摘要:

The attached fauna of one of the many hardgrounds from the Galena Group (Trentonian Substage) of the Upper Mississippi Valley is described. The fauna is composed of three principal elements,viz.(1) borers, includingCicatricula retiformisichnogen. et ichnosp. nov., (2) pelmatozoans with encrusting holdfasts, and (3) bryozoans. Analysis of the distribution of members of each population on the hardground shows that most are strongly aggregated. The nature of, and reasons for, such aggregations are considered in the light of comparable Recent shallow‐water marine populations. The community on this hardground, and those on other Galena Group hardgrounds, are immature. This is a consequence of frequent and damaging scour, which these organisms were poorly adapted to resis

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00608.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.tb00609.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Ordovician and Silurian graptolitic shales and deep‐water mudstones contain a sparse fauna of clustered, minute shells which are commonly believed to have been epiplankton attached to seaweed. Modern deep‐water organisms may preferentially attach to local firm areas on the soft sediment. It is suggested that the Ordovician and Silurian shells may also have been benthic animals attached to local firm regions of the sea floor. These substrates might have included algal fronds which had fallen to the bot

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00610.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.tb00611.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.tb00612.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

A jagged fracture array on a hypostome ofCeraurinellafrom Ordovician strata of northern Canada records an unsuccessful attempt at predation by an unknown animal. The traumatic injury was repaired from the interior during the same intermoult period that it had been inflicted.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00613.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.tb00614.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Dendroid stenolaemate bryozoan colonies with paraboloid bases developed initially in the same manner as stenolaemate colonies with broadly encrusting bases. Their unique shape is related to the narrowly cylindrical shape of the encrusted surface (algal stipe?) and to radially differentiated rates of growth from the point of colony origin. The colony shape is interpreted as an adaptation to unconsolidated substrates in relatively quiet though not necessarily deep water.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00615.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.tb00616.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Crinoid holdfasts occur throughout the Silurian sequence of Gotland, with a marked concentration to reefs and immediate reef surroundings. Four morphological groups are recognized: (1) Discoid holdfasts. (2) Cirriferous holdfasts, represented by (a)Rhizocrinus‐like holdfasts, (b) large radices with stout, often branching cirri, and (c) rhizoid holdfasts, formed by a complicated net of pseudocirri. (3) Creeping stems attached to the substrate by thin strands of stereome. (4) Coiling stems. Discoid attachments, cirriferous holdfasts (types b and c) and coiling stems show little preference to substrate and adapt morphologically to conditions at hand. Rhizoid holdfasts display the greatest variation and apparently occur within many different groups of crinoids.Rhizocrinusttkeholdfasts have been found only in quiet‐water deposits, while creeping stems were concentrated to more turbulent environments. Coiling stems were epizoic, attached to rugose corals, bryozoans, crinoid stems and similar supports. Growth, mode of life (attached or free), settling and fixation of larvae, and relation to substrate and other organisms ate discus

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00617.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY