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Homotryblium tasmaniense
Homotryblium tasmaniense Cookson and Eisenack, 1967
Holotype: Cookson and Eisenack, 1967, pl.20, figs.1-2
Paratype: Cookson and Eisenack, 1967
Locus typicus: Strahan, Tasmania
Stratum typicum: Paleocene
Original description: Cookson and Eisenack, 1967, p.133
Shell spherical, relatively thin-walled, two-layered, coarsely granular to spinulose, with radially arranged tubular appendages which are open distally and vary considerably both in length and width. Usually those of a single specimen are of approximately the same length, but their width may vary quite considerably. The wall of the shell in the vicinity of the points of insertion of the appendages is smooth to finely granular, so that the base of each appendage is surrounded by a narrow circular area that contrasts distinctly with the general surface of the shell.
The shell opens by the separation of the 5-, or more rarely, 6-sided plates, each with a centrally placed appendage, into which the wall of one half of the shell (apical) becomes subdivided, the total number, approximately seven or eight, depending on the number of appendages originally present. These plates eventually separate from one another, either individually or occasionally in groups, so that an archeopyle embracing the whole equatorial region is formed.
Dimensions: Holotype overall diameter c. 83 Ám, shell c. 55 Ám, appendages 12-18 Ám, 2-8 Ám wide, "funnel" 13-15 Ám wide. Range overall diameter c. 76-95 Ám, shell c. 48-57 Ám, appendages c. 5-24 Ám long, c. 2-10 Ám wide.
Affinities: Cookson and Eisenack, 1967, p.134
Of the two species of Homotryblium at present established, H. tenuispinosum Davey & Williams 1966 from the London Clay seems to be the one to which H. tasmaniense most closely approaches. However it differs from the English species in the almost regular development of the smooth or very finely granular zones that surround the bases of the appendages and the complete separation of the sulcal plates. H. tasmaniense is very abundant in those of the Esso T27 matrices that are richest in microplankton.
Holotype: Cookson and Eisenack, 1967, pl.20, figs.1-2
Paratype: Cookson and Eisenack, 1967
Locus typicus: Strahan, Tasmania
Stratum typicum: Paleocene
Original description: Cookson and Eisenack, 1967, p.133
Shell spherical, relatively thin-walled, two-layered, coarsely granular to spinulose, with radially arranged tubular appendages which are open distally and vary considerably both in length and width. Usually those of a single specimen are of approximately the same length, but their width may vary quite considerably. The wall of the shell in the vicinity of the points of insertion of the appendages is smooth to finely granular, so that the base of each appendage is surrounded by a narrow circular area that contrasts distinctly with the general surface of the shell.
The shell opens by the separation of the 5-, or more rarely, 6-sided plates, each with a centrally placed appendage, into which the wall of one half of the shell (apical) becomes subdivided, the total number, approximately seven or eight, depending on the number of appendages originally present. These plates eventually separate from one another, either individually or occasionally in groups, so that an archeopyle embracing the whole equatorial region is formed.
Dimensions: Holotype overall diameter c. 83 Ám, shell c. 55 Ám, appendages 12-18 Ám, 2-8 Ám wide, "funnel" 13-15 Ám wide. Range overall diameter c. 76-95 Ám, shell c. 48-57 Ám, appendages c. 5-24 Ám long, c. 2-10 Ám wide.
Affinities: Cookson and Eisenack, 1967, p.134
Of the two species of Homotryblium at present established, H. tenuispinosum Davey & Williams 1966 from the London Clay seems to be the one to which H. tasmaniense most closely approaches. However it differs from the English species in the almost regular development of the smooth or very finely granular zones that surround the bases of the appendages and the complete separation of the sulcal plates. H. tasmaniense is very abundant in those of the Esso T27 matrices that are richest in microplankton.