Papposphaera sagittifera
P. sagittifera combination coccospheres (Figs 17–22) Two new occurrences of combination coccospheres from West Greenland are shown in Figs 17, 19. The cell shown in Fig. 17 is particularly appealing because here the two groups of coccoliths have become partly separated to clearly show the morphologi...
| Main Authors: | , , |
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| Format: | Other/Unknown Material |
| Language: | unknown |
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Zenodo
2016
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| Subjects: | |
| Online Access: | https://doi.org/10.5281/zenodo.12534979 http://treatment.plazi.org/id/03EB512EFF9CFF8EFF0D794C90AFB51E |
| Summary: | P. sagittifera combination coccospheres (Figs 17–22) Two new occurrences of combination coccospheres from West Greenland are shown in Figs 17, 19. The cell shown in Fig. 17 is particularly appealing because here the two groups of coccoliths have become partly separated to clearly show the morphological characteristics of each of them. With reference to the combination coccospheres of P. sagittifera and T. borealis there is one issue of particular concern. It has become apparent that in each of the combination coccospheres illustrated by Thomsen et al. (1991) and also in the two new images reproduced here, the P. sagittifera HET calyx is in fact different from what is typically found in P. sagittifera HET when not forming part of a combination coccosphere. In the P. sagittifera combination coccosphere the four-winged rosette comprises wings that are fairly narrow, hardly ever stepwise elaborated on the inside, and with an angle proximally between the exterior edge of the wing and the connecting line between the two edges of the wing that leads to a much less flaring rosette in comparison with that generally found in P. sagittifera HET (Fig. 3A). The line distally connecting the exterior and interior edges of the wing deviates a few degrees from being perpendicular (Figs 18, 20). In Fig. 22 the wings of the individual rosette have been pushed apart only to confirm the description of the individual wing provided above. A stepwise elaboration of the distal inner edge of the individual wing is occasionally observed (Figs 18, 20, 22; arrows). The design of the individual wing and the reduced overall flaring of the rosette cause the individual rosette to appear with an overall triangular outline when viewed in a TEM (Figs 18, 20–21). The very same features as described above are evident when consulting Thomsen et al. 1991 (loc. cit. Figs 2–4, 9). A search among images of P. sagittifera HET has fortunately unveiled rare occurrences of this particular type of calyx scattered among others with the traditional stepwise and ... |
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