Why reptiles are an unscientific taxonomic unit?

When it comes to reptiles, many people think of cold-blooded, slow-moving and low IQ. In the eyes of ordinary people, reptiles are almost synonymous with inferiority, and the difference between them and our mammals is as clear as the definition in textbooks. But the public's misunderstanding and contempt for reptiles is actually unreasonable. More and more experts realize that reptiles are an unscientific taxonomic unit and advocate their abolition.

Galapagos elephant turtle

Linnaeus classification and systematic classification

Biological taxonomy was founded by naturalist Linnai, who classified and grouped organisms according to their different characteristics in order to facilitate identification. Later, classification experts created different levels of classification units. There are eight basic classification units, and the order from big to small is domain. Border? Door? Outline? Eyes? Branch? Genus? Kindness Is that the basic unit in front? Is General Gao big? , or? Asia is small? Used to indicate a larger or smaller unit.

At present, the unanimous view in academic circles is that classification should reflect the evolutionary relationship between species and reflect Darwin's common ancestor principle, that is, systematic classification. In other words, the creatures that should belong to the same taxon are those with a common ancestor, not those with similar appearance, but those with similar common ancestors are usually similar in appearance.

According to systematic taxonomy, each taxon represents an evolutionary branch of the phylogenetic tree. For a given unit, if it only contains a common ancestor and all its descendants, it is monophyletic; If it contains a common ancestor and some of its descendants, but not all of its descendants, it is a joint group; But if it does not include the nearest common ancestor, it is a complex group.

The pictures show simple systems, joint groups and complex groups.

Many scholars believe that a natural taxon can only be monophyletic, rejecting all joint taxa or complex taxa. In recent years, with the continuous maturity of classification methods, many previously recognized classifications are being greatly changed, and reptiles are questioned in this case.

The range of classical reptiles

Many living and prehistoric animals are classified as reptiles, and scientists divide reptiles into several subclasses according to the number and location of temporal holes. The temporal foramen is a hole located on the side of the skull and behind the orbit, where the masticatory muscles are attached, that is, the temple.

Lack of bow, double bow and closed bow? Temple? drawing of site

Diptera (Diptera) has upper and lower temporal holes on both sides of the skull, including all existing reptiles, prehistoric dinosaurs and pterosaurs.

Non-foraminifera (no bow), no temporal foramen, including the most primitive reptiles, Triceratops and Middle Dragons. Tortoise was once classified into this subclass, but later it was found to have temporal holes, but it was degenerated and was a basic double bow.

Inferior foraminifera (Hemiptera, Monoptera) has only one temporal foramen on each side of the skull, which is located below the posterior orbital bone, including Pansaurus, theropoda and so on. It flourished before the age of dinosaurs, but now there are no such animals (where did they go? Announced below).

ichthyosaurus

In addition, the subclass Broadbow was established, with only one enlarged upper temporal foramen on each side, and the lower temporal foramen degenerated, including plesiosaurs, fishes and other prehistoric marine reptiles. Later, it was found that this subclass was not established, and the wide bow feature was just an adaptation to marine life.

Systematic evolution of reptiles

According to modern system classification, the perfect classification unit must be single series. Reptiles, that is, real reptiles, include the latest common ancestor of all reptiles and all their descendants. The existing reptiles all belong to Diptera, and their common ancestor appeared in the late Paleozoic, which is divided into two evolutionary branches: the main dragon and the scale dragon.

Tortoise, pterosaur (plesiosaur) and ichthyosaur are also branches of Diptera, but their evolutionary position is still inconclusive. Only the latest DNA analysis results of 20 15 are quoted here. Plesiosaur belongs to pan-turtle, which belongs to the basic group of main dragon, while ichthyosaur is the basic group of scale dragon.

Phylogenetic relationship of reptile crown group

Lepidoptera includes Lepidoptera (snakes and lizards) and sauropods, which are the most prosperous reptiles in contemporary times. Black dragon, the ocean overlord in the late Mesozoic, also belongs to the scale dragon, and black dragon is actually a marine lizard.

The main dragon is the evolutionary backbone of reptiles, and the existing typical one is crocodile. It flourished in Mesozoic, and both dinosaurs and pterosaurs belonged to this subclass. Dinosaurs are the collective name of sauropods and ornithopods (hadrosaurs, stegosaurus and ceratosaurus, etc.). ), and sauropods are divided into sauropods (Liang Long, Brachiosaurus and Mamenxilong, etc. ) and theropod dinosaurs (Allosaurus, Tyrannosaurus Rex and Deinonychus, etc. It is particularly noteworthy that birds are direct descendants of small theropod dinosaurs, so they also belong to the big category of double bows. Birds do have two pairs of temples on their heads.

To sum up, the reptile canopy covers birds. ? Existing reptiles+birds? A single line was formed, but after birds were removed, it was just a parallel group.

Hoffman black dragon, the biggest black dragon.

Reptiles include all the reptiles that have appeared on the earth, their latest common ancestors and all their descendants. This common ancestor can be traced back to the most primitive amniotic animal, that is, the first animal that can lay eggs on earth.

Liang Long is a real crown reptile. Archaea was completely extinct before the dinosaur era (the end of Triassic), and now there are no living descendants, which we call parareptiles.

Hailong is a reptile similar to mammals, and it is the direct ancestor of mammals. Mammals only have a pair of temples, and the upper and lower temporal holes are combined into one, which is located in a lower position, which is the key feature of closed arch. The evolution from sea dragons to mammals comes down in one continuous line, and we are also sea dragons in a broad sense.

Phylogenetic relationship of reptile population

To sum up, the total reptile group = crown/true reptile+parareptile+arthropod, true reptile includes birds, and arthropod includes mammals. So the classic reptiles, birds and mammals form a big single line together, which is all amniotic animals (mammals also have chorionic eggs in the early stage of embryonic development, but they just hatch in the uterus and give birth to fetuses instead of laying eggs).

From the point of view of phylogeny, the crown group and the total group in the traditional sense are combined rather than single-line, so reptiles are an unscientific and unnatural concept. The most unscientific thing about this concept is that it wrongly expresses the intimacy between groups. For example, close relatives of crocodiles are birds, not turtles and lizards belonging to reptiles.

Reptiles have no common features.

According to the textbook, the common characteristics of reptiles are as follows: ① the body surface is covered with dry horny scales and nails; ② Unstable body temperature (cold-blooded); ③ The heart has three cavities (ventricular septal defect); ④ Lung breathing; ⑤ There are chorionic eggs (the eggshell is hard), and the reproductive development is not limited by water.

Crocodile, the largest reptile in existence

In fact, these are not the common characteristics of reptiles. Lung respiration and chorionic eggs are common features of reptiles, birds and mammals. Scales, three cavities and cold blood are just the common characteristics of some reptiles and fish or amphibians, while dinosaurs and pterosaurs are warm-blooded with four cavities like birds, some dinosaurs have feathers and crocodiles also have four cavities.

Other groups have key features that can be seen at a glance, and will not be confused with other animals, such as viviparous and lactation of mammals, amphibious and abnormal development of amphibians. Why don't reptiles have such characteristics? The true face of reptiles will soon surface. In fact, reptiles traditionally refer to all amniotic animals that are neither birds nor mammals. This is a typical concept of trash can classification.

Tyrannosaurus Rex and Triceratops

This classified trash can has brought us a lot of misleading, the most obvious is the understanding of dinosaurs. At first, experts thought dinosaurs were cold-blooded and clumsy, on the grounds that dinosaurs belonged to reptiles, not amniotic animals of birds or beasts. However, dinosaurs were completely different from reptiles today. Crocodiles and lizards have legs? Eight characters? Animals that crawl with their bellies close to the ground, while dinosaurs, like birds and mammals, have legs right below them and can stand up.

In fact, dinosaurs were more flexible than mammals of the same size. Tyrannosaurus rex and triceratops are bigger than elephants, but they still keep their curved hind legs, which proves that they can run like antelopes, while elephants have straight legs and can only pace slowly without making any jumps.

Many small theropod dinosaurs discovered in recent years have feathers. They have no wings and can't fly. The main function of feathers is to keep warm. They are warm-blooded animals like birds. The picture below shows the restored Hu, much like the original birds. If we live in Jurassic, do you still think the boundary between reptiles and birds is insurmountable?

Hu, the smallest dinosaur.

Scientists also found that both dinosaurs and pterosaurs had airbag structures, which proved that they both breathed like birds. This is a very efficient way of breathing, and you can inhale oxygen twice every time you exhale and inhale.

So the concept of reptile is not an evolutionary branch, but more like an evolutionary stage. Putting dinosaurs, crocodiles, turtles, snakes, lizards and other completely different animals together has formed a hodgepodge of reptiles, which has no scientific basis and should be abandoned.

Why didn't it be revised?

As early as 1970, paleontologist Robert? Buck suggested it? Pentium and bloody dinosaurs? This view has completely changed people's understanding of the concepts of dinosaurs and reptiles. Not long after, some scholars proposed to abolish reptiles, merge Diptera and Anpuda, including birds, into sauropods, and Anpuda, including mammals, became Anpuda.

Phylogenetic map of vertebrates

Due to the defects of systematic classification itself, it is difficult for academic circles to reach an agreement. If reptiles are abandoned, what should be done with amphibians and fish? Fortunately, the ancestors of amniotic animals, amphibians, have no other living offspring, so only living animals are considered and amphibians are directly excluded. In this way, amphibians only refer to the crown, including the common ancestor of contemporary amphibians and all their descendants (slippery subclass).

The handling of fish is more troublesome. The ancestor of quadrupeds-fish and other descendants. In order to describe their systematic relationship accurately, it is necessary to improve the classification level of fish. Amphibians, closed bows and lizards are all classes, quadrupeds are the upper classes, while quadrupeds and lungfish form an outline together, and the corresponding coelacanth is also an outline. Carnivorous finned fishes have been upgraded to a superfamily, and radial finned fishes (most of the existing teleost fishes) have also become a superfamily, which together constitute a higher class of teleost fishes. The classification level is completely insufficient.

On the contrary, the classification level of birds and mammals should be greatly depressed. Birds are descendants of theropoda and can only be a family. In the classical classification system, birds can be a large taxonomic unit, with 20 orders, 1 10,000 species, not a prehistoric group.

Harper carved that all birds are descended from dinosaurs.

Obviously, according to the system classification, the rank of classification unit depends largely on the time of appearance. In the early days, even the ghost group with no living offspring, or the surviving group with only a few offspring, can rise with the tide and become a large taxonomic unit as long as the branches and leaves of the sister group are unfolded. For example, there are only six species of lungfish and two species of coelacanth, but they are all units of upper class and class. On the contrary, there are more than 10,000 species of birds, but only one family.

The classification hierarchy in Linnaeus classification was originally used to express the size of classification units, which is a contradiction between them. Perhaps Linnaeus's system can't adapt to the new situation of scientific development, so some scholars advocate adopting the stepless classification system and abolishing all levels of families, orders and classes.

Some scholars believe that complex groups should be resolutely banned, but parallel groups can be retained to some extent. In this way, all the original classes can continue to be used. It is relatively easy to maintain the ideal haplotype for small and medium-sized taxonomic units below the goal, but it is too difficult for large units above the class.

Taleq fish belongs to the hope salamander, the ancestor of quadrupeds.

The biggest drawback of systematic taxonomy is probably that it can't solve the problem of species fixation of common ancestors. Fortunately, it is difficult for us to find direct ancestor fossils, most of which are collateral. This problem has not bothered us for the time being. If one day we really find a group of rodents that evolved into amniotic animals, how to determine its classification? Obviously, because its offspring are all amniotic animals, it must be at least one class, and we can't give it a species, genus, family and order. It's just a class, where Linnaeus's system completely collapsed.

In view of the fact that the concept of reptiles wrongly shows the kinship among dinosaurs, birds, crocodiles and lizards, I am afraid it is imperative to correct it. However, experts have not found a perfect solution to how to correct it, so the unscientific concept of reptiles has remained in our textbooks for the time being.

Are we really superior to reptiles?

Finally, we have to ask ourselves this question. Dinosaurs may also be warm-blooded animals and can stand. Our brains are developed and our teeth are chewed efficiently. Dinosaurs also have their own advantages. Its airbag system and hollow skeleton make it bigger. The largest sauropod dinosaur weighed more than four times as much as the largest land mammal in history.

Dinosaurs and mammals appeared almost at the same time, but it ruled the earth for 65.438+0.4 billion years. Our ancestors could only revolve around his feet. Without meteorites 66 million years ago, mammals could not see any hope of taking over the world.

According to the theory of evolution after Darwin, all living things have a common ancestor, and everyone has the same evolutionary time. The differences in morphology and habits are only adaptations to different environments. How can there be a difference between high and low?

We humans only have a history of 2 million years. How long can we survive after that? If one day, the end of the world comes, will the new rulers treat humans and mammals as inferior animals? I think it's time to abandon the stale ideas of lower organisms.