Question

1. which derived characters do mammals share with crocodiles? 2. which derived character makes mammals unique? fur 3. which derived character do crocodiles, birds, and snakes share but not mammals? additional skull openings fur eggs with shells

Explanation:

1. Mammals and crocodiles both have amniotic eggs and four - limbs. Amniotic eggs allow for reproduction on land, and four - limbs are a common tetrapod feature.
2. Fur is a unique characteristic of mammals among the given traits, providing insulation and other functions.
3. Crocodiles, birds, and snakes have additional skull openings which mammals do not have. This is a key distinguishing feature in their evolutionary and anatomical differences.

Answer:

1. Amniotic eggs, four limbs
2. Fur
3. Additional skull openings