Asterolampra distincta

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SPECIES Asterolampra distincta
Barker & Meakin (1944/45)

Taxonomic Information

Jr. Synonymy:

  • Asterolampra distincta Barker and Meakin, 1944/45, p. 18, pl. 3, fig. 3; Gombos, 1975, p. 315, pl. 6, figs 2, 8, 9; Fenner, 1978, p. 5, 11, pl. 18, fig. 3; Gombos, 1980, p. 235, pl. 3, figs. 14-18; Gombos, 1983, p. 568, pl. 1, figs. 9-10.


Morphometry:

Diameter Range: Diameter of valve 93.5 µm.




Species Description:

Mini Description: Areolated segments appear as crescent-shaped marginal undulations. The rays show slightly longer marginal prolongation than is evidenced in Asterolampra marginata. The central areolated portion exhibits coarser areolation than is observed in Asterolampra marginata. The radius of the central areolated. portion is reduced to not more than one half of the valve radius.
Original Name Asterolampra distincta Barker and Meakin, 1944/45: Valve of the only specimen seen small, diameter 93.5 µm, circular. Central space about two-fifths of the diameter broad, 12-sided, sides concave, surface cellulate. Marginal zone about one-twelfth of the diameter broad, with 12 cellulate segments opposite the angles of the central space, their inner edges uniformly convex. Intermediate hyaline zone divided by 12 straight rays between the angles of the central space and the midpoints of the inner edges of the marginal segments into facets each bearing a distinctly margined, broad, faintly striated, radial depression extending from near the adjacent side of the central space into the recess between the opposite marginal segments. Diameter of valve (fig. 3), 93.5 µm.

Additional Remarks

  • Remarks by Gombos (1980, p. 235):
This species appears to represent a step in the progression from Asterolampra marginata to Asterolampra insignis. In Asterolampra distincta the areolated segments appear as crescent-shaped marginal undulations, much as they do in Asterolampra marginata. The rays show slightly longer marginal prolongation than is evidenced in Asterolampra marginata. Also, the central areolated portion exhibits coarser areolation than is observed in Asterolampra marginata. In Asterolampra distincta the radius of the central areolated. portion is reduced to not more than one half of the valve radius. The development of rays in this species is asymmetric, i.e. the rays on one side of the valve are more protracted than those on the other side. This asymmetry is present in all specimens in the material from Corehole 15. The asymmetry may be quite subtle in some specimens and extremely pronounced in others, with the rays on one side being nearly twice as long as those on the other. Barker & Meakin described this species on the basis of a single specimen from the deposit at Joe's River, Barbados. In the Middle Eocene material from Corehole 15, Asterolampra distincta is very abundant. It may be that the example of this species observed by Barker & Meakin had been reworked into the Late Eocene Joe's River Formation.


Useful References

  • Barker, P.F., Meakin, S.H., 1944-45. New and rare diatoms. J. Quekett Microsc. Club, Ser. 4, 2 (no. 1): 18-22.
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