por What is the Cambrian?
He Cambrian It is the first geological period that integrates the Paleozoic Era. It ranged from 539 million years ago to 485 million years ago. During this geological period, the Earth witnessed the greatest diversification and massification of existing life forms.
In the Cambrian, the so-called “Cambrian explosion” occurred, in which a large number of multicellular animal species appeared that mainly inhabited the seas. In this period, chordates made their appearance, a phylum to which amphibians, reptiles, birds, mammals and fish belong.
The Cambrian period has been one of the geological eras most studied by specialists. They have evaluated the geological changes that occurred during the period, the evolution of existing living organisms, as well as the environmental conditions that existed at that time.
However, there are many aspects that remain to be clarified with the study of the various fossils that are still being recovered today.
Its name derives from Cambria, a Latinized form of Cymruwhich was what the Welsh called their country (Wales), and where, in 1831, the English geologist Adam Sedgwick identified this geological system for the first time.
Cambrian Characteristics
– The Cambrian period lasted 54 million years. It was a momentous period, filled with significant changes.
– There was a great diversification and evolution of living beings that populated the planet at that time. A large number of species and phyla appeared, some of which have even survived to the present day.
– It was divided into four epochs or series: Terreneuviense, Epoch 2, Miaolingian and Furongian.
– During the Cambrian, the most significant geological changes had to do with the separation and reorganization of the supercontinents and their fragments.
– The continents or fragments of Earth’s crust that were in the Cambrian were the result of the fragmentation of a supercontinent known as Pannotia. As a product of the fragmentation of Pannotia, four continents were formed: Gondwana, Baltica, Laurentia and Siberia.
– The speed of the continental drift was high, which caused these fragments to separate from each other relatively quickly. Gondwana moved towards the south pole, while the other four were located at the north pole of the planet.
– It is believed that during the Cambrian the surface of the continents was attacked by an important erosive process, in such a way that the landscape of these was rather that of an extensive plain.
Cambrian Climate
There are few records of the climate during the Cambrian. There are few fossils that allow studying the environmental characteristics of this period.
However, it can be affirmed that the climate during the Cambrian was much warmer than that of other geological periods. This is because there were no large pieces of ice on the planet.
Likewise, since almost the entire northern hemisphere was occupied by the immense Phantalassa Ocean, many affirm that the climate was temperate and oceanic.
Similarly, scholars agree that, in terms of climate, there were no seasonal oscillations. In such a way that it can be affirmed that, at least during the Cambrian, the climate was quite stable, without sudden changes in temperature.
Life Cambrian
While it is true that life appeared in the Archean eon, the life forms that existed when the Paleozoic Era began, specifically the Cambrian period, were very simple. They were only limited to very simple living beings, both unicellular and multicellular, generally with a soft body.
During the Cambrian period an unusual diversification of life forms occurred. Specialists called this process the “Cambrian explosion”.
Flora
The representatives of the Plantae kingdom that existed during the Cambrian period were quite simple. Mainly, there were some organisms capable of carrying out the process of photosynthesis.
These were unicellular, that is, they were made up of a single cell. Among these, we can mention some types of blue-green algae and other types of organisms that appeared later.
The latter were calcareous in appearance and were deposited on the seabed, forming small piles. But not all of them had this configuration, there were some that were grouped together forming small sheets, which as a whole became known as oncoids.
Algae were found in the seas, while on the earth’s surface the only plant specimens were some lichens, which are very simple forms of plants.
Similarly, there is evidence of the existence of another species of organisms from the Plantae kingdom, the acritarchs. These were living beings of which there is abundant fossil record.
Fauna
Animals found in the Cambrian period mainly inhabited water. They lived in the vast oceans that covered the planet.
Most of the animals that inhabited the Cambrian were complex invertebrates. Among the greatest exponents of this group are trilobites, some large invertebrates, and other groups, such as mollusks, sponges, and worms.
sponges
During the Cambrian period it was common for a large number of sponges to be found on the seabed, today classified within the poriferous phylum.
arthropods
Arthropods have always been a very large group of animals. It is currently the most abundant phylum in the animal kingdom. In the Cambrian it was not the exception, since there were a large number of animals belonging to this phylum.
Within this group, the most representative were the trilobites. These were a group of arthropods that were abundant during this period and were maintained until almost the end of the Permian period (last of the Paleozoic).
molluscs
This phylum underwent a great transformation, diversifying into several classes, some of which are still found today.
echinoderms
It is a phylum of animals that had a great extension and diversification during the Cambrian period. During this period, new species of echinoderms appeared that could adapt to the different environmental conditions that existed.
chordates
This was perhaps the most important group of animals that originated in the Cambrian period, since a large number of animal groups have diversified from them, such as vertebrates (amphibians, fish, reptiles, birds, mammals), urochordates and cephalochordates.
Cambrian subdivisions
The Cambrian period is divided into four epochs: Terreneuvian, Epoch 2, Miaolingian, and Furongian.
Terreneuviense
It was the earliest epoch of the Cambrian period. It had its beginnings 541 million years ago. Its beginning was marked by the appearance of fossil specimens of an organism known as Trichophycus pedum and its end was determined with the appearance of the trilobites.
During this time the diversity of living beings was still low, since it was in the following subdivisions in which it was expanded.
epoch 2
It began about 521 million years ago. Its beginning was determined by the appearance of the first trilobite fossils.
Specialists have established that the end of this era was determined by the extinction of a large number of animal specimens. This was due to a variation in environmental conditions, which prevented some species from surviving.
miaolingian
It was barely named after it in 2018. It is the third and penultimate epoch of the Cambrian. It began approximately 509 million years ago. During this time the trilobites began to increase in number and diversify.
furongian
It began 497 million years ago. Its beginning was marked by the appearance of a new species of trilobites, the Glyptagnostus reticulatus and its end, the appearance of a type of marine chordate animal known as a conodont.
References
Erwin, D. The Cambrian Explosion: The Construction of Animal Biodiversity. The Quarterly Review of Biology.
Lee, M., Soubrier, J., and Edgecombe, D. Rates of Phenotypic and Genomic Evolution during the Cambrian Explosion. Current Biology.