Insights into palaeobotany

Abstract

Palaeobotany is the science devoted to the study of fossil plants and their evolution. Prior to the 17 century, fossils were collected as curiosities and seen as freaks of nature (lusus naturae), but during the 18 century natural historians gradually began to understand them as the remains of formerly living organisms (Andrews 1980). The foundation of the scientific discipline was established in the early 19th century by the Frenchman Adolphe Brongniart (1801–1876), the Czech Kaspar Maria von Sternberg (1761–1837), and the German Ernst Friedrich von Schlotheim (1764– 1832), who are considered to be the “fathers” of modern Palaeobotany. They were among the first to apply the binomial system to fossil plants and to write systematic treatise with detailed descriptions and illustrations (Andrews 1980; Torrens 2005). The invention of thin sections and their application to permineralized fossils in 1831 was a major early technical breakthrough (Andrews 1980), enabling microscopy and the description of anatomical features, which greatly improved our knowledge of the relationships and biology of extinct plants. Advances like these led to our understanding of the plants that gave rise to the economically important coals of the Carboniferous Period. It was also soon realised that the geographic distributions of fossil plants conveyed information about Earth history. Fossil plants were central to the formulation of the concept of Gondwana (Suess 1885) and to the recognition of climate change through geological time (Heer 1861). Palynology, on the other hand, is the science devoted to palynomorphs, a general term for entities found in palynological preparations, including pollen and spores, but also cysts or other organisms or parts of organisms. Pollen grains have been described since the 17 century (e.g. Grew 1682). Palaeopalynology was established during the 19 century, with works such as that of Reinsch (1884) who published micrographs of fossil pollen and spores from Russian coal measure. During the 20 century, palaeopalynology became extremely useful for biostratigraphy (i.e. placing rock units in stratigraphic order based on the fossils they contain), not only for the coal industry, but also for petroleum exploration (e.g. Potonie 1934; Schopf 1957). During the first half of the 20 century the fossil record continued to inform on plant evolution through the discovery of key extinct groups that bridged major living clades, notably the pteridosperms (Oliver and Scott 1904), the early land plants of the Rhynie chert (Kidston and Lang 1921), and the progymnosperms (Beck 1960). One landmark synthesis was the ambitious Traité de Paléobotanique, which was edited by Édouard Boureau (1913–1999) and published in four volumes (Boureau 1964–1975). Other innovations included the further development of pollen analysis as a tool for the study of vegetation change during the Quaternary Period (Faegri and Iversen 1950). Today, palaeobotany and palaeopalynology continue to play important roles in developing our understanding of the evolution of plants and floras, climate change, and biostratigraphy. They are developing as interdisciplinary fields. Research areas such as geochemistry, molecular developmental biology, microbiology, biomechanics, and phylogenetics are transforming our approaches to, and perceptions of, the analysis of fossil plants and ancient ecosystems (Taylor et al. 2009). Likewise, advances in imaging methods including electron and confocal microscopy and more recently high-resolution X-ray computed tomography are opening new ways of looking at plant fossils. Issue 169 (4) and the first part of issue 170 (2) present a selection of articles showing the dynamism of Palaeobotany today. These contributions are summarized below.