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Hystrichokolpoma okinawaium
Hystrichokolpoma okinawaium Matsuoka, 1979, p.54,56-57, pl.1, fig.6; pl.2, figs.1-4; text-figs.4,5B. Holotype: Matsuoka, 1979, pl.2, figs.3-4; Fauconnier and Masure, 2004, pl.39, fig.4. Age: Early Pleistocene.
Original description Matsuoka, 1979:
Hystrichokolpoma okinawaia sp. nov. (Plate I, 6; Plate II, 1--4; Figs.4, 5)
Diagnosis: Cyst subspherical with finely granulose surface. Processes of two types: large hollow, relatively short cylindrical to tubiform with denticulate to foliate distal end; small slender processes, simple, bi- or tri-furcate near the base with recurved and patulate distal end. Holotype: Slide no. OKD-5, position 3WI, Plate II, 3--4. Kisembaru, KimSon, Kunigami-Gun, Okinawa Prefecture, Japan.
Paratypes: Slide no. OKD-5, position 8EIII, Plate I, 6; Slide no. OKD-3, position 2SIII, Plate II, 1--2. Kisembaru, Kim-Son, Kunigami-Gun, Okinawa Prefecture, Japan.
Description: The cyst is subspherical to ellipsoidal in equatorial view and subspherical in polar view. Its wall is composed of peri- and endophragms appressed between processes. The periphragm sculpture consists of fine granules or minute longitudinal striations. Processes formed from the periphragm indicate a paratabulation of 4', 0a, 6", 6c, 5"', lp, 1"", las, lps and 3s. The archeopyle with a free operculum is formed by loss of all apical series. The apical, precingular, postcingular and antapical paraplates are represented by large hollow, relatively short cylindrical to slightly tubiform processes with denticulate or sometimes weakly foliate open distal ends and indistinct rectangular bases. These processes do not communicate with the endocoel. On the basis of observations of some nearly entire specimens, the apical region has four large hollow processes like those of the pre-, postcingular
and antapical regions. The 2' process is the smallest among apical ones. Of the six precingular processes, 4", 5" and 6" are slightly larger than others, while 1" is the smallest. There is one anterior sulcal hollow process between the 1" and 6" processes, and it is smaller than the precingular
processes. The postcingular region has four large processes and one slender small process. The 1"' process is much reduced, bifid near its base, and its distal end is elongate aculeate. The other four processes have indistinct rectangular bases, the 5"' process being slightly smaller. The intermediate
lp process occupies a position between the 2'" and 1 .... processes. The antapical, relatively short and wide cylindrical process is the largest. On the dorsal side, this process has a triangular distal appendix. Slender processes are found in the paracingular and the parasulcal regions. There are six cingular processes, some of them bi- or trifurcate near their bases and others are simple oblate with long recurved patulate distal ends. The paracingulum is not noticeably displaced. In the parasulcal region, one intermediate and three slender small processes are observed. These slender small processes
are long oblate with patulate distal ends as are the cingular processes.
Discussion: The apical region bears four large processes whose sizes differ from each other. These differences in size may or may not directly reflect the original size of apical paraplates. The 1'" process, clearly present judging from its position beneath the lc process and at the left side of the 2'"
process, is quite different from other postcingular processes because of its significantly reduced size and shape. A much reduced paraplate 1"' also is known in some species of Spiniferites (e.g. Wall, 1967). McLean (1974) pointed out that Hystrichokolpoma tumescens and H. mentitum possibly
have six postcingular processes if compared with other previously mentioned dinoflagellate cysts. Judging from the figure shown by McLean (1974, pl.8, fig.2), H. tumescens has a distinct 6'" process. In H. okinawaia n. sp. one intermediate process in the parasulcal region seems to indicate the posterior
sulcal paraplate on the basis of its comparable position, just as in H. pacifica n. sp. Furthermore, the antapical process has an aberrant hexagonal base which is different from H. tumescens, and thus the 6'" process is not recognized.
Comparison with similar species: Hystrichokolpoma okinawaia n. sp. is generally similar to H. rigaudae Deflandre et Cookson 1955; H. rigaudae has a characteristic antapical process that is strongly tubiform with foliate distal end ornamented with small tubelets, while H. okinawaia is characterized
by a relatively short cylindrical antapical process with a characteristic distal end ornamented with triangular appendix. H. okinawaia also resembles H. unispinum (Williams and Downie, 1966, pl.17, figs.6, 7) but the latter has buccinate large processes and one slender small process on the original
cingular paraplates. H. rigaudae, described by Benedek (1972, pp.28--29, pl.8, fig.9), is closely similar to the present species in that its large processes, including the antapical, are not tubiform but almost cylindrical with a denticulate distal end, and possibly belongs to H. okinawaia.
Dimensions of Hystrichokolpoma okinawaia n. sp.
Cyst diameter: 55 µm (Holotype), 52-63 µm (Range)
Cyst length: 64, 41-59 µm (64 µm with apical part)
Antapical process length: 37, 34-41 µm
Antapical process width: 23, 19-25 µm
Large processes, length: 25, 22-28 µm
Small processes, length: 21, 19-25 µm
Original description Matsuoka, 1979:
Hystrichokolpoma okinawaia sp. nov. (Plate I, 6; Plate II, 1--4; Figs.4, 5)
Diagnosis: Cyst subspherical with finely granulose surface. Processes of two types: large hollow, relatively short cylindrical to tubiform with denticulate to foliate distal end; small slender processes, simple, bi- or tri-furcate near the base with recurved and patulate distal end. Holotype: Slide no. OKD-5, position 3WI, Plate II, 3--4. Kisembaru, KimSon, Kunigami-Gun, Okinawa Prefecture, Japan.
Paratypes: Slide no. OKD-5, position 8EIII, Plate I, 6; Slide no. OKD-3, position 2SIII, Plate II, 1--2. Kisembaru, Kim-Son, Kunigami-Gun, Okinawa Prefecture, Japan.
Description: The cyst is subspherical to ellipsoidal in equatorial view and subspherical in polar view. Its wall is composed of peri- and endophragms appressed between processes. The periphragm sculpture consists of fine granules or minute longitudinal striations. Processes formed from the periphragm indicate a paratabulation of 4', 0a, 6", 6c, 5"', lp, 1"", las, lps and 3s. The archeopyle with a free operculum is formed by loss of all apical series. The apical, precingular, postcingular and antapical paraplates are represented by large hollow, relatively short cylindrical to slightly tubiform processes with denticulate or sometimes weakly foliate open distal ends and indistinct rectangular bases. These processes do not communicate with the endocoel. On the basis of observations of some nearly entire specimens, the apical region has four large hollow processes like those of the pre-, postcingular
and antapical regions. The 2' process is the smallest among apical ones. Of the six precingular processes, 4", 5" and 6" are slightly larger than others, while 1" is the smallest. There is one anterior sulcal hollow process between the 1" and 6" processes, and it is smaller than the precingular
processes. The postcingular region has four large processes and one slender small process. The 1"' process is much reduced, bifid near its base, and its distal end is elongate aculeate. The other four processes have indistinct rectangular bases, the 5"' process being slightly smaller. The intermediate
lp process occupies a position between the 2'" and 1 .... processes. The antapical, relatively short and wide cylindrical process is the largest. On the dorsal side, this process has a triangular distal appendix. Slender processes are found in the paracingular and the parasulcal regions. There are six cingular processes, some of them bi- or trifurcate near their bases and others are simple oblate with long recurved patulate distal ends. The paracingulum is not noticeably displaced. In the parasulcal region, one intermediate and three slender small processes are observed. These slender small processes
are long oblate with patulate distal ends as are the cingular processes.
Discussion: The apical region bears four large processes whose sizes differ from each other. These differences in size may or may not directly reflect the original size of apical paraplates. The 1'" process, clearly present judging from its position beneath the lc process and at the left side of the 2'"
process, is quite different from other postcingular processes because of its significantly reduced size and shape. A much reduced paraplate 1"' also is known in some species of Spiniferites (e.g. Wall, 1967). McLean (1974) pointed out that Hystrichokolpoma tumescens and H. mentitum possibly
have six postcingular processes if compared with other previously mentioned dinoflagellate cysts. Judging from the figure shown by McLean (1974, pl.8, fig.2), H. tumescens has a distinct 6'" process. In H. okinawaia n. sp. one intermediate process in the parasulcal region seems to indicate the posterior
sulcal paraplate on the basis of its comparable position, just as in H. pacifica n. sp. Furthermore, the antapical process has an aberrant hexagonal base which is different from H. tumescens, and thus the 6'" process is not recognized.
Comparison with similar species: Hystrichokolpoma okinawaia n. sp. is generally similar to H. rigaudae Deflandre et Cookson 1955; H. rigaudae has a characteristic antapical process that is strongly tubiform with foliate distal end ornamented with small tubelets, while H. okinawaia is characterized
by a relatively short cylindrical antapical process with a characteristic distal end ornamented with triangular appendix. H. okinawaia also resembles H. unispinum (Williams and Downie, 1966, pl.17, figs.6, 7) but the latter has buccinate large processes and one slender small process on the original
cingular paraplates. H. rigaudae, described by Benedek (1972, pp.28--29, pl.8, fig.9), is closely similar to the present species in that its large processes, including the antapical, are not tubiform but almost cylindrical with a denticulate distal end, and possibly belongs to H. okinawaia.
Dimensions of Hystrichokolpoma okinawaia n. sp.
Cyst diameter: 55 µm (Holotype), 52-63 µm (Range)
Cyst length: 64, 41-59 µm (64 µm with apical part)
Antapical process length: 37, 34-41 µm
Antapical process width: 23, 19-25 µm
Large processes, length: 25, 22-28 µm
Small processes, length: 21, 19-25 µm