Citation: Discoaster hamatus Martini&Bramlette, 1963taxonomic rank: SpeciesTaxonomic discussion: This species seems to have an identical structure to that of the 6-rayed species D. calcaris (q.v.). Typically only large specimens (>c.10 microns) have well developed offset proximal extensions, associated smaller specimens lack these and are better placed in D. bellus for biostratigraphic rigour. Both the D. calcaris and D. bellus morphotypes have longer stratigraphic ranges than true D. hamatus. Browning et al. (2017) record that the smaller specimens (<15µm) occur above and below NN9 so for stratigraphic rigour the large specimens need to be used.
Distinguishing features: Parent taxon (D. pentaradiatus group): Symmetric 5-rayed, late Neogene, discoasters without large proximal boss This taxon: 5-rayed; ray tips with clockwise deflected (in distal view) proximal extensions.
Morphology: Symmetric 5-rayed discoaster; rays with clockwise deflected (in distal view) proximal extensions. The central area is small with a featureless distal surface and small proximal knob. Size: Usually only large specimens, (>10 µm) show the characteritic raytip development
Lith size: 10->25µm; Segments: 5->5; Data source notes: size from OD & illustrated specs
The morphological data given here can be used on the advanced search page. See also these notes
Geological Range: Notes: Defines Zone NN9 Last occurrence (top): at top of NN9 zone (100% up, 9.5Ma, in Tortonian stage). Data source: zonal marker (see e.g. Young 1998) First occurrence (base): at base of NN9 zone (0% up, 10.6Ma, in Tortonian stage). Data source: zonal marker (see e.g. Young 1998)
Plot of occurrence data:
Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
Histogram - Neptune occurrence data from DSDP and ODP proceedings. Pale shading <50 samples in time bin. Interpret with caution & read these notes
Taxon plotted: Discoaster hamatus, synonyms included - Discoaster hamatus;
Browning, E., Bergen, J. A., Blair, S. A., Boesiger, T. M. & de Kaenel, E. (2017). Late Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster in the circum North Atlantic Basin: Gulf of Mexico and ODP Leg 154. Journal of Nannoplankton Research. 37(2-3): 189-214. gs
Martini, E. & Bramlette, M. N. (1963). Calcareous nannoplankton from the experimental Mohole drilling. Journal of Paleontology. 37(4): 845-855. gs
Perch-Nielsen, K. (1972). Remarks on Late Cretaceous to Pleistocene coccoliths from the North Atlantic. Initial Reports of the Deep Sea Drilling Project. 12: 1003-1069. gs
Salomon, R. (1999). The Calcite Palace. Website - https://ina.tmsoc.org/galleries/CalcitePalace/index.htm. -. gs
Theodoridis, S. (1984). Calcareous nannofossil biostratigraphy of the Miocene and revision of the helicoliths and discoasters. Utrecht Micropaleontological Bulletin. 32: 1-271. gsO
Wei, W. (2003). Upper Miocene nannofossil bistratigraphy and taxonomy of Exxon core CH30-43-2 from the Gulf of Mexico. Journal of Nannoplankton Research. 25(1): 17-23. gs
Young, J. R. (1998). Neogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 225-265. gs
Discoaster hamatus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 15-9-2024
These terms and conditions contain rules about posting comments. By submitting a comment, you are declaring that you agree with these rules:
Although the administrator will attempt to moderate comments, it is impossible for every comment to have been moderated at any given time.
You acknowledge that all comments express the views and opinions of the original author and not those of the administrator.
You agree not to post any material which is knowingly false, obscene, hateful, threatening, harassing or invasive of a person's privacy.
The administrator has the right to edit, move or remove any comment for any reason and without notice.
Failure to comply with these rules may result in being banned from submitting further comments.
These terms and conditions are subject to change at any time and without notice.
{"commentics_url":"\/\/www.mikrotax.org\/comments\/","page_id":449768,"enabled_country":true,"country_id":0,"enabled_state":false,"state_id":0,"enabled_upload":false,"maximum_upload_amount":3,"maximum_upload_size":5,"maximum_upload_total":5,"captcha":true,"captcha_url":"https:\/\/www.mikrotax.org\/comments\/frontend\/index.php?route=main\/form\/captcha&page_id=449768","cmtx_wait_for_comment":"cmtx_wait_for_comment","lang_error_file_num":"A maximum of %d files are allowed to be uploaded","lang_error_file_size":"Please upload files no bigger than %.1f MB in size","lang_error_file_total":"The total size of all files must be less than %.1f MB","lang_error_file_type":"Only image file types are allowed to be uploaded","lang_text_loading":"Loading ..","lang_placeholder_country":"Country","lang_placeholder_state":"State","lang_text_country_first":"Please select a country first","lang_button_submit":"Add Comment","lang_button_preview":"Preview","lang_button_remove":"Remove","lang_button_processing":"Please Wait.."}
PN72 pl09-03.JPG
CalcPal-D_hamatus.jpg
Young1998_pl08_fig08.JPG
Young1998_pl08_fig09.JPG
Browning et al 2017 pl04 08.JPG
Browning et al 2017 pl04 10.JPG
Young1998_pl08_fig10.JPG
Browning et al 2017 pl04 05.JPG
Browning et al 2017 pl04 07.JPG
MartiniBramlette-1963-pl105-08.JPG
MartiniBramlette-1963-pl105-10.JPG
MartiniBramlette-1963-pl105-11.JPG
Theod84 pl12-13.JPG
Theod84 pl37-04.JPG
Theod84 pl37-05.JPG
Theod84 pl37-06.JPG
Wei 2003 pl1-17.JPG
Young1998_010-hamatus.jpg
Browning et al 2017 fig3-09.jpg
Comments