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Tanyosphaeridium magneticum
Tanyosphaeridium magneticum Davies, 1983, p.25, pl.8, figs.1–8,11–12; text-fig.20. Emendation: Torricelli, 2000, p.263.
Holotype: Davies, 1983, pl.8, fig.7; Fauconnier and Masure, 2004, pl.79, figs.2–3.
Locus typicus: Cornwall Island, District of Franklin, Canada
Stratum typicum: Valanginian
Original diagnosis: Davies, 1983, p. 25
Chorate dinoflagellate cysts with an elongate ovoidal endoblast, granulate ornament, and entire to denticulate, cylindrical to buccinate, tubiform processes concentrated around the apices of the cyst (14-17 on each end).
Archeopyle: apical.
Size: length - 33(38)48 µm; breadth - 20(23)25 µm.
Original description: Davies, 1983, p. 25
The process terminations are variable and would not suffice for specific separation since on one specimen there may be two or three types of process termination. The processes are located at the apex and antapex of the cyst; 0-3 cingular processes are present. After archeopyle separation 3-6 processes remain near the edge of the archeopyle; therefore, 8-12 processes are removed in the operculum . The arrangement of processes resembles the lines of magnetic force around a bar magnet.
Affinities:
Davies, 1983, p. 25: T. isocalamum is very similar in size, shape, ornament and process types but differs by having more evenly spaced processes and a well developed cingular series. T. variecalamum has well spaced processes with wide bases. Bourkidinium granulatum has fewer processes (9-15) on each end lacking all precingular and cingular processes, a slightly larger size (length - 35(46)62 µm; breadth - 20(24)29 µm) and tends to be more granulate than T. magneticum.
Tanyosphaeridium magneticum Davies, 1983; emend.
Emended diagnosis: Chorate cyst with an elongate ellipsoidal body with granulate ornamentation, bearing long, hollow, distally flared processes arranged mainly at the apex and antapex of the cyst. One to three cingular processes are always present. The shape of process tips varies from present. The shape of process tips varies from present. The shape of process tips varies from of processes from smooth to serrate. The archeopyle is apical, type tA.
Discussion: The holotype of Tanyosphaeridium magneticum (Davies, 1983; plate 8, 7) is reported as having two cingular processes, but the original description (p. 25) states that ‘‘the processes are located at the apex and antapex of the cyst, and 0–3 cingular processes are also present’’. Following the emendation of B. granulatum proposed by Nøhr-Hansen (1993) and modified herein, which includes in this taxon also forms with a precingular ‘corona’ of several processes, the specimen of T. magneticum illustrated by Davies (1983, plate 8, 5), which displays a clearly Davies (1983, plate 8, 5), which displays a clearly be assigned to B. granulatum. This discussion advocates a restriction of Davies’ (1983) original description to include in T. magneticum only forms with at least one cingular process
Comparisons: B. granulatum is very similar to T. magneticum in size and shape but entirely lacks cingular processes.
Remarks: The emendation of both T. magneticum and B. granulatum proposed in this study is an attempt to facilitate recognition. However, it is evident that T. magneticum possesses intermediate morphological features with respect to B. granulatum and other Tanyosphaeridium species, and all these forms possibly intergrade with each other. It is furthermore possible that, in badly preserved assemblages, the breaking of cingular processes could transform a cyst of T. magneticum in a B. granulatum. The most correct approach to the taxonomy of these forms still remains the ‘morphon concept’ proposed by Leereveld and Brinkhuis (1988).
Stratigraphic occurrence: Rare in the Upper Hauterivian of the Cismon core.
Holotype: Davies, 1983, pl.8, fig.7; Fauconnier and Masure, 2004, pl.79, figs.2–3.
Locus typicus: Cornwall Island, District of Franklin, Canada
Stratum typicum: Valanginian
Original diagnosis: Davies, 1983, p. 25
Chorate dinoflagellate cysts with an elongate ovoidal endoblast, granulate ornament, and entire to denticulate, cylindrical to buccinate, tubiform processes concentrated around the apices of the cyst (14-17 on each end).
Archeopyle: apical.
Size: length - 33(38)48 µm; breadth - 20(23)25 µm.
Original description: Davies, 1983, p. 25
The process terminations are variable and would not suffice for specific separation since on one specimen there may be two or three types of process termination. The processes are located at the apex and antapex of the cyst; 0-3 cingular processes are present. After archeopyle separation 3-6 processes remain near the edge of the archeopyle; therefore, 8-12 processes are removed in the operculum . The arrangement of processes resembles the lines of magnetic force around a bar magnet.
Affinities:
Davies, 1983, p. 25: T. isocalamum is very similar in size, shape, ornament and process types but differs by having more evenly spaced processes and a well developed cingular series. T. variecalamum has well spaced processes with wide bases. Bourkidinium granulatum has fewer processes (9-15) on each end lacking all precingular and cingular processes, a slightly larger size (length - 35(46)62 µm; breadth - 20(24)29 µm) and tends to be more granulate than T. magneticum.
Tanyosphaeridium magneticum Davies, 1983; emend.
Emended diagnosis: Chorate cyst with an elongate ellipsoidal body with granulate ornamentation, bearing long, hollow, distally flared processes arranged mainly at the apex and antapex of the cyst. One to three cingular processes are always present. The shape of process tips varies from present. The shape of process tips varies from present. The shape of process tips varies from of processes from smooth to serrate. The archeopyle is apical, type tA.
Discussion: The holotype of Tanyosphaeridium magneticum (Davies, 1983; plate 8, 7) is reported as having two cingular processes, but the original description (p. 25) states that ‘‘the processes are located at the apex and antapex of the cyst, and 0–3 cingular processes are also present’’. Following the emendation of B. granulatum proposed by Nøhr-Hansen (1993) and modified herein, which includes in this taxon also forms with a precingular ‘corona’ of several processes, the specimen of T. magneticum illustrated by Davies (1983, plate 8, 5), which displays a clearly Davies (1983, plate 8, 5), which displays a clearly be assigned to B. granulatum. This discussion advocates a restriction of Davies’ (1983) original description to include in T. magneticum only forms with at least one cingular process
Comparisons: B. granulatum is very similar to T. magneticum in size and shape but entirely lacks cingular processes.
Remarks: The emendation of both T. magneticum and B. granulatum proposed in this study is an attempt to facilitate recognition. However, it is evident that T. magneticum possesses intermediate morphological features with respect to B. granulatum and other Tanyosphaeridium species, and all these forms possibly intergrade with each other. It is furthermore possible that, in badly preserved assemblages, the breaking of cingular processes could transform a cyst of T. magneticum in a B. granulatum. The most correct approach to the taxonomy of these forms still remains the ‘morphon concept’ proposed by Leereveld and Brinkhuis (1988).
Stratigraphic occurrence: Rare in the Upper Hauterivian of the Cismon core.