Cambrian period


Also found in: Dictionary, Thesaurus, Medical.

See also: Geologic Timescale (table)Geologic Timescale
Era Period Epoch Approximate duration
(millions of years)
Approximate number of years ago
(millions of years)

Cenozoic Quaternary Holocene 10,000 years ago to the present  
Pleistocene 2 .
..... Click the link for more information.

Cambrian period

[Lat. Cambria=Wales], first period of the Paleozoic geologic era (see Geologic TimescaleGeologic Timescale
Era Period Epoch Approximate duration
(millions of years)
Approximate number of years ago
(millions of years)

Cenozoic Quaternary Holocene 10,000 years ago to the present  
Pleistocene 2 .
..... Click the link for more information.
, table) extending from approximately 570 to 505 million years ago. It was named by the 19th-century English geologist Adam Sedgwick, who first studied the great sequence of rocks characteristic of the period near Cambria, Wales. During the Cambrian, the continents and seas differed from present day configurations. Four major continents, Gondwanaland, Angara, and the two sections of Euramerica, were inundated with a rising sea level, accumulating thick sedimentary deposits (see sedimentsediment,
mineral or organic particles that are deposited by the action of wind, water, or glacial ice. These sediments can eventually form sedimentary rocks (see rock).
..... Click the link for more information.
). This sedimentary rock, i.e., conglomerate, sandstone, shale, and limestone, was formed in shallow seas that covered large areas of present-day North America, Europe, and Asia. In the United States, Lower Cambrian formations are found in the Appalachian; the sandstones near Waucoba Springs, S Calif.; and the thick layers of conglomerates and sandstones in Georgia, Tennessee, and North Carolina. Middle Cambrian rocks are found in New Brunswick, near Braintree, Mass. Upper Cambrian formations include the St. Croix sandstone of Wisconsin and the upper Mississippi valley, parts of the Arbuckle limestone of Oklahoma, and the Potsdam sandstone in New York's Adirondacks. In Russia, the Cambrian beds are remarkable in that they comprise mostly undisturbed and unconsolidated sand and clay despite their great age. The Cambrian rocks are the first rock layers to contain many easily recognizable fossils. The known Cambrian fauna—all marine—includes every phylum of invertebrates; the possibility that vertebrate fossils may be found cannot be excluded. The dominant animal was the trilobite, along with sea snails, brachiopods, sponges, and archaeocyathids. The ages of the various rock layers are distinguished according to the different genera of fossils they contain. The sudden appearance of highly developed and diversified fauna in Cambrian rock is best explained by the assumption that more primitive forms flourished during a missing stratigraphic interval between the close of the PrecambrianPrecambrian,
name of a major division of geologic time (see Geologic Timescale, table), from c.5 billion to 570 million years ago. It is now usually divided into the Archean and Proterozoic eons. Precambrian time includes 80% of the earth's history.
..... Click the link for more information.
 and the beginning of the Cambrian. Remnants of these early organisms were either destroyed by erosion or their soft bodies easily decayed in a short period of time. In addition, at the beginning of the Cambrian, numerous animals eventually developed skeletons, or hard parts, capable of leaving behind fossil remains.
References in periodicals archive ?
Besides, their evolution throughout the Ediacaran and Cambrian periods shows broad correlations with rising oxygen concentrations".
Our understanding of the Cambrian biodiversification event, as well as relevant biological events prior to the Cambrian period, has been greatly clarified since 1859 by the development of radiometric dating techniques.
The animals that appeared during the Cambrian period paved the pathway toward our modern ecosystems.
In browsing through various texts, I found nothing that would convey a better idea of risk management in general than the statement by the author of an article in the October 1993 issue of National Geographic that the evolution of life forms in the Cambrian period (i.e., upward of 500 million years ago) "was an ever escalating race, and new offenses followed new defenses." As an expression of the drive at the time, it fits the definition.
Amiskwia lived alongside many bizarre-looking creatures during the Cambrian period, about 543 million to 490 million years ago.
Despite their success, rangeomorphs and other Ediacaran organisms disappeared at the beginning of the Cambrian period about 540 million years ago, a period of rapid evolutionary development when most major animal groups first appear in the fossil record.
Tamisiocaris belongs to a group of animals called anomalocarids, a type of early arthropod that included the largest and some of the most iconic animals of the Cambrian period. They swam using flaps down either side of the body and had large appendages in front of their mouths that they most likely used to capture larger prey, such as trilobites.
The roughly 7-centimeter-long specimen represents Fuxianhuia protensa, which lived during the Cambrian period, before modern arthropod lineages evolved.
This cephalopod, whose living relatives include the octopus, squid, and cuttlefish, has roots that go back about 490 million years, into the Late Cambrian period, and six species of nautilus in two genera still swim the oceans today.
It was also believed to have lived during the middle Cambrian period 508 million years ago, hence its age, and was from the renowned Burgess Shale fossil deposit in British Columbia.
The findings resolve 'Darwin's dilemma': the sudden appearance of a plethora of modern animal groups in the fossil record during the early Cambrian period.
More than a century of hard looking has turned up some signs, fossils as well as traces of biological chemistry, of enigmatic animal life before the Cambrian period began about 541 million years ago.