Among the creatures on Earth, whether on land or at sea, chordates currently seem to be the most advanced and successful class of organisms, of which mammals are the evolutionary high points of the chordate phylum, and we humans are the pinnacle of mammals.
Mammals now dominate the earth, but not always, and in the process of evolution, organisms also have the phenomenon of "thirty years of Hedong, thirty years of Hexi", the vicissitudes of the sea, the ups and downs.
65 million years ago, the creatures that dominated the earth were not mammals, but huge, unusually fierce dinosaurs that defeated other creatures by brute force, and mammals at that time were nothing more than ants at the feet of dinosaurs.
But dinosaurs are still chordates, so what about before dinosaurs? That is, before reptiles and amphibians, there was no life on the earth's land, because the origin of life originally came from the vast ocean.
In the Cambrian Period, 542 million years ago, this epoch was the beginning of the Ezoogene on Earth, because from the Cambrian period onwards, there was a massive increase in the number of living species on earth, and left a lot of fossil evidence, known as the Cambrian explosion of life.
But the shortage of fossils left over from previous organisms has caused us to not know why life occurred on a large scale in just a few million years in the Cambrian Period, which has always been a mystery of biological evolution. It is also something that Darwin's theory of evolution cannot explain.
During the Cambrian period, the earth was dominated by invertebrates, including arthropods, mollusks, cephalopods and link animals, including octopuses, squids, and squid that we are familiar with today.
In the Ordovician period after the Cambrian, 480 million years ago, cephalopods developed unusually large, and the entire ocean of the earth was controlled by such creatures, and at this time, chordates were just beginning to appear, and fish were the first animals with vertebrae, skulls and full-body bones 400 million years ago.
But at that time, cephalopods occupied an absolute living space, and a giant nautilus could reach 11 meters long, preying on prey with tentacles, which was extremely fierce.
So some fish at that time were able to abandon the ocean, go to land and eventually evolve into amphibians, reptiles, and even later mammals, which were forced by cephalopods.
However, in the Cretaceous mass extinction, not only the dinosaurs on land were extinct, but also caused the disappearance of a large number of organisms in the oceans, including cephalopods that ruled the oceans for hundreds of millions of years, and then the supremacy of life on Earth was handed over to mammals and fish.
The extant cephalopods are mainly divided into subclasses of pupae and nautilus, of which the subclass of pupa includes what we often call octopus, squid and squid, and the subclass Nautilus is the nautilus.
To say a little more, we are often confused by octopus, squid and squid, and we can't tell which one is which, and the main difference is that octopus has eight brachiopods, and squid and squid are 10.
The octopus's head looks like a round ball, while the squid and squid's head looks flatter and pointed, and the octopus and squid can spray ink when they encounter danger, while the squid does not. That's the main difference between them.
Of the three cephalopods, octopuses have the highest IQ and strong memory, because the number of octopus neurons is among the highest even among mammals, with one-third of neurons concentrated in the brain and two-thirds concentrated in eight brachiopods.
These eight brachiopods can handle problems alone and can work together to solve problems, which is similar to a smartphone with eight sub-CPUs in addition to the main CPU, so many people say that octopus is like aliens.
To say that its IQ is second only to primates is far from such an exaggeration, and the number of neurons in octopuses is not as much as that of cats, let alone dogs.
In the brachiopods of cephalopods, there is a tentacle very special, called the stem wrist, look at the name you should guess, this brachiopod is the so-called "tintin", cephalopods use this tentacle to mate, its tip does not have a suction cup, but a groove to transport liquid.
Since cephalopods have no body, except for the head is the horn, all the organs in the body are concentrated in the head, of course, the genitals are no exception, so when they mate, similar to the picture below, there is a process into the brain, which must be very top.
Among them is a special species, which is a close relative of the octopus, called the ship slug, which has eight tentacles. Female shipworms have secretory glands that secrete to form a shell, but this shell is very thin, like paper, and is specially used to hatch the cubs, and when the cubs hatch, the female will abandon the shell.
Female ship slugs can grow up to 100 mm, while males are only about 20 mm in size and have no shell, so ship slugs are not shellfish in the strict sense.
Pictured above is a male shipworm, one of his eight brachiopods looks special, with a slender tentacle at the end, which is its stemming bowl. However, the male ship slug does not go directly to the female and sticks the tentacle into the person's head.
Due to the difference in body size, the male shipworm will slowly approach the female, and after meeting his goddess, he will take out the determination of the hero to break his wrist, cut off his own stemming wrist, and launch his beloved organ.
If the goddess is hit, this slender organ will be firmly nailed to the body of the goddess, and the dialogue at this time should be like this, the female: "Your Ding'er ~?!" Xiong: "No, it's your Ding'er!"!" ”。
If unfortunately not hit, then the male may explode in place, because the male has only one stem to dissolve the wrist, and after the wrist is broken, he will die within a few days.
So the love of the shipworm is really righteous, even if he already knows his end. Due to the small size of male ship slugs and their preference for living on the seabed, females live in upper-middle waters. Only females were found at first, and they didn't understand how they multiplied.
Paleontologists have also found that the female shipworm has this long moving object attached to it, thinking it is a parasite, and later we learned that it is the male's love arrow.
An octopus that behaves in the same way as a shipworm is called the blanket octopus, and the reason why it has such a strange name is because its tentacle arrow has a thin muscular membrane, similar to the bat in mammals.
It can help the blanket octopus to travel quickly in the water, and secondly, when in danger, the blanket octopus can open its tentacles and use the huge "blanket" to scare away opponents.
Similarly, the size of the male and female is hugely different, the female can grow to about two meters, while the male is only a few centimeters long, the male is looking for the female after birth, and when the female is found, he will also shoot his own stem wrist like a ship slug, and then float to the surface of the water, waiting for death.
However, due to the large difference in body size, the female does not feel anything at all during the whole mating process, so to speak, go out and sneak around, and then after a while the baby will be born.
This is the creature that once dominated the earth's oceans, they are very old, of which the Nautilus has not evolved at all for hundreds of millions of years, and still maintains its ancient appearance, so it is also called "living fossils in the ocean".