User:Abyssal/Portal:Cambrian

Portal topics: Activities; Culture; Geography; Health; History; Mathematics; Nature; People; Philosophy; Religion; Society; Technology; Random portal

The Cambrian Portal

Introduction

The Cambrian ( /ˈkæmbri.ən, ˈkeɪm-/ KAM-bree-ən, KAYM-) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordovician Period 485.4 Ma.

Most of the continents lay in the southern hemisphere surrounded by the vast Panthalassa Ocean. The assembly of Gondwana during the Ediacaran and early Cambrian led to the development of new convergent plate boundaries and continental-margin arc magmatism along its margins that helped drive up global temperatures. Laurentia lay across the equator, separated from Gondwana by the opening Iapetus Ocean. (Full article...)

Show new selections below (purge)

Selected natural world article

The annelids are a large phylum of segmented worms, with over 2,000 modern species including ragworms, earthworms and leeches. They are found in marine environments from tidal zones to hydrothermal vents, in freshwater, and in moist terrestrial environments. The basic annelid form consists of multiple segments, each of which has the same sets of organs and, in most polychaetes, a pair of parapodia that many species use for locomotion. Septa separate the segments of many species, but are poorly defined or absent in some. Septa also enable annelids to change the shapes of individual segments, which facilitates movement by "ripples" that pass along the body or by undulations. Although many species can reproduce asexually and use similar mechanisms to regenerate after severe injuries, sexual reproduction is the normal method in species whose reproduction has been studied.

Since annelids are soft-bodied, their fossils are rare – mostly jaws and the mineralized tubes that some of the species secreted. Although some late Ediacaran fossils may represent annelids, the oldest known fossil that is identified with confidence comes from about 518 million years ago in the early Cambrian period. Fossils of most modern mobile polychaete groups appeared by the end of the Carboniferous, about 299 million years ago. Scientists disagree about whether some body fossils from the mid Ordovician, about 472 to 461 million years ago, are the remains of oligochaetes, and the earliest certain fossils of the group appear in the Tertiary period, which began 65 million years ago. (see more...)

Did you know...

... that the 500-million-year-old Cambrian predator Hurdia was thought to be a number of separate organisms for 100 years, until the complete animal was reconstructed in March 2009?
... that the shrimp-like 510-million-year-old arthropod Waptia was named after two mountains?
... that Orsten, fossil-bearing lagerstätten in Sweden and elsewhere, are called "stinking stones" from organic content that has been preserved since the Cambrian Period?
... that the fordilloid Camya asy is one of four accepted Cambrian bivalves?
...that despite being known from many specimens, the fossil Fuxianhuia (pictured) remains one of the most controversial Cambrian arthropods?

Need help?

Do you have a question about Abyssal/Portal:Cambrian that you can't find the answer to?

Consider asking it at the Wikipedia reference desk.

Selected image

Agnostus pisiformis (Linnaeus, 1757) as depicted in the 47th plate of Ernst Haeckel's Kunstformen der Natur..
Photo credit: User:Micha L. Rieser

Selected science, culture, and economics article

Paleontology or palaeontology (/ˌpeɪliɒnˈtɒlədʒi, ˌpæli-, -ən-/) is the scientific study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments (their paleoecology). As a "historical science" it attempts to explain causes rather than conduct experiments to observe effects. Paleontological observations have been documented as far back as the 5th century BC. The science became established in the 18th century as a result of Georges Cuvier's work on comparative anatomy, and developed rapidly in the 19th century. The term itself originates from Greek: παλαιός (palaios) meaning "old, ancient," ὄν, ὀντ- (on, ont-), meaning "being, creature" and λόγος (logos), meaning "speech, thought, study".

Paleontology lies on the border between biology and geology. It now uses techniques drawn from a wide range of sciences, including biochemistry, mathematics and engineering. Use of all these techniques has enabled paleontologists to discover much of the evolutionary history of life, almost all the way back to when Earth became capable of supporting life, about 3,800 million years ago. As knowledge has increased, paleontology has developed specialized sub-divisions, some of which focus on different types of fossil organisms while others study ecology and environmental history, such as ancient climates. Body fossils and trace fossils are the principal types of evidence about ancient life, and geochemical evidence has helped to decipher the evolution of life before there were organisms large enough to leave fossils. (see more...)