All "epochs" of biological evolution from the Cambrian to the present

Cambrian, click on the image to enlarge

The name of the Phanerozoic refers to the "age of visible organisms". It began in the Cambrian period 542 million years ago and continues until now. . In order to explain the difference between the Phanerozoic and previous eras, we must first focus on the Cambrian (Cambrian Peroid). It was named by the British geologist Sedgwick in 1835, originating from the Cambrian region in northern Wales where strata of this period were discovered. The latter name can be traced back to the ancient Welsh Cymry, which means "resistance." Compatriots of the Anglo-Saxon Invasion”. Before it was established as an official geological era, the Cambrian was an important concept in Earth's history: it was the earliest period in which multicellular animal fossils were discovered. Later, multicellular animals before the Cambrian period were gradually discovered, such as the fauna that lived in southern Australia during the Ediacaran period more than 600 million years ago. The Cambrian period has therefore been re-understood as the age when bilaterian animals first appeared. The typical representative of this type of primitive animals is flatworms (worms have no bones or hard shells, so of course they will not leave fossils, but their caves will become fossil). In addition, the Cambrian period also produced an important event in the history of evolution, the "Cambrian Explosion". In a very short period of time (a very short time in a geological sense, but actually millions of years long), biological species suddenly became richer. , an explosive increase. It means that biological evolution may proceed in leaps, in addition to slow gradual changes.

The Cambrian Explosion, click on the image to enlarge

After the Cambrian was named, the deeper and earlier strata were naturally called "Precold" "Wuji" formation. It is not an era, but refers to all eras before the Cambrian. In the 20th century, people used to use the term "cryptozoic" (the age when life is hidden) to refer to this period, but it is rarely used now. It will still be from the birth of the earth to the beginning of the Cambrian (that is, before the beginning of the Phanerozoic). ) is called the Precambrian. Except for its final period - the Ediacaran, there is too little that can be studied in most of the Precambrian era, and there are no representative strata. Therefore, although it is also divided into Archean Eon and Proterozoic Eon epoch, but the boundary between the two - 2.5 billion years ago - is purely artificial, and the lower eras and epochs such as the Iron Age, the Orogeny, and the Ice Age are also ideal settings and are not based on reality. defined by the geological record. The beginning of the Archean Eon has also not been determined. Some people have suggested that the period before the Archean Eon, when there was no life on the earth and was as unpredictable as Hades, be called the Hadean Eon, but this term was not officially adopted in the 2004 edition of the Geological Timeline released by the International Commission on Stratigraphy (ICS).

In addition, a "Sinian Period" was originally defined at the end of the Proterozoic Eon and before the beginning of the Cambrian Period. It started about 800 million years ago and was an important period for the development of life to connect the past and the future. The name It comes from the ancient Indian name for China, "the land of the rising sun". But it is no longer used internationally. In the new geological time scale, the period originally referred to by the Sinian Period is basically replaced by the Glacial Period and the Ediacaran Period.

Imagination of the Permian, click on the image to enlarge

The Phanerozoic Era is divided into the Paleozoic Era, the Mesozoic Era and the Cenozoic Era, which are further subdivided into multiple eras. The names of these periods are most often associated with those weird and extinct creatures. It can be clearly seen from these names that Britain was the center of geology in the early years, especially the Paleozoic era: the names of the Ordovician and Silurian periods come from the names of the ancient Welsh peoples in the Cambrian region, and the English name of the Devonian period is a literal translation. It is the "Devonian", which represents the formation discovered in Devon, England. The Carboniferous originated from a set of coal formations in England. The literal translation of Permian is "Perm Period", and the stratigraphy was discovered in the city of Perm in the Ural Mountains of Russia. Permian is a free translation made in China based on the characteristics of the stratigraphy. In the Paleozoic Era, ferns, fish, and amphibians flourished. Then came the Mesozoic Era, the era of dinosaurs when giant reptiles made their grand appearance, which included the Triassic, Jurassic and Cretaceous periods. The Triassic is named after three sets of strata in southwestern Germany, the Jurassic is named after the Jura Mountains at the junction of Switzerland and Germany, and the Cretaceous is named after the white cliffs formed by chalk soil on the English Channel.

The dinosaurs died out 65.5 million years ago, and the mammals that originally lived in their shadow flourished in the Cenozoic Era and became the new rulers of the earth. The Cenozoic era was originally divided into the Tertiary and Quaternary periods, but became the Paleogene and Neogene in the new chronology.

It is divided into 7 epochs, from the earliest Paleocene to the latest Pleistocene and Holocene. In short, each one is "newer" than the last.

Paleozoic era

Precambrian era: 600-564

Early Cambrian era: 564-535 Middle period: 535-515 Late period: 515-500

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Ordovician 500-436

Laoliu 436-409

Early Devonian: 409-389 Middle: 389-378 Late: 378-360 < /p>

Early Carboniferous: 360-335 Late: 335-284

Permian 284-250

Mesozoic

Early Triassic :242-237 Middle period: 237-229 Late period: 229-208

Early to middle Jurassic period: 208-159 Late period: 159-140

Early Cretaceous period: 140-94 Late period: 94-64