Writing Based on Reading and Listening Directions: For this task, you will read a passage about an academic topic and yo

Pterosaurs are the earliest vertebrates known to have attained powered flight during their evolution. Their wings were formed by a membrane of skin, muscle, and other tissues stretching from the ankles to a dramatically lengthened fourth finger. Therefore, those who claim that pterosaurs never developed flying capabilities are mistaken in their findings.
    To begin, scientists argued in the reading passage that pterosaurs belonged to a cold-blooded class of animals. However, more careful study of their anatomy proves that pterosaurs were actually warm-blooded. If they had been warm-blooded, unlike snakes and other reptiles, pterosaurs would actually be able to fly.
    Furthermore, the anatomy of pterosaurs was highly modified from their reptilian ancestors by the demands of flight. Pterosaur bones were hollow and air-filled, like the bones of birds. They had a keeled breastbone that was developed for the attachment of flight muscles and an enlarged brain that, when studied by modern scientists, revealed specialized features associated with flight. In some later pterosaurs, the backbone over the shoulders fused into a structure known as a notarium, which served to stiffen the torso during flight, and provide a stable support for the scapula. We can draw the conclusion that the pterosaur’s weight was actually not heavy, and their wings could support their cruising through the air.
    Finally, there was considerable debate about whether pterosaurs ambulated as quadrupeds or as bipeds. In the 1980s, paleontologist Kevin Padian suggested that smaller pterosaurs with longer hind limbs, such as dimorphodons, might have walked or even run as a biped, in addition to flying, like road runners. However, a large number of pterosaur trackways were later found with a distinctive four-toed hind foot and three-toed front foot; these are the unmistakable prints of pterosaurs walking on all fours. So unlike birds who walk with two legs, pterosaurs walked with four.