cambrian
The Cambrian was the first period of the Paleozoic and lasted from 540 to 485 mya until it was succeeded by the Ordovician. The Cambrian period is one of the most important in the Earth's history; as it was the first time that major groups of animals first appeared in fossil records. This has led to this period of time being known as the "Cambrian Explosion", due to the short period of time in which the fossils appeared. The period was established by Adam Sedgwick, who named it after Cambria, the latin word for Wales, which was where Cambrian rocks were best exposed. The Cambrian follows the end of the Ediacaran period and the break up of the supercontinent Rodinia. As the Cambrian started Rodinia splintered in smaller continents, the largest of which was Godwana, which was composed of todays Africa, Antarctica, India, Australia and South America. At this point in time Scotland was separated from England and Wales and located on the Western side of the continent Laurentia, while England and Wales themselves were located on the Western edge of Godwana.
The Cambrian was sandwiched between two periods of glaciation, one at the end of the Proterozoic and the other during the Ordovician, meaning that during the Cambrian there was no significant ice formation. None of the continents were near the poles so land temperatures remained mild during the Cambrian. Sea levels also rose significantly due to the retreat of the Proterzoic ice. This means that many low lying areas were flooded, which include areas of Laurentia and much of the coast of Godwana. This opened up new marine habitats where species such as trilopbites flourished. Its also during the Cambrian that the seas became oxygenated. This occurred thanks to the reduction in levels of oxygen reducing bacteria. This event of oxygenating the oceans may have led to the "Cambrian Explosion'.
This expolsion of life caused the rapid diversification of lifeforms and produced the first offspring of many new phyla, which were the stems for many groups of modern species, such as the arthropods. While life prospered and diversified in the oceans, the land was comparatively barren and devoid of life. This was probably caused by the dry and rocky landscapes and the lack of vegetation. This limited life on land to nothing more complex than a microbial soil crust.
The Cambrian is unique in its unusually high proportion of lagerstätten. These are sites of exceptional preservation, where 'soft' parts of organisms are preserved as well as their more resistant shells.
This expolsion of life caused the rapid diversification of lifeforms and produced the first offspring of many new phyla, which were the stems for many groups of modern species, such as the arthropods. While life prospered and diversified in the oceans, the land was comparatively barren and devoid of life. This was probably caused by the dry and rocky landscapes and the lack of vegetation. This limited life on land to nothing more complex than a microbial soil crust.
The Cambrian is unique in its unusually high proportion of lagerstätten. These are sites of exceptional preservation, where 'soft' parts of organisms are preserved as well as their more resistant shells.