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Horologinella anabarensis
From Fensome et al., 2019:
Horologinella anabarensis Pestchevitskaya, 2001, p.96–100; text-figs.3–6; pl.I, figs.1–11; pl.II, figs.1–7. Holotype:
Pestchevitskaya, 2001, pl.II, fig.2. Age: late Berriasian–Hauterivian.
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Original description: [Pestchevitskaya, 2001] (translated from Russian with Google Translate):
Horologinella anabarensis Pestchevitskaya sp. n.
Table I, fig. 1-10; Table IP, fig. 1-7
Origin of the name. From the Anabar River.
Holotype. Prep. 18.1, specimen No. 26 CSGM, eastern shore of Anabar Bay, outcrop 1A, lower Valanginian, Euryptychites astieriptychus Zone; pl. II, fig. 2.
Material: 29 well-preserved specimens.
Description. The cyst is suturocavate, has the hourglass shape characteristic of the genus Horologinella. The epicyst is noticeably smaller than the hypocyst. The autophragm is dense, dark brown, smooth or rough. Along the edges of the paraplates it forms short (2-5 µm) bifurcate outgrowths that support a thin transparent ectophragm (Table 1, Fig. 5). These outgrowths emphasize the paratabulation of the precingular and postcingular series. The paratabulation of the apical and antapical regions is expressed by parasutural lines or small ribs, clearly visible on SEM. The cophoid formula of the paratabulation is as follows: 13′?, 7", 7c, 5s, 6", 1-2p?, 3"" (Fig. 3). Sometimes, two small additional paraplates are observed to the left of the sulcal region: one in the precingular, the other in the postcingular series (Pl. I, figs. 1, 2; Pl. II, figs. 2, 6). They can be interpreted as transitional paraplates of the corresponding series (t", t'"). The paracingulum is weakly left-curled and is emphasized by a strong equatorial constriction. The paraplates of the cingular region are delimited by thin parasutural lines. The parasulcus is wide (1″") at the border with the first antapical paraplate, and tapers noticeably toward the paracingulum (Pl. 1, Fig. 2; Pl. II, Fig. 2). The five sulcal paraplates (as, ras, rs, ls, ps) are marked by parasutural lines or narrow ribs. Many cysts clearly show a drop-shaped pore complex (Pl. II, Figs. 2–4). Sometimes two additional pores are observed: one on the anterior sulcal paraplate, the other on the border of the left, right, and posterior sulcal paraplates (Pl. I, Fig. 2; Pl. II, Figs. 4, 5). The operculum is formed by the detachment of all paraplates of the apical region. The archeopyle is free, type 1A (Plate I, Fig. 10).
Variability. The size and shape of the cyst vary. There are specimens with a very strong equatorial constriction and a convex shape of the epicyst and hypocyst (Pl. I, figs. 3, 5, 8-11; Pl. II, figs. 4, 6). At the same time, in some specimens the difference in the width of the paracingulum, epicyst and hypocyst is not very pronounced (Pl. I, figs. 1, 4, 6). It is not always possible to observe rows of parasutural outgrowths covered by ectophragm. Most likely, this is due to the degree of preservation of the palynomorphs. Additional paraplates are occasionally observed in the antapical region, which can be interpreted as posterior intercalary or as additional antapical (Plate I, Fig. 4; Plate II, Fig. 3). On some specimens, within the left and right sulcal paraplates, at the border with the pore complex, parasutural lines are noticeable, limiting smaller paraplates.
Comparison. The closest species is the type species Horologinella lineata Cookson et Eisenack, which has a clear paratabulation. It is interesting to note the similar shape and position of the first apical homologue, dorsal and precingular paraplates, as well as postcingular and posterior intercalary paraplates in H. anabarensis and H. lineata, which makes it possible to assume a very similar paratabulation scheme for these species (Plate II, Figs. 17, 18). The species H. anabarensis differs from the type species in the characteristic shape of the cyst with a large and wide hypocyst and a small epicyst.
The remaining species, assigned to the genus Horologinella, do not have tabulation, which distinguishes them greatly from the tabulated forms (Plate II, figs. 8-16, 19-20).
Remarks. The paratabulation pattern of the precingular and postcingular series, as well as the dorsal and antapical regions, is confirmed quite reliably (Table 1, Figs. 1, 4, 6-11; Table II, Figs. 1-7). - It is difficult to study the paratabulation of the apical region in detail, since the size of the paraplates is very small, and the possibility of observing the apical position of the cyst occurs extremely rarely. Some of the paraplates are clearly visible in the ventral and dorsal position of the cyst (Table І, Figs. 3, 4, 11; Table ІІ, Figs. 2, 4, 6). In Fig. 3, 5 they are shown in dark color and are limited by solid lines. However, since there are no observations of the cyst in the apical position, the shape and relative position of a number of dorsal paraplates of the apical region are quite controversial.
In the figures, the supposed paraplates are not filled in and are delimited by a dotted line. Informal notations are used to describe the paratabulation of the apical region. Asterisks mark the paraplates in contact with the precingular series. The paraplates surrounding the apical pore complex are designated by numbers. In some specimens, the shape of the paraplates 1*, 2*, 3* and the position of the parasutural lines suggest the existence of additional paraplates between the precingular series and the paraplates of the apical region (Plate I, Figs. 4, 11).
The large number and complex arrangement of the paraplates of the apical region make their interpretation difficult. They may completely constitute the apical series. However, the paraplates in contact with the precingular series may probably be interpreted as anterior intercalary. In any case, it should be emphasized that additional studies are required to reconstruct the complete paratabulation scheme of the apical region.
Location. Eastern coast of Anabar Bay, outcrop 1A, layer 12, sample 18; lower Valanginian, Euryptychites astieriptychus Zone.
Horologinella anabarensis Pestchevitskaya, 2001, p.96–100; text-figs.3–6; pl.I, figs.1–11; pl.II, figs.1–7. Holotype:
Pestchevitskaya, 2001, pl.II, fig.2. Age: late Berriasian–Hauterivian.
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Original description: [Pestchevitskaya, 2001] (translated from Russian with Google Translate):
Horologinella anabarensis Pestchevitskaya sp. n.
Table I, fig. 1-10; Table IP, fig. 1-7
Origin of the name. From the Anabar River.
Holotype. Prep. 18.1, specimen No. 26 CSGM, eastern shore of Anabar Bay, outcrop 1A, lower Valanginian, Euryptychites astieriptychus Zone; pl. II, fig. 2.
Material: 29 well-preserved specimens.
Description. The cyst is suturocavate, has the hourglass shape characteristic of the genus Horologinella. The epicyst is noticeably smaller than the hypocyst. The autophragm is dense, dark brown, smooth or rough. Along the edges of the paraplates it forms short (2-5 µm) bifurcate outgrowths that support a thin transparent ectophragm (Table 1, Fig. 5). These outgrowths emphasize the paratabulation of the precingular and postcingular series. The paratabulation of the apical and antapical regions is expressed by parasutural lines or small ribs, clearly visible on SEM. The cophoid formula of the paratabulation is as follows: 13′?, 7", 7c, 5s, 6", 1-2p?, 3"" (Fig. 3). Sometimes, two small additional paraplates are observed to the left of the sulcal region: one in the precingular, the other in the postcingular series (Pl. I, figs. 1, 2; Pl. II, figs. 2, 6). They can be interpreted as transitional paraplates of the corresponding series (t", t'"). The paracingulum is weakly left-curled and is emphasized by a strong equatorial constriction. The paraplates of the cingular region are delimited by thin parasutural lines. The parasulcus is wide (1″") at the border with the first antapical paraplate, and tapers noticeably toward the paracingulum (Pl. 1, Fig. 2; Pl. II, Fig. 2). The five sulcal paraplates (as, ras, rs, ls, ps) are marked by parasutural lines or narrow ribs. Many cysts clearly show a drop-shaped pore complex (Pl. II, Figs. 2–4). Sometimes two additional pores are observed: one on the anterior sulcal paraplate, the other on the border of the left, right, and posterior sulcal paraplates (Pl. I, Fig. 2; Pl. II, Figs. 4, 5). The operculum is formed by the detachment of all paraplates of the apical region. The archeopyle is free, type 1A (Plate I, Fig. 10).
Variability. The size and shape of the cyst vary. There are specimens with a very strong equatorial constriction and a convex shape of the epicyst and hypocyst (Pl. I, figs. 3, 5, 8-11; Pl. II, figs. 4, 6). At the same time, in some specimens the difference in the width of the paracingulum, epicyst and hypocyst is not very pronounced (Pl. I, figs. 1, 4, 6). It is not always possible to observe rows of parasutural outgrowths covered by ectophragm. Most likely, this is due to the degree of preservation of the palynomorphs. Additional paraplates are occasionally observed in the antapical region, which can be interpreted as posterior intercalary or as additional antapical (Plate I, Fig. 4; Plate II, Fig. 3). On some specimens, within the left and right sulcal paraplates, at the border with the pore complex, parasutural lines are noticeable, limiting smaller paraplates.
Comparison. The closest species is the type species Horologinella lineata Cookson et Eisenack, which has a clear paratabulation. It is interesting to note the similar shape and position of the first apical homologue, dorsal and precingular paraplates, as well as postcingular and posterior intercalary paraplates in H. anabarensis and H. lineata, which makes it possible to assume a very similar paratabulation scheme for these species (Plate II, Figs. 17, 18). The species H. anabarensis differs from the type species in the characteristic shape of the cyst with a large and wide hypocyst and a small epicyst.
The remaining species, assigned to the genus Horologinella, do not have tabulation, which distinguishes them greatly from the tabulated forms (Plate II, figs. 8-16, 19-20).
Remarks. The paratabulation pattern of the precingular and postcingular series, as well as the dorsal and antapical regions, is confirmed quite reliably (Table 1, Figs. 1, 4, 6-11; Table II, Figs. 1-7). - It is difficult to study the paratabulation of the apical region in detail, since the size of the paraplates is very small, and the possibility of observing the apical position of the cyst occurs extremely rarely. Some of the paraplates are clearly visible in the ventral and dorsal position of the cyst (Table І, Figs. 3, 4, 11; Table ІІ, Figs. 2, 4, 6). In Fig. 3, 5 they are shown in dark color and are limited by solid lines. However, since there are no observations of the cyst in the apical position, the shape and relative position of a number of dorsal paraplates of the apical region are quite controversial.
In the figures, the supposed paraplates are not filled in and are delimited by a dotted line. Informal notations are used to describe the paratabulation of the apical region. Asterisks mark the paraplates in contact with the precingular series. The paraplates surrounding the apical pore complex are designated by numbers. In some specimens, the shape of the paraplates 1*, 2*, 3* and the position of the parasutural lines suggest the existence of additional paraplates between the precingular series and the paraplates of the apical region (Plate I, Figs. 4, 11).
The large number and complex arrangement of the paraplates of the apical region make their interpretation difficult. They may completely constitute the apical series. However, the paraplates in contact with the precingular series may probably be interpreted as anterior intercalary. In any case, it should be emphasized that additional studies are required to reconstruct the complete paratabulation scheme of the apical region.
Location. Eastern coast of Anabar Bay, outcrop 1A, layer 12, sample 18; lower Valanginian, Euryptychites astieriptychus Zone.