paleontology

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The Paleontology ( ancient Greek παλαιός Palaios "old" ὤν ON , Gen. ὄντος ontos "being" and -logie ) is the science of living things and liver worlds of the geological past . The subject of paleontological research is fossils ( Latin fossilis "excavated"), that is, physical remains found in sedimentary rocks as well as other legacies and testimonies of living beings that are more than 10,000 years old.

The French zoologist and anatomist Henri de Blainville introduced the term palaeontology in 1825 , which gradually replaced the older terms oryctology (Greek ὀρυκτός oryktós "excavated") and petrefacts (Latin petrefactum "petrified").

history

Baron Georges Cuvier is considered to be the founder of paleontology.

The French natural scientist Georges Cuvier (1769–1832) is considered to be the founder of modern paleontology, which works according to scientific criteria . The British geologist Charles Lyell (1797–1875), who contributed to the theory of the ice age , disproved his view that catastrophes completely wiped out life on earth and that humans were only created after the last ice age. At the same time, the French amateur archaeologist Jacques Boucher de Perthes (1788–1868) was the first to recognize human creations in stone artifacts.

The French Marcellin Boule (1881–1942) created the possibility of distinguishing human tools from naturally created forms with his eolite experiment from 1905. The Swiss doctor Otto Hauser (1874–1932) made the professional introduction to cave and excavation research in France ( Le Moustier ) . There he encountered resistance from local research.

The first German paleontologist to represent Darwin's theory of descent was Ernst Haeckel (1834–1919). He was a zoologist and brought the development of humans to research through hominids. His opponent was Rudolf Virchow , who called him the "monkey professor". Haeckel's suggestions were taken up by the Dutch anatomist, geologist and military doctor Eugène Dubois (1858–1940) and the German paleontologist Gustav Heinrich Ralph von Koenigswald (1902–1982).

Since 1997, 21 palaeontology professorships have been given up in Germany, and eight of 27 university locations have been completely deleted.

Sub-areas

Analogous to the biology of recent living beings, neontology ("doctrine of new beings"), paleontology can be broken down as follows:

In addition, there is palichnology , which researches a wide variety of fossil traces of life (including footsteps and tracks , grave passages, traces of food).

The paleontology of macrofossils differs in its methodology from micropaleontology , which examines microfossils and the even smaller nannofossils with the aid of various microscopy techniques . Microfossils can be the remains of microorganisms as well as microscopic evidence of larger living things.

Paleontologists examine fossils and fossil groups of organisms from a variety of points of view and questions. A division into geologically and biologically oriented sub-areas is made:

Geological sub-areas

  • The theory of fossilization (taphonomy) describes the path from the death of an individual to the finished fossil . It also explains the formation of so-called fossil deposits , in which the remains of fossil living beings are particularly numerous ( concentrate deposits ) or particularly completely preserved ( preservation deposits ).
  • The temporal classification and the relation (correlation) of sedimentary rock formations and their strata based on their fossil content is the subject of biostratigraphy . For this purpose, among other things, special key fossils are selected by the biostratigraphers .
  • The biofacies analysis tries to characterize the formation area of ​​a sedimentary rock based on its fossil organisms and traces of life.

Biological sub-areas

Related branches of research

Methods

Geological mapping

Skeleton of the Seitaad ​​ruessi dinosaur as found (B). The white bones were visible on the surface. (Source: Sertich and Loewen, 2010)

The targeted search for fossils in a paleontological excavation is preceded by the geological mapping of the (presumably) fossil-bearing sedimentary rocks. The aim is to find new find points to clarify the situation of the already known horizons Fund to adjacent layers and rock units and the depositional environment sedimentological further characterize, were formed as whether sediments in a lake or a sea. Such an overview map is not necessary if the age, the stratigraphic classification and the lithology of the fossil-bearing rocks are already sufficiently known.

Paleontological dig

A systematic paleontological excavation is carried out layer by layer from the hanging wall , that is, starting with the youngest layer on top, to the lying , that is, in the direction of the older layers below. Accompanying the search for fossils, the geology of the stripped layers must be precisely described . The horizons are numbered consecutively. The numbering is transferred to the fossil finds so that they can be precisely assigned to the horizons.

If larger remains of organisms (such as dinosaur skeletons) are the target of the excavation, the position of individual bones and skeletal parts within a layer must be precisely documented with the aid of a grid laid over it. This is important to e.g. B. to reconstruct dying attitudes or deposition and transport processes and to distinguish bones of different individuals.

For the extraction of microfossils, rock samples are taken from the individual horizons and later processed in the laboratory.

Preparation and preparation

Dissection laboratory at the Field Museum of Natural History in Chicago, USA

Crumbly fossil remains are glued on site or fixed with alcohol-soluble chemicals for later preparation . Plaster of paris may also be required to protect bone finds . If fossils are spread over several rock slabs, they are often stuck together again at the break point.

The later preparation of the fossils in the laboratory is mostly done mechanically, i.e. with a scalpel and dissecting needles (compressed air chisel / airtool) under a magnifying glass or using a stereomicroscope . With the help of X-rays , fossil parts hidden by the rock can be localized. Damage during preparation is avoided in this way.

Often microfossils can be removed from the rock with the help of acid etching or other wet chemical processes (see micropalaeontology ).

Documentation, description, classification

For the further analysis of the fossils it is important to use different methods, i. H. graphically, photographically and, if necessary, to make filigree structures visible with a scanning electron microscope .

The photographic and / or graphic documentation forms the basis for the description and interpretation of a fossil find and its systematic classification . A new taxon can also be named within this framework .

reconstruction

From the fossil drawing, the original skeletal context (in animals) or organ context (e.g. in plants) can be reconstructed, taking into account known specimens and / or representatives of related groups. A reconstruction of the life picture can then take place. Interpretations of the function, way of life and mode of locomotion of fossil living beings are incorporated. If necessary, the death process of the animal is also reconstructed.

Palecological evaluation of the terrain data

Since the fossil contents of all layers of the find are precisely documented , an analysis of the fauna and flora composition and then a reconstruction of the food web can take place in the event that the respective organism remains were not transported from different places of origin, but come from the same ecosystem . The sedimentological description provides additional information on the transport and deposition processes that led to the formation of the fossil-bearing rock.

Conversely, fossils provide geologists with information on the nature of the sedimentation space, for example if the predominant fossil groups only under very specific environmental conditions (e.g. on the sea floor in clear water at temperatures between 18 and 20 ° C and a salinity of <2.5%) occurred.

The vertical sequence of horizons corresponds to a temporal one: By comparing the communities of different horizons, conclusions can be drawn about the development history of a prehistoric ecosystem.

Statistical Methods

If the samples are large enough, that is, enough individuals of a species have been found and documented in a horizon, they can be examined as an equivalent to a natural population with regard to the variability of body characteristics. The composition of the ecosystem can also be recorded quantitatively (e.g. predator-prey ratios).

Geochemical analysis

The chemistry of water bodies can influence the composition of skeletons and housings. Often times of the year and time of day fluctuations in the chemical and isotope composition can be recorded in accretionary growing hard parts . Some of these can be interpreted climatically (see also paleoclimatology ).

The chemical composition of skeletons can e.g. B. clarify with the help of microprobe analyzes . The analysis of the isotopic composition requires mass spectroscopic methods.

Histological examinations

The microscopic analysis of thin sections made of bones or housings provides information on the growth and earlier tissue properties of the respective hard parts. They sometimes contain important clues about the physiology and ontogeny of the hard part creator.

Biomechanical models

If the skeletons are fully preserved, the movements of fossil animals can be simulated in the form of computer models. In this way, it is possible to rule out certain behavior and lifestyles or to accept them as likely.

Phylogenetic analyzes

Relationships and family trees of fossil groups of organisms are now mainly determined using computer-aided cladistics methods . Combinations of characteristics of the fossil species to be examined are compared with one another and family trees are calculated in the form of branching schemes ( cladograms ) based on the principle of economy. Accordingly, the results of these analyzes represent the presumed course of evolution under the assumption of as few evolutionary steps as possible.

Stratigraphic relationship (correlation)

All fossil species that a site produces occur in a certain relatively narrow geological period. If these species are also known from other localities, a possible common formation period of the different find layers follows.

The comparison of several sedimentary rock sequences containing certain fossils and volcanic rocks (such as tuffs ) that can be dated by geochronological methods enables the assignment of more accurate ages (i.e. those with lower margins of error).

The biostratigraphic subdivision of predominantly terrestrial sediments of the Cenozoic era in Europe with the help of land mammal remains is particularly well developed .

See also

literature

Web links

Commons : Paleontology  - collection of images, videos and audio files
Wiktionary: Paleontologist  - explanations of meanings, word origins, synonyms, translations
Wiktionary: paleontology  - explanations of meanings, word origins, synonyms, translations
Wikisource: Paleontology  - Sources and Full Texts

Individual evidence

  1. ↑ Time: Where can you get something like that?
  2. ^ Sertich JJW, Loewen MA (2010) A New Basal Sauropodomorph Dinosaur from the Lower Jurassic Navajo Sandstone of Southern Utah. PLoS ONE 5 (3): e9789. doi : 10.1371 / journal.pone.0009789