Palaeobotanical Research Research Articles

Quaternary plant macrofossils from Robertson Cave, Naracoorte, South Australia: reproductive structures

The World Heritage Naracoorte Caves in southeastern South Australia are important palaeontological sites known primarily for their diverse vertebrate fossils. Some of the caves also contain well-preserved Quaternary plant macrofossils, but little palaeobotanical research has been undertaken to date. Here, we describe the angiosperm plant taxa represented by macrofossils of reproductive structures that have been extracted from the Robertson Cave sediment deposit; this has an age range of 820–24,230 years BP. We identified 29 angiosperm taxa representing 20 families. These represent some of the plant species that grew in the Naracoorte region during the Quaternary, and form a database for future plant identification and palaeovegetation reconstructions. Rachel A. Atkins [rachel.atkins@adelaide.edu.au], School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia and Environment Institute, The University of Adelaide, Adelaide, South Australia 5005, Australia; Robert S. Hill [bob.hill@adelaide.edu.au], School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia and Environment Institute, The University of Adelaide, Adelaide, South Australia 5005, Australia; Kathryn E. Hill [kathryn@debillenvironmental.com.au], School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia and DeBill Environmental, 13 Hawkesbury Ave, Kilburn, South Australia 5084, Australia; Samantha E.M. Munroe [Samantha.Munroe@csiro.au], School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005; Elizabeth H. Reed [liz.reed@adelaide.edu.au], School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia, Environment Institute, The University of Adelaide, Adelaide, South Australia 5005, Australia, and Earth and Biological Sciences (Palaeontology), South Australian Museum, Adelaide, South Australia 5000, Australia.

Geographic Range vs. Occurrence Records in Plant Distribution Mapping: The Case of Arbutus in the Old World

Species mapping methods play a central role in biogeographical questions, as they may generate a domino effect on further works based on species distribution. In light of the massive recent increase in the availability of online occurrence data, we highlight the strengths and limitations of the mapping methods most widely used to display the geographic distribution of plants, namely geographic range maps and occurrence record maps. We use the modern distribution of the genus Arbutus in western Eurasia, North Africa, and Macaronesia, for which no occurrence record map has been published yet, to discuss critical issues in data collection and representation. The occurrence record map of A. unedo, A. andrachne, A. canariensis, and A. pavarii shows how well this mapping method captures the details of peripheral and isolated stands as well as the variability of population density. A number of biogeographical issues are addressed by this approach, including the determination of the chorological centre of gravity in relation to historical dynamics, genetic patterns in relation to range porosity, and the autochthony status of marginal stands. These issues constitute the necessary foundation for additional palaeobotanical research and ecological modelling to investigate the past-to-future dynamics of Arbutus and other species of the Mediterranean–Atlantic area.

Polish Palaeobotany: 750 Million Years of Plant History as Revealed in a Century of Studies. Research on the Paleogene and Neogene (Tertiary)

Abstract On overview of over a hundred years of history of Polish palaeobotanical research on the Paleogene and Neogene (formerly Tertiary) is provided. Profiles of the researchers who laid the foundations for the development of paleofloristic research are presented. In particular, we describe individuals who have made significant research contributions, including M. Raciborski, J. Zabłocki, M. Kostyniuk, H. Czeczott, and W. Szafer. Research centers that were revived after World War II gathered scientists who continued and extended work in the field, including M. Łańucka-Środońowa, J. Oszast, A. Skirgiełło, J. Doktorowicz-Hrebnicka, J. Stachurska, and J. Mamczar. This tradition was maintained and developed by researchers of the next generation: L. Stuchlik, E. Zastawniak, A. Sadowska, M. Ziembińska-Tworzydło, I. Grabowska, H. Ważyńska, A. Hummel, Z. Baranowska-Zarzycka, and A. Kohlman-Adamska. Currently, the fourth generation of Polish palaeobotanists, including B. Słodkowska, E. Worobiec, G. Worobiec, P. Gedl, M. Garecka, E. Durska, and R. Kowalski, conduct multifaceted palaeobotanical research, with links to various fields of knowledge, including botany, geology, and palaeoclimatology. Studies of past changes in plant cover provide important insight current climate change.

Review: Phytogeography and history of Japanese beech forests: Recent advances and implications for vegetation ecology

AbstractIn this review, the phytogeography and history of Japanese beech (Fagus crenata Blume and F. japonica Maxim.) forests are re‐examined in light of recent phytogeographical and palaeobotanical research advances. I explain the floristics and the climatic and geological contrasts between Japanese beech forests on the Sea of Japan side and the Pacific side of the Japanese archipelago. We also review recent studies on the origin of dwarf evergreen shrub species occurring along the Sea of Japan. The old scenario that these dwarf evergreen shrub species diverged directly from counterpart species occurring on the Pacific coast of Japan is no longer supported. We propose more intricate speciation processes, including phylogenetic relations to extant Chinese species and inter‐species hybridization. We also review the results of recent palaeobotanical studies of forests on the Japanese islands in the Quaternary. The long persistence of beech forests through glacial/interglacial cycles of the Quaternary—with repeated spread and contraction of the geographical range—is confirmed. In addition, we briefly explain the phytosociological classification system of the Japanese beech forest and the geographical ranges of each vegetation type. We review studies of the geographic distribution of F. crenata and F. japonica at the population level, highlighting the need for further ecological and genetic studies of population dynamics near the range limits to understand historic migration processes better.

Holocene environmental changes in a prehistoric mining and metallurgical region in the light of paleobotanical studies of the bogs of the Brynica river drainage basin (southern Poland)

The analyses of human-environment interactions in prehistoric and medieval mining and metallurgical centres in Europe result in various assessments of the environmental impact of early metal ore mining and metallurgy. In some mining and metallurgical sites or areas, such as the prehistoric basin on the Greek island of Kythnos or the later Morvan and Mont Lozère areas in France as well as Tjursbosjön in Sweden, the impact was significant and lasting. In others, such as: Cors Fochno in Wales, the Falkenstein region in Austria, or the Northern Vosges Mountains in France, the environmental changes were limited and reversible.The results of palaeobotanical research (pollen analysis and analysis of plant macroremains) in peat cores from southern Poland enabled the Holocene vegetation transformations in one of the oldest mining regions in Central Europe to be reconstructed. They also provided new data, used to assess the impact of settlements as well as the development of metallurgy on the environment in the region and changes in bog ecosystems. The first changes in vegetation caused by human activity were observed at the boundary between the Neolithic and Bronze Ages. They are documented by pollen indicating shepherding activity and single grains of cereal pollen. The greatest intensity of change, reflected in sediment as a maximum concentration of charcoal, was recorded at the end of the Bronze Age and attributed to the Lusatian culture. The changes in the vegetation under the impact of human activity until the early Middle Ages were reversible and had a local scope. The intensification of slash-and-burn agriculture was indicated as the most probable and important cause.

Al-Ansab and the Dead Sea: Mid-MIS 3 archaeology and environment of the early Ahmarian population of the Levantine corridor.

Our field data from the Upper Palaeolithic site of Al-Ansab 1 (Jordan) and from a pollen sequence in the Dead Sea elucidate the role that changing Steppe landscapes played in facilitating anatomically modern human populations to enter a major expansion and consolidation phase, known as the „Early Ahmarian“, several millennia subsequent to their initial Marine Isotope Stage 4/3 migration from Africa, into the Middle East. The Early Ahmarian techno-cultural unit covers a time range between 45 ka–37 ka BP. With so far more than 50 sites found, the Early Ahmarian is the first fully Upper Palaeolithic techno-cultural unit exclusively and undisputedly related to anatomically modern human populations. In order to better understand the potentially attractive features of the Early Ahmarian environmental context that supported its persistence for over 8,000 years, we carried out a decennial research program in Jordan and in the Dead Sea. This included (1) a geoscientific and archaeological survey program in the Wadi Sabra (Jordan) with a particular focus on excavations at the Early Ahmarian site of Al-Ansab 1 alongside the detailed analysis of Quaternary sediments from the same area and (2) palaeobotanical research based on Quaternary lake deposits from the Dead Sea. Our pollen data from the Dead Sea indicate slow, low frequency vegetational variation with expanding Artemisia steppe, from 60 to 20 ka BP (MIS 3–2). Here, we see a reciprocal assimilation of southern and northern Levantine vegetation zones thereby enhancing a long-lasting south-to-north steppe corridor. The same integration process accelerated about 40 ka ago, when forested areas retreated in the Lebanese Mountains. The process then extended to encompass an area from Southern Lebanon to the Sinai Peninsula. We argue that, at the same time, the carriers of the Early Ahmarian techno-cultural unit extended their habitat from their original Mediterranean biome (in the North) to the Saharo-Arabian biome (to the South). Our excavation of Al-Ansab 1, a campsite at the eastern margins of the Early Ahmarian settlement area, indicates far reaching annual movements of small, highly mobile hunter-gatherer groups. We assume a low degree of settlement complexity, still allowing for habitat extension of the Early Ahmarian into the margins of the Levantine corridor. Due to our radiometric dates, our combined archaeological and environmental record sheds light on an evolved phase of the Early Ahmarian, around 38 ka ago, rather than the starting phase of this techno-cultural unit. Possible application of our model to the starting phase of the Early Ahmarian remains an aspect of future research.

Comparing pollen data from moss cushions and a volumetric sampler: the study in the city of Florence (Italy)

In Italy, aerobiological monitoring is usually carried out by the regional agencies for environmental protection (ARPA [Agenzia Regionale per la Protezione Ambientale]) using volumetric samplers. Another widespread method for the study of airborne pollen is the analysis of moss cushions, generally used to relate pollen rain to flora and vegetation. In this study, we compare the data coming from these two pollen monitoring methods: volumetric samplers and moss cushions. The study was carried out in the city of Florence (Italy) and took into consideration two different spans of time. The two pollen monitoring methods show quantitative and qualitative differences. The main discrepancy seems to be the direct consequence of the different preservation time of the grains in the moss cushions depending on the features of the pollen grains. The study also provides an estimate of the period of pollen accumulation and preservation in moss cushions, which turned out to be more than five years. The two sampling methods furnish complementary information; volumetric samplers especially suited for aerobiological studies and moss cushions for environmental and palaeobotanical research.

The Early Holocene vegetation changes in the vicinity of the Gorbunovo peat bog in the Middle Urals (Russia)

The paper presents the results of a comprehensive palaeobotanical research of lacustrine and peat deposits of archaeological Mesolithic sites discovered at the Gorbunovo peat bog (Middle Urals). Pollen and plant macrofossil data, as well as a biome model were used to describe the vegetation changes in the study area in the Early Holocene. It was found out that in the second half of the Pre-Boreal and the first half of the Boreal periods of the Early Holocene (approximately to 9,800–9,600 cal BP), the vicinity of the Gorbunovo peat bog was dominated by cold deciduous forests. Larch, spruce-larch and birch forests and meadow communities with periglacial elements were widespread. Various aquatic plants could be found in the pond, though it started to turn into swamp. In the second half of the Boreal period (approximately at 9,600–9,500 cal BP), the taiga biome, including pine and birch-pine forests with occurrence of spruce started to prevail. Periglacial communities became degraded. Aggressive water logging led to the formation of a peat bog.

Tracing insular woodiness in giant Daucus (s.l.) fruit fossils from the Early Pleistocene of Madeira Island (Portugal)

AbstractPlants on oceanic islands can evolve insular syndromes such as secondary woodiness, a generalized trend found in island floras worldwide. This phenomenon occurs through evolution in situ. It is triggered by ecological and physiological stimuli that transform herbaceous annuals into woody perennials. However, well‐dated and informative fossils that could help track and frame the evolution of this syndrome are lacking. Remarkably, in Madeira Island (Portugal), there are good examples of Apiaceae that evolved secondary woodiness, like the giant neoendemic Melanoselinum (≡ Daucus). Apiaceae has a very scarce fossil record, despite being a cosmopolitan family and an economically important crop. Here we describe the oldest Daucus s.l. fossil known to date and the first fossil evidence of a plant with insular woodiness. The fossils are preserved as mummified/compressed mericarps within 1.3‐million‐year‐old fluvio‐lacustrine sediments of the Funchal unit, Upper Volcanic complex, near Porto da Cruz. We assign them to the extant neoendemic species Melanoselinum (≡ Daucus) decipiens. The mericarp morphology shows remarkable stasis since the Calabrian stage of the Early Pleistocene. Our results demonstrate that in the Madeiran Daucinae clade, insular woodiness developed at least 1.3 million years ago, indicating a coeval or earlier immigration to Madeira Island of a Daucus sp. Our results reinforce the role of palaeobotanical research in oceanic islands, supported by stratigraphy and geochronology studies, as a key element for the understanding of plant palaeobiogeography, ecology and evolution worldwide. We expect this contribution to shed light on the evolutionary origins of carrots, and related plant groups, an important element of human food, and to better comprehend the evolution of plant insular woodiness.

Get the picture?

Geologist and science writer Nina Morgan hears of a formidable force in palaeobotany Morgan, N. Distant Thunder: Get the picture? Geoscientist 29 (9), 26, 2019 https://doi.org/10.1144/geosci2019-052; Download the pdf here Passionate about palaeobotany, and a pioneer in the study of coal geology, Marie Stopes [1880-1958] is best known to the public at large as a sex symbol for her enthusiastic promotion of birth control and best-selling books such as Married Love, first published in 1918. Blessed with a formidable intellect, as well as a flamboyant and determined nature, she was nothing if not controversial. Left, Marie Stopes (taken in 1904) [Author unknown; Public domain] In 1902, at a time when few women attended universities, Stopes obtained a double honours degree in botany and geology from University College London (UCL)—after just two years of study. She went on to become the first woman to obtain a PhD in botany from the Botanical Institute in Munich, where university rules had to be altered to allow her to graduate. In 1904, she was appointed Demonstrator in Palaeobotany at Manchester University, overcoming opposition from some in the Senate who opposed the idea of a young woman teaching men. In 1905, she became the youngest Doctor of Science in Britain, and in 1907 she travelled to Japan to spend two years carrying out palaeobotanical research. Along the way she prepared museum catalogues, participated in international discussions, went down coal mines and carried out pioneering work on Carboniferous calcite-rich concretions known as coal-balls. Strong minded In 1910, Stopes was elected a fellow of UCL and, for the rest of her life, made regular appearances in the geology department. As a young Assistant Lecturer at UCL during the 1950s, Eric Robinson [born 1929] recalls how he was delegated to receive her when she visited the department because the then professor, Sydney Hollingworth [1899-1966], chose not to meet her.

Ginkgo leaf cuticle chemistry across changing pCO2 regimes

Cuticles have been a key part of palaeobotanical research since the mid-19th Century. Recently, cuticular research has moved beyond morphological traits to incorporate the chemical signature of modern and fossil cuticles, with the aim of using this as a taxonomic and classification tool. For this approach to work, cuticle chemistry would have to maintain a strong taxonomic signal, with a limited input from the ambient environment in which the plant grew. Here, we use attenuated total reflectance Fourier Transform infrared (ATR-FTIR) spectroscopy to analyse leaf cuticles from Ginkgo biloba plants grown in experimentally enhanced CO2 conditions, to test for the impact of changing CO2 regimes on cuticle chemistry. We find limited evidence for an impact of CO2 on the chemical signature of Ginkgo cuticles, with more pronounced differences demonstrated between the abaxial (lower leaf surface) and adaxial (upper leaf surface) cuticles. These findings support the use of chemotaxonomy for plant cuticular remains across geological timescales, and the concomitant large-scale variations in CO2 concentrations.

The impact of postglacial palaeoenvironmental changes on the properties of sediments in the kettle hole at the site of Jurki (NE Poland)

This research is focused on a small kettle hole located within the Morąg moraines (Ilawa Lake District, NE Poland). The study objective was to determine the impact of palaeoenvironmental changes in sedimentation and properties of sediments filling the bottom of the kettle hole. Sedimentological, geochemical, and palaeobotanical studies enabled us to distinguish several development phases of the kettle hole, and cluster analysis performed on physicochemical data yielded seven local geochemical zones (Ju I/I to Ju I/VII ). The beginning of biogenic sedimentation in the conditions of a small water body, functioning in the Late Glacial period (4.20–4.10 m), was determined on the basis of palaeobotanical research. Sediments deposited in the lake during its further evolution were rich in microelements such as Ca, Na, Mg, and K, and to a smaller extent – Fe and Mn (Ju I/I–III local geochemical zones). The Late Glacial lacustrine period ended with the accumulation of very silty, pollen-free gyttja, with a stratigraphic hiatus (Ju I/IV , 3.40–3.20 m). The sediments were enriched with SiO2ter, which indicates an increased rate of slope erosion, and concretions of Fe-Mn occurring below this layer (Ju III ) provide evidence for lowering of the water level and even desiccation. In the Holocene, the lacustrine period ended with the accumulation of coarse detrital gyttja (3.20–2.60 m). Palaeobotanical data indicate that the next group of sediments were deposited in the Late Subboreal and Subatlantic periods (2.60–0.0 cm, Ju I/V–VII ; sedge peat). Their properties were varied and related to hydrologic conditions, limited denudation, and vegetation succession. There was also a significant change in the trophic conditions of the water and consequently in the sediments of the kettle hole, which changed during the lacustrine period from basic to acid, and strongly acid in the surface layer. This reaction may be related to a change in the water regime as well as to human impact in the environment, which led to the colonization of the peat bog by Sphagnum moss.

Eemian and Vistulian (Weichselian) development of the meltout depression on the watershed between the Mroga and Mrożyca Rivers (Central Poland) based on lithological and pollen analysis

The lithological and palaeobotanical research conducted in a closed-drainage depression located in the watershed zone between the Mroga and Mrożyca Rivers (Central Poland) allowed for the reconstruction of its palaeogeography in the period subsequent to the retreat of the last ice sheet (Wartanian Stage of the Odranian Glaciation). The purpose of this article is to gather and synthesise the obtained results, as well as to reconstruct the processes of development and filling in the studied depression over the last 135,000 years. The post-glacial evolution of the relief was recorded in the mineral and biogenic sediments deposited on glacial formations. The modern closed-drainage depression is a trace of a fossil extensive glacial meltout depression. The post-glacial development of the land relief within the depression involved three stages, dominated by different types of morphogenesis, i.e. the deglaciation stage during the Wartanian Stage of the Odranian Glaciation, the Eemian Interglacial-Early Vistulian aggradation stage, and the Vistulian aggradation-denudation stage. High thickness of the identified biogenic sediments suggests considerable transformations of the relief of the watershed during the two cycles of temperate climate – the Eemian Interglacial and the Holocene. The thickness of the mineral sediments suggest low dynamics of the environment during the Last Glacial Maximum (LGM), and undermine the hypotheses on the determining effect of periglacial conditions on the character of the relief of Central Poland. The obtained results constitute an inspiration and starting point for another research project concerning the reconstruction of the watersheds in Central Poland.

The history of vegetation of the Eemian Interglacial in the Great Polish Lowland

The subject of this paper is the history of vegetation in the Eemian Interglacial in southern Great Poland determined in the course of palaeobotanical research. Pollen analysis was conducted for lacustrine deposits from two localities (Grudzielec near Kalisz and Lechitów near Góra). The obtained pollen diagrams show diagnostic features of the Eemian. The succession of vegetation in both studied localities is characterised by three distinctive phases: protocratic with dominant pine-birch and birch-pine forest and communities of mixed pine-oak and oak forest. mesocratic with predominant hazel and well developed hornbeam-lime forest, and a telocratic one with widespread fir-spruce and pine forest. Moreover, the vegetation succession in top sections of the studied profiles was recognised as typical of the Early Vistulian. The presence of taxa with higher climatic requirements enabled the assessment of palaeoclimatic conditions in the Eemian climatic optimum of southern Great Poland. The development of vegetation in the Eemian Interglacial corresponds with the changes recorded in the nearby localities of Great Polish Lowland and other regions of Poland, as well as those of neighbouring countries. Some minor differences between the studied profiles result from different geographical location of the localities and various genesis of sedimentation basins.

Palaeontological evidence of membrane relationship in step-by-step membrane fusion.

Studies on membrane fusion in living cells indicate that initiation of membrane fusion is a transient and hard to capture process. Despite previous research, membrane behaviour at this point is still poorly understood. Recent palaeobotanical research has revealed snapshots of membrane fusion in a 15-million-year-old fossil pinaceous cone. To reveal the membrane behaviour during the fusion, we conducted more observations on the same fossil material. Several discernible steps of membrane fusion have been fixed naturally and observed in the fossil material. This observation provides transmission electron microscope (TEM) images of the transient intermediate stage and clearly shows the relationship between membranes. Observing such a transient phenomenon in fossil material implies that the fixing was most likely accomplished quickly by a natural process. The mechanism behind this phenomenon is clearly worthy of further enquiry.

New dimensions in palaeobotanical research: ultrastructural studies on plant fossils

In recent years palaeobiology has developed from a primarily descriptive science into a technically advanced and intellectually attractive field, with ramifications applicable to phylogeny, evolution, taphonomy and palaeoclimate. A combination of light microscopy (LM) with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) is often used in the study of fossilised organs and organelles. Details of the surface microtopography, which can be seen only through SEM provide evidence of taphonomic processes and influences. Ultrastructural investigation of palynofossils can help resolve a number of problems concerning the interpretation of morphology, development and biology of fossil spores and pollen, and provide new significant data about their systematics. Studies of fine structure of fossil plant cuticles can be help determine the degree of cuticle preservation and organisation of structural components, and interpret the physical environment in which the plants lived and thrived. Ultrastructural studies of fossil plant cuticle may also reveal the presence of delicate structures such as infection pegs formed as a result of fungal infection or changes in the ultrastructure of the cuticle proper due to fungal infection. SEM study of Late Cretaceous fusainised angiosperm flowers has enabled their identification in terms of modern orders and families, thus greatly improving our knowledge of angiosperm evolution and radiation. SEM study of fossil charcoals (fusain) is also useful in understanding the past role of wildfire and ancient fire-prone plant communities.

Pollen identification multimedia software: a microtaxonomic palaeobotanical research tool

The utility of the graphically pollen identifiable software as a capacity building, microtaxonomic palaeobotanical research tool is briefly described. The software accompanying a user manual (a booklet) enables many levels of users to learn palynology “at the click of a mouse”. The rationale and operation of the pollen identification system like the parent software IDAO is based on the principle of co-efficient of similarity and character weighting (vide Gower, 1971; Grard, 2000). A total of 145 selected genera belonging to 60 dicot and 2 monocot families have been listed. Out of selected genera, 14 are mangroves and most of the remaining genera come from the evergreen forests of Western Ghats. The vector drawings of weighted 136 pollen character states (in 30 character-interfaces) are also provided. The two major parts of this application, the Graphical Pollen Identification System and the Results are explained. A plate with the pollen digital images of 24 pollen types exemplifies palyno-diversity providing clues for parent-plant determination.

On the history of palaeobotanical research in the Weisselster Basin

On the history of palaeobotanical research in the Weisselster Basin

Palaeobotanical research of the Early Miocene deposits overlying the main coal seam (Libkovice and Lom Members) in the Most Basin (Czech Republic)

Palaeobotanical research of the Early Miocene deposits overlying the main coal seam (Libkovice and Lom Members) in the Most Basin (Czech Republic)

When Earth started blooming: insights from the fossil record

Recent palaeobotanical studies have greatly increased the quantity and quality of information available about the structure and relationships of Cretaceous angiosperms. Discoveries of extremely well preserved Cretaceous flowers have been especially informative and, combined with results from phylogenetic analyses of extant angiosperms (based mainly on molecular sequence data), have greatly clarified important aspects of early angiosperm diversification. Nevertheless, many questions still persist. The phylogenetic origin of the group itself remains as enigmatic as ever and, in some cases, newly introduced techniques from molecular biology have given confusing results. In particular, relationships between the five groups of extant seed plants remain uncertain, and it has sometimes proved difficult to reconcile estimates of the time of divergence between extant lineages made using a 'molecular clock' with the fossil record. One result, however, is becoming increasingly clear: a great deal of angiosperm diversity is extinct. Some groups of angiosperms were evidently more diverse in the past than they are today. In other cases, fossils defy assignment to extant groups at the family level or below. This raises the possibility that evolutionary conclusions based solely upon extant taxa that are merely relics of groups that were once much more diverse might be misled by the effects of extinction. It also introduces the possibility that some early enigmatic fossils might represent lineages that diverged from the main line of angiosperm evolution below the most recent common ancestor of all extant taxa. These, and other questions, are among those that need to be addressed by future palaeobotanical research.