If the world's rarest animal is anything, it is the coelacanth, they are considered to be the earliest ancestors of humans, scientists have always thought that they disappeared 6,000 years ago, but in 1938, scientist Smith inadvertently discovered the figure of coelacanth, coelacanth reappeared.
Since its reappearance in 1938, only a few dozen coelacanths have been discovered, and for these two reasons, coelacanths are considered the world's number one protected animal. Today we will take a look at this mysterious fish.
<h1 class="pgc-h-arrow-right" data-track="25" what is > coelacanth</h1>
Coelacanth is a fish with "legs". Also known as "empty spiny fish" because of the hollow spine. The appearance of coelacanth is similar to that of most living fish. But the structure of the fin is very special. Each fin has a well-developed fleshy stalk with a central axis bone, and the small bones at the tip of the fin are attached to the central axis bone and connected to the body. The arrangement and shape of the endoskeleton is very similar to that of the primitive tetrapod, the fishstone salamander. The caudal fin has a prominent central axis, shaped like a spear, so it is also called speartail fish. Coelacanths can live for more than 100 years, so they do not mature until they are 50 years old, and it takes 5 years to conceive once.
Coelacanths first appeared about 400 million years ago, they appeared in the Devonian period, early lived in the dry freshwater rivers and lakes, at that time, their main respiratory organs were nostrils and swim bladders, and later due to environmental changes, after the Triassic, they came to the ocean and gradually became breathing with gills.
There were no animals on land in ancient times, and the animals that now live on land have ancestors migrated from the sea. During the period of evolution of fish and other footless animals to land animals, the total fin fish represented by coelacanths had very developed legs (in fact, they should be fins), and even like amphibians, they could crawl on rocks and trees. With changes in geography, climate and other environmental changes, 330 million years ago, they partially climbed onto land and evolved into amphibians, initially evolving into frog-like and clear-chi animals, and then evolving into birds and four-legged mammals, from which they produced higher animals such as humans.
<h1 class="pgc-h-arrow-right" data-track="45" > why scientists consider coelacanths to be human ancestors</h1>
Scientists make this judgment because the total fin fish has an appendage bone arm similar to that of primitive tetrapods; second, it has an internal nostril necessary for the lung respiratory tract on the mouth cover. According to fossil speculation, its pectoral and ventral fins should have the function of supporting the body and regulating movement. The third is that coelacanths retain a liquid-filled cord for life, while in other vertebrates, the spinal cord is ossified as part of the spine.
The other part of the coelacanth moved to the sea and made its home at the bottom of the deep sea. Because the temperature of the deep sea is almost constant, the water flow is also very slow, neither as drastic environmental changes on land, nor as many predators as on land - animals that pose a threat to survival, the environment is very stable, the need for evolution is not great, so it can pass more than 60 million years, or almost primitive form.
Disappeared for 60 million years, human understanding of coelacanth is almost zero, it can be known to humans again, thanks to scientist Smith,
Indigenous fishermen living in South Africa and the island of Madagascar accidentally catch a strange fish in the sea of East London, South Africa. The fish is a magnificent 1.5-meter-long, 57-kilogram fish: the lilac-purple skin is dotted with white spots, and the whole body shines with a blue-green metallic luster, like a piece of porcelain with a colored glaze.
The shape of the big fish is extremely strange. It is covered with hard scales, its tail resembles the shape of the tip of a spear, and the most peculiar is its four legs-like fins. The captain saw the fish very strangely, so he sketched the fish and took it to consult Professor Smith, a ichthyologist at the University of Graevestown in South Africa. Professor Smith was surprised to find that this was an ancient creature of coelacanth.
Unfortunately, when Professor Smith drove to the surface of East London with the captain, all he saw was a pile of fish bones, purple-lead scales and huge fins. It turned out that when the captain left the ship and landed, the fishermen who did not know the details had already eaten the fish meat, and Professor Smith could only make these bones into specimens, and no live coelacanth was found for more than ten years, so the scientific community would be suspicious of the existence of coelacanth.
It was not until 1952 that a live coelacanth was caught near the Comoros Islands, located between the east coast of Africa and the island of Madagascar. Subsequently, by July 1955, a total of 15 such fish had been caught at a depth of 150-270 metres offshore the Comoros Islands. Only then did scholars who were skeptical of this finally have to believe that the existence of coelacanths is a fact.
Later, scientists observed its behavior and found that its pectoral fins could almost rotate and support postures in all directions. This confirms the inference that the fins evolved from fins to limbs, and also supports the idea that the total fin fish were the ancestors of tetrapods.
<h1 class="pgc-h-arrow-right" data-track="47" > summary</h1>
At present, scientists still have questions, that is, why did the coelacanth continue to evolve into amphibians with its kind, but chose to return to the deep sea. But it is foreseeable to provide more natural information for the study of the evolutionary process from fish to man.