摘要:

Fluctuating water depths in platform seas covering central North America during late Llandovery time introduced shifts in the spectrum of coral‐algal, pentameran, and stricklandian communities. Opportunistic orthotetacean brachiopods were common during these times of community replacement. A pavement constructed by their flat shells was sometimes used as the initial substrate for attachment by the spat of pentameran brachiopods. Both orthotetacean and pentameran shells served as the initial substrate for stricklandian brachiopods. With the decline of a pentameran or stricklandian population, disarticulated shells provided a substrate for repopulation. An assemblage of immaturePentamerusin life position indicates that the typical umbo‐down posture was an early result of maximum packing. Development of more advantageously placed individuals severely restricted the growth of others trapped between the substrate and the beak regions of surrounding neighbors. After pentameran assemblages were buried in life position, scouring of the sea bottom frequently produced erosion surfaces which truncated their thin shells. These surfaces were sometimes penetrated by boring organisms, and were firm enough for brachiopod repopulat

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00595.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00596.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Classification should at least to some extent show phylogenetic relationships. It is therefore reasonable to base any classification on a discussion of phylogeny and analysis of phylogenetically relevant features. Adaptational features likely to evolve many times must be sorted out in the discussion of relationships, but may be useful to describe the evolution inside phyletic lineages defined by other means. The Proetida, as defined by Fortey&Owens 1975, are taken as an example of a heterogeneous taxon based on purely morphological features. A phylogenetic approach to ontogenetical, morphological and functional criteria seems to indicate that the Proetida fall into at least three groups without close relationships.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00597.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00599.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Phosphatic microfossils etched from Upper Cambrian (Trempealeauan Stage) Limestones of the Whipple Cave Formation, Nevada, and other contemporaneous formations in western North America, are colonies, the individuals of which are arranged irregularly around one or more nuclei. No secondary growth has occurred. During their lifetime, however, the individuals partially filled their chambers with phosphatic matter. The highly differentiated morphology of the colonies is strikingly similar to the living ascidian tunicateBotryllus.Ecological conditions and size range of the fossils are likewise similar to those of the Ascidiacea. If recognized as an ascidian,Palaeobotryllus taylorin.g., n.sp. extends the known occurrence of Tunicata into the Upper Cambrian.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00600.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The article analyses the relationships between mobile corals, the associated benthic fauna and the physical character of their substrates. Different types of coral mobility are here classified under three headings: (1) Passive rotation by water movement or by intervention of infaunal, benthic or nektic organisms. (2) Lifelong towing by a symbiotic sipunculid worm. (3) Auto‐mobility, defined as self‐induced movement which allows unburial, righting and lateral migration. In each case the morphology of the skeleton reflects the type of mobility, which can therefore be traced in the fossil record. Two examples of auto‐mobile corals,Cycloseris(Recent) andChomatoseris (= Anabacia)(Jurassic) are reviewed in detail; their main common architectural features are concentric growth and lack of epitheca. Both genera prefer loose, muddy sands. Mobility in corals allows them to flourish under circumstances unfavourable for sedentary forms. They are good indicators of loose, soft, sand substrates ranging from lagoonal through peri‐reefal to deeper water environments. Though relatively few in species at any given time, mobile corals are geographically widespread and may be locally extremely abundant (>1500 per m2). World distribution maps are given for the RecentCycloseris cyclolites, Diaseris distorta, Heteropsammia, HeterocyathusandManicina areolataand for the JurassicChomatoseris.Cet article analyse Ies relations entre les coraux mobiles, la faune benthique associée et les propriétés physiques de leur substrat. On peut classer les différents types de mobilité chez les coraux selon trois catégories: (1) Rotation passive due aux mouvements de l'eau, à l'intervention de l'endofaune, d'organismes benthoniques ou nectoniques. (2) Remorquage par un ver Sipunculide symbiotique. (3) Auto‐mobilité, définie comme mouvements propres, permettant au polypier de s'extraire du sédiment, de se retourner et de se déplacer latéralement. Dans tous les cas la morphologie du squelette est liée au type de mobilité qui peut done être reconnu chez les fossiles. Deux exemples de coraux auto‐mobiles sont ici revus en détail:Cycloseris(actuel) etChomatoseris(=Anabacia) (Jurassique); les traits communs entre ces deux formes sont la croissance concentrique et l'absence d'épithèque. Les deux genres préfèrent les sables boueux meubles. La mobilité chez les coraux permet leur épanouissement dans des circonstances défavorables aux formes sédentaires. Ce sont de bons indicateurs de fond meuble (sable ou sable vaseux). On les trouve dans les lagons, les zones péri‐récifales et jusque dans des eaux plus profondes. Les genres mobiles, dont le nombre connu est encore faible, ont cependant une large distribution géographique et peuvent localement être représentés par de nombreux individus (>1500 par m2). Des cartes de répartition mondiale sont établies pour les coraux actuelsCycloseris cyclolites, Diaseris distorta, Heteropsammia, Heterocyathus, Manicina ar

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00601.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Algal borings in the shells of the articulate brachiopodsPlaesiomys subquadrata(Hall) andHebertella sinuata(Hall) from the Richmond Formation of Ohio are empty, or partially to entirely filled with pyrite. The pyrite occurs as single framboids and other crystal forms, or in chains filling the bores. The borings provide some insight into the early diagenetic history of the Richmond sediments near Cincinnati. Pyritization probably occurred within a few years, only a short distance (a few centimeters) below the sediment surface through the activities of sulfur‐reducing bacteria. Pyrite precipitated around a nucleus such as a bacterium or algal cell, or developed within an organic structure such as an algal cell or organic membran

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00602.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00603.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Megafossil evidence does not fill the ‘evolutionary gap’ between land plants and their hypothetical green algal ancestors. Rare Late Silurian vascular plant megafossils provide little information about the morphological, physiological, biochemical, and ecological steps that preceded their evolution. Dissociated trilete spores, spore tetrads, cuticle‐ and tracheid‐like structures far exceed the abundance and diversity of Silurian vascular plant megafossils, and appear millions of years before them. In reference to whole‐bodied organisms, these or analogous structures belong to land plants or emergent aquatics; they may represent plants evolutionarily intermediate between green algae and descendent vascular plants at the bryophyte or pre‐bryophyte stages. Changes in the cellular biochemistry of pre‐Devonian land plants in response to the selective pressures of terrestrial life may have led to the origin of lignin and cutin, neither of which has any counterpart among the algae, and to the evolutionary surge of the vascular plants in the Early Devonian represented by the plant megafossil record. Positive correlation between abundance and diversity of trilete spores and shallow‐water, nearshore sites reinforces conclusions based on morphology that a terrestrial flora existed well prior to the appearance of vascular pl

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00604.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

International funding of scientific activities is mostly of catalyst size only. Systematic efforts to track down the catalysing situations in these activities are made by the funding organizations. Great attention is devoted to meetings, while the catalysts of current activities between meetings are neglected. Regular primary publications are the closest counterparts in the current work of meetings but are out of size and inconvenient in structure for catalytic support. Circulars, newsletters and annotated directories (many hybrids occur) are very important catalysts of more manageable size. Taken together they represent considerable amounts of largely concealed labour and costs. Standards are badly needed for making the organization of information elements in directories efficient. Each entry in a directory should add a research profile to the scientists' identity and address. Directories may remain a jungle product, but scientists' considerable efforts in producing them merit a reconsideration of the organization of their contents and the provision of advice for their production and distribution.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00605.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY