What does the new classification of the animals look like?

Answer

There are many more than 5 classes in the animal kingdom! The first classification is in phyla, the most important of which are: the sponges, cnidarians, flatworms, roundworms, arthropods, mollusks, annelids, echinoderms, and chordates. Each phylum is then further subdivided into classes. The classes of vertebrates (= a subphylum of the chordates) used to be: fish, amphibians, reptiles, birds and mammals. Classification is artificial anyway. Everything depends on the working method. Traditionally, the common features, especially anatomical ones, were used. But even if you use it, you still have to notice that the format “fishing” e.g. is very general. This group includes the hagfish, marine fish that have no spine, jaws or other skeletal parts outside of a skull. Also the lampreys / lampreys (the brook lamprey occurs in our watercourses) that do have a spinal column next to a skull pan, but no jaws or other skeletal parts yet. We also have cartilaginous fish (sharks, rays) that have jaws but no bone, only a cartilaginous skeleton. The bony fishes differ in the ray fins (which occur in our regions) and the lobe fins (eg lungfish). This results in a division into 9 classes: the aforementioned 5 classes of fish plus amphibians, reptiles, birds and mammals. But the story doesn’t end here. There are also big differences between turtles, crocodiles, snakes and lizards, which are all reptiles.

Modern classification no longer only looks at common characteristics, but mainly at derived characteristics. That is the basis of the method called “cladistics”: organisms are placed in a clade (= group) when they have a common ancestor and no organisms outside the clade have that same ancestor. Thus, the organisms within one clade have unique, common derived traits (coming from that last common ancestor).

This is mainly analyzed by determining the sequence of building blocks in the DNA (nucleotides) or in proteins (amino acids) and comparing them between species. This can also be applied to extinct species if DNA or protein can be obtained from fossil bones eg. For example, birds show more similarities with dinosaurs than with any other animal group (reptiles or mammals, for example). They are therefore counted in the same clade as the dinosaurs (and the latter are therefore not extinct as a group!).

On the basis of cladistics, the group of still living “reptiles” should be replaced by several groups or classes: the tortoises, the lizards and snakes, the crocodiles. This results in 11 classes. In fact, one should also divide the mammals into three groups: platypus; marsupials; mammals with a placenta and full development within the womb. That brings us to 13.

Who ultimately determines the classification? This is done gradually on the basis of scientific studies (publications) and conferences where most experts can reach a consensus. But new insights will always lead to new classifications (or at least adjustments).