Hostname: page-component-848d4c4894-5nwft Total loading time: 0 Render date: 2024-06-08T09:50:38.470Z Has data issue: false hasContentIssue false
  • English
  • Français

The calcareous nannofossil species Nephrolithus frequens Górka (1957) and its morphotypes

Published online by Cambridge University Press:  20 May 2016

Thomas Ehrendorfer
Thomas Ehrendorfer*
Affiliation:
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
Get access Rights & Permissions [Opens in a new window]

Abstract

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.

Type
Research Article
Information
Journal of Paleontology , Volume 68 , Issue 2 , March 1994 , pp. 191 - 200
Copyright
Copyright © The Paleontological Society 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Åberg, M. 1966. Electron microscopic studies on Nephrolithus (Coccolithophoridae). Acta Universitatis Stockholmiensis Stockholm Contributions in Geology, 13:63–67.Google Scholar
Cepek, P., and Hay, W. W. 1969. Calcareous nannoplankton and biostratigraphic subdivision of the Upper Cretaceous. Transactions of the Gulf Coast Association of Geological Societies, 19:323–336.Google Scholar
Ehrendorfer, T., and Aubry, M.-P. 1992. Calcareous nannoplankton changes across the Cretaceous/Paleocene boundary in the Southern Indian Ocean (Site 750), p. 451–470. In Wise, S. W. Jr., Schlich, R., et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, 120. College Station, Texas (Ocean Drilling Program).Google Scholar
Górka, H. 1957. Coccolithophoridae z górnego mastrychtu Polski środkowej [Les Coccolithophoridés du Maestrichtien supérieur de Pologne]. Acta Palaeontologica Polonica, 2:235–284.Google Scholar
Moshkovitz, S. 1974. A new method for observing the same nannofossil specimens both by light microscope and scanning electron microscope and preservation of types. Israel Journal of Earth Sciences, 23:145–147.Google Scholar
Perch-Nielsen, K. 1968. Der Feinbau und die Klassifikation der Coccolithen aus dem Maastrichtien von Dänemark. Kongelige Danske Videnskabernes Selskab Biologiske Skrifter, 16:1–96.Google Scholar
Pospichal, J. J., and Wise, S. W. Jr. 1990. Maestrichtian calcareous nannofossil biostratigraphy of Maud Rise ODP Leg 113 Sites 689 and 690, Weddell Sea, p. 465–487. In Barker, P. F., Kennett, J. P., et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, 113. College Station, Texas (Ocean Drilling Program).Google Scholar
Reinhardt, P. 1970. Synopsis der Gattungen und Arten der mesozoischen Coccolithen und anderer kalkiger Nannofossilien. Teil II. Freiberger Forschungshefte, C, 265:41–111.Google Scholar
Reinhardt, P., and Górka, H. 1967. Revision of some Upper Cretaceous coccoliths from Poland and Germany. Neues Jahrbuch Geologische und Paläontologische Abhandlungen, 129:240–256.Google Scholar
Shipboard Scientific Party. 1988. Site 690, p. 183–292. In Barker, P. F., Kennett, J. P., et al. (eds.), Proceedings of the Ocean Drilling Program, Initial Reports, 113. College Station, Texas (Ocean Drilling Program).Google Scholar
Shipboard Scientific Party. 1989. Site 750, p. 277–337. In Schlich, R., Wise, S. W. Jr., et al. (eds.), Proceedings of the Ocean Drilling Program, Initial Reports, 120. College Station, Texas (Ocean Drilling Program).Google Scholar
Stott, L. D., and Kennett, J. P. 1990. Antarctic Paleogene planktonic foraminifer biostratigraphy: ODP Leg 113, Sites 689 and 690, p. 549–569. In Barker, P. F., Kennett, J. P., et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, 113. College Station, Texas (Ocean Drilling Program).Google Scholar
Watkins, D. K. 1992. Upper Cretaceous nannofossils from Leg 120, Kerguelen Plateau, Southern Ocean, p. 343–370. In Wise, S. W. Jr., Schlich, R., et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, 120. College Station, Texas (Ocean Drilling Program).Google Scholar
Wind, F. H. 1983. The genus Nephrolithus Górka, 1957 (Coccolithophoridae). Journal of Paleontology, 57:157–161.Google Scholar