trunks and heads. Early pterosaurs also had long tails and probably could have run on their hindlegs, certainly handy for an animal with wings for forelimbs. These early pterosaurs, however, could have used their forelimbs for walking because their arm and hand bones were only slightly enlarged—most of the wing was supported by the gigantic fourth finger.
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