[ad_1]
The Cambrian Period, spanning from 542 to 488 million years ago, saw the sudden emergence of complex multicellular organisms during the Cambrian explosion. All modern animal phyla, except bryozoans, had a representative during this period. The period is divided into three periods and ended with the Cambrian-Ordovician extinction event.
The Cambrian Period is a major division of geologic time, spanning from about 542 to 488 million years ago. It is the first period of the larger Paleozoic era. The Cambrian is characterized by the appearance of a wide range of complex and fossilizable multicellular organisms. Prior to this, multicellular organisms were more like simple colonies (sponges and medusoids) than differentiated animals.
Over a period of about 10 to 20 million years at the beginning of the Cambrian, an event called the Cambrian explosion occurred, referring to the sudden appearance of numerous well-preserved animal fossils. During the Cambrian explosion, all major body types emerged. The Cambrian period takes its name from Cambria, an older name for Wales, where fossils from the Cambrian era were first found.
The period preceding the Cambrian period is referred to as the Precambrian. The Cambrian Period was long thought to mark the emergence of multicellular fossils in general, but discoveries of the so-called Ediacaran biota in the last fifty years have shown that multicellular organisms existed before the Cambrian. However, these were not as complex as their Cambrian descendants, with whom they have only tenuous connections. It was originally thought that there were no land plants during the Cambrian period, but molecular dating has shown that this is not true, and in fact there were some primitive land plants as early as 700 million years ago and land fungi up to 1000 million years ago. does. Many of these were simple opaque or sheet-like organisms.
Many important species first emerged during the Cambrian Period: trilobites, brachiopods, arthropods (water scorpions), and conodonts (the precursors of all vertebrates). All modern animal phyla, with the exception of bryozoans, a phyla of reef-building organisms, had a Cambrian representative.
The Cambrian Period is the first geological area to be defined by the occurrence of a few fossils rather than arbitrary time-based subdivision. The beginning of the period is defined by the appearance of trilobites and its end occurs during the Cambrian-Ordovician extinction events, the first major extinction event of the Phanerozoic eon, a time period encompassing 542 million years ago to Today. This extinction event wiped out about half of all animal species.
The Cambrian Period can be divided into three distinct periods, each about 12 million years long: the Early Cambrian, the Middle Cambrian, and the Furongian. After the Cambrian period came the Ordovician period.
[ad_2]