Paleontology

A sheet of Neuropteris, of the upper Carboniferous.

Philogeny and temporary distribution of cartilaginous fish in geological times, taking into account the fossil record.

Intensity of extinctions along the Fanerozoic, according to the diversity of marine genres identified in the fossil record.

The paleontology (from the Greek «παλαιος» palaios = ancient, «οντο» onto = to be, «-λογία» -logy = treatise, study, science) is the natural science that studies and interprets the past of life on Earth through fossils. It falls within the natural sciences, it has its own body of doctrine and it shares fundamentals and methods with geology and biology with which it is closely integrated. It can be subdivided into paleobiology, taphonomy and biochronology, and exchanges necessary information with other disciplines (study of the evolution of living beings, biostratigraphy, paleogeography or paleoclimatology, among others).

Among its objectives are, in addition to the reconstruction of living beings that lived in the past, the study of their origin, their changes over time (evolution and phylogeny), the relationships between them and their environment (paleoecology, evolution of the biosphere), their spatial distribution and migrations (paleobiogeography), extinctions, fossilization processes (taphonomy) or the correlation and dating of the rocks that contain them (biostratigraphy).

Paleontology was (and is) very important in allowing us to understand that the Earth and its living beings are constantly changing, going back many billions of years in the past. This understanding, developed hand in hand with advances in the knowledge of geological processes, led to a change in the perception of time, giving rise to the concept of "deep time".

Paleontology allows us to understand the current composition (biodiversity) and distribution of living beings on Earth (biogeography) —before human intervention—, it has provided essential evidence for the solution of two of the greatest scientific controversies of the past century, the evolution of living beings and the drift of the continents, and, looking to our future, it offers tools for analyzing how climate change can affect the biosphere as a whole. In addition, paleontology, by generating knowledge about stages in the history of the Earth where environments and living beings were often radically different from those observed today, allows the development of hypotheses or speculation about the origin and potential presence of life on Earth. other celestial bodies.

"Paleontology has the answer not only to rebuild and describe the history of life, but also to explore the ecological processes that develop during periods of time of geological dimensions and therefore inaccessible to experimental approaches."

Lukas Hottinger, 1997

Principles

Icnitas de dinosaurio terópodo en el yacimiento de Valdecevillo (Enciso, La Rioja, Spain).

Excavation of the Grand Dolina deposit in Atapuerca (Burgos).

The primary purpose of Paleontology is the reconstruction of organisms from the past, not only their skeletal parts, but also the organic parts that disappeared during fossilization, restoring the appearance they had in life, their ethology, etc. To do this, he uses the same principles already established: actualism, comparative anatomy, organic correlation and functional correlation.

• Production postulate: fossils are direct or indirect products of organisms that lived in the past (paleobiological entities).
• Biological update: the beings of the past were governed by the same physical and biological laws, and had the same needs as the current ones. It allows this principle, for example, to assert that the fish of the Silurico had gills, because they have the current fish (although they are not the same); and that the dinosaurs lay eggs, such as crocodiles, which has been subsequently corroborated by the found fossils of eggs, and nests, preserved in some deposits.
• Comparative anatomy: It allows the extinct organisms to be placed on the site that corresponds to them from the general table of living beings, thus obtaining the reference point necessary to apply the principle of organic correlation. Although fossils only provide a small anatomical part of an extinct taxon, the comparative anatomy allows us to infer and complete certain anatomical or physiological characteristics absent from them.
• Organic correlation principle: Postulated by Cuvier. Each organic being forms a set whose parts are complemented, determining all others and therefore can be recognized by any fragment, ultimately suffocating a piece of bone to identify it.
• Functional correlation: Known better as functional morphology, it is the part of the Paleontology that deals with the relationships between form and function, i.e., that tries to relate the structures observed in fossils to the function they performed in the organism when it was alive. It uses various methods or lines of analysis.

1. Comparison of groups with homologous structures: This method, which leads the paleontologist to compare the structures of some extinct groups with those of their corresponding current representatives, is sometimes less reliable, as the same structures or anatomical parts in a particular group may have been profoundly modified throughout evolution and perform very different functions. Similarly, a same group can occupy very different ecological niches over time. For example, current marine mammals and their terrestrial predecessors have morphology and occupy very different ecological niches. The previous extremity in both groups, despite integrating the same number of bone parts in a similar anatomical position, has undergone profound modifications in the forms derived from marine life, and represents an adaptation to a very different medium and function (the swimming) of which their terrestrial ancestors (the march or the displacement on the ground). Comparison of forms and of homologue structures should be taken with great caution.
2. Comparison of similar structures: This is truly the most fruitful and reliable method in Functional Morphology. Thus it can be said that, while evolutionary analysis constitutes the field of action of homology, the morpho-functional analysis constitutes the field of analogy. This analysis usually starts from the comparison of structures with a similar form to infer a similar function in both groups (form-function correlation principle). But such structures that have the same form can have very different origins and the groups that present them may not have a philtic relationship between them. Thus paleontologists reason correctly that the pectoral fins of a fish and the previous extremities of a dolphin and an ictiosaur perform the same function. Something similar can be said of the wing of a flying reptile (pterosaurus), of that of a bird and of a flying mammal (murciélago). All this can be analyzed even in biological groups that do not have current representatives and that we only know for their fossils. When biological analogues are not available, the use of mechanical analogs can be used.

• Principle of stratigraphic overlap: Initiated by William Smith recovering the ideas of Nicolaus Steno (Steno Stratet Superposition Law), an earlier century. In a normal stratigraphic series (not inverted) the strata of the lower part are always older than those of the superior. The fossil content of such strata must comply with the same principle. However, it is necessary to exempt the re-elaborated fossils (which have suffered one or more cycles of exhumation—by erosion of the substrate in which they lie—and re-sedimentation), and therefore are older than the sediments that enclose them, or those corresponding to endobiont organisms—those who live or spend part of their lives buried in the substrate—these most recent remnants.
• Principle of stratigraphic correlation: Portraits belonging to the same time are characterized by a similar fossil content. This principle, in practice, is true but with nuances, since other factors such as physical barriers or climate condition this.

Disciplines of Paleontology

Recreation of organisms from the past (Pteranodon of the upper Cretaceous).

Modern paleontology places ancient life in context through the study of how physical changes in world geography and climate have affected the evolution of life, how ecosystems have responded to these changes, and have adapted to the changing environment and how these mutual responses have affected current patterns of biodiversity.

Skull of tyranosaurus at the Institute of Paleontology Miquel Crusafont.

It is divided into three fields of study:

Paleobiology

Studys the organisms of the past in all their aspects, both systematic and physiological, ecological, evolutionary, etc. Some paleobiological specialties are:

Fossil and reconstruction of the Marrella splendens basal arthropod, of the Middle War of Canada.

• Paleozoology. It is responsible for the study of extinct animals, from their fossil remains, and their taxonomy. Here are disciplines such as Paleoanthropology, Paleoentomology or, within Paleoherpetology, Dinosaurology. More often it is divided into Vertebrados Paleontology and Invertebrate Paleontology.
• Paleobotany. It is responsible for the study of extinct plant or fungal beings and their taxonomy. It's a less widespread discipline than the previous one. Disciplines such as Paleopalinology or study of fossil pólenes and spores are included.
• Micropathology. It is the study of microscopic fossils (microphosiles and nanophosiles), for which special sampling techniques are used, preparation and observation with the microscope.
• Paleoicnology. It is responsible for the study of the signs of activity (fossil works) of organisms of the past.
• Paleoecology. It is responsible for the study of the ecology of the living beings of the past and the reconstruction of the environments and ecosystems present on Earth over the course of geological time.
• Paleobiogeography. It studies the paleogeographic distribution of the living and biomas of the past and the causes of such distribution. It is an application of paleontology to descriptive and historical biogeography.
• Paleogenetics. It addresses the analysis of genetic material preserved in remains of ancient organisms, including molecular evolution studies, phylogenia and molecular clocks.
• Paleobiology of conservation (or paleobiology for conservation). It uses the information of paleontology to contribute to the conservation problems of current biodiversity.

Taphonomy

It is in charge of the study of fossilization processes and the formation of fossil deposits. It is divided into two main fields: Biostratinomy, which studies the processes that occurred from the production of remains or signs to burial or passage to the lithosphere, and Fossildiagenesis, which studies processes after burial. Prior taphonomic analysis is essential for any biostratigraphic, paleoecological, or paleobiogeographic study, among others, in order to assess taphonomic bias (i.e., to what extent taphonomic phenomena distorted paleontological information) or, similarly, the degree of taphonomic fidelity (i.e., how closely fossil assemblages resemble the communities from which they came). fate of the remains of current organisms.

Biochronology

Studys the age of paleobiological entities, their temporal ordering, and the dating of past biotic events. It is closely related to Biostratigraphy, the application of Paleontology to Stratigraphy.

Relations with other sciences

Transit Ursus deningeri in the cave of Goikoetxe (Busturia, Vizcaya).

Paleontology can be considered as a temporal division of Biology. Biology provides information about living beings without which it is impossible to make a correct interpretation of fossils (this is one of the bases of actualism). Paleontology, for its part, reveals and informs the biologist what life was like in the past and its evolution, thus constituting the historical aspect of biology.

Fossils have an intrinsic value since their study is essential for Geology (correlations, interpretation of sedimentary environments, determination of relative ages, etc.). Regarding the applied aspect, there are numerous examples that relate certain organisms with the genesis of mineral deposits (such as phytoplankton with oil, coal, phosphates, etc.). Historical geology is inconceivable without the support of paleontological data that gives us information on paleogeography, paleoclimatology, paleo-oceanography, water chemistry, etc.). In the same way, Paleontology needs other disciplines such as Biochemistry, Physics or Mathematics (especially Statistics).

Paleontology is one of the main disciplines studied in the karst sciences object of speleology, dealing with the study of vestiges in underground cavities.

Techniques of extraction, preparation and conservation of fossils

There are different techniques commonly used in paleontology for the preparation of fossil remains.

Mechanical methods

Mechanical cleaning of a paleontological sample in the laboratory.

The physical boundaries of fossils represent areas of weakness, since the chemical constitution is different from the matrix that encloses them. Therefore, to separate them you can use percussion methods (hammer and chisel).

• abrasion techniques: The pioneer was the sandblasting machine. Generally now a gas (compressed air, nitrogen or carbon dioxide) is used to propel an abrasive powder; in this case the abrasive power depends on the pressure of the gas and the size and characteristics of the abrasive dust.
• Heat: Very abrupt temperature changes are used to separate by differential dilation.
• Percussion and removal techniques: A Pneumatic Fossil Cleaner is used with special tips (major size for outburst and thinner tips for delicate work). To do this we must rebuild the disposition of the fossil before beginning, as well as check the petrology of the rock and support the specimens in an element that absorbs the vibrations (such as a sandbag).

Chemical methods

They are used depending on the nature of the fossils and the rock.

Using a technique called chemical disintegration, water is treated with detergents that lower the surface tension at the clay-water interface for clayey rocks or silts. Hydrogen peroxide has a similar effect. Acids are also widely used in the extraction of fossils: hydrochloric acid (HCl(aq)), hydrofluoric acid (HF(aq)), nitric acid (HNO₃), formic acid or acetic acid.

Microfossil extraction techniques

Wash-tamized system for the reduction and concentration of a sample with microfossils.

You have to distinguish techniques depending on the type of rock.

• Calcareous rocks: Acetic acid (CH) is used₃COOH) or formic (HCOOH) for phosphatic fossils. In this case the sample is placed in a polyethylene glass and added acetic (10-15 %) or phormic that acts faster and can be used to greater concentration although it is more corrosive. The acid can attack the phosphate in low carbonate samples so it is interested to add calcium carbonate powder (obtaining calcium acetate). Alternatively, successive attacks in the sample to solve this problem are used a solution (7 % concentrated acetic acid, 63 % water and 30 % of the filtered fluid from the digestion of previous samples).
• Siliceous rocks: Chlorhydric acid is used at 10%.
• Yellow rocks: In this case, oxygenated water or detergents are used.
• Palinological techniques: Fluorohydric acid or hydrochloric acid is used. First, samples are covered by hydrochloric acid (HCl) to remove carbonates, then washed and centrifuged three or four times. A second treatment is given, with fluoric acid (HF), to remove silicates. At the end of the reaction, organic residue should be visible. The sample is cleaned of acids by decantation and centrifugal, and then by insoluble fluorosilicate crystals.

Concentration techniques

Heavy liquids such as bromoform (CHBr₃, bp 2.89) and tetrabromoethane (C₂H₂Br_{4) are used.} , pe 2.96), but they are very toxic. The safest alternative is the use of sodium polytungstate (3Na₂WO₄.9WO ₃.H₂O) soluble in water which allows to vary its Pe. 2.75 or slightly higher is ideal to avoid high viscosity and precipitation problems. Filtration is carried out with appropriately sized sieves based on the fossil groups.

Thin sections

Thin lamina with fusulin fossils seen under the petrographic microscope.

Thin sections are carried out when fossils and microfossils have a composition the same as that of the matrix and cannot be extracted without damaging them or when sections, details or their tissue structure are to be observed.

Consolidants and adhesives

Consolidation or hardening is necessary for the conservation and handling of many specimens. Adhesives and consolidants must be easily removable if necessary. For those fossils that have undergone mechanical extraction methods, fractures are sealed with acetyl-polyvinyl and poly-methyl-methacrylate resins soluble in ethyl-acetate. The latter shrinks when it dries, so it cannot be used as a consolidant. Cyanoacrylate is used to repair small pieces of fossils (its stability is unknown and it is practically insoluble). Chemical preparation methods require adhesives and consolidants to protect fossils from chemical attack and as framework and reinforcement. Polybutyl methacrylate, polymethyl methacrylate and cyanoacrylate are adhesives with similar acid resistance. In all preparation methods it is necessary to keep a meticulous control of all the steps carried out.

Paleontological study methods and analysis

Within the variety of topics and disciplines in paleontology, some methodological approaches tend to be the most common. The first steps in the study of a fossil remains include its anatomical description and its comparison with the known anatomy of other beings, followed by a classification proposal that assigns a scientific name to the remainder and a belonging to some taxonomic group. This is usually complemented with a phylogenetic analysis, in which a series of features are observed in the fossil under study to quantify its anatomy in a matrix of characters. This matrix is analyzed by means of cladistic methods to generate phylogenetic trees that allow understanding with which fossil and current organisms it was most related.

Additional studies may include analysis of specific chemical elements and isotopes of interest in preserved tissues, data that often provide valuable information about the environment in which the organism lived and died, or about its way of life. Within paleobiology, usual methods include, in addition to functional morphology, the quantification of shape (morphometry) and its analysis using different multivariate statistical techniques to understand the relationships between shape and environment (ecomorphology). The analysis of the physical properties of biological forms is called biomechanics, and it is also an active area in paleontology. Another area of study includes the analysis of the variations in shape suffered by organisms throughout life (ontogenetic variation), and their evolution. In more integrative phases of analysis (paleoecology), paleoenvironmental reconstruction implies the confluence of data and evidence from multiple subdisciplines (sedimentology, ichnology, micropaleontology, etc.). Both basic and multivariate statistics usually play a leading role in the study of all kinds of numerical data in paleontology.

History of Paleontology

This section is an extract from History of paleontology.[chuckles]edit]

Duria Antiquior - An Older Dorset is a watercolor painted by the geologist Henry De la Beche in 1830, based on fossils discovered by Mary Anning. At the end of the century xviii and at the beginning of the century xix rapid and dramatic changes occurred in thought about the history of life on Earth.

The history of paleontology runs through the history of efforts to understand the history of life on Earth through the study of the fossil record left by living organisms. Since it has to do with the understanding of the living organisms of the past, paleontology can be considered as a field of biology, but its historical development has been closely linked to geology and effort to understand the history of the Earth itself.

In ancient times, Jehophanes (570-480 B.C.), Herodote (484-425 B.C.), Eratosthenes (276-194 B.C.), and Estraboon (64 B.C.-24 AD) wrote about the fossils of marine organisms indicating that their land had ever been underwater. During the Middle Ages, the Persian naturalist Ibn Sina (known as Avicena in Europe) treated fossils in his writing The book of healing (1027), in which he proposed a theory of the petrifying fluids that Alberto de Saxony would extend in the century xiv. Chinese naturalist Shen Kuo (1031-1095) proposed a theory of climate change based on evidence of petrified bamboo.

In modern Europe, the systematic study of fossils emerged as an integral part of the changes in the philosophy of nature that occurred during the Age of Reason. The nature of fossils and their relationship with life in the past reached greater understanding during the centuries xvii and xviiiat the end of the century xviii the work of Georges Cuvier decided a long debate about the reality of extinction, which led to the emergence of paleontology associated with anatomy compared as scientific discipline. The growing knowledge of the fossil record also played a growing role in the development of geology, especially stratography.

In 1822, the term "paleontology" was coined by Henri Marie Ducrotay de Blainville (editor of the French scientific journal) Journal de physique) to refer to the study of ancient living organisms through fossils, and during the first half of the century xix geological and paleontological activities became more organized with the growth of geological societies and museums and with the growing number of geologists and fossil specialists. This fact contributed to a rapid increase in knowledge about the history of life on Earth, and to a significant progress towards the definition of the geological temporal scale based mostly on fossil evidence. Since the knowledge of the history of life continued to improve, it became increasingly evident that there was some successive order during the development of life. This statement would encourage early evolutionary theories on the transmutation of species.

After Charles Darwin published The Origin of Species In 1859, much of the paleontology approach addressed the understanding of evolutionary pathways, including human evolution and evolutionary theories.

During the second half of the century xix A tremendous expansion of paleontological activity occurred, especially in North America. The trend continued during the century xx when various regions of the Earth opened for the systematic gathering of fossils, as demonstrated by a series of important discoveries in China, near the end of the century xx. Many transitional forms have been discovered, and there is now abundant evidence of how all kinds of vertebrates are related, much of them in the form of transition forms. During the last two decades of the century xx increased interest in the mass extinctions and the role they play in the evolution of life on Earth. The interest in the cluster explosion was also renewed, during which the body planes of most animal filos arose. The discovery of fossils of the biota of Ediacara and the development of paleobiology extended the knowledge of life long before the Warm.

Famous paleontologists

The story includes a good number of noteworthy paleontologists:

Othniel Charles Marsh (1831-1899). One of the contestants in the so-called "War of the Bones".

Ivan Efremov (1908-1972). He defined taphonomy, the science that studies fossilization processes and the formation of fossil deposits.

Adolf Seilacher (1925-2014). He introduced ethology as a classification criterion for fossil tracks.

Recommended bibliography

• Aguirre, E. (Coord.) (1989). Paleontology. Senior Scientific Research Council. New trends, 10. 433 pp. ISBN 978-84-00-06968-1
• Benedetto, J. L. (2018). The Gondwana Continent over time, National Academy of Sciences 475 p. Córdoba, Argentina.
• Camacho, H.H. (2008). The fossil invertebrates. Vázquez Mazzini Editors, 950 p. (Volume I and II). Buenos Aires. ISBN 978-987-22121-7-9
• Domènech, R. and Martinell, J. (1996). Introduction to fossils. Masson. 288 pp. ISBN 84-458-0404-9
• Lacasa, A. (2010). Testimonies from the past. History, myths and beliefs about fossils. Editorial Millennium, 32: 177 pp. ISBN 978-84-9743-392-1
• Martínez Chacón, M. L. and Rivas, P. (Eds.) (2009). Paleontology of invertebrates. Sociedad Española de Paleontología, Instituto Geológico y Minero de España, Universidad de Oviedo, Universidad de Granada. 524 pp. ISBN 978-84-613-4625-7
• Meléndez, B. (1977). Paleontology. Take 1. General and invertebrate part. Editorial Paraninfo. 715 pp. ISBN 84-283-0005-4 (2nd Ed.)
• Meléndez, B. (1979). Paleontology. Take 2. Broken. Fish, Amphibians, Reptiles and Birds. Editorial Paraninfo. 542 pp. ISBN 84-283-1001-7
• Meléndez, B. (1990). Paleontology. Volume 3 Volume 1. Mammals (1 part). Editorial Paraninfo. 383 pp. ISBN 84-283-1742-9
• Raup, D. M. and Stanley, S. M. (1978 [1971]). Principles of Paleontology. Editorial Ariel. 456 pp. ISBN 84-344-0145-2
• Roger, J. (1980 [1977]). Paleoecology. Editorial Paraninfo, S. A. 203 pp. ISBN 84-283-1038-6
• Rudwick, M. J. S. (1987 [1976]). The meaning of fossils. Episodes of History of Paleontology. Hermann Blume. Col. Nature Sciences. 347 p. ISBN 84-7214-371-6
• Sanz, J.L. (2007). Dragon Hunters. Editorial Ariel. 420 pp. ISBN 978-84-344-5316-6
• Simpson, G. G. (1985 [1983]). Fossils and Life History. Scientific press. Col. Scientific American Library. 240 pp. ISBN 84-7593-007-7
• VV. AA (1988). Lecture course on the history of paleontology. Royal Academy of Exact, Physical and Natural Sciences. Col. History of Science. 215 pp. ISBN 84-600-5332-6