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Geiselodinium tyonekense
Geiselodinium tyonekense Engelhardt, 1976, p.122
Holotype: Engelhardt, 1976, pl.1, fig.14
Paratypes: Engelhardt, 1976
Locus typicus: Cook Inlet, Alaska
Stratum typicum: Miocene
Original description: Engelhardt, 1976, p. 122
Proximate cyst without a distinct cingulum or sulcus. Pericorpus elliptical, with broadly rounded to triangular apical horn and sharply pointed antapical horn. Antapical horn displaced in lateral view, which gives an asymmetric profile to the cyst; antapical horn, 7 Ám to 10 Ám long. Periphragm thin (less than 1 Ám) and non-tabulate. Surface has irregularly spaced granules (0.5 Ám to 1 Ám) and occasional baculae (and echinae?) which are not uniform in size. Pericoel 1 Ám to 5 Ám wide in equatorial region.
Endocorpus distinct and elliptical in outline, Iying in close proximity to pericorpus in equatorial region and projecting slightly into bases of apical and antapical horns. Endophragm thin (less than 1,um); compression folds apparent in most specimens. Surface of endocorpus scabrate.
Tabulation indistinct. The archeopyle is a compound apical aperture, but the exact nature cannot be discerned (Pl. 1, fig. 14).
Dimensions: Based on 25 specimens; average values are in parentheses. Pericorpus, length, 45 Ám (57 Ám), 66 Ám; width, 38 Ám (42 Ám), 47 Ám. Endocorpus, length, 37 Ám (44 Ám), 55 Ám; width, 30 Ám (38 Ám), 44 Ám.
Affinities:
Engelhardt, 1976, p. 122: Geiselodinium tyonekensis is probably related to the extant genus Peridinium. Wall and Dale (1968) have illustrated the cysts of P. wisconsinense Eddy, which are similar to the cysts of G. tyonekensis. Tabulation is more apparent, and the surface ornamentation is more pronounced along the cingulum in P. wisconsinense than in G. tyonekensis. The Type B cysts that are described and illustrated by Norris and McAndrews (1970) are also similar to G. tyonekensis. The archeopyle in the Type B cysts is described as attached apical (Aa + 3I). The granulate-baculate-fimbriate ornamentation on the periphragm is irregularly spaced and formed in irregular groups, while inG. tyonekensis the granulation is not grouped, but is scattered over the surface of the periphragm. The overall dimensions of G. tyonekensis are smaller than the Type B cysts, but they do overlap in size range. The cysts are also smaller than those of P. wisconsinense.
Holotype: Engelhardt, 1976, pl.1, fig.14
Paratypes: Engelhardt, 1976
Locus typicus: Cook Inlet, Alaska
Stratum typicum: Miocene
Original description: Engelhardt, 1976, p. 122
Proximate cyst without a distinct cingulum or sulcus. Pericorpus elliptical, with broadly rounded to triangular apical horn and sharply pointed antapical horn. Antapical horn displaced in lateral view, which gives an asymmetric profile to the cyst; antapical horn, 7 Ám to 10 Ám long. Periphragm thin (less than 1 Ám) and non-tabulate. Surface has irregularly spaced granules (0.5 Ám to 1 Ám) and occasional baculae (and echinae?) which are not uniform in size. Pericoel 1 Ám to 5 Ám wide in equatorial region.
Endocorpus distinct and elliptical in outline, Iying in close proximity to pericorpus in equatorial region and projecting slightly into bases of apical and antapical horns. Endophragm thin (less than 1,um); compression folds apparent in most specimens. Surface of endocorpus scabrate.
Tabulation indistinct. The archeopyle is a compound apical aperture, but the exact nature cannot be discerned (Pl. 1, fig. 14).
Dimensions: Based on 25 specimens; average values are in parentheses. Pericorpus, length, 45 Ám (57 Ám), 66 Ám; width, 38 Ám (42 Ám), 47 Ám. Endocorpus, length, 37 Ám (44 Ám), 55 Ám; width, 30 Ám (38 Ám), 44 Ám.
Affinities:
Engelhardt, 1976, p. 122: Geiselodinium tyonekensis is probably related to the extant genus Peridinium. Wall and Dale (1968) have illustrated the cysts of P. wisconsinense Eddy, which are similar to the cysts of G. tyonekensis. Tabulation is more apparent, and the surface ornamentation is more pronounced along the cingulum in P. wisconsinense than in G. tyonekensis. The Type B cysts that are described and illustrated by Norris and McAndrews (1970) are also similar to G. tyonekensis. The archeopyle in the Type B cysts is described as attached apical (Aa + 3I). The granulate-baculate-fimbriate ornamentation on the periphragm is irregularly spaced and formed in irregular groups, while inG. tyonekensis the granulation is not grouped, but is scattered over the surface of the periphragm. The overall dimensions of G. tyonekensis are smaller than the Type B cysts, but they do overlap in size range. The cysts are also smaller than those of P. wisconsinense.