Back
Hystrichosphaeridium paracostatum
Hystrichosphaeridium paracostatum Cookson and Eisenack, 1974
Holotype: Cookson and Eisenack, 1974, pl.25, fig.12
Age: Albian-Senonian
Transalation Cookson and Eisenack, 1974: GSC, courtesy R. Fensome
Original diagnosis: Cookson and Eisenack, 1974, p.65
Shell spherical, thin-walled, frequently slightly ellipsoidal, provided with numerous radial processes. Their number is evidently variable; in the optical cross-section one counts about 14-20 . They are occasionally cylindrical, however, generally they have the shape of a wide funnel with frequently slightly broadened bases, and display different lengths and breadths in one and the same specimen. Distally they become wider more or less suddenly, and terminate in more or less numerous, frequently bent backwardly, fine points. A constant characteristic feature is the fine and dense longitudinal striation of the delicate processes, which is probably rather brought about by fine foldings than by "reinforcement-list". The shell itself is finely granular. Lists, of the type extending from the bases of the processes, are not present on it. In form, the processes resemble the bell-shaped middle perianthium of the Easter-lily.
The species greatly reminds one of the H. costatum Davey & Williams 1966 from the Oxfordian. However, the processes are shorter in comparison to the radius of the central shell. Also the ribs on the periphragm are missing which, in the case of the H. costatum form a polygonal reticulation pattern (of which, however, nothing is to be seen in the illustration furnished by Davey & Williams 1966, Plate 10, Figure 4).
If it were not so much younger, the H. paracostatum could be viewed as sub-species of the H. costatum. A close relationship between both species seems probable.
Dimension: Type: diameter of central shell about 50 µm, overall about 80 µm; the broad process measures about 19 x 19 µm. The diameters of the central shells of the remaining specimens lie between about 50-70 µm. The total diameter attains 110 µm.
Occurrence: In the Balcatta No. 1 bore, at 170-210 ft., and in Madura No. 1 bore, at 966-988 ft.; in both bores seldom. One specimen was found in the Roma-series.
Remarks: Cookson and Eisenack, 1974, p.66
The close relationship between our species and the H. salpingophorum can not be mistaken, in particular if one does not consider the holotype of Deflandre (1937, Pl. 10, Fig. 1), but considers the specimen figured by Davey & Williams (1966, Plate 10, Figure 6).
However, Davey & Williams (page 62) furnish an exact formula for the distribution of the processes which, despite their frequency can not be ascertained in our specimens, so that we can not identify our specimen with the H. salpingophorum.
It should be added here that it is not apparent from the illustrations by Davey & Williams how they - and this applies also to other species - could have arrived at these formulas.
Up to now, only very few species have been studied with a sufficient degree of accuracy with respect to the distribution of the processes (Gocht, 1969, page 37, Text-Figure 27) in order to rely on the results. It is difficult to see how the frequently insufficient material of Davey & Williams could have led to accurate formulas. One becomes particularly sceptical if one reads (and we quote) "with variable number of sulcal processes", the more so if despite one"s best intention nothing resembling a "sulcus" or a sulcal arrangement can be recognized.
Holotype: Cookson and Eisenack, 1974, pl.25, fig.12
Age: Albian-Senonian
Transalation Cookson and Eisenack, 1974: GSC, courtesy R. Fensome
Original diagnosis: Cookson and Eisenack, 1974, p.65
Shell spherical, thin-walled, frequently slightly ellipsoidal, provided with numerous radial processes. Their number is evidently variable; in the optical cross-section one counts about 14-20 . They are occasionally cylindrical, however, generally they have the shape of a wide funnel with frequently slightly broadened bases, and display different lengths and breadths in one and the same specimen. Distally they become wider more or less suddenly, and terminate in more or less numerous, frequently bent backwardly, fine points. A constant characteristic feature is the fine and dense longitudinal striation of the delicate processes, which is probably rather brought about by fine foldings than by "reinforcement-list". The shell itself is finely granular. Lists, of the type extending from the bases of the processes, are not present on it. In form, the processes resemble the bell-shaped middle perianthium of the Easter-lily.
The species greatly reminds one of the H. costatum Davey & Williams 1966 from the Oxfordian. However, the processes are shorter in comparison to the radius of the central shell. Also the ribs on the periphragm are missing which, in the case of the H. costatum form a polygonal reticulation pattern (of which, however, nothing is to be seen in the illustration furnished by Davey & Williams 1966, Plate 10, Figure 4).
If it were not so much younger, the H. paracostatum could be viewed as sub-species of the H. costatum. A close relationship between both species seems probable.
Dimension: Type: diameter of central shell about 50 µm, overall about 80 µm; the broad process measures about 19 x 19 µm. The diameters of the central shells of the remaining specimens lie between about 50-70 µm. The total diameter attains 110 µm.
Occurrence: In the Balcatta No. 1 bore, at 170-210 ft., and in Madura No. 1 bore, at 966-988 ft.; in both bores seldom. One specimen was found in the Roma-series.
Remarks: Cookson and Eisenack, 1974, p.66
The close relationship between our species and the H. salpingophorum can not be mistaken, in particular if one does not consider the holotype of Deflandre (1937, Pl. 10, Fig. 1), but considers the specimen figured by Davey & Williams (1966, Plate 10, Figure 6).
However, Davey & Williams (page 62) furnish an exact formula for the distribution of the processes which, despite their frequency can not be ascertained in our specimens, so that we can not identify our specimen with the H. salpingophorum.
It should be added here that it is not apparent from the illustrations by Davey & Williams how they - and this applies also to other species - could have arrived at these formulas.
Up to now, only very few species have been studied with a sufficient degree of accuracy with respect to the distribution of the processes (Gocht, 1969, page 37, Text-Figure 27) in order to rely on the results. It is difficult to see how the frequently insufficient material of Davey & Williams could have led to accurate formulas. One becomes particularly sceptical if one reads (and we quote) "with variable number of sulcal processes", the more so if despite one"s best intention nothing resembling a "sulcus" or a sulcal arrangement can be recognized.