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The Carboniferous Portal

Introduction

The Carboniferous (/ˌkɑːrbəˈnɪfərəs/ KAR-bə-NIF-ər-əs) is a geologic period and system of the Paleozoic era that spans 60 million years from the end of the Devonian Period 358.9 Ma (million years ago) to the beginning of the Permian Period, 298.9 Ma. It is the fifth and penultimate period of the Paleozoic era and the fifth period of the Phanerozoic eon. In North America, the Carboniferous is often treated as two separate geological periods, the earlier Mississippian and the later Pennsylvanian.

The name Carboniferous means "coal-bearing", from the Latin carbō ("coal") and ferō ("bear, carry"), and refers to the many coal beds formed globally during that time. The first of the modern "system" names, it was coined by geologists William Conybeare and William Phillips in 1822, based on a study of the British rock succession.

Carboniferous is the period during which both terrestrial animal and land plant life was well established. Stegocephalia (four-limbed vertebrates including true tetrapods), whose forerunners (tetrapodomorphs) had evolved from lobe-finned fish during the preceding Devonian period, became pentadactylous during the Carboniferous. The period is sometimes called the Age of Amphibians because of the diversification of early amphibians such as the temnospondyls, which became dominant land vertebrates, as well as the first appearance of amniotes including synapsids (the clade to which modern mammals belong) and sauropsids (which include modern reptiles and birds) during the late Carboniferous. Land arthropods such as arachnids (e.g. trigonotarbids and Pulmonoscorpius), myriapods (e.g. Arthropleura) and especially insects (particularly flying insects) also underwent a major evolutionary radiation during the late Carboniferous. Vast swaths of forests and swamps covered the land, which eventually became the coal beds characteristic of the Carboniferous stratigraphy evident today.

The later half of the period experienced glaciations, low sea level, and mountain building as the continents collided to form Pangaea. A minor marine and terrestrial extinction event, the Carboniferous rainforest collapse, occurred at the end of the period, caused by climate change. Atmospheric oxygen levels, originally thought to be consistently higher than today throughout the Carboniferous, have been shown to be more variable, increasing from low levels at the beginning of the Period to highs of 25-30%. (Full article...)

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Ctenophora is a phylum of marine animals characterized by "combs" consisting of cilia they use for swimming. Adults range from a few millimeters to 1.5 m (4 ft 11 in) in size. Their bodies consist of a mass of jelly, with one layer two cells thick on the outside and another lining the internal cavity. Almost all ctenophores consume tiny animal prey. The phylum has a wide range of body forms, including the egg-shaped cydippids with retractable tentacles that capture prey, the flat generally combless platyctenids, and the large-mouthed beroids, which prey on other ctenophores.

Despite their soft, gelatinous bodies, fossils thought to represent ctenophores have been found in lagerstätten as far back as the early Cambrian, about 525 million years ago. The position of the ctenophores in the tree of life has long been debated, and the majority view at present, based on molecular phylogenetics, is that ctenophores are more primitive than the sponges, which are more primitive than the cnidarians and bilaterians. A recent molecular phylogenetics analysis concluded that the common ancestor of all modern ctenophores was cydippid-like, and that all the modern groups appeared relatively recently, probably after the Cretaceous–Paleogene extinction event 66 million years ago. Evidence accumulating since the 1980s indicates that the "cydippids" are not monophyletic, in other words do not include all and only the descendants of a single common ancestor, because all the other traditional ctenophore groups are descendants of various cydippids. (see more...)

Did you know...

... that siltstone deposits have allowed three-dimensional fossils of the extinct mushroom crinoid to be excavated from Indiana?
...that eighty years on, scientists are still debating whether the Palæozoic fossils known as Chitinozoans (SEM image pictured) represent plants, animals or eggs?
... that Arthropleuridea is an extinct class of myriapods which includes, at over 2 meters long, the largest terrestrial arthropods that ever lived?

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Plants of the Carboniferous age from Meyers Konversationslexikon.
Photo credit: Bibliographisches Institut.

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The history of paleontology traces the history of the effort to study the fossil record left behind by ancient life forms. Although fossils had been studied by scholars since ancient times, the nature of fossils and their relationship to life in the past became better understood during the 17th and 18th centuries. At the end of the 18th century the work of Georges Cuvier ended a long running debate about the reality of extinction and led to the emergence of paleontology as a scientific discipline.

The first half of the 19th century saw paleontological activity become increasingly well organized. This contributed to a rapid increase in knowledge about the history of life on Earth, and progress towards definition of the geologic time scale. As knowledge of life's history continued to improve, it became increasingly obvious that there had been some kind of successive order to the development of life. After Charles Darwin published Origin of Species in 1859, much of the focus of paleontology shifted to understanding evolutionary paths.

The last half of the 19th century saw a tremendous expansion in paleontological activity, especially in North America. The trend continued in the 20th century with additional regions of the Earth being opened to systematic fossil collection, as demonstrated by a series of important discoveries in China near the end of the 20th century. There was also a renewed interest in the Cambrian explosion that saw the development of the body plans of most animal phyla. (see more...)