摘要:

The science of paleoecology suffers from a lack of conceptual frameworks. Paleoecologists have been overconcerned with the inadequacies of the fossil record: as a result, community palmecology has historically developed very slowly. At the community ecosystem level, the need for a theoretical framework is so great that paleoecology must ‘borrow’ the hypotheses of modem ecology. Consideration of the stability‐time hypothesis of Sanders in conjunction with the physical setting of transgression and regression has permitted the structuring of three community types and the interpretation of their behavior under variations in the physical environment. These community types (opportunistic. stable mature, relict mature) are recognizable in the fossil record and examples are given from the Upper Pennsylvanian of the Appalachian

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1975.tb00931.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Atrypid communities are described from the Silurian succession of southern Norway. These atrypids show striking variation in their mode of occurrence, several features of which are described quantitatively. Mature, well‐developed communities occur in calcareous rocks which were apparently deposited in a well‐aerated shallow environment. Stunted communities (identified by small shell size despite maturity) occur in carbonate‐poor sediments deposited in deeper and less turbulent environments. Other communities are composed of immature shells which were apparently killed by a catastrophic event. Communities are also seen in which catastrophe was not total, and survivors can be recognised. The atrypid niche was taken over by other animal communities when major environmental changes took

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1975.tb00932.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

A temporal succession of three marine animal communities of early Silurian age is described from the Midland Valley of Scotland. These formed part of an offshore onshore series of communities developed on the platform of a prograding delta under regressive tectonic conditions. All three communities were trophically structured in the same way as their modern analogues. In the earliest (isorthid‐Glassia) community filterers and collectors were dominant; the absence of swallowers is attributable to the nature of the substrate. Soft‐bodied swallowers, revealed only by their network of fine burrows, dominated the succeeding (Skenidioides‐Dicaelosia) community. Filterers, which so dominated the hard‐bodied fauna, were of only secondary importance: they lived clustered together in small aggregations, the sediments around which were reworked by the swallowers. A major fall of volcanic ash followed by an increase in the variability of the physical environment resulted in the abrupt replacement of this community by theEoplectodonta‐Visbyellacommunity. Filterers were again dominant, with collectors subordinate; swallowers were comparati

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1975.tb00933.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1975.tb00934.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

A quick transgressive event occurs near the top of the Wenlock Limestone. The initiation of this is thought to be synchronous, proving the top of the Wenlock Limestone to be diachronous and younging southwards. As a result the top of this rock unit cannot be used satisfactorily as a time line. It is suggested that the initiation of the transgression be taken as the practical means for the correlation of the Wenlock‐Ludlow Series boundary. The Birmingham Siltstone Formation is erected for the strata between Dudley and Ludlow which are younger than Wenlock Limestone and older than the transgression. The Wenlock Limestone of Usk was deposited after the transgression and is unrelated to the main Wenlock Limestone. Thus it is treated as a separate entity and named here the Usk Limestone Formatio

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1975.tb00935.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The periostracum in certain bivalves is imbedded with calcified, spiculelike structures analogous if not homologous to cuticular spicules found in the Aplacophora and Polyplacophora (chitons). Although rare or absent in most living bivalves, calcified periostracal structures are apparently an ancestral feature in some bivalve groups, i.e. the Mytilacea, Permophoridae, Myoida. and Anomalodesmata. Ancestors of the Bivalvia and Polyplacophora may have been covered with a flexible, spiculestudded cuticle. Shell plates in these two classes may have originated through a modification of the mechanism of spiculelike cuticular calcification. resulting in a primordial shell with simple prismatic structure.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1975.tb00936.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Neotrigonia(Molluscs, Pelecypoda). the only surviving genus of the once diverse and widespread Trigoniacea, was collected live from depths of 6–80 m on sandy mud bottoms off southeastern Australia. The two species collected.Neotrigonia gemmaIredale, 1924 andNeotrigonia margaritacea(Lamarck), 1804, are structurally similar and differ mainly in size and coloration.Neotrigoniahas such primitive features as an unfused mantle and filibranchiate ctenidia. Its foot is large, active and muscular and the ctenidial ciliary pattern resembles that of the Unionacea. The shell is non‐streamlined and has pronounced radial omamentation.Neotrigonialives infaunally near the sediment surface, filter feeds. and is capable of fairly rapid burrowing. The burrowing facility, conferred by the foot, is unexpected in light of shell morphology. This suggests that shell morphology alone is not necessarily a reliable guide to the life habits of fossil trigoniace

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1975.tb00937.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1975.tb00938.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The lack of hinge spines on the left side of the ventral valve in Chonetacea is demonstrated here for the first time. This morphological peculiarity has a special bearing on the evolutionary trends of the Strophochonetinae. The existence of several species of Chonetacea, both in the Armorican Massif, the Cantabrian Mountains, and Aragon, is a new fact which confirms very close relations between these three areas during Lower Devonian times.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1975.tb00939.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Phosphatic nodules are abundant in the Glauconitic Marl (Cretaceous, Cenomanian) of south‐east England, particularly where the sequence is condensed. Some of the nodules are derived from the underlying Upper Greensand, and are phosphatic fossil fragments, fossil moulds, and calcareous concretions. Concretions in particular show signs of a complex history of multiple phases of boring, encrustation, phosphatisation, and glauconitisation. Phosphate and glauconite are both replacements after fine‐grained carbonate sediment and cement. The majority of the phosphates are whole and fragmentary moulds of fossils. The origin of theses nodules involved: (1) infilling of shells, (2) burial, (3) prefossilisation‐cementation of fossil infillings. probably by high magnesian calcite, (4) dissolution of aragonitic shell material, (5) disinterment and exposure of moulds on the sea floor, followed by (6) phosphatisation. boring. and enerustation by various organisms, and sometimes glauconitisation. Many nodules bear evidence of several cycles of cementation, exposure, mineralisation, boring and enerustation.The closest Recent analogues to the Glauconitic Marl phosphates appear to be the phosphatic crust and nodules forming today off the coast of southern California. The features described and processes inferred from the Glauconitic Marl occurrences appear to have been widespread in nodular phosphatic f

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1975.tb00940.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY