摘要:

Existing methods of quantitative paleobiogeographic analysis, based on the statistical use of binary similarity coefficients, are shown to be defective. A new method employing a formal probability frequency function which relates the number of shared taxa to sample size and inferred population size for a pair of areas, is introduced. It assumes random selection of taxonomic samples by the fossil record from larger complete populations originally occurring in the areas concerned. Quantitative assessment of population diversity as well as population similarity expressed as percentage overlap with attendant error estimates result from the method, but the final phase of analysis remains, of necessity, both manual and inexact. Utility of the method is demonstrated by working simulated data and actual data pertaining to late Cretaceous ammonites.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00584.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.tb00585.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Tubiform fossils conventionally referred toSerpulacf.advenaSalter and species ofSpirorbisLamarck from the British Lower Limestone Shales and Border Group (Lower Carboniferous) are re‐examined. They occur in peritidal carbonate environments of schizohaline aspect. These fossils superficially resemble calcareous polychaete tubes but have skeletal characters, including molluscan wall structure, numerous internal septa, and protoconch, which indicate that they represent a new group of substrate‐attached, disjunctly coiled gastropods. They resemble archaeogastropods in internal morphology of the skeleton but show parallels in external form and occurrence with the extant Vermetidae. There are two principal modes of occurrence: (1) erect tubes forming intertidal biostromes associated with non‐skeletal algal laminites, and (2) prostrate discoidal tubes encrusting subtidal skeletal stromatolites or occasionally forming larger irregular bioherms. These biostromes and bioherms are comparable in structure to Recent vermetid reef develop

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00586.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.tb00587.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Ectoproct colonies with membraniporiform, celleporiform and Iunulitiform A growth‐forms have particular habitat preferences on the continental shelf. A colonial capability model for each growth‐form, based on a functional analysis of its structure at different levels, tries to portray the adaptive range of the growth‐form and includes inferences from the structure of the individual zooids, their polymorphs, their arrangement within the colony as controlled by budding patterns, and their relation to external environmental stresses. Each encrusting growth‐form on the Sahul Shelf, northwest Australia, has distinct structural and functional characters which can be arranged in adaptive architectural trends. Deviations from the fundamental membraniporiform growth‐form include the development of vertical growth, the sacrifice of individual zooids, the incorporation of substrate within the colony, and variations in the heterozooids. The celleporiform growth‐form is subdivided to recognize the massive, ‘nodular’ colony as a s

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00588.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.tb00589.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

It has recently been suggested that the foramen of siphonotretacean and acrotretacean brachiopods functioned as an exhalant siphon and that it was a feature of the dorsal valve. In representatives of these superfamilies the pedicle was considered to have emerged from between the valves. Re‐examination of the evidence on which these arguments were based suggests that some of it is capable of more than one interpretation. The remainder, together with consideration of the mantle canal patterns, cemented mode of attachment, and comparative morphology of some discinaceans and siphonotretaceans, strongly supports the traditional view that the foramen of these forms was located in the ventral valve and that it served as a pedicle openin

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00590.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

A review is given of observations and interpretations of the attachment in Isocrinida. It is concluded that all adult Isocrinida discard distal parts of their column and live attached by distal cirri to the bottom or to objects lying on the bottom. From time to time the column may break below a nodal and the isocrinid drift along the bottom until it regains attachment with the cirri. In undisturbed environments a considerable length of the tapering distal part of the column may be maintained, and several specimens may be connected by the entangled distal parts of the columns lying on the bottom. Specimens ofSeirocrinus subangularisattached to tree trunks in the Lower JurassicPosidoniashale of Holzmaden, Germany, have been interpreted as pseudoplanktic. These are all adult specimens with distal parts of their column discarded before they attached themselves to the trunks. Furthermore, since adult specimens cannot swim to the surface, they must have attached themselves to sunken trunks lying on the bottom.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00591.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.tb00592.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Nilssoni–scanicusZone deposits (Silurian, early Ludlow) from the Leintwardine and Long Mountain districts of Britain, and the Cǎlǎrasi Borehole, Moesian Platform of Romania, have yielded a species of monograptid which, whilst resembling rare LudlowMonoclimacisspecies, has strong morphological affinities with Devonian monograptids such asMonograptus ramstalensisJaeger. Because of the occurrence of such structures at a surprisingly low horizon the writers urge caution in identifying age from monotypic assemblages. The difficulties surrounding the affinities of the low Ludlow species necessitates a provisional open nomenclature asMonograptussp. The possible evolutionary significance is discusse

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1977.tb00593.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY