TPO 47 integrated writing skill

According to the reading passage, author lists three theories to support that Pterosaurs were not capable of powered flight, since, lecturer holds opposite view and she states that Pterosaurs may have been capable of powered flight, also, she points out some competing theories, which contradict passage's arguments.
Firstly, the essay assumes that ancient reptiles such as Pterosaurs were probably cold-blooded animals, they had a slow metabolism and they were unable to produce a lot of energy to have powered flight. However, the listening material claims that Pterosaurs had a dense fur covering, which is a sign of warm-blood animals such as birds, so, they would have supplied energy needed to powered flight.
Secondly, the writer indicates that Pterosaurs were probably so heavy that they would not have been able to flap their wings fast enough to stay aloft for any length of time. On the contrary, the speaker argues that Pterosaurs' anatomical features shows that they had light weight, thus, their weight was low enough to keep them airborne.
Finally, the passage discusses that large Pterosaurs would not have had big, powerful muscles in their back legs to launch themselves into the air. In contrast, she reckons that birds only use their hind legs, but, Pterosaurs used all their four limbs to push off the ground, therefore, they had not trouble in having powered flight.