Paleontology

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This is a photograph of the skeleton of Alligator prenasalis. Credit: Ghedoghedo.

Paleontology is a study of fossils.

Paleontology is a large subject due to the inclusion of fossils from the rock record, taxonomic classification of these fossils, and the occasional find of residual organic material that sometimes contains genetic material.

Theoretical paleontology[edit]

Def. the "[s]tudy of the forms of life existing in prehistoric or geologic times"[1] is called paleontology.

Clades from the paleontological rock record sometimes display a clade asymmetry. "(Our two cases of Metazoa and mammals represent the first filling of life's ecological "barrel" for multicellular animals, and the radiation of mammals into roles formerly occupied by dinosaurs.)"[2]

Fossils[edit]

Main sources: Sediments/Fossils and Fossils
This may be an ammonite fossil. Credit: Halvard : from Norway.

Def. "[t]he mineralized remains of an animal or plant" or "[a]ny preserved evidence of ancient life, including shells, imprints, burrows, coprolites, and organically-produced chemicals"[3] is called a fossil.

Derived terms include ichnofossil, index fossil, living fossil, mesofossil, microfossil, and trace fossil.[3]

Micropaleontology[edit]

The image shows Nummulitid foraminiferans from the Eocene near Al Ain, United Arab Emirates. Credit: Mark A. Wilson.

Micropaleontology is a study of fossil micro-organisms, including foraminifera, which have applications in stratigraphic correlation and age dating along with paleoecology and paleoclimatology.

The image at the right shows microspheric and megalospheric Nummulitid specimens.

Paleobotany[edit]

Main source: Paleobotany
This image is of Gingkoites huttoni from Scalby Ness, Scarborough, England. Credit: Ghedoghedo.

Paleobotany is the study of plant or plant-like fossils.

The image at the right shows fronds impressed onto shale in a specimen on display at the Paläontologische Museum München. The fossil is from Scalby Ness, Scarborough, England.

Palynology[edit]

Main source: Palynology
A spore tetrad (green) and trilete spores (blue, ~30-35μm diameter) from a late Silurian sporangium (Burgsvik beds, Sweden) are shown. Credit: Smith609.

Although regarded as a separate field of its own, in a real sense palynology is the micropaleontological equivalent of paleobotany that involves the study of fossil pollen and spores.

The image at right contains a spore tetrad (in green) of genus Scylaspora and trilete spores (blue, ~30-35μm diameter) from a late Silurian sporangium (Burgsvik beds, Sweden).

Invertebrate paleontology[edit]

These are bryozoan fossils in an Ordovician oil shale from Estonia. Credit: Mark A. Wilson.

Invertebrate paleontology is a study of fossil invertebrate animals, those which lack a backbone. Included are magafaunas whose study doesn't require a microscope, found in various phyla. Applications include stratigraphic dating and correlation, and paleo-ecology.

At the right is an example of invertebrate paleontology, specifically bryozoan fossils in an Ordovician oil shale from Estonia.

Vertebrate paleontology[edit]

This is a photo of a Mosasaurus hoffmannii skeleton. Credit: Ghedoghedo.

Vertebrate paleontology is any study of prehistoric animals with backbones, e.g. fish of various kinds, marine and terrestrial reptiles, dinosaurs, birds, and mammals.

As a representative of vertebrate paleontology, the image at the right shows a skeleton of Mosasaurus hoffmannii on display at the Natural History Museum of Masstricht.

Geologic time[edit]

Main sources: Times/Geologics and Geologic time
This clock representation shows some of the major units of geological time and definitive events of Earth history. Credit: .

At right is a geologic clock representation. It shows some of the major units of geological time and definitive events of Earth history. The Hadean eon represents the time before fossil record of life on Earth; its upper boundary is now regarded as 4.0 Ga (billion years ago).[4] Other subdivisions reflect the evolution of life; the Archean and Proterozoic are both eons, the Palaeozoic, Mesozoic and Cenozoic are eras of the Phanerozoic eon. The two million year Quaternary period, the time of recognizable humans, is too small to be visible at this scale.

The following four timelines show the geologic time scale. The first shows the entire time from the formation of the Earth to the present, but this compresses the most recent eon. Therefore the second scale shows the most recent eon with an expanded scale. The second scale compresses the most recent era, so the most recent era is expanded in the third scale. Since the Quaternary is a very short period with short epochs, it is further expanded in the fourth scale. The second, third, and fourth timelines are therefore each subsections of their preceding timeline as indicated by asterisks. The Holocene (the latest epoch) is too small to be shown clearly on the third timeline on the right, another reason for expanding the fourth scale. The Pleistocene (P) epoch. Q stands for the Quaternary period.

Siderian Rhyacian Orosirian Statherian Calymmian Ectasian Stenian Tonian Cryogenian Ediacaran Eoarchean Paleoarchean Mesoarchean Neoarchean Paleoproterozoic Mesoproterozoic Neoproterozoic Paleozoic Mesozoic Cenozoic Hadean Archean Proterozoic Phanerozoic Precambrian
Cambrian Ordovician Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous Paleogene Neogene Quaternary Paleozoic Mesozoic Cenozoic Phanerozoic
Paleocene Eocene Oligocene Miocene Pliocene Pleistocene Holocene Paleogene Neogene Quaternary Cenozoic
Gelasian Calabrian Pleistocene Pleistocene Pleistocene Holocene Quaternary
Millions of Years

Paleoecology[edit]

Paleoclimatology[edit]

Holocene[edit]

Main sources: History/Holocene and Holocene

The Holocene starts at ~11,700 b2k and extends to the present.

Pleistocene[edit]

The Pleistocene dates from 2.588 x 106 to 11,700 b2k.

People appear.

Pliocene[edit]

Main sources: History/Pliocene and Pliocene

The Pliocene ranges from 5.332 x 106 to 2.588 x 106 b2k.

Miocene[edit]

Main sources: History/Miocene and Miocene

The Miocene dates from 23.03 x 106 to 5.332 x 106 b2k.

Oligocene[edit]

Main sources: History/Oligocene and Oligocene

The Oligocene dates from 33.9 ± 0.1 x 106 to 23.03 x 106 b2k.

The Oligocene Epoch covers 34 - 23 Mya.[5]

"As the Earth began to cool, the tropical plants that had previously been found relatively widespread began to recede towards the equator where it was still warm. The general tropical plants began a transition to more forest like areas. The first grasses also appeared in the late Oligocene. The appearance of these grasses led to to evolution of various herbivore animals. With bodies low to the ground, animals would take advantage of the new grasses that appeared."[5]

Eocene[edit]

Main sources: History/Eocene and Eocene

The Eocene dates from 55.8 ± 0.2 x 106 to 33.9 ± 0.1 x 106 b2k.

Paleocene[edit]

Main sources: History/Paleocene and Paleocene

The Paleocene dates from 65.5 ± 0.3 x 106 to 55.8 ± 0.2 x 106 b2k.

Cenozoic[edit]

Main sources: History/Cenozoic and Cenozoic

After the dinosaurs became extinct, the Cenozoic began.

Cretaceous[edit]

Main sources: History/Cretaceous and Cretaceous
A juvenile Chasmosaurus fossil is seen from the side. Credit: Philip Currie.

"The Cretaceous period is the third and final period in the Mesozoic Era. It began 145.5 million years ago after the Jurassic Period and ended 65.5 million years ago, before the Paleogene Period of the Cenozoic Era."[6]

The image on the right shows a juvenile Chasmosaurus fossil seen from the side.

"The Ceratopsidae are one of the more immediately recognizable groups of dinosaurs. Characterized by sharp beaks and flamboyant horns and frills, these herbivores almost all lived in what is now Western North America right at the end of the Cretaceous period, 100 to 66 million years ago."[7]

"Chasmosaurus belonged to this group [...] The 75 million-year-old fossilized Chasmosaurus was spotted in 2010 within the Dinosaur Park Formation in Alberta, Canada. In 2013, paleontologists completely unearthed it, and this week, they have described what is undoubtedly a rare specimen."[7]

“For the first time ever, we have a complete skeleton of a baby ceratopsid.”[8]

"Only its forelimbs are completely missing."[7]

"The adult variants are certainly distinctive, with large openings in their head ornaments earning them their appropriate name, which literally means “opening lizard.” Fully grown, they reach a size of up to 4.8 meters (16 feet) and a weight of roughly 2 tonnes (2.2 tons)."[7]

"This juvenile Chasmosaurus is an adorable 1.5 meters (4.9 feet) in length, and would have weighed less than 100 kilograms (220 pounds). It’s so young that its vertebrae had not properly fused, its limbs were not fully articulated (joined up), and it had a particularly short snout. Due to its ornamental opening being fully enclosed by a single bone, scientists have deduced it is likely a species called Chasmosaurus belli."[7]

“We've only had a few isolated bones before to give us an idea of what these animals should look like as youngsters, but we've never had anything to connect all the pieces. All you need is one specimen that ties them all together. Now we have it!”[8]

Jurassic[edit]

Main sources: History/Jurassic and Jurassic
This is an example of Neophyllites antecedens showing suture marks. Credit: Günter Knittel.

"The Jurassic Period takes place after the Triassic Period and before the Cretaceous Period. This period is well known for the reign of the dinosaurs of its time and the global tropical landscape."[9]

"The Jurassic is a geologic period and system that extends from about 199.6±0.6 Ma (million years ago) to 145.5±4 Ma; that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles. The start of the period is marked by the major Triassic–Jurassic extinction event. However, the end of the period did not witness any major extinction event."[10]

Aalenian[edit]

Leioceras opalinum, Graphoceratidae; has a diameter: 4.5 cm; Lower Aalenian, Middle Jurassic; between Ohmenhausen and Reutlingen, Germany. Credit: H. Zell.

Leioceras opalinum is an ammonite from the Aalenian.

Hettangian[edit]

Psiloceras spelae tirolicum has its first occurrence at the Triassic-Jurassic boundary as geochron for the base of the Jurassic. Credit: Axel von Hillebrandt et al.
Fossil shell of Psiloceras planorbis from Germany, on display at Galerie de paléontologie et d'anatomie comparée in Paris. Credit: Hectonichus.
This is an example of Psiloceras psilonotum from the Hettangian. Credit: Günter Knittel.

Psiloceras psilonotum, Psiloceras spelae tirolicum and Psiloceras planorbis are from the Hettangian.

Triassic[edit]

Main sources: History/Triassic and Triassic
This is an example of Psiloceras tilmanni from the Jurassic. Credit: Günter Knittel.

Although the example of Psiloceras tilmanni is from the Jurassic. Its lowest occurrence is in the New York Canyon section of Nevada USA which may be Triassic.

Ladinian[edit]

This is the earliest Ladinian crinoid from the Atlasov Cape section. Credit: Alexander M. Popov.

The Atlasov section of the Ladinian contains the crinoid on the right.

Anisian[edit]

Ussuriphyllites amurensis (Kiparisova) is from the Lower-most Anisian, Atlasov Cape area. Credit: Alexander M. Popov.

An example of Ussuriphyllites amurensis (Kiparisova) is on the right. It is from the Lower-most Anisian, Atlasov Cape area.[11]

Olenekian[edit]

Olenekoceras meridianum (Zakharov) is found in the Upper Olenekian, Atlasov Cape area. Credit: Alexander M. Popov.

Olenekoceras meridianum is a "typical Late Olenekian [fossil which] differs in its lithology from the same zone of Russian Island, where the Zhitkov Suite has been rec- ognized (Zakharov, 1997; Zakharov et al., 2004)."[11]

Induan[edit]

Hindeodus parvus is now recognized as the index fossil, occurring in the Zone above the P-T boundary. Credit: Yin Hongfu, Zhang Kexin, Tong Jinnan, Yang Zunyi and Wu Shunbao.

Hindeodus parvus, a conodont, on the right, is now recognized as the index fossil for the Triassic Induan.

Mesozoic[edit]

Main sources: History/Mesozoic and Mesozoic

With another mass extinction Mezozoic era started. Now dinosaurs rule.

"A high diversity of terrestrial vertebrates with dinosaurs as the dominant group is strongly indicated but not much of it is yet recorded."[12]

For much of the dinosaur era, the smallest sauropods are larger than anything else in their habitat, and the largest are an order of magnitude more massive than anything else that has since walked the Earth.

Permian[edit]

Main sources: History/Permian and Permian

The Permian lasted from 299.0 ± 0.8 to 251.0 ± 0.4 Mb2k.

Pennsylvanian[edit]

The Pennsylvanian lasted from 318.1 ± 1.3 to 299.0 ± 0.8 Mb2k.

History/Mississippian|Mississippian[edit]

The Mississippian lasted from 359.2 ± 2.5 to 318.1 ± 1.3 Mb2k.

Carboniferous[edit]

The Carboniferous began 359.2 ± 2.5 Mb2k and ended 299.0 ± 0.8 Mb2k.

Devonian[edit]

Main sources: History/Devonian and Devonian

The Devonian spanned 416.0 ± 2.8 to 359.2 ± 2.5 Mb2k.

Silurian[edit]

Main sources: History/Silurian and Silurian

The Silurian spanned 443.7 ± 1.5 to 416.0 ± 2.8 Mb2k.

Upper Ordovician[edit]

Sandbian[edit]

Nemagraptus gracilis, Sandbian graptolites, are from the Caparo Formation, Venezuelan Andes. Credit: J.C. Gutiérrez-Marco, D. Goldman, J. Reyes-Abril, and J. Gómez.

"The Lower Sandbian Nemagraptus gracilis Zone comprises one of the most widespread, and easily recognizable graptolite faunas in the Ordovician System. The base of the N. gracilis Zone also marks the base of the Upper Ordovician Series".[13]

Middle Ordovician[edit]

This is an image of Amplexograptus sp., probably A. perexcavatus (Lapworth, 1876), from the Middle Ordovician near Caney Springs, Tennessee. Credit: Wilson44691.

On the right is an image of Amplexograptus sp., probably A. perexcavatus (Lapworth, 1876), from the Middle Ordovician near Caney Springs, Tennessee USA.

Lower Ordovician[edit]

Eurypterids[edit]

This is an image of an Eurypterus lacustris fossil, Muséum national d'histoire naturelle, Paris. Credit: FunkMonk.

Although present in the Ordovician around 460 million years ago, about 410 million years ago, the first large marine predators (eurypterids), an order of arthropods, experienced a dramatic decline and are extinct.[14]

Cambrian[edit]

Main sources: History/Cambrian and Cambrian

The Cambrian lasted from 542.0 ± 1.0 to 488.3 ± 1.7 Mb2k.

Guzhangian[edit]

The image shows an exoskeleton of the cosmopolitan agnostoid trilobite Lejopyge laevigata. Credit: Shanchi Peng et al.

"The GSSP level [for the Guzhangian] contains the lowest occurrence of the cosmopolitan agnostoid trilobite Lejopyge laevigata [in the image on the left] (base of the L. laevigata Zone)."[15]

Paleozoic[edit]

Main sources: History/Paleozoic and Paleozoic

The Paleozoic era spanned 542.0 ± 1.0 to 251.0 ± 0.7 Mb2k.

The mollusks, arthropods, fish, reptiles, and amphibians appeared.

Next 550 mya, after the death of vendobionts, a new era began-the Paleozoic.

After extinction, new spieces named vendobionts appeared.

650 million years ago (mya) a mass extinction happened (mass extinction-is a period when many spieces of animals or plants die).

Proterozoic[edit]

Def. the "eon from 2,500 Ma to 541.0±1.0 Ma, the beginning of the Phanerozoic, marked by the build up of oxygen in the atmosphere and the emergence of primitive multicellular life"[16] is called the Proterozoic.

First era of prehistoric multicellular life.

Hypotheses[edit]

Main source: Hypotheses

To construct an hypothesis in paleontology requires statements of generalization usually using universals. Establishing that a phenomenon has occurred may require a proof of concept. Demonstrating a change from contemporary knowledge needs a control group for comparison.

  1. Ammonites are alive today.

See also[edit]

References[edit]

  1. "paleontology, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. March 8, 2012. Retrieved 2012-07-22. 
  2. Stephen Jay Gould, Norman L. Gilinsky and Rebecca Z. German (June 1987). "Asymmetry of lineages and the direction of evolutionary time". Science 236 (4807): 1437-41. doi:10.1126/science.236.4807.1437. http://www.laputan.org/pub/papers/Gould-87.PDF. Retrieved 2011-08-02. 
  3. 3.0 3.1 "fossil, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. May 22, 2012. Retrieved 2012-07-22. 
  4. stratigraphy.org. "International Commission on Stratigraphy 2008". Retrieved 9 March 2009. 
  5. 5.0 5.1 Gaidheal1 (April 13, 2011). "Paleogene Period, In: Wikiversity". Retrieved 2012-07-24. 
  6. Gaidheal1 (May 16, 2012). "Cretaceous Period, In: Wikiversity". Retrieved 2012-07-24. 
  7. 7.0 7.1 7.2 7.3 7.4 Robin Andrews (15 January 2016). "Incredibly Preserved 75 Million-Year-Old Baby Dinosaur Discovered". iflscience. Retrieved 2016-01-16. 
  8. 8.0 8.1 Philip Currie (15 January 2016). "Incredibly Preserved 75 Million-Year-Old Baby Dinosaur Discovered". iflscience. Retrieved 2016-01-16. 
  9. Gaidheal1 (April 13, 2011). "Jurassic Period, In: Wikiversity". Retrieved 2012-07-24. 
  10. "Jurassic, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. 24 July 2012. Retrieved 2012-07-24. 
  11. 11.0 11.1 Yuri D. Zakharov, Alexander M. Popov and Galina I. Buryi (April 2005). "Triassic Ammonoid Succession in South Primorye: 4. Late Olenekian – Early Anisian zones of the Atlasov Cape Section". Albertiana 32: 36-9. http://paleo.cortland.edu/Albertiana/issues/Albertiana_32.pdf#page=21. Retrieved 2015-01-24. 
  12. Alexander Mudroch, Ute Richter, Ulrich Joger, Ralf Kosma, Oumarou Idé, Abdoulaye Maga (February 2011). "Didactyl Tracks of Paravian Theropods (Maniraptora) from the ?Middle Jurassic of Africa". PLoS ONE 6 (2): e14642. doi:10.1371/journal.pone.0014642. PMID 21339816. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0014642. Retrieved 2011-09-14. 
  13. J.C. Gutiérrez-Marco, D. Goldman, J. Reyes-Abril, and J. Gómez (2011). J.C. Gutiérrez-Marco, I. Rábano and D. García-Bellido. ed. A Preliminary Study of Some Sandbian (Upper Ordovician) Graptolites from Venezuela, In: Ordovician of the World. Madrid: Instituto Geológico y Minero de España. pp. 199-206. ISBN 978-84-7840-857-3. http://digital.csic.es/bitstream/10261/60947/1/ORDOVICIAN%20OF%20THE%20WORLD_199_206.pdf. Retrieved 2015-01-15. 
  14. Phillip Levin, Donald Levin (January 2002). The Real Biodiversity Crisis. 3270. 3. http://www.americanscientist.org/issues/num2/2002/1/the-real-biodiversity-crisis/3. Retrieved 2011-08-02. 
  15. Shanchi Peng, Loren E. Babcock, Jingxun Zuo, Huanling Lin, Xuejian Zhu, Xianfeng Yang, Richard A. Robison, Yuping Qi, Gabriella Bagnoli, and Yong’an Chen (March 2009). "The Global Boundary Stratotype Section and Point (GSSP) of the Guzhangian Stage (Cambrian) in the Wuling Mountains, Northwestern Hunan, China". Episodes 32 (1): 41-55. http://www.stratigraphy.org/GSSP/Guzhangian.pdf. Retrieved 2015-01-21. 
  16. "Proterozoic, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. 1 January 2015. Retrieved 2015-02-13. 

External links[edit]

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