Foreword: In 2023, the movie "Megalodon 2: The Abyss" starring Wu Jing and Jason Statham has been widely discussed once it is broadcast, and the megalodon in the movie has also shocked many people.
The images of these bloodthirsty beasts are deeply engraved in our memory.
But you know what?
The evolution of sharks can be described as a tragic epic, they appeared on the earth as early as 400 million years ago, and experienced several mass extinction events before surviving with difficulty...
Past lives of sharks
On October 12, 2018, a mainland expedition team found fossils at Zhuo Oyou Peak on the Qinghai-Tibet Plateau, which were inferred to date back to the late Triassic period, that is, 220 million years ago, and the fossils were shark fossils.
Today, there are more than 500 species of sharks recorded, and although there are many species of sharks, many such as the Greenland sleeping shark and the mako shark are endangered.
So, how far back can we know sharks go?
About 420 million years ago, in the Devonian period, the ancestors of sharks first appeared, and during this period, plategils became the representative of the predecessor of sharks, a group of ancient fish that are considered to be the ancient ancestors of sharks.
The presence of plate-gill classes marked the beginning of the evolution of sharks, which inhabited ancient seas between the Devonian and Carboniferous periods and exhibited some characteristics similar to those of modern sharks.
These archaic plate-gills have some striking features, such as a stiff dorsal fin and distinctive fin spines, which foreshadow some of the key developments in the evolution of sharks later.
During this ancient period, life was constantly trying and evolving, laying the foundation for the evolutionary process that followed, and the evolution of plate gills marked the beginning of the shark's previous life, and their presence provided some important genetic and morphological characteristics for the later evolution of sharks.
During this period, marine ecosystems began to take on a more complex appearance, with various life forms competing and cooperating with each other to build ancient ecological chains.
But the oceans of this era are also fraught with challenges, life forms need to adapt to changing environments, and the struggle between competition and predation makes it possible for only adaptable creatures to survive in this ancient arena.
Plategill and other ancient fishes evolved over a long period of time to adapt to the deep, shallow, and different temperatures, and became one of the main organisms in the oceans at that time.
The presence of plate-gills laid the foundation for the shark's previous life and laid the groundwork for the long evolutionary process that followed, and their characteristics and adaptability became the key to the shark's later ability to thrive in all corners of the planet.
In this ancient ocean, the shark's past life began a long and constant journey of exploration, establishing the shark's unique place in the evolutionary history of life on Earth.
Sharks evolve gradually
Over the course of hundreds of millions of years, sharks have evolved a series of unique and striking features in the Earth's oceans, and cartilaginous bones are a prominent feature in the evolution of sharks, which are softer and more flexible than other fish with hard bones.
This cartilaginous structure gives the shark excellent mobility and the ability to swim quickly, allowing it to chase prey in different marine environments and adapt to a variety of waters.
The body structure of multi-fins is another important feature of shark evolution, compared to the single dorsal fin of some fishes, sharks have multiple dorsal fins, and the stability of swimming and the flexibility to cope with different currents and ocean conditions have become the biggest role of multidorsal fins.
This multi-fin structure gives sharks the advantage of chasing prey and evading predators in a variety of environments, most notably the shark's powerful biting device.
Some sharks have sharp, serrated teeth that are specialized in tearing and slicing their prey, while others have sharp, triangular teeth that are used to hunt fast-swimming prey.
Over time, sharks have not only gradually improved their morphology, but also changed their behavior and ecological roles significantly, and sharks have become predators at the top of the marine food chain, playing a key role in maintaining the ecological balance of the ocean.
They indirectly affect the distribution of other marine organisms and the structure of ecosystems by controlling the population of prey species, and the excellent survival strategy of sharks is manifested not only in their unique physiological structure, but also in their adaptability to environmental changes.
They are able to migrate to different bodies of water and adapt to different water temperature and salinity conditions, and this high degree of adaptability allows sharks to be widely distributed across the globe and occupy a diverse ecological niche.
Why did the dinosaurs go extinct and the sharks remain intact?
During the Cretaceous-Paleogene period, about 65 million years ago, one of the most devastating events in Earth's history occurred, causing the extinction of a large number of organisms, including the dinosaurs that ruled the planet for 165 million years.
But sharks on the ocean floor survived the catastrophe, largely due to their excellent adaptability and survival strategies.
Sharks have a wide range of ecological adaptations, being able to adapt to different water areas, water temperatures, and salinity conditions, which allows them to relocate to a viable marine environment after an extinction event, quickly adapting to new ecosystems.
Sharks use viviparity, that is, hatching pups in the body, which is relative to oviparity, so that the pups have a stronger ability to survive at birth and can better adapt to changes in the environment, thus improving the chances of survival.
Sharks have successfully found their way to survive in this new environment through their strong adaptability and survival strategies, and the evolution of adaptation has allowed sharks to maintain the survival of their species in the face of severe environmental changes, and has laid a solid foundation for subsequent evolution.
The trials of survival during this period also strengthened the shark's place on the planet as an integral part of the marine ecosystem.
The experience and adaptability accumulated in its long evolutionary process have left a strong imprint on the survival of sharks in the long history of the earth, and at the same time show us the tenacity and miracle of life in extreme environments.
Nowadays, sharks have also become the overlord of the seabed, and they have become the fierce predators in people's mouths, and they have become the "submarine wolves" in the ocean.