l'aventure des crocodyliformes par un paléontologue
Crocos !
Paléontologue
The following text was written several years ago with Peggy Vincent from the MNHN (Paris). Its is published here with her autorization. Many thanks Peggy !
Traduction
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How does he/she work?
Paleontology is the study of fossilized remains (any fossils: plants or animals) found in geological formations. Our knowledge of past life on our planet is the result of more than 200 years of paleontological research. Professional paleontologists may specialize in one specific field, for example in the study of fossilized plant remains (paleobotanist), micro-organisms (micropaleontologist) or animals possessing backbones, which include dinosaurs and marine reptiles. Some use fossil records to reconstruct the biology, diversity and evolution of the fossil groups studied, and, therefore, they mainly concentrate on anatomical aspects of the fossils. Other paleontologists may focus on the age of sedimentary rocks or ancient climate conditions, and will therefore use collections of fossilized plants or animals to narrow down the age of rocks (biostratigraphy) or characterize past environmental conditions (paleoenvironments).
Most people think that paleontologists spend the majority of their time in the field searching for or collecting fossils. Although fossil collection is undoubtedly essential for further study, professional paleontologists usually spend most of their time in museums or universities studying and describing their discoveries. Additionally, paleontologists may spend a large amount of their time teaching students, as well as keeping fossils in good conditions, writing projects for funding, since fieldwork generally involves teams of numerous people working for several weeks and thus requires considerable financial support.
Discovery, excavation and preparation
Fossil discovery is often the result of chance and a large number of specimens kept in museum and university collections have been found by amateur, “lucky” collectors.Paleontologists do not search for fossils randomly; they usually concentrate their exploration on localized areas. How do they choose them? Paleontologists search for fossils where sedimentary rocks are exposed and thus easily accessible (quarries, mines, building excavations, deserts, sea cliffs, etc.). They first use geological maps to locate the appropriate rocks that may contain fossils. In order to find Mesozoic marine reptiles, for instance, paleontologists focus their research on marine sedimentary rocks of the Triassic, Jurassic or Cretaceous ages. Then the fieldwork entails prospecting for new localities. Fossil hunters patiently survey the sedimentary rock, inspecting fossil fragments exposed to the surface of the ground. Only after successful prospecting work will the fossil hunters start digging.
Sedimentary rocks are usually very hard, and scientists have to use appropriate instruments to dig. Most of the time, hammers, chisels, punches and trowels are much more helpful than brushes. Fossil hunting requires patience and tenacity. Scientific expeditions do not often lead to major discoveries: partial or complete skeletons are very rarely found. Geolocalization and the precise sedimentary succession in which fossils have been found are recorded in the field and are useful for further comparison. Once discovered, fossils need to be excavated. This is a delicate operation, as fossils are always very fragile. Most of the time, fossils are not entirely removed from the rock. The hunter carefully digs out the rock around the fossil so that part of the sediment pod encompassing the fossil is conserved. Bones are sometimes covered by tissue or paper before being enclosed in plaster. Once the plaster has dried, the fossil-bearing block is removed form the surrounding rock and brought to the laboratory for further preparation and cleaning by lab specialists.
Tiny fossil teeth, bones, or invertebrates are easy to remove and transport to the laboratory. Collecting and transporting large fossils such as bones of large mosasaurs require special skills. As fossil bones are considerably heavier than the original bone, package and transport with motor vehicles and in some cases aircrafts is often required for larger specimens. In the laboratory, the first step is to clean up the fossils and remove them from their surrounding protective plaster and rock matrix. Technicians and paleontologists then use a cleaning tool (engraver, awl, brush..) or chemical solutions (acetic or formic acid) to meticulously remove the whole matrix rock from fossils. Damaged fossils collected in several pieces are then reassembled. Finally, fragile fossils are consolidated with diluted glue or resin painted over them. The study of microfossils requires a microscopic observation, so micropaleontologists have to crush the rock sample with a mortar then apply part of the powder into a thin section to inspect it with a microscope. In all cases, cleaning and repairing fossils takes a long time and requires the special skills of professionals.
Study
Subsequent to preparation, the study of newly discovered specimens begins. Paleontologists usually spend thousands of hours in their lab studying specimens. They have to examine, identify (bones are most often broken and incomplete), measure, photograph, describe, and run multiple tests on the fossils found, as well as compare them with fossils kept in different paleontological collections. Methods and techniques for studying fossils are constantly improving. As such, paleontologists have a large array of available techniques. Some examples include: comparative anatomy, computer modeling of locomotion, or soft-tissue reconstruction. These investigations usually lead to new questions and help to elaborate hypotheses about evolution or paleobiology.
The information gathered from the study of fossils has to be shared with other researchers all over the world. Scientists thus write articles published in scientific journals where they present their research. They describe all the available details concerning the fossils or assemblages of fossils: age, size, anatomical description, taphonomical aspects, etc.
These articles will be read by various colleagues from different countries and may therefore be the basis for further work. For example, scientists can potentially provide data on the evolutionary relationships of organisms using the diverse subdivisions of the field of paleontology, which in turn gives a deeper understanding of actual biodiversity.
Editoral process
Most people think that scientists are paid for their publications in the scientific journal, but it is not the case ! On the contrary, to plublish in some free online papers such as the scientific journal series "PLOS", the scientists, or their labs, must pay. The price is of nearly 1.600$ for a publication in PLOS ONE ! But most of the specialised scientific publications are free for publication, but the subscription is relatively expensive for university libraries.
When a scientist want to publish in a scientific journal, he must first ensure that his paper tallies with the aims and scope of the journal. He must prepare and format his paper (pagination, format of the references...) according to the recommandations provided by the journal.
Exemple of "recommendations to authors" for publications in Journal of Vertebrate Paleontology.
When the paper is ready, the scientist submit it to the editor (now online). The editor will send the paper to at least two reviewers, two scientists specialist in the paper research field.
These two reviewers will provide comments, criticisms, and suggestions to improved the paper. At the end, the reviewers suggest to the editor to publish as is, publish with minor modifications, publish with major modification, or to reject the paper.
The comments provided by the reviewers are sent to the author, as the decision letter, where it is specified if the paper is accepted, rejected, or needs modifications with a new process of review, or not.
Here an exemple for one of my paper first accepted with major revision, and then accepted definitely.
Exemple of editorial process: the reviewers first recommanded a publication with major revision; I changed the text according to the comments; the reviewers recommanded the publication with minor revision; finally, the paper is accepted.
Knowledge transmission and curator work
Transmission of knowledge to the public or to students is an essential and important task of the job, so most paleontologists also spend a great amount of their time taking care of university or museum responsibilities.
Professional paleontologists can work in museums. They carry out their own research and teach and consult on exhibits. Fossils are great attractions in natural history museums and some, like vertebrates, need expert anatomists that know how to reconstruct and mount them appropriately. Complete skeletons are scarcely found and fossils are always very fragile, so nowadays most specimens in museum exhibitions are plastic casts. In this way, a full-size reconstruction of the entire specimen can give an impression of how they may have looked. Fossil displays in museums are often just a fraction of the fossils the museum owns in its collections. The majority of specimens is often fragmentary or not particularly spectacular, and is therefore kept in storage. Museums may create plaster molds of important discoveries for further exchange with other institutions, hence increasing the variety of specimens in exhibitions.
Professional paleontologists can also be college and university professors. Most work in geology or biology departments, where they usually teach general geology courses or evolutionary biology in addition to paleontology.
How to become a paleontologist
In order to become a paleontologist, undergraduate students need a strong background in sciences and must learn both biology and geology. It should be noted that young PhD graduates in paleontology do not get the job they want with certainty; interesting positions rarely become available. Professional paleontologists usually work for museums or universities, and are responsible for collections, teaching, exhibitions and research. A small number of paleontologists also work for government surveys or oil companies.