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Figure 9.8 Stratigraphie ranges of the main foraminiferan groups. Based on various sources. Figure 9.8 Stratigraphie ranges of the main foraminiferan groups. Based on various sources. Figure 9.9 Descriptive morphology of the radiolarians. Figure 9.9 Descriptive morphology of the radiolarians. The acritarchs are a mixed bag of entirely fossil, hollow, organic-walled microfossils that are impossible to classify. The acritarchs are probably polyphyletic they include a wide range of forms, probably...
Class Scaphopoda
Scaphopods are generally rare as fossils. The Scaphopoda, or elephant-tusk shells, have a single, slightly curved high conical shell, open at both ends Fig. 13.25a . They lack gills and eyes, but have a mouth equipped with a radula and surrounded by tentacles they also possess a foot, similar to that of the bivalves, adapted for burrowing. Scaphopods are mainly carnivorous, feeding on small organisms such as foraminiferans and spending much of their life in quasi-infaunal positions within soft...
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O mUHHI Knockout phenotype Phase II expression HoxD-9, D-10, D-11, D-12, D-13 Figure 6.9 Hox genes and the development of the tetrapod limb. a The sequence of growth of a tetrapod limb bud, reading from top to bottom, showing how the stylopod humerus femur , zeugopod forearm calf and autopod hand foot differentiate. The pattern is determined by turning on filled squares and off open squares of Hox genes D-9 to D-13. b, c Interpretation of the forelimbs of the osteolepiform fish Eusthenopteron b...
The origin of seeds
The first plants with seeds are known from Late Devonian rocks, and seed bearers rose to prominence during the Carboniferous. After the end of the Carboniferous, and the extinction of arborescent lycopsids, ferns and horsetails, seed-bearing plants, or gymnosperms, took an increasingly dominant role in floras around the world. Seeds in gymnosperms are naked, that is, they are not enclosed in ovaries as they are in flowering plants angiosperms . Seeds follow from the fertilization of an ovule,...
Box The chitinozoan Rosetta Stone
But what really were chitinozoans Material from the Ordovician of Estonia, described as the chitinozoan Rosetta Stone, may have partially solved the problem. Individual vesicles are linked together in a coiled, chain-like structure each vesicle belongs to the same species, Desmochitina nodosa Eisenack Fig. 9.22 . It is unlikely that these were eggs of a metazoan, because larvae would be unable to escape from the tightly sealed and connected chambers. Therefore Paris and Nolvak 1999 postulated...
Origin Of The Vertebrates
The skeleton of vertebrates is made from bone and cartilage. Bone consists of a network of collagen fibers on which needle-like crystals of hydroxyapatite a form of apatite, calcium phosphate, CaPO4 accumulate. Hence bone has a flexible component and a hard component, which explains why bones may undergo a great deal of strain before they break, and also why bones do not break along simple brittle faces. Cartilage is a flexible, gristly tissue, usually unmineralized, and containing collagen and...
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Figure 15.22 Generalized phylogenetic model for rhabdopleurid and graptolite evolution. From Rickards amp Durman 2006. Figure 15.22 Generalized phylogenetic model for rhabdopleurid and graptolite evolution. From Rickards amp Durman 2006. The Dendroidea is the older of the two main groups with important geological records, first appearing in the Middle Cambrian and disappearing during the Late Carboniferous. The dendroid rhabdosome was multibranched, like a bush, with its many stipes connected...
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Figure 16.10 Evolution of the ray-finned bony fishes a the Carboniferous palaeonisciform Cheirodus, a deep-bodied form b the Triassic holostean Semionotus c the Cretaceous teleost Mcconichthys d evolution of actinopterygian jaws from the simple hinge of a palaeonisciform left to the more complex jaws of a holostean middle and the fully pouting jaws of a teleost right . a, b, based on Moy-Thomas amp Miles 1971 c, based on Grande 1988 d, based on Alexander 1975. Figure 16.10 Evolution of the...
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Figure 12.20 a Cluster analysis of bryozoan growth forms across a shelf-slope transition, showing an inner shelf A clastic dominated , inner shelf B carbonate dominated , outer shelf and slope. The cluster analysis, using a distance coefficient x-axis and average group linkage, indicates the presence of four distinctive assemblages. b Distribution of growth forms across the onshore-offshore gradient within the assemblages identified by cluster analysis. Based on Hageman et al. 1997. Figure...
Mesozoic Arms Race
Figure 13.26 Stratigraphie range of the main mollusk groups. benthos of the Paleozoic, although many more localized, often nearshore, assemblages were dominated by mollusks. During the Paleozoic, bivalves were common in nearshore environments, often associated with lingulide brachiopods, although the class also inhabited a range of deeper-water clastic environments and by the Late Paleozoic bivalves had invaded a variety of carbonate environments. However, at the end of the Paleozoic, the...
Class Gastropoda
The gastropods, the belly-footed mollusks, are the most varied and abundant of the mol-luskan classes today. The group includes the snails and slugs, forms both with and without a calcareous shell. During a history spanning the entire Phanerozoic, gastropods evolved creeping, floating and swimming strategies together with grazing, predatory and parasitic trophic styles. Most gastropods are characterized by torsion in which the mantle cavity containing the gills and anus, excretory and...
Box Dating origins
There was a sensation in 1996 when Greg Wray of Duke University and colleagues announced new molecular evidence that animals had diversified about 1200 Ma. This estimate predated the oldest animal fossils by about 600 myr. In other words, the molecular time scale seemed to be double the fossil age. This proposal suggested three consequences i the Precambrian fossil record of animals and presumably all other fossils was even more deficient than had been assumed ii the Cambrian explosion,...
Box Columnal classification
The majority of crinoid assemblages are represented by disarticulated ossicles. Conventional taxonomy based on a description of complete, articulated specimens is thus not possible. Nevertheless, ossicles have many distinctive features, arguably with more well-defined characteristics than many groups of macrofossils Fig. 15.3 . Single stems consist of many ossicles with a central canal or lumen usually carrying nerve fibers. Both the ossicles and lumens have distinctive shapes that are the...
The Origin Of Life 1
There have been many scientific models for the origin of life, some of them now rejected by the evidence, and others still available as potentially valid hypotheses Medieval scholars believed that many organisms sprang into life directly from nonliving matter, a form of spontaneous generation. For example, frogs were said to arise from the spring dew and maggots were said to come to life in rotting flesh. However, careful tests proved that there was no truth in these ideas. Louis Pasteur in...
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Figure 20.5 Sepkoski's three-phase coupled logistic model for diversification of animal life in the sea. a The family-level diversification curve for marine animals, showing the three evolutionary faunas from Fig. 20.4, each shaded differently. Numbers I to V are the five big mass extinctions, in sequence from left to right, Late Ordovician, Late Devonian, end-Permian, Late Triassic and Quaternary-Cretaceous. b The handover from the Cambrian to the Paleozoic fauna involved a shift in...
Class Cephalopoda
The cephalopods are the most highly organized of the mollusks, with the greatest complexity of any of the spiralian groups. The close association of a well-defined head with the foot modified into tentacles is the source of their name, meaning head-footed. High metabolic and mobility rates, a well-developed nervous system, and sharp eyesight associated with an advanced brain, are ideal adaptations for a carnivorous predatory life mode. The funnel or hyponome is also modified from the foot, and...
Early Mollusks
The Early Cambrian was a time of experimentation, with a variety of short-lived, often bizarre, molluskan groups, such as the helcio-nelloids, dominating many faunas Peel 1991 . Most workers now agree that the first mol-lusks were descended from forms like living flatworms - probably spiculate animals with radula and gills situated posteriorly. These mollusks were similar to modern soft-bodied aplacophorans, a group of shell-less mollusks. The aplacophorans and the shelled mollusks shared a...
Taphonomy and the quality of the fossil record
Plants and animals with hard tissues are most frequently preserved in the fossil record. Soft tissues usually decay rapidly, but rapid burial or early mineralization may prevent decay in cases of exceptional preservation. Physical and chemical processes may damage hard tissues during transport and compaction. Plants may be preserved as permineralized tissues, coalified compressions, cemented casts or as hard parts. There has been a longstanding debate about the fidelity and quality of the...
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across a range of the depth zones represented by Seilacher's classic bathymetric sequence of ichnofacies. In fact, they are mostly restricted to marginal marine, intertidal and shallow shelf zones, but that is related to the commonest occurrences of the required substrates. Trace fossils depend on sediments. The ichno-facies scheme highlights the important roles of broad sedimentary environment marine or continental, deep oceanic, shelf or intertidal, Figure 19.12 The major ichnofacies, and...
Box The Rhynie Chert a window on earliest land life
Rhynie is a remote village in northeast Scotland consisting of only 50 or so houses the bus stops there once a day. In 1914, Dr William Mackie, a physician, found traces of plant fossils in some speckled black and white chert rocks. He cut thin sections and took his specimens to Glasgow, where Robert Kidston, the foremost expert in Britain on floras of the Carboniferous, confirmed that the chert contained nearly perfectly preserved plants. Kidston, together with William Lang, Professor of...
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Figure 14.14 Pathological trilobites a Onnia superba - the fringe in the lower part of the photograph has an indentation and a smooth area, probably regeneration following an injury during molting x4 b Autoloxolichas - the deformed segments on the left-hand side may be either genetic or the result of repair following injury x3 and c Sphaerexochus - only two ribs are developed on the right-hand side, probably a genetic abnormality x25 . Courtesy of Alan Owen. Figure 14.14 Pathological trilobites...
Box How many species are there today
So far, 1.7-1.8 million species of plants and animals have been named and described formally about 270,000 plant species and over 1 million insects . The rate of discovery of new species is highly variable within different groups of organisms. About three new bird species, about one new mammal genus and some 7250 new insect species are named each year. It might seem easy to use such figures to produce an estimate of global diversity on the assumption that, at some time in the future, all...
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The Anapsida turtles and relatives_ The oldest anapsids were small insect eaters. During the Permian and Triassic, some unusual anapsids came on the scene. The most diverse of these were the procolophonids Fig. 16.19a , small animals with triangular skulls and broad teeth adapted to a diet of tough plants and insects. The turtles appeared first in the Late Triassic, being represented by Proganochelys Fig. 16.19b . Modern turtles have no teeth, but Proganochelys still had some on its palate. The...
Echinoderms
Clearly we stood among the ruins of some latter-day South Kensington Here, apparently, was the Pal amp ontological Section, and a very splendid array of fossils it must have been. . . . The place was very silent. The thick dust deadened our footsteps. Weena, who had been rolling a sea urchin down the sloping glass of a case, presently came, as I stared about me, and very quietly took my hand and stood beside me. And at first I was so much surprised by this ancient monument of an intellectual...
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Figure 3.11 Is the fossil record controlled by the rock record a Plot of number of marine geological formations and extinction rate against the last 500 myr of geological time. Note how closely the rock and fossil curves follow each other. b Plot of diversification curves for marine families of animals from analyses by Sepkoski i and Benton ii , compared with iii the sea-level curve for the Phanerozoic fine line and the percentage of platform flooding heavy line . Note the approximate matching...
Box Fossil annelids and their jaws
The annelids are segmented protostomes that are represented today by animals such as the earthworms and leaches. Recent species are important, widely distributed, benthic predators and occur from intertidal to abyssal depths. Modern molecular studies suggest they form a sister group to the mollusks and, in fact, share a number of morphological characters such as the possession of chaetae. In general the group has a fairly sparse fossil record, appearing fleetingly in Lagerst tte deposits such...
Ventral 1
Figure 15.11 Echinoid morphology a internal anatomy in cross-section b dorsal and c ventral views of Echinus. Based on Smith 1984. Figure 15.11 Echinoid morphology a internal anatomy in cross-section b dorsal and c ventral views of Echinus. Based on Smith 1984. The echinoid's various organs are suspended within the test and supported by fluid. The water vascular system copes with a number of functions. The stone canal rises vertically, from the central ring around the esophagus, to unite with...
Evolution And Development
Biologists have long sought a link between ontogeny development and phylogeny evolutionary history . In 1866, Ernst Haeckel, a German evolutionist, announced his Biogenetic Law, that ontogeny recapitulates phylogeny. His idea was that the sequence of embryonic stages mimicked the past evolutionary history of an animal. So, in humans, he argued, the earliest embryonic stages were rather fish-like, with gill pouches in the neck region. Next, he argued was an amphibian stage and a reptile stage,...
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Box 4.7 Ecology of extinction events We now have a massive amount of data across all the big five Phanerozoic extinction events, but are taxon counts a good guide to the severity of each extinction Probably not There is a strong ecological dimension to each event. George McGhee and his colleagues 2004 have ranked the ecological severity of each event and the order of severity is in fact different from that established from taxon counts. First, the ecological impacts of the five Phanerozoic...
Frameworks
Six distinct aspects of Tuscany we therefore recognize, two when it was fluid, two when level and dry, two when it was broken and as I prove this fact concerning Tuscany by inference from many places examined by me, so do I affirm it with reference to the entire earth, from the descriptions of different places contributed by different writers. Nicolaus Steno 1669 The Prodromus of Nicolaus Steno's Dissertation Concerning a Solid Body Enclosed by Process of Nature Within a Solid Before the...
Hemichordates
What was the character of the vegetation that clothed this earliest prototype of Europe is a question to which at present no definite answer is possible. We know, however, that the shallow sea which spread from the Atlantic southward and eastward over most of Europe was tenanted by an abundant and characteristic series of invertebrate animals - trilobites, graptolites, cystideans, brachiopods, and cephalopods, strangely unlike, on the whole, to anything living in our waters now, but which then...
Brachiopoda
It is no valid objection to this conclusion, that certain brachiopods have been but slightly modified from an extremely remote geological epoch and that certain land and fresh-water shells have remained nearly the same, from the time when, as far as is known, they first appeared. Charles Darwin 1859 On the Origin of Species The brachiopods are one of the most successful invertebrate phyla in terms of abundance and diversity. They appeared first in the Early Cambrian and diversified throughout...
Fossil plants
Fungi have a long fossil record, perhaps dating back to the end of the Precambrian, but they are not true plants. Green algae, and their relatives, are close to the origin of green plants. Plants moved onto land in the Ordovician and Silurian, a move enabled by the evolution of vascular tissues, waterproof cuticles and stomata, and durable spores. Various non-seed-bearing plants arose during the Devonian, but tree-like lycopsids, equisetopsids and groups such as ferns became established by the...
Regressive Surface Of Marine Erosion
Figure 2.8 Current status of the development of a new, internationally accepted chronostratigraphy for the Ordovician System. New global series and stages are correlated with the comparable chronostratigraphic divisions used in North American and the United Kingdom and Ireland. GSSP, global standard section and point. Figure 2.8 Current status of the development of a new, internationally accepted chronostratigraphy for the Ordovician System. New global series and stages are correlated with the...
Subphylum Hexapoda
The Hexapoda, essentially the insects, can be divided into pterygotes with wings and apterygotes without wings and include the springtails, dragonflies, cockroaches and locusts. The group may prove to have as many as 10 million living species when the rich faunas of the tropics have been completely described. The subphylum also includes the onychophorans, with flexible segmented bodies and unjointed limbs propelled by changes in blood pressure analogous to the water vascular system of the sea...
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Upland cordaite-dominated vegetation on calcrete soils Lowland vegetation dominated by cordaites with minor pteridosperms, sphenopsids, and rare lycopsids Figure 18.19 The early conifer Cordaites, about 25 m tall. Based on Thomas amp Spicer 1987. Figure 18.19 The early conifer Cordaites, about 25 m tall. Based on Thomas amp Spicer 1987. of China, but seen today as a typical urban tree in parts of North America and Europe. Ginkgos were more diverse in the Mesozoic. Leaf shape varies from the...
Spicule Morphology
Commonly the spongin skeletons decay and unfused spicular skeletons disintegrate shortly after death leaving only a selection of hard parts, such as spicules Fig. 11.5 . Spicule morphology is thus a fundamental means of identification of those spiculate forms. Spicules may be large megascleres , acting as part of the skeleton, or small microscleres , scattered throughout the sponge and rarely preserved. Five basic types of spicule have been recognized 1 Monaxons single axial forms that may grow...
Growth And Form
Paleontologists must interpret fossil species, and their ranges of variation, solely from the morphology, or external shape, of the specimens. There are problems in deciding where one species ends and another begins. When there are close living relatives, it may be possible to compare the modern species with the fossils. But how are paleontologists to decide just what is a species of dinosaur or trilobite For modern plants and animals, system-atists ideally apply the biological species concept...
Merodont Hinge Ostracode
Figure 14.22 Descriptive terminology of the ostracode animal a , including muscle scars b and hinge structures c . Based on Armstrong amp Brasier 2005. Figure 14.22 Descriptive terminology of the ostracode animal a , including muscle scars b and hinge structures c . Based on Armstrong amp Brasier 2005. Articulatory structures are variably developed along the hinge line. Three main types of hinge are known Fig. 14.22c . Adont hinges lack teeth but have a long median element on the right valve...
Box Jumping bristletails
Paleontologists need keen eyesight. The slab in Fig. 19.1 shows a clean, slightly undulating surface, with some long cracks and obscure little markings here and there. But is there anything of importance on the slab It might not at first seem so. The slab comes from the Lower Permian Robledo Mountains Formation of southern New Mexico Minter amp Braddy 2006 , where most surfaces show tracks of one sort or another amphibians, reptiles, scorpions, spiders, millipedes and insects. Trace fossils are...
Wileyblack Well
A John Wiley amp Sons, Ltd., Publication This edition first published 2009, 2009 by Michael J. Benton and David A.T. Harper Blackwell Publishing was acquired by John Wiley amp Sons in February 2007. Blackwell's publishing program has been merged with Wiley's global Scientific, Technical and Medical business to form Wiley-Blackwell. Registered office John Wiley amp Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK Editorial offices 9600 Garsington Road, Oxford, OX4 2DQ,...
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where an RNA replicase and a self-replicating membrane-bound vesicle combine to form a protocell. Inside the vesicle, the RNA replicase functions, and might add a function to improve the production of the vesicle wall through a ribozyme. At this point, the RNA replicase and the vesicle are functioning together, and the protocell has become a living cell, capable of nutrition, growth, reproduction and evolution. Read a general introduction to RNA world at http www.blackwellpublishing.com...
Box Alternating ichnofacies
Many sedimentary sequences show a mix of ichnofacies, as would be expected, since no ichnofacies is exclusive to a single location or water depth. The Cardium Formation of Alberta, Canada has produced abundant trace fossils from a sequence of muds and sandstones Pemberton amp Frey 1984 Fig. 19.14 . The normal quiet-water sedimentation produced mud, silt and fine sand layers, and diverse trace fossils of the Cruziana ichnofacies, mainly representing the activities of mobile carnivores and...
Box Ediacaran arthropods
Are they or aren't they Some paleontologists believe they can identify some of the Ediacaran animals as arthropods or proto-arthropods others dispute this. Parvancorina Fig. 14.2 , for example, is a possible candidate, with its shield-shaped outline, strong axial ridge and arched anterior lobes, together with a convex profile. It really looks like a juvenile trilobite molt stage, but did not have a mineralized skeleton. Not convinced Beautifully preserved fossils from a new Cambrian Lagerst...
Box Palynology
Palynomorphs, fossil pollen and spores, provide evidence about ancient paleoenvironments, often when other fossils are absent, and they are key tools in biostratigraphy see pp. 26-32 . Fossil pollen and spores have proved to be essential in understanding the biostratigraphy of the Late Paleozoic, Mesozoic and Cenozoic, especially in terrestrial rock sequences. Pollen analysis is also a routine part of studies of Quaternary paleoenvironments, especially those studied by archeologists. They can...
Box Classification of the tracheophytes
Tracheophytes are the vascular land plants, and include modern ferns, horsetails, conifers and flowering plants, as well as numerous extinct groups. The basal groups are distinguished in terms of branching patterns and sporangial morphology. Simple vascular plants with dichotomously branching stems and terminal sporangia Mid Silurian to Early Devonian Small to large plants with lateral sporangia and usually small leaves Horsetails vertical stems with jointed structure and a whorl of fused...
Box Dinosaur speeds
When you walk along a beach, you leave tracks with a particular stride length the distance from one foot-fall to the next by the same foot . If you begin to run, the stride length increases, and the faster you go, the longer the stride length. An English expert in biomechanics, R. McNeil Alexander, spotted something more there was a constant relationship between stride length and speed, providing you took account of the size of the animal measured by the height of the hip from the ground , and...
Funnel Organism
Solenogastres 1 ' Caudofoveata J ' Polyplacophora Monoplacophora Bivalvia Scaphopoda Gastropoda Cephalopoda Figure 13.1 Pseudocladograms of molluskan evolution hypothetical archemollusk HAM evolution integrated with a cladistic-type framework. Model a demonstrates a split into the Aculifera and Conchifera, whereas b indicates a division into the Aplacophora and Testaria. Based on Sigwart amp Sutton 2007. Box 13.2 Kimberella and Odontogriphus join the mollusks A modest-sized, disk-shaped fossil...
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Figure 13.21 Life attitudes and buoyancy of the ammonites. a Supposed life orientations of a selection of ammonite genera, with the center of gravity marked x the center of buoyancy is marked with a dot and the extent of the body chamber is indicated with subparallel lines. b Relationship of some ammonite morphotypes to water depth and the development of anoxia. a, from Trueman, A.E. 1940. Q. J. Geol. Soc. Lond. 96 b, from Batt 1993. Figure 13.21 Life attitudes and buoyancy of the ammonites. a...
Subphylum Trilobitomorpha
The trilobitomorphs are highly derived arthropods lacking specialized mouthparts, and with tagmata comprising the cephalon, thorax and pygidium, together with trilobitomorph appendages that have lateral branches developed from the walking limbs. The trilobito-morphs include mainly the trilobites and over 15,000 species are known. Trilobites were a unique and very successful arthropod group, common throughout the Paleozoic until their extinction at the end of the Permian. There is no doubt that...