The calcareous nannofossil species Nephrolithus frequens Górka (1957) and its morphotypes
A complete morphologic intergradation from biperforate to multiperforate specimens of Nephrolithus frequens Górka (1957) occurs in the uppermost Maastrichtian chalk at southern high-latitude ODP Holes 750A (Kerguelen Plateau, southern Indian Ocean) and 690C (Maud Rise, Weddell Sea). Previous workers...
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Cambridge University Press (CUP)
1994
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Online Access: | http://dx.doi.org/10.1017/s0022336000022782 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022336000022782 |
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crcambridgeupr:10.1017/s0022336000022782 2024-03-03T08:49:20+00:00 The calcareous nannofossil species Nephrolithus frequens Górka (1957) and its morphotypes Ehrendorfer, Thomas 1994 http://dx.doi.org/10.1017/s0022336000022782 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022336000022782 en eng Cambridge University Press (CUP) https://www.cambridge.org/core/terms Journal of Paleontology volume 68, issue 2, page 191-200 ISSN 0022-3360 1937-2337 Paleontology journal-article 1994 crcambridgeupr https://doi.org/10.1017/s0022336000022782 2024-02-08T08:33:26Z A complete morphologic intergradation from biperforate to multiperforate specimens of Nephrolithus frequens Górka (1957) occurs in the uppermost Maastrichtian chalk at southern high-latitude ODP Holes 750A (Kerguelen Plateau, southern Indian Ocean) and 690C (Maud Rise, Weddell Sea). Previous workers have assigned taxonomic importance to the number of pores of the central area. Two subspecies, N. frequens subsp. frequens and N. frequens subsp. miniporus , were recently differentiated (Pospichal and Wise, 1990) based on this character (four or more pores and two pores, respectively). The observation of specimens of Nephrolithus frequens with three pores in the central area indicates that there is no “natural” breaking point in a progression from two to numerous pores and that specimens of N. frequens with different pore numbers should be considered morphotypes of a single species exhibiting a high intraspecific variability. In addition, our observations using the scanning electron microscope and light microscope illustrate that in well-preserved specimens each pore in the central area is surrounded by two cycles of elements. The margin consists of two cycles, with the elements of the inner cycle extending proximally about twice as far as the elements of the outer cycle. Article in Journal/Newspaper Weddell Sea Cambridge University Press Weddell Sea Kerguelen Indian Weddell Maud Rise ENVELOPE(3.000,3.000,-66.000,-66.000) Journal of Paleontology 68 2 191 200 |
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Open Polar |
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Cambridge University Press |
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crcambridgeupr |
language |
English |
topic |
Paleontology |
spellingShingle |
Paleontology Ehrendorfer, Thomas The calcareous nannofossil species Nephrolithus frequens Górka (1957) and its morphotypes |
topic_facet |
Paleontology |
description |
A complete morphologic intergradation from biperforate to multiperforate specimens of Nephrolithus frequens Górka (1957) occurs in the uppermost Maastrichtian chalk at southern high-latitude ODP Holes 750A (Kerguelen Plateau, southern Indian Ocean) and 690C (Maud Rise, Weddell Sea). Previous workers have assigned taxonomic importance to the number of pores of the central area. Two subspecies, N. frequens subsp. frequens and N. frequens subsp. miniporus , were recently differentiated (Pospichal and Wise, 1990) based on this character (four or more pores and two pores, respectively). The observation of specimens of Nephrolithus frequens with three pores in the central area indicates that there is no “natural” breaking point in a progression from two to numerous pores and that specimens of N. frequens with different pore numbers should be considered morphotypes of a single species exhibiting a high intraspecific variability. In addition, our observations using the scanning electron microscope and light microscope illustrate that in well-preserved specimens each pore in the central area is surrounded by two cycles of elements. The margin consists of two cycles, with the elements of the inner cycle extending proximally about twice as far as the elements of the outer cycle. |
format |
Article in Journal/Newspaper |
author |
Ehrendorfer, Thomas |
author_facet |
Ehrendorfer, Thomas |
author_sort |
Ehrendorfer, Thomas |
title |
The calcareous nannofossil species Nephrolithus frequens Górka (1957) and its morphotypes |
title_short |
The calcareous nannofossil species Nephrolithus frequens Górka (1957) and its morphotypes |
title_full |
The calcareous nannofossil species Nephrolithus frequens Górka (1957) and its morphotypes |
title_fullStr |
The calcareous nannofossil species Nephrolithus frequens Górka (1957) and its morphotypes |
title_full_unstemmed |
The calcareous nannofossil species Nephrolithus frequens Górka (1957) and its morphotypes |
title_sort |
calcareous nannofossil species nephrolithus frequens górka (1957) and its morphotypes |
publisher |
Cambridge University Press (CUP) |
publishDate |
1994 |
url |
http://dx.doi.org/10.1017/s0022336000022782 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022336000022782 |
long_lat |
ENVELOPE(3.000,3.000,-66.000,-66.000) |
geographic |
Weddell Sea Kerguelen Indian Weddell Maud Rise |
geographic_facet |
Weddell Sea Kerguelen Indian Weddell Maud Rise |
genre |
Weddell Sea |
genre_facet |
Weddell Sea |
op_source |
Journal of Paleontology volume 68, issue 2, page 191-200 ISSN 0022-3360 1937-2337 |
op_rights |
https://www.cambridge.org/core/terms |
op_doi |
https://doi.org/10.1017/s0022336000022782 |
container_title |
Journal of Paleontology |
container_volume |
68 |
container_issue |
2 |
container_start_page |
191 |
op_container_end_page |
200 |
_version_ |
1792506541513900032 |