1. Viviparity: Kangaroos are viviparous animals, meaning that they give birth to live young rather than laying eggs.
2. Lactation: Female kangaroos produce milk to feed their young.
3. Hair or Fur: Kangaroos have fur, which is a characteristic feature of mammals.
4. Warm-blooded: Kangaroos are endothermic animals, meaning that they can maintain a constant body temperature regardless of external conditions.
5. Synapsid Skull: Kangaroos have a synapsid skull structure, which is characterized by a single temporal fenestra (opening behind the eye) and a lower jaw made up of a single bone called the dentary.
6. Four-chambered Heart: Kangaroos have a four-chambered heart, consisting of two atria and two ventricles, which is a common feature among mammals.
7. Diaphragm: Kangaroos possess a diaphragm, which is a muscular structure that separates the thoracic and abdominal cavities and plays a crucial role in respiration.
8. Altricial Young: Kangaroo joeys are born in an underdeveloped state and require extensive parental care for growth and development.
These characteristics collectively support the classification of kangaroos as mammals, placing them within the mammalian class of animals.