Back
Rhombodinium ornatum
Rhombodinium ornatum (Vozzhennikova, 1967, p.103–104, pl.42, figs.1–3; pl.43, figs.1–4; pl.44, figs.1–12; pl.45, figs.1–3) Williams et al., 2015, p.311. Emendations: Lentin and Vozzhennikova, 1989, p.223; Vasilyeva in Andreeva-Grigorovich et al., 2011, p.53.
Originally Kisselevia, subsequently (and now) Rhombodinium.
Holotype: Vozzhennikova, 1967, pl.44, fig.6, lost according to Lentin and Vozzhennikova (1989, p.223).
Lectotype: Vozzhennikova, 1967, pl.44, fig.1 (as holotype of Kisselevia ornata forma reticulata); Lentin and Vozzhennikova, 1989, pl.1, figs.1–2; Lentin and Vozzhennikova, 1990, pl.9, fig.1; designated by Lentin and Vozzhennikova (1989, p.223).
Age: Eocene.
Original description: Vozzhennikova (1960) 1967, p. 103-104
Theca divided by the transverse furrow into two almost equal parts. Epitheca triangular with a small apical outgrowth. Hypotheca trapeziform with a short, acutely pointed antapical horn. Lateral angles slightly drawn out, or not drawn out. Thecal sculpture reticulate or reticulate spinous. Thecal armour divided into plates (fields) by colored sutures, which permit some recognition of the shape and position of the plates but do not allow an exact assessment of their number. The plate formula is suggested tentatively as: on the epitheca, na + 3cp + (5 6) np; on the hypotheca, (5?) zd + 2cp' + na'. The pylome takes the place of the middle intermediate plate. Transverse furrow equatorial and approximately annulate although its ends are separated from each other by a short distance. The central field occurs on the hypotheca but does not extend to the antapex. It corresponds with the position of the longitudinal furrow. Pylome trapeziform.
Emended diagnosis: Lentin and Vozzhennikova, 1989, p. 223
Outline roundly pentagonal with two short antapical horns, of which the right is slightly reduced. The endophragm is thin and similar in outline to the periphragm. Periphragm very thin, ornamented with a delicate reticulum which may be reduced over the narrow pandasutural areas, particularly on the hypocyst. The reticulum is absent or very reduced on paraplates 2', 4', 2" and 6". Low, very delicate pore-like elements are present at the angles where the reticular elements join. The reticulum may be more strongly developed along the paraplate margins. The archeopyle is formed by the loss of the quadra 2a paraplate. The operculum is free or remains attached.
Size: Lectotype: length 103 µm, width 96 µm. Range: length 99-103 µm, width 94-120 µm.
-----------------------------------------------------------------------------------------------------------------------------------------------------
Emendation by Vasilyeva in Andreeva-Grigorovich et al., 2011, p.53:
Diagnosis. The peridinioid circumcavate cyst strongly compressed dorso-ventrally, with short apical, two lateral and two or one antapical horns. The antapical horns are usually unequal or may be strongly reduced. Epicyst is approximately equal to hypocyst. The endocyst is rounded pentagonal or rhombic in outline. The endophragm is thin, smooth. The pericel is narrow but the endophragm contacts occasionally with the periphragm. The pericyst is pentagonal or rhombic in outline. The periphragm is tabulated by the formula: 4′, 3a, 7′′, 5c, 5′′′, 2′′′′. The
periphragm has short intratabulated structures-processes (tubes) supporting the ectophragm. The ectophragm present by discrete reticulate fields (plates) according to the tabulation formula. Parasutural regions are not usually ornamented. The ventral plate (sulcus area) is ornamented by reticulate ectophragm. Periarcheopyle intercalàry, rounded, trapezium, elongate. The cingulum distinct.
Description. Peridiniod circumcavate cyst is compressed dorso-ventrally. The pericyst is pentagonal or rhombic in outline with short apical and lateral horns. The antapical horns are usually unequal and the left one is longer. The endocyst is large, roundly pentagonal to rhombical in outline. The endophragm is thin, smooth. The pericel is narrow. The periphragm is dense, smooth with short hollow tubes located intercalaryly and forming ectophragm. The ectophragm is presented by limited fields and plates doubling the cyst tabulation. The ectophragm plates are formed by the distinctive irregular reticulum which includes pore-like structures. These structures are distal ends of tubes which are connected by reticulum. The ectophragm plates are distinctly outlined so paratabulation formula of thes specias is clear.
This is Wetzelielloideae type: 4′, 3a, 7′′, 5c, 5′′′, 2′′′′ (fig. 20). The parasutural areas are not usually covered by reticulate ectophragm or contain rare reticulate ectophragm as sutural area between 1′′′′ and 2′′′′ plates on the ventral side of hypocyst. The ornamentation-free sutural zones make the distinctive paratabulation of this species. The archeopyle is formed by quadra middorsal anterior intercalar plate 2a. The archeopyle is round trapeziform or deltaform. The operculum is usually attached or free. The specimens with partly attached operculum (soleiform archeopyle) are not observed.
The paracingulum is distinct, indicated by transverse prominent furrow without the ectophragm. The paracingulum is sometimes ornamented with narrow reticulum on the dorsal side. Very thin, interrupted wrinkle is located in the center of transverse furrow. Central ventral plate (sulcal area) often has no ectophragm or has only its discrete elements. Two asymmetrical reticulate fields – one on the hypocyst another – on the epicyst can be sometimes observed. Small 2′, 4′ and narrow 2′′, 6′′ side plates are usually weakly differentiated. Well preserved specimens contain two prominent and reticulate plates on both apical sides of cyst (fig. 20). Some specimens include fine organic granules often located opposite to one of the plate.
Notes. The paratabulation pattern of Kisselevia ornata can be traced quite clearly in well-preserved material. In cases where the specimens are significantly flattened in the dorsoventral direction, the ornamented elements of the ectophragm on the ventral and dorsal sides of the cyst are practically combined, and it is almost impossible to examine the paratabulation of the cyst in a light microscope. So, in table. XLII, 1, 3a (Vozzhennikova, 1967) and text-figure 39 (Lentin, Vozzhennikova, 1990) show a pattern of Kisselevia ornata ornamentation, displaying paratabulation of the ventral side on the epicyst and the dorsal side on the hypocyst.
Comparison. According to J.K. Lentin and T.F. Vozzhennikova (Lentin, Vozzhennikova, 1989), the genus Kisselevia differs from the genus Charlesdowniea, newly isolated by the authors, in the two-layer structure of the cyst, i.e. the genus Kisselevia has an endo- and periphragm; the distinct network structure of this species belongs to the periphragm. Representatives of the newly formed genus Charles-downiea have three shells, endo, peri and ectophragm (Lentin, Vozhennikova, 1989). The materials we have studied on the species Kisselevia ornata allow us to confidently conclude that this species has three shells (Fig. 21). The structure of the walls is clearly visible on the lateral sides of the cyst and is confirmed by pore-like formations on the mesh structure of the ectophragm plates. The species Kisselevia ornata is the type species for the genus Kisselevia (Willams, Lentin, Fensome, 1989), therefore, the separation of the genus Charlesdowneia Lentin et Vozzhennikova, 1989 on this basis is not justified. The newly selected J.K. Lentin and T.F. Vozzhennikova's taxon of the genus level Charlesdownica Lentin et Vozzhennikova, 1989 (Lentin et Vozzhennikova, 1989; 1990) is not fundamentally different in structure from the type species of the genus Kisselevia Vozzhennikova, 1963, since it has a similar three-layer structure of the walls. Most likely, the species composition of the genus Kisselevia Vozzhennikova, 1967 should be revised.
Composition of the species. T.F. Vozzhennikova (1967) identified two forms within the species Kisselevia or-pata: K. ognata f. ornata and K. ornata f. reticulata. The first form has short spines in the corners of the cellular structure, which are clearly visible on the lateral sides of the cyst. The form K. ornata f. reticulata have no spines (Vozzhennikova, 1967). As a result of the revision (Lentin, Vozzhennikova, 1989), both forms were combined under a single species name, since this character has not been consistently traced. The specimen isolated by T.F. was chosen as the lectotype of K. ornata. Vozzhennikova (1967) as a holotype for the form K. ornata f. reticulata (Lentin, Vozzhennikova, 1989). The material we studied allows us to conclude that the presence or absence of spines depends solely on the preservation of the material. Specimens with damaged ectophragm appear mostly smooth. Well-preserved specimens have a distinct cellular structure on the lateral sides of the cyst. On them, “spines” are visible - outgrowths of the epiphragm that support the ectophragm. We therefore adhere to the opinion of J.K. Lentin regarding the association of two forms of K. ornata f. ornata and K. ornata f. reticulata under the general species name Kisselevia ornata (Lentin, Vozzhennikova, 1989).
Originally Kisselevia, subsequently (and now) Rhombodinium.
Holotype: Vozzhennikova, 1967, pl.44, fig.6, lost according to Lentin and Vozzhennikova (1989, p.223).
Lectotype: Vozzhennikova, 1967, pl.44, fig.1 (as holotype of Kisselevia ornata forma reticulata); Lentin and Vozzhennikova, 1989, pl.1, figs.1–2; Lentin and Vozzhennikova, 1990, pl.9, fig.1; designated by Lentin and Vozzhennikova (1989, p.223).
Age: Eocene.
Original description: Vozzhennikova (1960) 1967, p. 103-104
Theca divided by the transverse furrow into two almost equal parts. Epitheca triangular with a small apical outgrowth. Hypotheca trapeziform with a short, acutely pointed antapical horn. Lateral angles slightly drawn out, or not drawn out. Thecal sculpture reticulate or reticulate spinous. Thecal armour divided into plates (fields) by colored sutures, which permit some recognition of the shape and position of the plates but do not allow an exact assessment of their number. The plate formula is suggested tentatively as: on the epitheca, na + 3cp + (5 6) np; on the hypotheca, (5?) zd + 2cp' + na'. The pylome takes the place of the middle intermediate plate. Transverse furrow equatorial and approximately annulate although its ends are separated from each other by a short distance. The central field occurs on the hypotheca but does not extend to the antapex. It corresponds with the position of the longitudinal furrow. Pylome trapeziform.
Emended diagnosis: Lentin and Vozzhennikova, 1989, p. 223
Outline roundly pentagonal with two short antapical horns, of which the right is slightly reduced. The endophragm is thin and similar in outline to the periphragm. Periphragm very thin, ornamented with a delicate reticulum which may be reduced over the narrow pandasutural areas, particularly on the hypocyst. The reticulum is absent or very reduced on paraplates 2', 4', 2" and 6". Low, very delicate pore-like elements are present at the angles where the reticular elements join. The reticulum may be more strongly developed along the paraplate margins. The archeopyle is formed by the loss of the quadra 2a paraplate. The operculum is free or remains attached.
Size: Lectotype: length 103 µm, width 96 µm. Range: length 99-103 µm, width 94-120 µm.
-----------------------------------------------------------------------------------------------------------------------------------------------------
Emendation by Vasilyeva in Andreeva-Grigorovich et al., 2011, p.53:
Diagnosis. The peridinioid circumcavate cyst strongly compressed dorso-ventrally, with short apical, two lateral and two or one antapical horns. The antapical horns are usually unequal or may be strongly reduced. Epicyst is approximately equal to hypocyst. The endocyst is rounded pentagonal or rhombic in outline. The endophragm is thin, smooth. The pericel is narrow but the endophragm contacts occasionally with the periphragm. The pericyst is pentagonal or rhombic in outline. The periphragm is tabulated by the formula: 4′, 3a, 7′′, 5c, 5′′′, 2′′′′. The
periphragm has short intratabulated structures-processes (tubes) supporting the ectophragm. The ectophragm present by discrete reticulate fields (plates) according to the tabulation formula. Parasutural regions are not usually ornamented. The ventral plate (sulcus area) is ornamented by reticulate ectophragm. Periarcheopyle intercalàry, rounded, trapezium, elongate. The cingulum distinct.
Description. Peridiniod circumcavate cyst is compressed dorso-ventrally. The pericyst is pentagonal or rhombic in outline with short apical and lateral horns. The antapical horns are usually unequal and the left one is longer. The endocyst is large, roundly pentagonal to rhombical in outline. The endophragm is thin, smooth. The pericel is narrow. The periphragm is dense, smooth with short hollow tubes located intercalaryly and forming ectophragm. The ectophragm is presented by limited fields and plates doubling the cyst tabulation. The ectophragm plates are formed by the distinctive irregular reticulum which includes pore-like structures. These structures are distal ends of tubes which are connected by reticulum. The ectophragm plates are distinctly outlined so paratabulation formula of thes specias is clear.
This is Wetzelielloideae type: 4′, 3a, 7′′, 5c, 5′′′, 2′′′′ (fig. 20). The parasutural areas are not usually covered by reticulate ectophragm or contain rare reticulate ectophragm as sutural area between 1′′′′ and 2′′′′ plates on the ventral side of hypocyst. The ornamentation-free sutural zones make the distinctive paratabulation of this species. The archeopyle is formed by quadra middorsal anterior intercalar plate 2a. The archeopyle is round trapeziform or deltaform. The operculum is usually attached or free. The specimens with partly attached operculum (soleiform archeopyle) are not observed.
The paracingulum is distinct, indicated by transverse prominent furrow without the ectophragm. The paracingulum is sometimes ornamented with narrow reticulum on the dorsal side. Very thin, interrupted wrinkle is located in the center of transverse furrow. Central ventral plate (sulcal area) often has no ectophragm or has only its discrete elements. Two asymmetrical reticulate fields – one on the hypocyst another – on the epicyst can be sometimes observed. Small 2′, 4′ and narrow 2′′, 6′′ side plates are usually weakly differentiated. Well preserved specimens contain two prominent and reticulate plates on both apical sides of cyst (fig. 20). Some specimens include fine organic granules often located opposite to one of the plate.
Notes. The paratabulation pattern of Kisselevia ornata can be traced quite clearly in well-preserved material. In cases where the specimens are significantly flattened in the dorsoventral direction, the ornamented elements of the ectophragm on the ventral and dorsal sides of the cyst are practically combined, and it is almost impossible to examine the paratabulation of the cyst in a light microscope. So, in table. XLII, 1, 3a (Vozzhennikova, 1967) and text-figure 39 (Lentin, Vozzhennikova, 1990) show a pattern of Kisselevia ornata ornamentation, displaying paratabulation of the ventral side on the epicyst and the dorsal side on the hypocyst.
Comparison. According to J.K. Lentin and T.F. Vozzhennikova (Lentin, Vozzhennikova, 1989), the genus Kisselevia differs from the genus Charlesdowniea, newly isolated by the authors, in the two-layer structure of the cyst, i.e. the genus Kisselevia has an endo- and periphragm; the distinct network structure of this species belongs to the periphragm. Representatives of the newly formed genus Charles-downiea have three shells, endo, peri and ectophragm (Lentin, Vozhennikova, 1989). The materials we have studied on the species Kisselevia ornata allow us to confidently conclude that this species has three shells (Fig. 21). The structure of the walls is clearly visible on the lateral sides of the cyst and is confirmed by pore-like formations on the mesh structure of the ectophragm plates. The species Kisselevia ornata is the type species for the genus Kisselevia (Willams, Lentin, Fensome, 1989), therefore, the separation of the genus Charlesdowneia Lentin et Vozzhennikova, 1989 on this basis is not justified. The newly selected J.K. Lentin and T.F. Vozzhennikova's taxon of the genus level Charlesdownica Lentin et Vozzhennikova, 1989 (Lentin et Vozzhennikova, 1989; 1990) is not fundamentally different in structure from the type species of the genus Kisselevia Vozzhennikova, 1963, since it has a similar three-layer structure of the walls. Most likely, the species composition of the genus Kisselevia Vozzhennikova, 1967 should be revised.
Composition of the species. T.F. Vozzhennikova (1967) identified two forms within the species Kisselevia or-pata: K. ognata f. ornata and K. ornata f. reticulata. The first form has short spines in the corners of the cellular structure, which are clearly visible on the lateral sides of the cyst. The form K. ornata f. reticulata have no spines (Vozzhennikova, 1967). As a result of the revision (Lentin, Vozzhennikova, 1989), both forms were combined under a single species name, since this character has not been consistently traced. The specimen isolated by T.F. was chosen as the lectotype of K. ornata. Vozzhennikova (1967) as a holotype for the form K. ornata f. reticulata (Lentin, Vozzhennikova, 1989). The material we studied allows us to conclude that the presence or absence of spines depends solely on the preservation of the material. Specimens with damaged ectophragm appear mostly smooth. Well-preserved specimens have a distinct cellular structure on the lateral sides of the cyst. On them, “spines” are visible - outgrowths of the epiphragm that support the ectophragm. We therefore adhere to the opinion of J.K. Lentin regarding the association of two forms of K. ornata f. ornata and K. ornata f. reticulata under the general species name Kisselevia ornata (Lentin, Vozzhennikova, 1989).