What did the first fish look like How was the world s first fish born?

The earliest fish - the shield fish - adolescent growth.

There is no first theory, the origin of fish is very early, and fish have lived in the ocean since there were no humans in the world. While some ancient species have become extinct over hundreds of millions of years of evolution, others have emerged. According to the literature, fish were first found in the Ordovician strata dating from 400 million years ago, but the fossils of fish were incomplete at that time, and it was not until the late Silurian period that the concept of fossils and early vertebrate relationships was fully obtained.

During the Devonian period, a variety of ancient and modern fish appeared. The Devonian era can be described as both the first age of fish and the heyday of fish, at that time, because there were not many other vertebrates, so some people called Devonian City "the age of fish". In the Cenozoic Era, the fish groups were very diverse, becoming the largest group of vertebrates, and it was the heyday of the development of fish.

Analysis of fossils from the Devonian period shows that ancient fishes can be divided into four main groups: jawless, shieldy, cartilaginous fishes, and bony fishes. Jawless animals are the most abundant in the Silurian and Devonian periods, and are recognized as the earliest vertebrates.

Shield fishes were the first jawed species that flourished during the Devonian period, but were mostly extinct at the end of the period. It has been suggested that cartilaginous fishes and bony fishes evolved from shields in two directions, but there is still no evidence to confirm this. Cartilaginous fishes are considered to be the most "primitive" fishes, but it is generally accepted that cartilaginous fishes and bony fishes are two parallel branches.

The first bony fishes were the ancient cod, which led to the vast majority of existing bony fishes. The typical primitive type of inner nostril fishes in bony fishes is represented by doublefin fish and skeletal scalefish, the latter being the earliest Devonian totalfin fish. The total-finned fishes are considered to be the direct ancestors of the earliest amphibians.

On December 22, 1938, someone caught a large fish on the southeast coast of Africa, its body was meters, weighing 58 kilograms, and after expert research and confirmation, it was believed that this fish should belong to a new family of the order Total Fins. The appearance of this living fossil speartail fish has given us a great inspiration. As we all know, human beings have evolved over a long journey; Fish landed to evolve into amphibians, then completely out of the water to evolve into terrestrial reptiles and mammals, and finally evolved into humans.

Specifically, the total-finned fish is divided into two branches, one of which (the bony scale) is detached from the water. Gradually evolve into a human being; The other, which is more conservative (colacanths), never leaves the water. The current speartail fish are descendants of the latter.

Speartails are living fossils that provide us with many things that cannot be obtained from fossil material.

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The first fish were jawless, and as the name suggests, they were fish that did not have upper and lower jaws. Unable to hunt by opening and closing their mouths, they suck water containing tiny animals and sediment into their mouths, and one of them is covered with hard bone fragments called "helmet beards" and lives on the bottom of the sea. They first appeared in the Early Cambrian period more than 500 million years ago and were the first fish to differentiate.

The main representatives of jawless in the oceans at that time were armored fishes.

Later, due to genetic mutations, the first fish with jaws appeared, and jawed fish were able to hunt actively and effectively. Under the natural selection of "natural selection, survival of the fittest", more and more jawed fish began to appear, and jawless fish fell into disadvantage in the hunting competition.

In order to survive, some fish have evolved super-strong jaws that can split sharks in two, while others have begun to explore new horizons.

The emergence of jawed fish has made the competition for survival in the ocean more and more fierce, and the food chain of "big fish eat small fish, small fish eat shrimp" has been formed since then.

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Extended Information: According to fossil research, the first animals on Earth originated in the ocean. After a long geological period, early marine animals gradually evolved into various branches, enriching the early life forms on earth.

Prehistoric animals appeared before the advent of humans and flourished during their respective periods of activity. Later, they became extinct one after another in a constantly changing environment. However, the animals on Earth continue to evolve and reproduce from the lower to the higher, from the simple to the complex, and have the diversity they have today.

Scientists divide the extant animals known to humans into two major types: invertebrates and vertebrates, according to the presence or absence of a vertebrate in their bodies.

The oldest fish in the world are Arowana, sawfish, octocks, analcanths, and Senegalese multifinfish.

1. Arowana

This Arowana appeared during the Jurassic era, and today, they are found growing in the Amazon River Basin, parts of Africa, Asia, and Australia. They are sometimes used as ornamental fish, but they are unusually greedy and ferocious, preying on small animals, including birds and bats, and they can jump up to about 2 meters in the air. In China, Arowana are known as "Arowana" because of their appearance, and they are also seen as a porter of good luck.

Second, sawfish

This endangered animal appeared in the Cretaceous period and can survive in seawater, rivers and even field streams, and is found 100 kilometers inland. It is about 7 meters long and looks a lot like a shark. Although they are usually friendly, they are fierce when provoked.

Based on one particular fossil, we know that the giant prehistoric sawfish was probably the food of the large carnivorous dinosaur Jingmia because its spine bones were found stuck between the dinosaur's teeth.

Three, eight-eyed eel

Also known as lamprey, seven stars, and small brittle bones, lamprey is one of the few remaining jawless vertebrate fish-like animals. The lamprey fossils that were found are 100 million years old, before the appearance of dinosaurs. Therefore, lampreys are called "living fossils", which are of great significance for the study of biological evolution.

Lampreys and hagfish are the only jawless vertebrates left in the world.

Fourth, anal acanth

Widely considered to be living fossils, the anal ecanthus is the oldest animal that has survived to this day. They were thought to have been extinct in the Cretaceous period, but in 1938 a living specimen was caught in South Africa. Since then, more analcanths have only been spotted and photographed, and in 1999 a second analcanth was spotted in Indonesia.

Anaecanths are large carnivores, about 2 meters long, that prey on small fish, including small sharks, and are often found in deep, dark waters.

5. Senegalese multifinfish

Due to their reptilian appearance and jagged dorsal fin, this African fish is often referred to as the "dinosaur eel", reminiscent of the pointed backs of dinosaurs. They are not a type of eel, but a member of the multifinned fish family. Multifinfish lived in the Cretaceous era because they were thought to be related to dinosaurs and could live away from water for a long time.