Back
Cribroperidinium janinae
From Fensome et al., 2019:
Cribroperidinium janinae Górka, 1982, p.106,108,110, pls.1–2; text-figs.A–D. Holotype: Górka, 1982, pl.1, fig.3. Age: early Hauterivian.
---------------------------------------------------------------------------------------------------
Original description: [Górka, 1982] (translated from French):
Cribroperidinium janinae n. sp.
(Pl. 1-2; Fig. A-D)
Holotype: No. 31 (Pl. 1, Fig. 3).
Type stage: Lower Hauterivian.
Type locality: Szamotuly Geo 21 (depth 810.00 m).
Name origin: janinae - in honor of Dr. Janina Sztejn, micropaleontologist at the Institute of Geology in Warsaw.
Diagnosis: More or less spherical cyst with gonyaulacean paratabulation, small apical horn, helical paracingulum, and precingulate archaeopyle (P3'').
Material: Several hundred pyritized and generally well-preserved specimens. To remove pyrite, the specimens were immersed for two hours in concentrated nitric acid.
Dimensions: (in μm): Holotype
Total length 135-150 150
Total width 133-140 137
Length of apical horn 13-22 17
Width of paracingulum 4-5 5
Description: Cyst with a more or less spherical outline and divided by the very narrow paracingulum into two approximately hemispherical halves: the epicyst and the hypocyst. The paracingulum is helical, levorotatory, most often in the form of a very narrow groove with a single edge. More rarely, the paracingulum shows a ventral deviation of the two parallel parasutures. The precingulate archaeopyle (type P3") is a large pentagonal opening with rounded sides. Some specimens have an operculum in place, sometimes slightly dislocated, or partially attached. The Gonyaulacean-type paratabulation is shown in the schematic drawings of text-fig. A-D. The epicyst with the apical region (plates 1'-4'), whose plate 1' is remarkably elongated, often adheres to the "as" plate and to the plates (1"-6") of trapezoidal outline. The epicyst is provided with a small apical and conical horn. The hypocyst, almost the same size as the epicyst, is composed of plates 1"'-6"', of trapezoidal outline, whose plate 1'" is very small. The antapical part is complicated; additional ridges from plates 3"'-5"' are joined to that of plate 1"", which is asymmetrical and very small. The smaller supplementary ridges are also developed on the 2'" and 6'" plates.
The parasulcus, as mentioned above, is best seen on the hypocyst, where it marks the boundaries between the paraplates. The 4'"/5'" parasutures are located almost mid-dorsally below the large archaeopyle, due to the relatively small surface area occupied by the 1'-3' plates. The parasulcus is elongated on the ventral side. The elongated "as" plate, between the 1" and 6" plates of the epicyst, and the irregular and incomplete "ras" plate at the boundary of the epicyst and hypocyst are clearly visible. Further down, the rhomboidal plate "rs" is present on the hypocyst between the 6"' plate and the ls plate, elongated and adjacent to the 1p plate, which is irregularly elongated. The latter limits the irregular plate "ps" and the 1"" plate, which is asymmetric. Between the "ras" and 1" plates, the oval imprint of the flagellum insertion is observed. The ornamentation depends on the shape of the parasutural ridges, which are developed on the 2"'-5"' plates of the hypocyst. It sometimes includes additional and incomplete ridges between the paraplate boundaries, as well as more or less dense tubercles covering the surface of the paraplates and the edge of the paracingulate. The cyst wall generally appears to be formed of a single layer; however, the presence of two closely contiguous layers at the edge of isolated plaques and opercula is sometimes difficult to observe.
DISCUSSION
In fossil dinoflagellates, traces of cyst membrane growth are observable in the form of intercalary listellae. In this regard, Gocht (1979) distinguished two growth types (A and B). In type A, characteristic of the genus Peridinium, the edges of two neighboring plates grow toward each other, and the growth zone consists of two striations. In type B, superposition and growth are detectable on the edges of the same plates where the growth zone is separated from the other plates by intercalary listellae. This type B exists in species of the genus Gonyaulacysta and, undoubtedly, also, with some modifications, in representatives of the genus Cribroperidinium, including Cribroperidinium janinae n. sp. In the latter case, the growth zones, marked by sutural listellae at the plate boundary, are more visible on the hypocyst, especially on the 2'"-5'" plates. The sulcal plates are devoid of growth traces.
Cribroperidinium janinae n. sp. By its more or less spherical general shape, wall thickness, gonyaulacean-type paratabulation, the presence of the precingulate archaeopyle and growth striations as well as a distinct parasulcus, it is comparable to Cribroperidinium ventriosum (O. WETZEL 1933) LENTIN and WILLIAMS 1973. It differs by its shorter apical horn, the absence of perforation in the apical region, and the "F" plate, very typical of C. ventriosum. Furthermore, growth traces are absent on the sulcal plates of these two species; they are also lacking on the edges of the equatorial plates of C. ventriosum.
Cribroperidinium janinae Górka, 1982, p.106,108,110, pls.1–2; text-figs.A–D. Holotype: Górka, 1982, pl.1, fig.3. Age: early Hauterivian.
---------------------------------------------------------------------------------------------------
Original description: [Górka, 1982] (translated from French):
Cribroperidinium janinae n. sp.
(Pl. 1-2; Fig. A-D)
Holotype: No. 31 (Pl. 1, Fig. 3).
Type stage: Lower Hauterivian.
Type locality: Szamotuly Geo 21 (depth 810.00 m).
Name origin: janinae - in honor of Dr. Janina Sztejn, micropaleontologist at the Institute of Geology in Warsaw.
Diagnosis: More or less spherical cyst with gonyaulacean paratabulation, small apical horn, helical paracingulum, and precingulate archaeopyle (P3'').
Material: Several hundred pyritized and generally well-preserved specimens. To remove pyrite, the specimens were immersed for two hours in concentrated nitric acid.
Dimensions: (in μm): Holotype
Total length 135-150 150
Total width 133-140 137
Length of apical horn 13-22 17
Width of paracingulum 4-5 5
Description: Cyst with a more or less spherical outline and divided by the very narrow paracingulum into two approximately hemispherical halves: the epicyst and the hypocyst. The paracingulum is helical, levorotatory, most often in the form of a very narrow groove with a single edge. More rarely, the paracingulum shows a ventral deviation of the two parallel parasutures. The precingulate archaeopyle (type P3") is a large pentagonal opening with rounded sides. Some specimens have an operculum in place, sometimes slightly dislocated, or partially attached. The Gonyaulacean-type paratabulation is shown in the schematic drawings of text-fig. A-D. The epicyst with the apical region (plates 1'-4'), whose plate 1' is remarkably elongated, often adheres to the "as" plate and to the plates (1"-6") of trapezoidal outline. The epicyst is provided with a small apical and conical horn. The hypocyst, almost the same size as the epicyst, is composed of plates 1"'-6"', of trapezoidal outline, whose plate 1'" is very small. The antapical part is complicated; additional ridges from plates 3"'-5"' are joined to that of plate 1"", which is asymmetrical and very small. The smaller supplementary ridges are also developed on the 2'" and 6'" plates.
The parasulcus, as mentioned above, is best seen on the hypocyst, where it marks the boundaries between the paraplates. The 4'"/5'" parasutures are located almost mid-dorsally below the large archaeopyle, due to the relatively small surface area occupied by the 1'-3' plates. The parasulcus is elongated on the ventral side. The elongated "as" plate, between the 1" and 6" plates of the epicyst, and the irregular and incomplete "ras" plate at the boundary of the epicyst and hypocyst are clearly visible. Further down, the rhomboidal plate "rs" is present on the hypocyst between the 6"' plate and the ls plate, elongated and adjacent to the 1p plate, which is irregularly elongated. The latter limits the irregular plate "ps" and the 1"" plate, which is asymmetric. Between the "ras" and 1" plates, the oval imprint of the flagellum insertion is observed. The ornamentation depends on the shape of the parasutural ridges, which are developed on the 2"'-5"' plates of the hypocyst. It sometimes includes additional and incomplete ridges between the paraplate boundaries, as well as more or less dense tubercles covering the surface of the paraplates and the edge of the paracingulate. The cyst wall generally appears to be formed of a single layer; however, the presence of two closely contiguous layers at the edge of isolated plaques and opercula is sometimes difficult to observe.
DISCUSSION
In fossil dinoflagellates, traces of cyst membrane growth are observable in the form of intercalary listellae. In this regard, Gocht (1979) distinguished two growth types (A and B). In type A, characteristic of the genus Peridinium, the edges of two neighboring plates grow toward each other, and the growth zone consists of two striations. In type B, superposition and growth are detectable on the edges of the same plates where the growth zone is separated from the other plates by intercalary listellae. This type B exists in species of the genus Gonyaulacysta and, undoubtedly, also, with some modifications, in representatives of the genus Cribroperidinium, including Cribroperidinium janinae n. sp. In the latter case, the growth zones, marked by sutural listellae at the plate boundary, are more visible on the hypocyst, especially on the 2'"-5'" plates. The sulcal plates are devoid of growth traces.
Cribroperidinium janinae n. sp. By its more or less spherical general shape, wall thickness, gonyaulacean-type paratabulation, the presence of the precingulate archaeopyle and growth striations as well as a distinct parasulcus, it is comparable to Cribroperidinium ventriosum (O. WETZEL 1933) LENTIN and WILLIAMS 1973. It differs by its shorter apical horn, the absence of perforation in the apical region, and the "F" plate, very typical of C. ventriosum. Furthermore, growth traces are absent on the sulcal plates of these two species; they are also lacking on the edges of the equatorial plates of C. ventriosum.