The Cambrian period is the first of the Paleozoic Era. It began approximately 541 million years ago and lasted until about 485 million years ago. It was during this period that our planet witnessed a great diversification and proliferation of life. The Cambrian fauna was the protagonist of the so-called "Cambrian Explosion." This period saw the appearance of a large number of multicellular animal species that began to populate the seas.
In this article we are going to tell you all the characteristics and evolution of the Cambrian fauna.
Cambrian period
Before we begin, let's review some of the main characteristics of this period in geological time. It is one of the geological eras that has been most studied by paleontologists. This is because there have been a great number of geological changes and evolutions of existing living organisms. All of this was due to a drastic change in the environmental conditions of that time. We know that this period lasted approximately 56 million years. Among its main characteristics, we find a diversification and evolution of the living beings that inhabited the planet.
Thanks to these changes, numerous new phyla of living beings emerged and have survived to the present day. Geologically, among the most significant changes were the rearrangement and fragmentation of existing supercontinents. The vast majority of specialists agree that various fragments of Earth's crust existed during the Cambrian period and resulted from the fragmentation of an even larger supercontinent. This supercontinent, called Pannotia, broke apart into four others known as Gondwana, Baltica, Laurentia, and Siberia. If you would like to learn more about the characteristics of this period, you can visit our article on [the topic].
The speed of continental drift during this period was much higher than it is today. This caused the fragments to separate with greater speed. Regarding the climate, there are few records but there are some fossils with which the environmental characteristics have been studied. It is stated that during the Cambrian the temperatures were considerably higher than those of other geological periods. This is because there were hardly any ice fragments on the planet. Almost the entire northern hemisphere was covered by the Phantalassa Ocean and the climate was temperate and oceanic in type.
Regarding climate, we also know that there were some seasonal fluctuations, so it is argued that there weren't too many abrupt changes. However, some specialists claim that a drop in global temperature was observed at the end of the Cambrian. This caused some continents that moved more slowly to become covered in ice.
Life Insurance
Regarding life during this period, we find the so-called Cambrian explosion, thanks to an unusual diversification of all life forms. Although life appeared in the Archean eon, it wasn't until the Cambrian period that it was able to diversify, as the rest of life was very simple. This phenomenon is known because most species were able to evolve. A great diversity of living beings appeared almost simultaneously. Thanks to the fossil record, a great deal of information has been recovered. The reasons for the Cambrian explosion have not been able to precisely establish what caused life to diversify.
It is estimated that they were the following causes:
- Increase in atmospheric oxygen
- Increased ozone levels in the ozone layer and protection from harmful ultraviolet radiation.
- Increase the sea level. This meant that the possibilities of housing a greater number of habitats, ecological niches and, therefore, a greater number of species could be increased.
Cambrian fauna
Cambrian fauna primarily inhabited water. All ecosystems were very extensive and located in the oceans. Most of the animals that made up the Cambrian fauna were complex invertebrates. These included trilobites, some large invertebrates, and other groups such as mollusks, sponges, and worms. We will now analyze the most abundant species of Cambrian fauna one by one:
Sponges
During this period, it was common to find large numbers of sponges on the seabed. Today, they are classified in the phylum Porifera. Their main characteristic is the presence of poles throughout their structure. These pores help circulate and filter nutrients from the water. The fossil record of these organisms has provided information about their development during that time. Thanks to this fossil record, we know that some sponges resembled tree-like structures, while others were cone-shaped.
Arthropods
They were the most highly developed and numerous animals. Today, they remain the most abundant phylum in the animal kingdom. The Cambrian fauna was no exception. Within this group, we find some of the most representative, such as the trilobites . They were abundant during this period and persisted almost until the end of the Permian period . They were among the first animals to develop sight.
Cambrian fauna: mollusks
Mollusks underwent great transformations diversified into various classes. Some of them are still found today. We have gastropods and cephalopods, among others.
Echinoderms
It had a lot of expansion and diversification during this period. New species of echinoderms appeared that could adapt to the different existing environmental conditions. The class that survived the longest was the crinoid.
Cambrian fauna: chordates
The most important group of animals to have originated during this period was the Cambrian. Thanks to these animals, we know that the Cambrian fauna diversified into a large number of groups, including vertebrates such as amphibians, fish, reptiles, birds, and mammals. The distinctive characteristic of these animals is the presence of a structure known as the notochord. This is the origin of the name chordates. The notochord is a tubular cord that extends along the entire dorsal side of the organism and serves a structural function. They also possess a central nervous system, a post-anal tail, and a perforated pharynx.
I hope that with this information you can learn more about the Cambrian fauna and its characteristics.