Aves

1. Forelimbs are modified into wings.

2. The body is covered with feathers and scales.

3. Skin is dry only a single preen gland is present.

4. Mammary glands are absent.

5. A diaphragm is absent.

6. A toothless beak is present.

Mammals

1. Wings are absent except in bats.

2. Feathers and scales are absent. Hair are present.

3. Skin bears a number of sweat and oil glands.

4. Mammary glands are absent.

5. A muscular partition called diaphragm is present between thorax and abdomen.

6. Jaws do not form beak. Teeth are present.