Introduction

A thin blanket of soft white to buff-coloured ooze covers one-sixth of the Earth's surface. Seen under the microscope this sediment can be a truly impressive sight. It contains countless numbers of tiny shells variously resembling miniature flugelhorns, shuttlecocks, water wheels, hip flasks, footballs, garden sieves, space ships and chinese lanterns. Some of these gleam with a hard glassy lustre, others are sugary white or strawberry coloured. This aesthetically pleasing world of microscopic...

Excystment structures

If some acritarchs were resting cysts, comparable to those produced by the dinoflagellates, then the contents must have escaped through an opening, the excystment structure. Excystment structures are not found in all acritarchs but sufficient are known to Fig. 9.1 Acritarchs. (a) Leiosphaeridium, x400. (b) Baltisphaeridium, x250. (c) Acanthodiacrodium, x400. (d) Visbysphaera, x700. (e) Diexallophasis, x250. (f) Tunisphaeridium, x345. (g) Micrhystridium, x1200. (h) Ammonidium, x390. (i)...

Biological and evolutionary consequences of the Cambrian explosion

Eukaryotic organisms have the ability to produce proteinaceous membranes capable of mineralization and are able to pump ions through their cell walls. The incorporation of the citric acid cycle into cell metabolism provided the increase in available energy Calcareous Phosphatic 1 Siliceous < Agglutinated 1 Organic-walled Fig. 7.7 Repercussions of the Cambrian explosion showing the stratigraphical ranges of the major microfossil groups of the Phanerozoic. required for biomineralization....

The origin of life and the early biosphere

Planet Earth is believed to have formed from the coalescence of dust particles at some time close to 4.55 Ga. While this accretion and the ensuing phase of catastrophic impacts would have caused a molten surface, the crust appears to have been cool by about 3.85 Ga. If any life forms were synthesized before this date they must have been hyperthermophile heat-tolerant bacteria, similar to those found living around volcanic vents or deep in the Earth's crust today. The oldest rocks on the Earth...

Cyst surface features

Dinoflagellate cysts can be smooth or bear granules, ridges, indentations, raised crests or develop short spines, processes or horns Fig. 10.4 . Processes can be plate centred or form groups. Tabular ornament is sutural if it defines plate boundaries or intertabular if it defines the central parts of plates. Processes that are situated at the intersection of paraplate boundaries are gonal and those along boundaries are intergonal. Where a reflected cingulum is present, that portion apical to it...

Spore and pollen taxonomy

The names of fossil spores sporae dispersae follow the rules of the International Code of Botanical Nomenclature ICBN, Greuter amp Hawksworth et al. 2001 . This code formally recognizes whole-plant taxa eutaxa , and form-genera and species parataxa, i.e. dispersed spores, pollen grains, dissociated leaves, roots, fruits, seeds and other parts of plants . Morphology provides the only means of classifying dispersed spores and these are defined on the basis of the nature of the germinal opening,...

Dinoflagellates and ebridians

Dinoflagellates meaning whirling whips are second only to the diatoms as primary producers in the world's oceans. They are single-celled organisms generally between 20 and 150 im in maximum diameter, with both plant and animal characteristics. Most dinoflagellates are distinguished by a dinokaryon, a special form of eukaryote nucleus. Their carotenoid pigments dinox-anthin and peridinin give to these organisms flame-like colours and produce 'red tides' when populations bloom. Many living...

Geological history and applications

Scolecodonts first appeared in the Lower Ordovician and diversified rapidly Underhay amp Williams 1995 and had their acme in the Palaeozoic. Most work on fossils has been conducted on material from glacial erratics in Poland Kielan-Jaworowska 1966 Szaniawski 1968 and on outcrop and borehole material from the Baltic region e.g. Nakrem et al. 2001 Erikson 2002 . They are uncommon in the Mesozoic and Cenozoic Jansonius amp Craig 1971 Sch fer 1972 Szaniawski 1974 Germeraad 1980 Courtinat et al....

General history of chitinozoans

Figure 11.3 shows a provisional phylogeny for Chitinozoa. The oldest chitinozoans may be the Desmochitina-like sacs from the upper Precambrian Chuar group of Arizona 750 Ma, Bloeser et al. 1977 , but this affinity has not yet been demonstrated conclusively. During the Ordovician, morphologically smooth vesicles of desmochitinid and conochitinid type were characteristic, the latter stock gradually dwindling through the Silurian and dying out at the end of it. There is a general evolutionary...

Motile stage

Pellicle Cell Membrane Position

Dinoflagellate cells range in size from 5 to 2000 m Fig. 10.1 . These organisms are amongst the most primitive of the eukaryotes and have been regarded as intermediates between prokaryotes and eukaryotes. Fig. 10.2 opposite Dinoflagellate motile stage. a Schematic section through the wall of an unarmoured dinoflagellate. b Schematic section through the wall of an armoured dinoflagellate. c , d Tabulation of a hypothetical peridinialean motile stage c ventral side d dorsal side. e , f Motile...

Emergence of eukaryotes to the Cambrian explosion

The divide between prokaryote and eukaryote cells can be regarded as one of the largest discontinuities within the living world. Eukaryotes differ from prokaryotes in the presence of a proper membrane-bound nucleus to contain the DNA in genes arranged on chromosomes plus a generally larger cell size and presence of cell organelles such as mitochondria and chloroplasts. Reproduction in eukaryotes may be asexual, involving strictly controlled cell division by mitosis, or sexual, involving...

Acritarch ecology

Poor understanding of taxonomy, biological affinity and rarity in modern environments hinder palaeoecological interpretations. Acritarchs have mostly been found in marine strata, especially in shales and mudstones, but also occur in sandstones and limestones. Non-marine examples are first reported from Recent strata. Lagoonal facies are characterized by low diversity and monospecific assemblages of sphaeromorph and netromorph acritarchs and prasinophytes. The boundary between nutrient-rich...

B lntine

Angiosperm Spore Wall

Fig. 13.6 Wall structures and surface ornament found in spores and pollen grains diagrammatic . a The wall structure in the extant Lycopodium. b Wall structure of the extant genus Anemia Anemia . c Tectate wall of angiosperm pollen. d Wall structure and surface ornament of angiosperm pollen. The latter terms are also applied to the surface ornament of spores. Abbreviations of the sporoderm layers EN, endospore PE, perispore OEX, outer exospore IEX, inner exospore. a After Uehara et al. 1991 b...

Pollen Triporate

Monoporate Zonosulcate Monosulcate-bisaccate Fig. 13.10 Morphology and terminology of tricolpate and related pollen grains. Fig. 13.10 Morphology and terminology of tricolpate and related pollen grains. Fig. 13.11 Diagrammatic representation of pollen grains mentioned in the text. a Abies Pleistocene , x250. b Pinus Recent , x350. c Tsuga Recent , x1200. d Podocarpus Cretaceous , x500. e Aquilapollenites Cretaceous , x1400. f Woodhousia Cretaceous , x1140. g Picea, x325. h Alnus, x1400. i...

Microfossils in stratigraphy

Microfossils Stratigraphy

The succession of rocks exposed at the surface of the Earth can be arranged into a stratigraphical column, with the oldest rocks at the base and the youngest ones at the top Fig. 3.1 . Although the absolute ages have been determined from studies of radioactive isotopes, it is customary to use the names of stratigraphical units, mostly distinguished on the basis of differences in their included fossils. These units are arranged into a number of hierarchies relating to rock-based stratigraphy...

Microfossils as thermal metamorphic indicators

Microfossils with a mineral skeleton are commonly composed of high or low magnesium calcite or calcium phosphate whereas palynomorphs are composed of organic materials such as sporopollenin, chitin and pseudochitin. These materials, though highly resistant, are susceptible to weathering, reworking by erosion, oxidation and to thermal metamorphism. Pristine palynomorphs have transparent to very pale green-yellow walls and often have to be stained to see the material under the microscope. Less...

Cyanobacteria life history

Endospore Cyanobacteria

Cyanobacteria are an extremely ancient group which have never developed the controlled division of cells by mitosis or meiosis. Sexual reproduction is therefore unknown, and multiplication is entirely vegetative asexual , usually brought about by fragmentation, binary fission, or the formation of endospores, Fig. 8.3 Order Chroococcales. a Recent Synechocystis. b Precambrian Archaeosphaeroides. c Precambrian Huroniospora. d Precambrian Myxococcoides. e Recent Anacystis. f Fossil Renalcis. g...

Life cycle of the higher plants

Transfer Pollen Grains

In gymnosperms Fig. 13.7 and angiosperms Fig. 13.8 the gametophyte generation is reduced to a few cells represented by the ovum or ovule female and the pollen grain male . In gymnosperms the megaspo-rangium ovule produces an exposed egg that is fertilized by a free-swimming sperm or one introduced through a pollen tube. Modern angiosperm pollen grains contain a tube cell nucleus which controls the development of the pollen tube and a generative cell nucleus, which divides before fertilization....

Life cycles of lower land plants

Tetrads Spore

Primitive vascular land plants differ from their algal ancestors in their development of special conducting vascular tissues. Nonetheless, the alternation of generations found in the life cycle of the algae was inherited by the vascular plants. This comprises a life cycle alternating between a spore-producing sporophyte generation reproducing asexually with spores and a gamete-producing gametophyte generation that reproduces sexually with male and female gametes Fig. 13.1 . Bryophyta mosses,...

Dinoflagellate life history

Life History Cell

Sexual reproduction is known to occur in very few living dinoflagellates. Asexual vegetative reproduction predominates and involves a division of the cell into two halves by binary fission. Details of the life Fig. 10.5 Idealized life cycle involving sexual reproduction and cyst formation. Section A, cells are motile and haploid section B, cells are motile and diploid section C, cells are non-motile except excysted cell on left and diploid. Reproduced from Stover et al. in Jansonius amp...

Applications of dinoflagellate cysts

Dinoflagellate cysts are ideal biostratigraphical indices. Williams amp Bujak 1985 provide a detailed review of cyst biozones with subsequent modifications to be found in Stover et al. in Jansonius amp McGregor 1996, vol. 2, pp. 641-750 . Powell 1992 provides an accessible laboratory manual for identifications and biozonations. Late Triassic dinoflagellate assemblages are known from Alaska, Arctic Canada, Australia, England and Austria only one biozone has been recognized, the Rhaetogonyaulax...

Endolithic cyanobacteria

A variety of marine cyanobacteria bore into the surface of hard calcareous substrates such as shells and limestone by chemical dissolution Fig. 8.5d . This endolithic boring is for protection rather than for food. Under conditions of CaCO3 supersaturation the vacated borings are filled with micritic carbonate and the substrate thereby acquires an outer micrite envelope. Eventually, boring may lead to the destruction of the substrate and the formation of lime mud. If the filaments extend...

Cyanobacterial ecology

Polluted Cyanobacteria

Cyanobacteria are very self-sufficient. They can tolerate extremely low oxygen concentrations and some can live anaerobically. They are, with certain other bacteria, the only organisms that can fix their own nitrogen, either with the aid of heterocyst cells in aerobic conditions, or without in anaerobic conditions. Cyanobacteria also have a wide resistance to high and low temperatures, ranging from polar climates to hot thermal springs. They are also very resistant to ultraviolet light. Their...

Precambrian Jellyfish Fossil

Platysolenites

Fig. 7.1 a The Serial Endosymbiotic Theory suggests that eukaryote organelles arose from successive endosymbioses between different kinds of prokaryote and an amitochondriate host bacterium such as Thermoplasma. b The Neomuran Hypothesis indicates a common ancestry in a gram-negative bacterium followed by secondary acquisition of mitochondria and chloroplasts by serial endosymbiosis in different lineages. diameter Schopf amp Klein 1992 Knoll 1994 while sterane biomarkers typical of eukaryotes...

Applications of acritarchs

Acritarchs have been used largely to correlate upper Precambrian and Palaeozoic rocks. Papers by Martin 1993 and Vidal amp Knoll 1993 illustrate their potential in Precambrian rocks and by Molyneux et al. 1996 in the Palaeozoic, whilst Wall 1965 examined their value in some Mesozoic strata. Geographically distinct acritarch provinces in the Ordovician, Silurian and Devonian may assist the reconstruction of ancient ocean currents or climatic belts. However generalized interpretations are more...

Geological history

Sediments from deltaic and lacustrine deposits of Mid-Ordovician to Early Silurian age yield cryptospore monads, dyads, triads and tetrads. Nodospora has thickenings of sporoderm along the contacts between members of the tetrad. Some dyads and tetrads have Box 13.1 Higher taxonomic categories and diagrams of representative genera found within the Turma Triletes, Suprasubturma Acavatitriletes AZONOTRILETES Wall of more or less uniform thickness LAEVIGATI Wall more or less laevigate RETUSOTRILETI...

Antapical horns

Fig. 10.6 Examples of cyst from the Prorocentroidia and Bilidinea. a Recent Prorocentrum Prorocentroidia , about x350. b Recent Gymnodinium Gymnodinoidia , about x350. c Fossil Dinogymnodinium Gymnodinoidia . d Recent Polykrikos Bilidinea , about x500. e Recent Noctiluca Noctilucea , about x180. f Fossil Nannoceratopsis Bilidinea , about x680. g Recent Ornithocercus Bilidinea , about x275. a From Chapman amp Chapman 1973 b from Kofoid amp Swezy 1921 d after Dodge 1985 f based on Sarjeant 1974 g...

Second Edition

Senior Lecturer in Micropalaeontology, Department of Earth Sciences, University of Durham, UK Professor of Palaeobiology, Department of Earth Sciences, University of Oxford, UK 2005 Howard A. Armstrong and Martin D. Brasier 350 Main Street, Maiden, MA 02148-5020, USA 550 Swanston Street, Carlton, Victoria 3053, Australia The right of Howard A. Armstrong and Martin D. Brasier to be identified as the Authors of this Work has been asserted in accordance with the UK Copyright, Designs, and Patents...

Calcareous nannoplankton coccolithophores and discoasters

Sketch Vacuole

Calcareous nannoplankton are a heterogeneous group of calcareous forms, including coccoliths, discoasters and nannoconids, ranging in size from 0.25 to 30 im. In the fossil record they are found in fine-grained pelagic sediments and can be sufficiently abundant to become rock-forming, for example the Upper Cretaceous chalk. Coccolithophores are unicellular planktonic protozoa with chrysophyte-like photosynthetic pigments, but they differ from most other Chrysophyta in having two flagella of...

The living bacterium

Schematic Diagram Bacteria Budding

Bacterial cells are small about 0.25-25 im and of spherical, rod or corkscrew shape, and collectively referred to as cocci, bacilli and spirilla Fig. 8.2a . These cells may be solitary or arranged in filamentous trichomes with or without branching. Most of the bacilli and all of the spirilla possess a whip-like flagellum one or more per cell , but these are very thin and are rarely preserved. Bacteria may feed either on preformed organic matter heterotrophy or synthesize organic material from...

Ebridians

The ebridians are unicellular, marine and planktonic with an endoskeleton of silica, but unlike that of the similar silicoflagellates, they are solid with a tetraxial or triaxial symmetry. Ebridians possess two flagella of unequal length and lack photosynthetic pigments, surviving instead by the ingestion of food especially diatoms with the aid of pseudopodia. Reproduction is mostly by asexual division. Classification of ebridians is complicated by their uncertain biological status, resembling...

Micropalaeontology evolution and biodiversity

Micropalaeontology brings three unique perspectives to the study of evolution the dimension of time, abundance of specimens allowing statistical analysis of trends and long complete fossil records, particularly in marine groups. Despite these features giving special insights into the nature of evolutionary processes, micropalaeontologists have until recently concentrated mainly on documenting the ascent of evolutionary lineages, such are described in the separate chapters in this book. Micro-...

Acritarch affinities and biology

Acritarchs are considered to be the resting cysts of phytoplanktonic eukaryotic algae. The presence of dinosterane and 4a-methyl-24-ethylcholestane, two biomarkers characteristic of dinoflagellates, in samples of Neoproterozoic including the Bitter Springs Chert and Cambrian age indicate acritarchs are likely ancestors of the dinoflagellates Moldowan amp Talyzina 1999 . This conclusion is supported by RNA sequence data that indicate the dinoflagellates diverged before the Foraminifera and the...

Class Peridinea

Subclass Prorocentroidia These are thought to be the most primitive dinoflagellates. They have two flagella of equal length inserted at the anterior end of the motile cell, which is unarmoured. Dinoflagellate cysts are unknown but may be included amongst the acritarchs. Prorocentrum Fig. 10.6a is a living genus Box 10.1 Higher level classification of dinoflagellates based on Cavalier-Smith 1998 involved in red tides. The theca is divided into two equal valves by a longitudinal suture. Subclass...

Microfossils stable isotopes and oceanatmosphere history

The skeletons of foraminifera and other CaCO3 fossils take up chemical signals from sea water as they grow. The most important of these chemical signals are the stable isotopes of oxygen and carbon. These signals, when extracted from the CaCO3 in a mass spectrometer, may be used to reconstruct past environmental changes such as temperature and ocean fertility, and to provide a high-resolution chemostratigraphy. The oxygen isotope technique was pioneered in the 1950s by Cesare Emiliani and the...

General history of dinoflagellates

Cyst Freshwater Dinoflagellates

Although the apparent primitive organization implies great age for the group, the acme of peridinalean history appears to have been reached in the Mesozoic and Cenozoic Eras. Dinosterane and 4a-methyl-24-ethylcholestane, two dinoflagellate biomarkers in samples of Upper Proterozoic and Cambrian age Moldowan amp Talyzina 1999 , and RNA sequence data indicate the dinoflagellates diverged before the Foraminifera and the Radiolaria which both have a Cambrian fossil record. It is evident that Late...

Group Acritarcha

Downie 1973, 1974 , Fensome et al. 1990 and Doming in Benton 1993, pp. 33-34 have reviewed the classification of the acritarchs. Informal groupings have been established on overall morphology, wall structure and type of excystment opening. None of the published schemes reflects biological affinity or evolution and some workers prefer to list taxa alphabetically. Biometrical studies e.g. Servais et al. 1996 and the chemistry of the vesicle e.g. Colbath amp Grenfell 1995 may offer the potential...