Meristems
Although all parenchyma cells in a plant have the potential for growth and production of new cells, unless a plant has been wounded, cell production normally occurs in meristem-atic tissue, which consists of parenchyma cells that remain capable of dividing and producing daughter cells throughout the life of the plant. Because of these meristems, vegetative growth in plants is indeterminate, which means that the plant body is not fixed in its development but is potentially capable of continuous...
Cuticle And Cuticlelike Material
Isolated sheets of resistant material in the fossil record are routinely referred to as cuticle or cuticle-like sheets early records of this type of microfossil include specimens from the Early Ordovician of Tunisia Combaz, 1967 and early Middle Ordovician of Saudi Arabia Le H riss et al., 2007 . The affinities of the organisms that produced the cuticle were probably very diverse and included not only plants, but animals, fungi, and perhaps lichen-like associations. Although most cuticle sheets...
Sieve Elements
Sieve elements are thin-walled cells that are alive at maturity, although the protoplast is greatly changed, and they generally lack nuclei. Sieve elements are elongated and function as the basic photosynthate-conducting cell type in the phloem of vascular plants. The walls of sieve elements contain sieve areas, circular-to-elliptical parts of the wall that are thinner. Each sieve area FIG. 7.11 includes a number of sieve pores, which allow for transport from one sieve element to the next FIG....
Nomenclature Of Fossil Plants
Historically, paleobotanists have utilized a somewhat artificial classification system, since in almost all instances and discussed with other paleobotanists. The other reason is that some identical plant parts may be attached to different plants, for example the Carboniferous lycopsid rooting organ Stigmaria, a morphogenus, has been found attached to different genera of stems. In a case like this, the name of the part is maintained, even though the entire plant has subsequently been...
Trimerophyte Evolution
The trimerophytes demonstrate more complex morphology and anatomy than rhyniophytes, their presumed ancestors, although both groups are coeval. In the trimerophytes, plant architecture is monopodial or pseudomonopodial. Laterals are produced in a variety of patterns, including helical Psilophyton sterile branches , alternately and distichous Psilophyton fertile branches , tristichous Trimerophyton , and tetrastichous Pertica . In Pertica the ultimate branch-lets consist of slender,...
Sphenophyllales 1
Members of the Sphenophyllales were relatively small plants probably lt 1 m tall that formed a portion of the understo-rey in many Carboniferous forests. Sphenophyllaleans can be traced from the Devonian into the Triassic, but they are best known from petrified and compressed remains from the Carboniferous. Although the order was widespread in the late Paleozoic, Triassic representatives have only sporadically been documented from a few countries, including Japan Asama and Naito, 1978 Asama and...
Molds And Casts
In addition to two-dimensional plant parts, such as leaves, three-dimensional structures, such as stems, seeds, or fruits, can also be carried into sites where sediment is accumulating and buried. During flood events, massive trunks and tree branches can be moved some distance before they are eventually deposited. If these plant parts became crushed over time, they would be preserved as compression or impression fossils. If, however, the sediment surrounding the three-dimensional plant parts...
I Je
figure 7.14 Longitudinal section of Zea mays xylem showing annular A and helical thickenings B Extant . Bar 60 pm. figure 7.15 Sieve elements S and companion cells C in Cucurbita sp. Note conspicuous sieve plate Extant . Bar 50 pm. figure 7.15 Sieve elements S and companion cells C in Cucurbita sp. Note conspicuous sieve plate Extant . Bar 50 pm. At maturity companion cells exhibit dense cytoplasm and have numerous protoplasmic connections with their associated sieve tube member....
A Glaophyton Major
The best known plant from the Rhyme chert is Aglaophyton major FIG. 8.13 , a macroplant originally described as Rhynia major, but transferred to a new genus by Edwards based on a reexamination of the original Kidston and Lang slides and the discovery of new specimens D.S. Edwards, 1986 . In a very real sense, A. major is the Arabidopsis of the Devonian, not because its genome is well known, but because the plant and its life history are known in such detail FIG. 8.14 . Aglaophyton major is now...
Leaf Evolution
True leaves appear to have evolved at least twice in plant evolution. Microphylls are believed to have evolved from enations Chapter 8 and represent a synapomorphy for the Lycophyta. They are generally, but not always, small, have a single vascular bundle, and a leaf trace that leaves no gap when it departs the stele. The evolution of microphylls is discussed in more detail in Chapter 9. Megaphylls evolved from branching systems generally have more complex vasculature and produce a leaf gap...
Coal And Charcoal
Technically, coal FIG. 1.30 comes under the definition of a compression fossil, since it represents a complex, heterogeneous mixture of macromolecular organic compounds derived from plant material that has been compressed over time Scott, 1987 . In general, the lower the rank of the coal the degree of coalification , the more details of plant structure one can observe. The higher the rank, the more the coal has been metamorphosed and the higher the carbon content. Ranks from lowest to highest...
Conclusions Fnb
Despite the enormous amount of information that has been accumulated about fossil lycopods, there are still gaps in our understanding of their evolution. During the Carboniferous in Euramerica the lycopsids were well represented by at least four major orders. These included the large arborescent forms Lepidodendrales e.g., Diaphorodendron, Lepidodendron, and Lepidophloios with stigmarian rooting structures the smaller woody types Isoetales e.g., Chaloneria with cor-mose rooting organs and the...
Rhynie Chert Plants
There can be little doubt that the Rhynie chert organisms have had a profound influence on many of our hypotheses figure 8.10 Section of Rhyme chert showing closely spaced upright axes and matrix Devonian . Bar 600 pm. figure 8.10 Section of Rhyme chert showing closely spaced upright axes and matrix Devonian . Bar 600 pm. figure 8.11 Harlan P. Banks. Courtesy H. N. Andrews. figure 8.11 Harlan P. Banks. Courtesy H. N. Andrews. about the early evolution of land plants. In recent years, however,...
V Mor
figure 8.84 Branch of Pertica quadrifaria Devonian . Bar 2.0 cm. Yunia is a Siegenian Pragian, Lower Devonian plant with spiny axes that shares some features with Pertica Hao and Beck, 1991 . The axes dichotomize in a cruciate arrangement and each contains a conducting strand with one or two protoxylem strands, depending on the level of the axis. Conducting elements have annual scalariform sculpture patterns. Closely associated sporangia are elongate and bear tri-lete spores with a relatively...
A Jlc
Phylum Anthocerotophyta hornworts Dendrocerotaceae Phylum Bryophyta bryophytes Marchantiophytina liverworts or hepatophytes Treubiopsida Marchantiopsida thalloid liverworts Marchantiales Sphaerocarpales Calobryales Ricciales Marchantiaceae, Ricciaceae Jungermanniopsida leafy liverworts Jungermanniales Lophoziaceae, Scapaniaceae, Frullaniaceae, Porellaceae, Lejeuneaceae Bryophytina Mosses sensu lato Sphagnopsida Sphagnum mosses Bryopsida Mosses sensu stricto true mosses Bryales Dicranales...
Plant Organography 1
The vascular plant sporophyte consists of a shoot axis stem, roots, and laterals. The primary shoot stem and leaves and the root arise in the embryo and are responsible for elongation figure 7.2 Longitudinal section of Coleus stem showing apex and axillary buds arrows Extant . Bar 600 pm. figure 7.2 Longitudinal section of Coleus stem showing apex and axillary buds arrows Extant . Bar 600 pm. growth, that is, vertical growth, in the plant. Laterals leaves and branches are borne at nodes on the...
Pseudoborniales 1
The Pseudoborniales represents a unique order that is known from relatively few localities and, to date, is represented by a single species, Pseudobornia ursina. In 1894, the noted paleobotanist A. G. Nathorst FIG. 10.3 collected a number of Late Devonian fossils from Bear Island Bj0rn0ya , south of Spitsbergen. Included in the collection were a number of interesting compression and impression specimens consisting of axes bearing whorled, lateral appendages. The only other fossils that have...
Land Plant Ancestors 1
For many years the green algae Chlorophyta were the group thought to be most likely to have given rise to the land plants. Today most regard the green algae and embryophytes together as a monophyletic group, the Viridiplantae, which consists of two monophyletic lineages, the Chlorophyta and the Streptophyta. Included in the Streptophyta are all embryophytes, that is bryophytes and vascular plants, and a distinct group of green algae traditionally known as the Charophyceae, which includes the...
Conclusions Ugx
The lycopsids have an extensive geologic history, extending back into the Late Silurian Kotyk et al., 2002 . They were widespread during the Late Mississippian and most of the Pennsylvanian, representing the dominant group of plants in most of the vast Euramerican paleoequatorial coal-swamp ecosystems. The widespread coal-mining operations that have uncovered Carboniferous rocks have been responsible, in large part, for the abundant, well-preserved fossil specimens of this group. The...
Other Enigmatic Organisms
Although a great deal of information is known about Protosalvinia initially named Foerstia , the biological affinities of this Devonian organism remain problematic Niklas and Phillips, 1976 Niklas et al., 1976 Schopf, 1978b Gray and Boucot, 1979 . Like Spongiophyton, it has been interpreted as a fern, alga, bryophyte, or some form of semiaquatic organism. It is typically found compressed FIG. 6.15 , but may assume a variety of morphologic shapes, ranging from nearly circular to clavate. Some of...
Palynology 1
The science of palynology or, perhaps in a geologic context, paleopalynology is devoted to the study of pollen grains and spores, and also encompasses the investigation of other organic microfossils, such as chitinozoans, acritarchs Javaux and Marshall, 2006 , scolecodonts, dinoflagellates, certain types of microscopic algae, microforaminifera, rotifers, testate amoebae, chitinous fungal remains, and other forms of organic debris sometimes termed varia. Characteristic features such as grain...
Gametophyte Generation
I n this chapter, in fact throughout this book, the primary focus is on the sporophyte generation of vascular plants. This is not by choice, but rather reflects the general paucity of information about the gametophyte phase in most fossil plants. Although there is some information about the game-tophytes in certain seed plants Millay and Eggert, 1974 Chapter 14 , information about fossil vascular plant game-tophytes is generally rare. Until recently this has been especially true in discussions...
Conclusion
Although land surfaces must have been available for colonization soon after life evolved in the Precambrian, the earliest record of terrestrial animals begins around 425 Ma Ward et al., 2006 and that of plants somewhat earlier, with microfossil evidence from the Ordovician discussed below . This delay in colonization of terrestrial habitats has been related to oxygen levels in the paleoatmosphere Berner et al., 2007 and specifically to the lack of a sufficient ozone shield to protect...
Geochronology And Biostratigraphy
Perhaps the most widespread application of palynology is in geochronology, the dating of events in the history of the Earth. Palynomorphs and certain microfossils can be used in geochronology, that is, dating rock units. Fossils can only provide a relative date for strata, that is in relation to other units. Absolute dating relies on other methods to give a specific date see radiometric . Dating with paly-nomorphs is possible because many change through time or possess unique features that...
Zosterophyllophytes 1
The zosterophyllophytes or zosterophylls are the second major group of vascular plants established by Banks 1975 , as the Zosterophyllophytina. They range from Late Silurian to Late Devonian and represent some of the most interesting early vascular plants, in part because there is a considerable amount of anatomical and morphological detail known about them. They demonstrate diversity as early at the Ludlovian Late Silurian Kotyk et al., 2002 and were widespread geographically by the Early...
Trimerophytes 1
The third major group that was culled from the original Psilophytales by Banks is the Trimerophytophyta. Trimerophytes1 were generally more complex than either the rhyniophytes from which they are thought to have descended or the zosterophyllophytes. Trimerophytes demonstrate monopodial branching of the main axes, with lateral axes showing either dichotomous or trifurcate branching. As with rhyniophytes, the sporangia are terminal, although typically they are fusiform to elongate and aggregated...
Form And Function In Fossil Plants
From many plant fossils, it is possible to understand the relationship between form and function in ancient plants, that is, what advantages or limitations are imposed on the growth and development of a plant based on certain biomechanical properties For example, are all arborescent treelike plants constructed of cells and tissue systems of the same type If not, in what other ways can plants grow to tower over their neighbors Studies of this type examine the anatomical and morphological...
Reproduction On Land
A primitive land plant requires several adaptations in order to reproduce on land. One of these is a method to move gametes from one gametophyte to another in order to effect fertilization, and the other is some method of spore dispersal in which the dispersal units are protected from the desiccating environment. In addition, it is important to move the sporo-phytic reproductive units up off the substrate, both to prevent infection by microbes and presumably to disperse spores further, in order...
Unaltered Plant Material
Some plant parts are found as fossils in an unaltered form, either as body fossils or as chemical fossils. Pollen grains and spores FIG. 1.58 I , diatom frustules, cuticle envelopes, various types of resins, such as amber FIG. 1.59 and calcium carbonate remains of certain types of algae are all examples of unaltered plant fossils. In some instances even the soft parts are sufficiently preserved so that comparisons can be made at the cytoplasmic and ultrastructural level Wolfe et al., 2006 ....
Heterokontophyta
Bacillariophyceae ACRITARCHA We have lingered in the chambers of the sea By sea-girls wreathed with seaweed red and brown Till human voices wake us, and we drown. T.S. Eliot, The Love Song of J. Alfred Prufrock The algae are a large informal grouping of heterogeneous, polyphyletic or paraphyletic groups of primarily aquatic organisms ranging from tiny, flagellated unicells only a few microns in diameter to multicellular organisms up to 80m long, such as the giant kelps Graham and Wilcox, 2000 ....
Life History Biology
There remain a number of significant gaps in our understanding of the transitional steps required to move from a charophycean algal ancestor to a land plant. One of these involves significant differences in the life histories of these two groups of organisms Nishiyama, 2007 . In the haplobi-ontic life cycle of a charophycean alga, zygotic meiosis leads to the formation of haploid zoospores, each of which develops into a mature haploid organism. In this life history the only cell that is diploid...
Acritarcha Acritarchs
At one time, spiny vesicular microfossils were often termed hystrichosphaerids a designation that alludes to their morphology regardless of their biological affinities. In 1961, Evitt conclusively demonstrated that many hystrichosphaerids were the cysts of dinoflagellates. Consequently, the remaining hystrichosphaerids whose affinities remain uncertain or unknown are placed in the artificial group Acritarcha Evitt, 1963 b,c . As a result the acritarchs represent a highly heterogeneous group of...
Bryqphyta Bryqphytes
Living bryophytes are represented by 900 genera and nearly 24,000 species. They are not a conspicuous portion of the Earth's flora, although they may dominate the vegetation in certain special environments, for example Sphagnum in certain types of bogs. Most bryophytes are small plants, many lt 2 cm long. The largest forms rarely exceed 60 cm in length e.g., species in the genus Dawsonia . In general, bryophytes are most abundant in relatively moist areas. They range throughout the world and...
Fungianimal Interactions
Despite the obvious role fungi play in modern ecosystems as decomposers, parasites, and mutualists, the interactions between fungi and animals are not extensively documented in the fossil record. A common fungus-animal interaction known from the Paleozoic to the recent is evidence of borings made by endolithic fungi also algae and bacteria in calcium carbonate skeletons of marine invertebrates Gatrall and Golubic, 1970 Grahn, 1981 . This represents a trace fossil or ichnofossil , in that no...
Impressions
When a paleobotanist splits a rock that contains fossil plant fragments along a bedding plane, it is sometimes possible to see the carbonaceous film of a compression along one face, and a negative imprint of the plant part, with little or no carbon adhering, on the other face FIG. 1.32 these two faces are called part and counterpart in paleobotany. The fossil with little or no carbonaceous material is called an impression FIGURE 1.34 Impression of Sigillaria leaf bases showing parichnos scars...
Other Rhyniophytes
As mentioned earlier, Cooksonia, a plant that has been historically regarded as the oldest vascular plant, is included in this group. Compressed specimens have been described from localities all over the world, including North America, Great Britain, North Africa, Europe, Siberia, and South America e.g., Fig. 8.59 . Some Cooksonia specimens discovered in Wales are known from deposits as old as the Ludlovian other specimens suggest that the taxon extended into the Early Devonian Emsian ....
Aglaophyton With Cyanobacteria
FIGURE 3.45 Intercalary glomalean chlamydospore Devonian . Bar 70 im. The fossil record of Glomeromycota is believed to be ancient, extending well back into the Paleozoic. Spores and hyphae of a glomeromycotan type have been reported from rocks as old as the Cambrian Pirozynski and Daple, 1989 , and from 460-455 Ma Upper Ordovician rocks Redecker et al., 2000 . Palaeoglomus grayi has aseptate coenocytic hyphae and spores that resemble living Glomus spores Redecker et al., 2002 . In these...
Spongiophytaceae
The Spongiophytaceae an artificial taxon used to include a variety of enigmatic early organisms, some of which may represent or be related to vascular land plants Krausel, 1954 Krausel and Venkatachala, 1966 . Some organisms included in this family show features of vascular plants, but not all as a result, they are sometimes interpreted as depicting transitional stages in the evolution of true vascular land plants. Spongiophyton is a thalloid fossil that has been reported from numerous Devonian...
Lichens 1
Lichens are unique, double organisms that consist of two unrelated components, an alga and or cyanobacterium pho-tobiont and a fungus mycobiont . The organisms that make up the lichen live in a close symbiotic relationship in which the photobiont gains mechanical protection, increased water availability, reduced desiccation, and an improved ability to obtain nutrients from the mycelium of the fungus. The fungus, in turn, gains organic nutrients synthesized by the photobiont s that is, a source...
Further Reading
After all, I guess it doesn't matter whether you look down through a microscope or up through a telescope as long as you look. it is the presence of green vegetation on the surface of the Earth that makes it a pleasant and interesting place to live. Frequently, we take this green mantle for granted, forgetting that for most of earth history the landscape was barren. Cyanobacteria, algae, and algal-like organisms must have lived in terrestrial habitats before true land plants evolved, but surely...
Paleoecology
Palynology has also been extensively used as a method of characterizing past depositional systems paleoenvironments Farley and Traverse, 1990 . Here palynomorphs play an important role in defining, for example, the extent of a marine or terrestrial environment. In other instances, certain types of palynomorphs may provide valuable information about water depth, temperature, salinity, and nutrient levels where the organisms once lived. In a few cases where vertebrates and invertebrates are found...
about the authors
Thomas N. Taylor is a distinguished Professor in the Department of Ecology and Evolutionary Biology, and Curator of Paleobotany in the Natural History Museum and Biodiversity Research Center at the University of Kansas. He also holds a courtesy appointment in the Department of Geology. He received his Ph.D. in botany from the University of Illinois, and was a National Science Foundation Postdoctoral Fellow at Yale University. He is a member of the National Academy of Sciences. His research...
Compressions
As sediments accumulate, such as in an oxbow lake, water is squeezed out, so the sediments become much more compact, and plant fragments contained within them become flattened Rex and Chaloner, 1983 Chaloner, 1999a . Internal structure is usually obliterated as the cells become flattened, and frequently all that is left is a delicate carbonaceous film that conforms to the original outline of the plant part. This type of fossil is called a compression FIG. 1.13 , and it is one of the most common...
E Grh
tracheids with thicker walls. When the tree goes dormant in the fall, either due to seasonal deciduousness leaf drop or to cold temperatures if it is evergreen, the cambial cells cease to divide. The following spring, the cambium begins producing earlywood again. The contrast between the late-wood of the previous growing season and the earlywood of the present season is the ring boundary, which can be very sharp and visible to the naked eye. Secondary phloem, the tissue produced to the outside...
Preservation How Plant Fossils Are Formed And Preserved
A relatively small fraction of the plants and other organisms that live on the Earth at any particular time will ever become fossils. Most dead plant material is decayed by aerobic oxygen-loving fungi and bacteria. So, the first requirement for fossilization is that dead plants must be deposited in an environment where air is excluded, that is an anaerobic environment. This usually involves deposition in a body of water discussed below , but not always. Once deposited, the plants must be buried...
Plant Tissues And Primary Growth 1
A plant tissue is a group of cells having a similar origin, structure, or major function. Plant tissues contain a characteristic complement of one or more types of cells simple tissues figure 7.13 Transverse section of Lepidodendron stem showing extensive periderm P Pennsylvanian . Bar 1 mm. figure 7.13 Transverse section of Lepidodendron stem showing extensive periderm P Pennsylvanian . Bar 1 mm. contain one cell type and complex tissues, more than one type. Under the system of Sachs 1875 ,...
Systematics And Classification 1
This book emphasizes the origin, evolution, and diversity of the major groups of plants based on the fossil record, and their relationships through geologic time floristic changes through time are discussed to a lesser extent. To do this, we need to address the systematics of plants. The field of system-atics is concerned with classifying, naming, and determining the evolutionary relationships of taxa. Taxon pl. taxa is a general name to indicate any level of organization i.e., a species, a...
B
FIGURE 1.42 Diagrammatic representations of the steps involved in the preparation of the coal ball peel technique. A. Section of coal ball slab calcium carbonate matrix containing plant material crosshatched B. coal ball slab after acid etching to partially expose plant material C. etched coal ball slab surface with cellulose acetate sheet in place D. cellulose acetate sheet peel being pulled from the surface with adhering plant material and E. coal ball peel containing embedded plant material....
Depositional Environments Of Fossil Plants
Fossil plants are found in almost all regions of the Earth, the most notable exceptions being recent volcanic islands or in rocks that have been extensively metamorphosed FIG. 1.9 . Marine plants, such as various forms of algae Chapter 4 , are generally found in rocks deposited in marine environments e.g., nearshore deposits, carbonate shelves, etc. . Although land plants are occasionally found in marine rocks, generally, wherever terrestrial sedimentary rocks occur, there is a good chance that...
Determining Paleoclimate From Fossil Plants
Understanding climates of the past has become more and more crucial to appreciating the changes occurring on our warming planet today, and paleobotany is very important in providing baseline data to reconstruct past climates and in calibrating paleoclimate models based on physical parameters Steppuhn et al., 2007 . This area is rapidly expanding, so we will only cover a few of the many ways in which plant fossils can be used to reconstruct paleoclimate Data from fossil tree rings...