Is the platypus, this incompletely evolved Australian mammal, viviparous or oviparous?

The platypus is one of the most primitive mammals. It is an incompletely evolved mammal, with very few species; within its genus there is only one animal, the platypus, and it is also one of the lowest mammals. The platypus has a beak and feet like a duck, while its body and tail resemble those of a beaver. It appeared 25 million years ago and still lives in Australia today. Because the platypus population is relatively small and its distribution is relatively limited, no subspecies have yet been found. So is the platypus viviparous or oviparous? According to Australian animal data, although the platypus is a mammal, it is oviparous. The platypus lays its eggs in a nest, 2-3 eggs each time. The eggs are even smaller than sparrow eggs and stick to each other. After two weeks of incubation, the baby platypus is born. During the incubation period, the entrance to the burrow is blocked. The hatched young are very incompletely developed. The platypus has neither a pouch nor nipples. Bundles of mammary glands open directly onto the mammary area of the abdomen. The young use a retractable tongue to feed on the milk from the mammary area. The lactation period is about five months. They rely on breast milk for 4 months before they can go out and forage on their own, and at over 2 years old they are considered adults. Their lifespan is generally 10-15 years.

Because the platypus can lay eggs like a reptile or bird; after the eggs hatch, it can also feed milk to its young like a mammal, which contradicts scientists' existing division between mammals and non-mammals. After much controversy and research, scientists finally concluded that this strange creature belongs to the “monotremes” family, that is, “egg-laying mammals.” This animal represents a link in the evolution from reptiles to mammals.

The platypus is covered all over with soft, dense, short brown fur. Compared with the echidna, its braincase is smaller, and its brain is hemispherical, smooth and without convolutions. Its limbs are very short, with five toes bearing hooked claws, and webs like thin membranes between the toes, much like duck feet. When walking or digging, the webs fold back toward the palm. Its whole body is covered with soft fur, like a layer of fine waterproof clothing. Its bill is extremely broad and flat, mounted on its head like a mask, shaped like a duck's bill, soft in texture, somewhat like leather, and covered with nerves, able to receive electrical signals emitted by other animals like a radar scanner. With this powerful tool, the platypus finds food and distinguishes direction in the water. Inside the bill there are broad keratinized gums, but no teeth. Its tail is large and flat, accounting for 1/4 of its body length, and acts as a rudder when swimming in the water.

Adult platypuses have a length of 40-50 cm, and females weigh between 700-1600 grams, while males weigh between 1000-2400 grams.

The platypus has a very low body temperature, and it can fluctuate rapidly.