a characteristic feature of Class Aves (birds) is that their endoskeleton is fully ossified (bony) and the long bones are hollow with air cavities (pneumatic) to assist in flight. Neophron (Vulture) is listed as an example of Class Aves. In contrast, Macropus (Kangaroo) and Ornithorhynchus (Platypus) are Mammals, and Hemidactylus (Wall lizard) is a Reptile , , .