The Neogene Portal

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Ordovician bryozoans.
Ordovician bryozoans.
The Bryozoa are a phylum of aquatic invertebrate animals. Typically about 0.5 millimetres (0.020 in) long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia. Individuals in bryozoan colonies are called zooids, since they are not fully independent animals. All colonies contain autozooids, which are responsible for feeding and excretion. Colonies of some classes have various types of non-feeding specialist zooids. Zooids consist of a cystid that provides the body wall and produces the exoskeleton and a polypide that contains the internal organs and the lophophore or other specialist extensions. Colonies take a variety of forms, including fans, bushes and sheets.

Mineralized skeletons of bryozoans first appear in rocks from Early Ordovician period, making it the last major phylum to appear in the fossil record. This has led researchers to suspect that bryozoans had arisen earlier but were initially unmineralized, and may have differed significantly from fossilized and modern forms. Early fossils are mainly of erect forms, but encrusting forms gradually became dominant. It is uncertain whether the phylum is monophyletic. Bryozoans' evolutionary relationships to other phyla are also unclear, partly because scientists' view of the family tree of animals is mainly influenced by better-known phyla. Both morphological and molecular phylogeny analyses disagree over bryozoans' relationships with entoprocts, about whether bryozoans should be grouped with brachiopods and phoronids in Lophophorata, and whether bryozoans should be considered protostomes or deuterostomes. (see more...)

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Holotype specimen of Oligochlora semirugosa preserved in amber.
Holotype specimen of Oligochlora semirugosa preserved in amber.

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Laelaps by Charles R. Knight.

The painting Laelaps by Charles R. Knight depicts two Dryptosaurus fighting.
Photo credit: User:Sergiodlarosa

Selected article on the Neogene in human science, culture and economics

Illustration of trilobite fossils by Joachim Barrande.
Illustration of trilobite fossils by Joachim Barrande.
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...)

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History - History of paleontology - Timeline of paleontology

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Culture - Treatise on Invertebrate Paleontology - Vertebrate Paleontology

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