Extant mammals can be divided into three broad categories, namely protozoa and theropods. Isn't that just two? Don't worry, because the theropod subclass is divided into the post-mammal subclass and the true subclass, and although it is not the same taxon as the previous protozoa subclass, it can be put together.
The true beast is our most common mammal, cats, dogs, cattle and sheep, and even we humans belong to the true beast. Later, the order of the beasts refers to various marsupials, such as kangaroos, koalas and so on. The post-beast order is more primitive than the real beast. The most primitive of mammals are the species of the protozoa subclass, including echidnas and platypus.
In fact, the appearance of the echidna is not particularly strange, and the platypus looks the most bizarre.
And it was not until 1798, when the British governor of New South Wales sent platypus specimens and sketches to the British Museum, that Europe and the entire scientific community did not know of the existence of this animal, and no one believed it at all, believing that the governor of New South Wales deliberately made things happen, stitching together the furs of several animals and sending them to the British Museum.
However, the staff searched for half a day and did not find the seam, coupled with follow-up observation records, the academic community slowly accepted that there was really such a strange animal.
There is only one single-hole order under the protozoa suborder, and the platypus is the only species of the single-for-hole order and the platypus family.
As one of the oldest primitive mammals, the platypus has many little-known secrets and many characteristics that are not typical mammals.
First of all, the meaning of single-fortrend is that instead of differentiating the birth canal, urethra, and anus, there is only one cloaca to do these tasks, similar to reptiles.
Second, adult single-for-hole animals do not have teeth, but do occur in infancy and fall out as they grow.
In addition, the shoulder blades, ear bones, and digestive tract of single-for-resents are different from most other mammals.
In addition, there are many peculiarities in the platypus, and they are all quite interesting. Let's elaborate on the three most representative characteristics of platypus.
Although platypus was first recognized by the scientific community in 1798, it was not until 1884 that it was determined that platypus was an oviparous. There had been speculation before, but there was no conclusion, so the British scientific community decided to send professional people to Australia to look for platypus.
In 1884, the British zoologist William Hay Caldwell was sent to Australia, where he organized more than 150 Indigenous Australians to set up a research site in northern Queensland and found platypus nests and eggs.
When the news reached Britain, there was another upheaval in the scientific community — there were actually oviparous mammals.
Although the platypus itself is quite large, its eggs are very small, only about 11 mm in diameter, which is one size smaller than a quail egg.
After about 10 days of incubation, the female platypus will lie flat in the nest and the cubs will instinctively crawl to the mother's abdomen to feed.
And although the platypus is a mammal, it does not evolve nipples, but has a depression in the abdomen, where the sweat glands are specialized into mammary glands, which secrete milk directly from the lactation hole (specialized pores) for the cubs to eat.
There are only a handful of extant mammals that are poisonous, and platypus is one of them.
They have a hollow spike at the ankle of the hind paw, and venom is generated from the venom glands and can be secreted along the hole in the middle of the spike and injected into the place where the spike is pierced. However, only adult male platypus can produce venom, and the amount of venom is more abundant during breeding.
Platypus venom can kill small and medium-sized animals and is not life-threatening at the same dose. But the platypus's venom has an effect, that is, it will amplify the pain around the poison injection site, making people extremely sensitive to pain, usually lasting for days to weeks, even if the wound is healed, it will continue to be painful for a period of time.
Most mammals hunt either by sight or by smell or hearing, and the platypus abandons all of this.
Come, let's take a closer look at the picture below, careful friends should be able to see that the platypus's eyes and the ear holes behind the eyes are in a slender groove. The platypus forages in the water, and when it dives into the water, the groove closes to protect the eyes and ear holes of the platypus, and the nostrils above the platypus flat mouth close underwater to prevent choking.
Eyes and ears can't be used, noses can't be used in water, so what does the platypus rely on to sense prey? This answer is high-end, they rely on inducing bioelectric fields to determine the orientation of prey (and some dolphins can do the same).
Animals produce an electric field when their muscles move, while platypuses rely on electrical receptors located at the back of the mouth and mechanical stimulation receptors widely spread over the mouth to detect the electric fields generated by animal movement in water.
After detecting the electrical signal, the platypus can turn its head to face its mouth in different directions, thereby comparing the signal strength and determining the specific position of the prey.