Fish and dragons are mixed together: It looks like a fish but it’s not a fish, and it’s called a dragon but it’s not a dinosaur?

Ichthyosaurs are a type of marine reptiles that appeared in the Early Triassic and specialized into fish-like forms. They rapidly differentiated into many species in the early Late Triassic and reached their peak in the Jurassic. Whether in terms of body shape, internal structure or lifestyle, they are highly adapted to marine life and can be regarded as the most successful group of reptiles in the Mesozoic ocean. There are many giants with a body length of more than 10 to 20 meters, such as the famous Shonisaurus or Sastorius, and there are also very small ones, such as Mixosaurus.

Mixosaurus is one of the smallest ichthyosaurs discovered so far. It is only about 1 meter long, but its small body hides many important evidences of the evolutionary process of ichthyosaurs: its morphology has both the primitive characteristics of early ichthyosaurs and the advanced characteristics of later ichthyosaurs. For example, its tail is as flat and long as that of a cup-vertebrated ichthyosaur (primitive characteristic), but it has the prototype of the crescent-shaped tail fin of the later ichthyosaur - a diamond-shaped tail fin growing on the upper and lower parts of the tail vertebrae, and a dorsal fin (advanced characteristic). This mixed morphology is also the origin of its name. Their Latin name Mixosaurus means "mixed lizard".

In addition, although their limbs have evolved into flippers suitable for swimming, they still retain the five-toed features common in terrestrial animals, while later members of the ichthyosaur family have been reduced to three toes.

The front flippers are significantly larger than the rear flippers, which is another significant feature of their evolution into advanced ichthyosaurs. It is also an excellent change for high-speed movement in water, because their tails only provide forward propulsion and cannot prevent them from sinking due to the weight of the body. Moreover, due to the streamlined body, it can effectively reduce the resistance of the water, and the sinking process will be a dive. Is this good? This is not good.

Therefore, the more animals can move at high speeds in the water, the more they need huge front flippers or pectoral fins that are consistent with this mode of movement to maintain balance and turn, including fish in modern oceans or mammals such as whales and dolphins. For Mixed Ichthyosaurs, larger front flippers not only solved the problem of sinking, but also provided convenience for catching agile prey.

When they find prey, they swing their tails left and right to speed up, and use their slender snouts with cone-shaped teeth to catch fish that are careless and don't dodge. The weapon they use to find prey is the huge eyes on both sides of their heads with excellent vision.

Their excellent body structure makes them a successful species widely distributed around the world. Their fossils have been found in large numbers in many places in the world, and many genera and species have been established, mainly concentrated in Europe, North America and southwestern my country. For example, among the marine reptile fossils found in the Middle Triassic strata in Luoping, Yunnan, the number of ichthyosaurs accounts for the vast majority, and they are thriving.

Moutai mixed fish dragon

It is precisely because of their wide distribution and high degree of differentiation, as well as the incomplete fossil specimens collected, that despite the fact that they have been studied for more than a hundred years, there is still some confusion in their classification. For example, the Maotai ichthyosaur was classified as an invalid species after several disputes and studies because its fossils were broken. However, this kind of little guy, who seems to be destined to be related to the word "mixed", is of great significance to our understanding of the recovery of the marine ecosystem after the Permian mass extinction and the evolution of ichthyosaurs.