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Sphenolithus belemnos
Edited by Lyndsey on Thu, 10/03/2011 - 12:35
Sphenolithus belemnos Bramlette and Wilcoxon, 1967
Description: Dart-shaped, apical spine well-developed. Lateral elements much smaller than proximal elements.
Remarks: This species has a well developed monolithic spine with straight extinction. It can be distinguished from other species of this type by the nature of its base. This has a tall well-developed proximal cycle, but only diminutive lateral elements, overall the base is distinctly elongate, and merges smoothly into the spine.
Size: Length 4-8 microns, width 2-4 microns.
Original description:
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Neogene: Sphenolithus; Sphenolithus belemnos
Comments
These photos are not S. belemnos
If you look at the photos with the original description, you will see that what is illustrated here is clearly not the same bug. In the original photos the basal cycle, immediately below the apical spine is distinctly asymmetric with one of the two elements being much smaller. In the same view (at 45 degrees to the nichols) the column shows a single dark line with 2 visible elements not the 3 seen in these photos.
I've just been through this section in excruciating detail. The forms illustrated here range considerably higher than those that resemble the original illustrations. You can see the original photos in either P.N. 1985 or in the Aubry Handbook and you'll see what I mean.