Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

Journal of Paleontology

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by SUZUKI, N. Search for Related Content GeoRef GeoRef Citation

ONTOGENETIC GROWTH AND VARIATION IN THE SKELETAL STRUCTURE OF TWO LATE NEOGENE SPHAEROPYLE SPECIES (POLYCYSTINA RADIOLARIANS)

¹ Institute of Geology and Paleontology, Graduate School of Geoscience, Tohoku University, Sendai 980-8578, Japan, <norinori{at}mail.tains.tohoku.ac.jp>

Two four-shelled species characterized by a pylome-bearing outermost shell—Sphaeropyle robusta and its descendant, Sphaeropyle langii—are selected for morphological study. Both species are morphologically identical to three-shelled Actinomma morphotypes, morphotypes A and B, respectively. Furthermore, the number of pores on half a circumference of the primary cortical shell, the distinguishing feature between Sphaeropyle robusta and Sphaeropyle langii, accounts for the same between Sphaeropyle robusta and morphotype A, and between Sphaeropyle langii and morphotype B. It suggests that the three-shelled morphotypes A and B are juvenile forms of the four-shelled Sphaeropyle robusta and Sphaeropyle langii, respectively. This is strongly supported by the same stratigraphic distributions of each pair. The quantitative analysis of morphological variations in both species also revealed that they have nearly identical morphology, except for the number of pores on half a circumference of the primary cortical shell. In addition, the size range of primary and secondary cortical shells and the range of the number of radial spines increase in Sphaeropyle langii, while the length range of radial spines decrease.

This article has been cited by other articles:

				T. Itaki and K. R. Bjorklund Conjoined radiolarian skeletons (Actinommidae) from the Japan Sea sediments Micropaleontology, September 1, 2007; 53(5): 371 - 389. [Abstract] [Full Text] [PDF]