Review paperEighty years of chitinozoan research: From Alfred Eisenack to Florentin Paris
Introduction
Alongside the acritarchs (generally related to phytoplanktonic organisms), the spores and pollen grains (related to land-plants) and the scolecodonts (elements of the jaws of polychaetes), the chitinozoans are considered today as one of the major groups of the Palaeozoic organic-walled microfossils (palynomorphs). The group was first discovered and described some 80 years ago by Eisenack (1930), who proposed the name Chitinozoa for these bottle- or urn-shaped organic microfossils. Since the 1960s the chitinozoans have become very important in biostratigraphy, and today they are widely considered as one of the major groups providing solid biostratigraphical correlations at local, regional and global scales, with a similar or, in some intervals, even more precise resolution than that of the graptolites and conodonts, considered as the two ‘classical’ biostratigraphic fossil groups of the Ordovician, Silurian and Devonian. In addition, chitinozoans have the advantage that they can be easily found in both limestones and mudstones, unlike graptolites and conodonts, respectively.
During the last 40 years, Florentin Paris, ‘Directeur de Recherches’ at the Centre National de la Recherche Scientifique (CNRS) at the University of Rennes (Brittany, France), was the driving force behind chitinozoan research. He contributed to all aspects of chitinozoan investigations: taxonomy, biostratigraphy, palaeobiogeography, palaeoecology, palaeobiodiversity and biogeochemistry. The stratigraphical information provided by his work proved to be crucial for the understanding of regional geology and palaeobiogeography, first of all of Brittany, but later of the entire Armorican Terrane Assemblage, southern Europe and most areas of the ‘northern Gondwana domain’.
This paper attempts to outline the main trends in chitinozoan research of the last 80 years, i.e. since the pioneering work by Alfred Eisenack in the early 1930s to the standards reached at the beginning of the 21st century. We do not attempt to provide an exhaustive list of all the chitinozoan papers that have been published since 1930; readers are invited to consult the listed bibliography to find the references not cited herein. Because Florentin Paris was one of the major actors in chitinozoan research during the last 40 years, this review will inevitably highlight his contribution during that period. This review paper is the first of a set of papers of a special issue on Palaeozoic marine palynomorphs respectfully dedicated to Florentin Paris.
Section snippets
The first discoveries: Alfred Eisenack
It was Alfred Eisenack, a German amateur collector, trained as a chemist and working as a school teacher, who first discovered and defined the Chitinozoa in the 1930s. He continued research after World War II as a scientific collaborator at the University of Tübingen. In the first half of the 20th century Eisenack studied the numerous fossils contained in the erratic boulders strewn by glaciers along the south-eastern coast of the Baltic Sea near the town of Königsberg in Eastern Prussia, the
Taxonomical concepts and classification
Of the different Palaeozoic marine organic-walled microfossil groups the chitinozoans are very important, with over 1200 papers describing chitinozoans published up to the 2000s. After the first species defined by Eisenack in the 1930s, only a few species were described between 1940 and 1955, but the number of new species exploded in the last part of the 1950s and in particular in the 1960s, with over 100 new descriptions during this decade (Servais and Paris, 2000). These numbers were never
Chitinozoan biostratigraphy
Some fossil groups, such as the ammonites of the Jurassic and Cretaceous, are considered stratigraphic index fossils. In the Lower Palaeozoic, the classical stratigraphic fossils for the Cambrian are the trilobites, while the planktonic graptolites were considered for many years the most important index fossils for the Ordovician, Silurian, and Lower Devonian (Lapworth, 1879, Webby, 1998). With the development of micropalaeontology in the second half of the 20th century, the conodonts also
Biogeographical distribution patterns of the chitinozoans
As a fossil group commonly interpreted as belonging to the plankton, the chitinozoans have for a long time been considered to be of limited use in biogeographic reconstructions. Like the graptolites and the acritarchs, they have been considered (e.g., Fortey and Mellish, 1992) to be geographically widespread and often of cosmopolitan distribution, which is an advantage for global correlations, but a disadvantage for defining biogeographic provinces or establishing palaeogeographic boundaries.
Chitinozoan biodiversity
Research in micropalaeontology and palynology has undergone a cyclic evolution through time. Strongly supported by the oil industry in the second half of the 20th century, micropalaeontological studies were mostly focused on stratigraphy, and, since most palynologists were stratigraphers, this became, as indicated above, the main trend in chitinozoan research. At the beginning of the 1980s an additional focus became important for Palaeozoic palaeontologists: the study of palaeogeography and the
Florentin Paris' impact on chitinozoan research and ‘northern Gondwanan’ studies
This short review on chitinozoan research, from the first discovery in 1930 to the present day, clearly shows that Florentin Paris was one of the major contributors of chitinozoan studies in the last part of the 20th and the beginning of the 21st centuries. At the beginning of his career he focused his research on the detailed stratigraphic documentation of chitinozoan faunas, establishing a high-resolution chitinozoan biostratigraphy of the Ordovician of southwestern of Europe. On the basis of
Acknowledgments
We are particularly grateful to Jaak Nõlvak, Thijs Vandenbroucke and Jacques Verniers for reviewing the paper and for adding useful ‘background information’. This study is a contribution to the IGCP 591 “The Early and Middle Palaeozoic Revolution” project. It was supported by the Natural Science and Engineering Research Council of Canada (Grant RGPIN/4226-2006 to Aicha Achab). It is a Natural Resources Canada — Earth Sciences Sector Contribution 20120108. We wish to thank Kheira Boumendjel,
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2015, International Journal of Coal GeologyCitation Excerpt :The earliest chitinozoans, an extinct group of organic-walled microfossils and tentatively assigned to ontogenetic vesicles of unknown soft-bodied organisms (Paris and Nõlvak, 1999), have been recorded from the Cambrian Stage 5 (mid-Cambrian) of southern China (Shen et al., 2013). Recently, detailed reviews on chitinozoans have been published by Grahn and Paris (2011) and Servais et al. (2013). Poorly preserved and graphitized chitinozoans have even been extracted from high-grade metamorphic gneisses (Hanel et al., 1999).
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