CATALOG - Tergestiella adriatica


Folder trail: Farinacci -> T -> Tergestiella -> Tergestiella adriatica
Folders this level: T. adriatica, T. calumnia, T. gemma, T. mediterranea, T. robusta,

Original descriptions of taxa. For coccolithophores, and many calcispheres, these are pages from the Catalog of Calcareous Nannofossils. In other cases (e.g. non-calcifying haptophytes) the data is directly complied on this site. The "Catalogue of Calcareous Nannofossils" was compiled by Prof A. Farinacci 1969-1989 and updated by Richard Howe 2000-2016 - see also this page.
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Current identification/main database link: Tergestiella adriatica Kamptner, 1941

Compiled data

Citation: Tergestiella adriatica Kamptner 1941
Rank: Species
Type locality: Yugoslavia
Type level: Recent
Standardised type level: 150_HOLOCENE
Type repository: Vienna, Natural History Museum
Repository Country: Austria
Farinacci catalog page (& compiler): 04195 (Farinacci)
Language: DE


Notes
Translation of description (from Google translate with light editing)

Description:
The shells are isodiametric. Their diameters are 10.6-11.7µm depending on their position to the observer. An opening is not present. The coccoliths are circular, touching each other marginally, and there are invariably 12 present. Their position on the cell is analogous to that of a regular pentagonal-dodecahedron. They show a comparatively complicated sculpture. Above all, they allow four concentric zones to be distinguished in the vertical direction. The basal zone has a diameter of 4.3 µm and is about 0.5 µm high. This is followed by the main zone with the largest diameter (5.7 µm); Its height is 1 µm; It flattens itself against the edge provided with about 28 notches in convex curvature. The next zone is followed by the flat-dome-shaped, 4-fold-wide third, with approximately 14 notches. And as a fourth zone, a flat central hump of 2.5 mm diameter is placed on it. The total height of a coccolith thus amounts to approximately 2 µm. In the side view, the similarity of the calcreous structure to a placolith of the genus Coccolithus is very striking.

Remarks:
A conspicuous and remarkable character of this genre is, without a doubt, the twelvefold number of the shell elements and their combination into a formal skeleton, which is formally arranged mathematically. This is not the first such case. In the last few years, HH Gran and T. Braarud (1935, p. 388) have described a form of Pontosphaera bigelowi, also composed of twelve coccoliths, which, according to the drawings of the authors, looks much more like a regular pentagonal-dodecahedron and the shell-elements themselves have a regular pentagonal shape; And it should be cup-shaped discoliths. The calcareous elements of Tergestiella adriatica, however, differ considerably from ordinary discoliths owing to their complicated sculpture, and have hardly any close relations with them. They are much more likely to be understood as a derivative of the placolith type. The genus Tergestiella thus has its systematic place behind the genus Coccolithus. The skeletal element would have been thought to have emerged from the circular placolith type by the loss of the central perforation. Such an assumption is somewhat encouraged by Lohmann, who thought that the rhabdoliths of the genera Rhabdosphaera and Discosphaera also emerged from placoliths by loss of perforation.

The regular construction of the shell, which is analogous to a pentagonal-dodecahedron, requires an explanation, since one could also think of a random arrangement or of a rhombic-dodecahedron. If, however, we examine the various possibilities of the shell-formation, we see a distinct tendency which forces the coccoliths to arrange themselves into a  pentagonal-dodecahedron.
For this purpose we must compare the two polyhedra geometrically. In this case, the radius of the shell element of Tergestiella is to be equated with that of the circle inscribed in the polyhedral surface and to be fixed as a constant quantity. We then conclude that the Pentagonal-dodekahedron is more concentrated than the Rhombic-dodekahedron. In the case of the former, the single polyhedral surface (regular pentagon) has a smaller surface area, and this also applies, of course, to the total surface area of ​​the body. The distance of the boundary surfaces from the body center is smaller, as is the volume of the ball inscribed in the body. This latter circumstance appears particularly worthy of note, since the morphological behavior of Tergestiella is to be understood only from the viewpoint of spatial economy.

In a pentagonal-dodecahedron, we see, as any of the five-circle-bound boundaries (which, according to our assumption, correspond to a coccolith), are touched round the whole of five equilibrium neighbors. In the case of the rhombic dodecahedron, however, each circle is directly touched by four neighboring paths, and these groups are grouped into two pairs, between which there is a gap at two opposing points. Thus the circles (coccoliths) are more closely grouped on the pentagonal-dodecahedron than on the rhombic-dodecahedron. In this case, the area between the circles is reduced.

A similar regularity in the structure of a coccosphere is to be expected from the outset only if the shell elements do not exceed twelve, and if their boundaries are circular; For, beyond the twelve, the probability is very small that the coccoliths may be combined to such regular order. In the formation of the shell in the sense of a regular structure, several moments have thus co-operated: (1) the circular form of the coccoliths, (2) the constancy of their radius, (3) their twelve-fold number. It may be assumed that the first-mentioned moment was first present, since the circular form of coccoliths is certainly a primitive property. We cannot make any statement on the chronological order in which the other two preconditions began to take effect. However, there is the realization that the interaction of all three moments necessarily led to the arrangement of the coccoliths in the manner of a pentagonal-dodecahedron when the cell was dominated by the tendency to minimize the surface area between the skeletal elements.

As regards the systematic classification of Tergestiella, the following should be noted. The absence of a central perforation on the calcareous elements would indicate the family of the Syracosphaeraceae; But the circular shape speaks against such an accommodation. The coccoliths are even more or less elliptical even in the rather primitive Acanthoica, and the elliptical shape is still more pronounced in the other Syracophaeraceae. The primitive feature of the circular shape of the coccoliths is nowhere more present in the region of the recent Syracosphaeraceae. If Gran and Braaruud (1935, fig. 67) draw regular five-sided coccoliths, it is quite improbable that they are related to discoliths from the family of the Syracosphaeraceae, assuming the proper reproduction of the object. The idea that Pontosphaera bigelowi is more closely related to Tergestiella is not very remote. The circular shape of the coccoliths, as well as their other sculpture, are still most closely related to a close relationship with the genus Coccolithus, from which the shell elements may have emerged by the loss of the central pore.

References:

Kamptner, E. (1941). Die Coccolithineen der Südwestküste von Istrien. Annalen des Naturhistorischen Museums in Wien. 51: 54-149. gs


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Tergestiella adriatica: Catalog entry compiled by Anna Farinacci and Richard Howe. Viewed: 16-12-2019

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