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Dingodinium albertii
From Fensome et al., 2019:
Dingodinium? albertii Sarjeant, 1966c, p.210–211, pl.21, fig.3; pl.23, fig.1. Emendation: Pestchevitskaya, 2018, p.95,97. Holotype: Sarjeant, 1966c, pl.21, fig.3. Taxonomic senior synonym: Dingodinium cerviculum, according to Haskell (1970, p.60) and Khowaja-Ateequzzaman et al. (1990, p.274) — however, Pestchevitskaya (2018, p.95) retained the two species separately. Questionable assignment: Sarjeant (1966c, p.210); however, Duxbury (1977, p.29) retained this species in Dingodinium without question. Age: early Barremian.
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Original diagnosis: Sarjeant 1966, p. 210
A cavate dinoflagellate cyst with thin outer shell, irregularly ovoidal to subpolygonal in outline, drawn out into a blunt, stout apical horn; inner body thin, spheroidal, with dense cover of large, pointed tubercles. Outer shell possess clear helicoid cingulum marked by folds or ridges; further folds or ridges, less prominent, define tabulation. Intercalary archaeopyle apparently formed.
Dimensions: Holotype: over all length 66 µm, breadth 52 µm, length of inner body 40 µm, breadth 45 µm. Paratype: overall length 57 µm, breadth 48 µm, length of inner body 37 µm, breadth 39 µm. Overall lengths 50-66 µm, breadths 37.5-52 µm.
Original description: Sarjeant 1966, p. 210-211
The outer shell is basically ovoidal to polygonal; but it is extremely thin and is deformed in variable fashion in the seven specimens examined. It bears folds or ridges which simulate a tabulation and is drawn out into a short apical horn with a blunt, slightly rounded tip. The inner body is spheroidal and typically broader than long. The periphragm is smooth; the endophragm is smooth or very minutely granular. The latter bears a moderately dense cover of tubercles; these are conical and do not exceed 1 µm in height. There is some suggestion that the tubercles show a degree of alignment, but this could not be confirmed. The archaeopyle is situated on the upper flanks of the epitract, in a position corresponding to the intercalary archaeopyle described by Evitt (1961, text-fig. 7). The tabulation pattern was not sufficiently clear, however, to permit certainty as to whether the archaeopyle corresponded in position to an intercalary plate; it is equally possible to visualize formation by loss of the equivalent of the anterior part only of a precingular plate.
Affinities:
Sarjeant, 1966, p. 211
Dingodinium? albertii differs from all other described species in the realtive shapes of outer shell and inner body and in the ornamentation of the inner body.
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Emendation by Pestchevitskaya, 2018 (p. 683, 685, 688):
Diagnosis emended. Proximate, camocavate dinocysts with combination archeopyle pr[tA1‒4]ta1–3. Pericyst rounded with short and wide conical apical horn, endocyst rounded. Periphragm transparent, smooth, endophragm thicker, spinous or granulate. Pericoel wide. Tabulation of cladopixiaceous type, expressed by sutural features, stressed by folds and low psilate crests on pericyst, formula 1pr, 4', 3a, 7'', Xc, 6''', 1p, 1''''. Cingulum and sulcus expressed by sutural features on endocyst, by folds and low psilate crests on pericyst.
Description (Fig. 4a). The dinocysts are proximate, camocavate. The pericyst is rounded, almost as wide as long, in the apical area forming a short widelyconical horn; sometimes it is very short and has a smoothened transition to the main cyst body on the ventral side. The endocyst is smaller, spherical, and sometimes slightly ovoid. The pericoel is wide, the maximum width is nearer the antapical area on the ventral and lateral sides, especially in the region of postcingular plates 5'''–6'''. On the dorsal side, in the region of intercalary plates, the pericoel is very narrow or can be absent. The periphragm is transparent, thin, easily folded and generally smooth, but can be granulate near the apical horn. The endophragm is denser, ornamented by relatively large spines or granules. The tabulation is of cladopixiaceous type, expressed on the endocyst by sutural features, and on the pericyst by low smooth septa, often emphasized by folds. In the apical area, the crests become very low, sometimes tabulation is expressed by sutural features. The tabulation formula is: 1pr, 4', 3a, 7'', Xc, 6''', 1p, 1''''. The cingulum and sulcus are delimited on the pericyst by crests and are usually emphasized by folds; and on the endocyst, by sutural features.
Comparison. The species D. albertii is distinguished from the most closely similar species D. cerviculum Cookson et Eisenack, 1958 by the spherical pericyst and endocyst and the short apical horn, less elongated pericyst and endocyst, and the shorter and wider horn. In its general morphology, D. albertii is very similar to D. europaeum (Sarjeant, 1985), D. cooksoniae (Pocock, 1972), and D. minutum (Dodekova, 1975), although the first of the three has a smooth diaphragm, and the second has a narrow pericoel and pericyst and endocyst somewhat stretched in height. D. minutum is distinct in the relatively deep cingular notch, and also the endocyst ornamentation with densely spaced granules and pillars, which are sometimes connected by crests to form reticular ornamentation, which is not observed in D. albertii.
Remarks. The revision of the diagnosis is based on new data on tabulation, which support the partiform structure of the cyst with features characteristic of the family Cladopixiaceae. The tabulation formula and archeopyle morphology are emended. It is shown that the pericyst carries crests, which emphasize the tabulation. Some authors considered D. albertii as a junior synonym of D. cerviculum, arguing that the morphological differences are insignificant, and supposing the existence of intermediate forms (Haskell, 1969; Mehrotra and Sarjeant, 1984, etc.). The author’s material from Siberia and the Russian Platform supports the point of view of Australian palynologists, according to whom these species are nevertheless clearly morphologically distinct in the shape of the apical horn, pericyst, and endocyst (Stover and Helby, 1987a). It is noteworthy that the present author has previously assigned the morphotypes with an isometric cyst and a short horn to D. minutum (Pestchevitskaya, 2010), following the broad understanding of its morphology of Poulsen (1996). He included in this species forms that closely resemble D. albertii in general morphology and endocyst ornamentation. The archeopyle type was considered to be a distinguishing feature: apical for D. minutum as interpreted by Dodekova (1975) and intercalary for D. albertii in Sarjeant’s (1966) opinion. However, the published detailed morphological studies support the presence of intercalary plates in representatives of the genus Dingodinium and their presence in the combination archeopyle of composite type (Stover and Helby, 1987a; Pestchevitskaya, 2010). As a result, within the same species, the archeopyle can look intercalary (when only intercalary plates are lost), apical (when all are lost), or combination (when plates are not completely torn off and it is possible to establish the detailed morphology of the operculum). A review of the morphology of the Jurassic and Early Cretaceous members of the genus Dingodinium shows that D. minutum is readily distinguished by the presence of a relatively deep cingular notch and by the specific ornamentation of the endocyst (Fig. 3), whereas forms with a short apical horn and isometric cyst and a wide pericoel should be assigned to D. albertii. Another debatable issue is the separation of the species D. albertii and D. jurassicum. The presence in some specimens with a wide pericoel and isometric shape of peri- and endocyst of a very short and weakly expressed apical horn led some authors (Riding et al., 1999, 2017) to assign those specimens to the latter species. However, the study of a new material showed that it possible to construct a series of intermediate forms from these morphotypes to the typical representatives of D. albertii (Pl. 8, figs. 1–6, 15–17, 19; Fig. 4a). Note that a series of intermediate forms from these morphotypes to the typical representatives of D. jurassicum with an ellipsoid endocyst and pericyst with no apical horn was not observed.
Dingodinium? albertii Sarjeant, 1966c, p.210–211, pl.21, fig.3; pl.23, fig.1. Emendation: Pestchevitskaya, 2018, p.95,97. Holotype: Sarjeant, 1966c, pl.21, fig.3. Taxonomic senior synonym: Dingodinium cerviculum, according to Haskell (1970, p.60) and Khowaja-Ateequzzaman et al. (1990, p.274) — however, Pestchevitskaya (2018, p.95) retained the two species separately. Questionable assignment: Sarjeant (1966c, p.210); however, Duxbury (1977, p.29) retained this species in Dingodinium without question. Age: early Barremian.
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Original diagnosis: Sarjeant 1966, p. 210
A cavate dinoflagellate cyst with thin outer shell, irregularly ovoidal to subpolygonal in outline, drawn out into a blunt, stout apical horn; inner body thin, spheroidal, with dense cover of large, pointed tubercles. Outer shell possess clear helicoid cingulum marked by folds or ridges; further folds or ridges, less prominent, define tabulation. Intercalary archaeopyle apparently formed.
Dimensions: Holotype: over all length 66 µm, breadth 52 µm, length of inner body 40 µm, breadth 45 µm. Paratype: overall length 57 µm, breadth 48 µm, length of inner body 37 µm, breadth 39 µm. Overall lengths 50-66 µm, breadths 37.5-52 µm.
Original description: Sarjeant 1966, p. 210-211
The outer shell is basically ovoidal to polygonal; but it is extremely thin and is deformed in variable fashion in the seven specimens examined. It bears folds or ridges which simulate a tabulation and is drawn out into a short apical horn with a blunt, slightly rounded tip. The inner body is spheroidal and typically broader than long. The periphragm is smooth; the endophragm is smooth or very minutely granular. The latter bears a moderately dense cover of tubercles; these are conical and do not exceed 1 µm in height. There is some suggestion that the tubercles show a degree of alignment, but this could not be confirmed. The archaeopyle is situated on the upper flanks of the epitract, in a position corresponding to the intercalary archaeopyle described by Evitt (1961, text-fig. 7). The tabulation pattern was not sufficiently clear, however, to permit certainty as to whether the archaeopyle corresponded in position to an intercalary plate; it is equally possible to visualize formation by loss of the equivalent of the anterior part only of a precingular plate.
Affinities:
Sarjeant, 1966, p. 211
Dingodinium? albertii differs from all other described species in the realtive shapes of outer shell and inner body and in the ornamentation of the inner body.
---------------------------------------------------------------------------------------------------
Emendation by Pestchevitskaya, 2018 (p. 683, 685, 688):
Diagnosis emended. Proximate, camocavate dinocysts with combination archeopyle pr[tA1‒4]ta1–3. Pericyst rounded with short and wide conical apical horn, endocyst rounded. Periphragm transparent, smooth, endophragm thicker, spinous or granulate. Pericoel wide. Tabulation of cladopixiaceous type, expressed by sutural features, stressed by folds and low psilate crests on pericyst, formula 1pr, 4', 3a, 7'', Xc, 6''', 1p, 1''''. Cingulum and sulcus expressed by sutural features on endocyst, by folds and low psilate crests on pericyst.
Description (Fig. 4a). The dinocysts are proximate, camocavate. The pericyst is rounded, almost as wide as long, in the apical area forming a short widelyconical horn; sometimes it is very short and has a smoothened transition to the main cyst body on the ventral side. The endocyst is smaller, spherical, and sometimes slightly ovoid. The pericoel is wide, the maximum width is nearer the antapical area on the ventral and lateral sides, especially in the region of postcingular plates 5'''–6'''. On the dorsal side, in the region of intercalary plates, the pericoel is very narrow or can be absent. The periphragm is transparent, thin, easily folded and generally smooth, but can be granulate near the apical horn. The endophragm is denser, ornamented by relatively large spines or granules. The tabulation is of cladopixiaceous type, expressed on the endocyst by sutural features, and on the pericyst by low smooth septa, often emphasized by folds. In the apical area, the crests become very low, sometimes tabulation is expressed by sutural features. The tabulation formula is: 1pr, 4', 3a, 7'', Xc, 6''', 1p, 1''''. The cingulum and sulcus are delimited on the pericyst by crests and are usually emphasized by folds; and on the endocyst, by sutural features.
Comparison. The species D. albertii is distinguished from the most closely similar species D. cerviculum Cookson et Eisenack, 1958 by the spherical pericyst and endocyst and the short apical horn, less elongated pericyst and endocyst, and the shorter and wider horn. In its general morphology, D. albertii is very similar to D. europaeum (Sarjeant, 1985), D. cooksoniae (Pocock, 1972), and D. minutum (Dodekova, 1975), although the first of the three has a smooth diaphragm, and the second has a narrow pericoel and pericyst and endocyst somewhat stretched in height. D. minutum is distinct in the relatively deep cingular notch, and also the endocyst ornamentation with densely spaced granules and pillars, which are sometimes connected by crests to form reticular ornamentation, which is not observed in D. albertii.
Remarks. The revision of the diagnosis is based on new data on tabulation, which support the partiform structure of the cyst with features characteristic of the family Cladopixiaceae. The tabulation formula and archeopyle morphology are emended. It is shown that the pericyst carries crests, which emphasize the tabulation. Some authors considered D. albertii as a junior synonym of D. cerviculum, arguing that the morphological differences are insignificant, and supposing the existence of intermediate forms (Haskell, 1969; Mehrotra and Sarjeant, 1984, etc.). The author’s material from Siberia and the Russian Platform supports the point of view of Australian palynologists, according to whom these species are nevertheless clearly morphologically distinct in the shape of the apical horn, pericyst, and endocyst (Stover and Helby, 1987a). It is noteworthy that the present author has previously assigned the morphotypes with an isometric cyst and a short horn to D. minutum (Pestchevitskaya, 2010), following the broad understanding of its morphology of Poulsen (1996). He included in this species forms that closely resemble D. albertii in general morphology and endocyst ornamentation. The archeopyle type was considered to be a distinguishing feature: apical for D. minutum as interpreted by Dodekova (1975) and intercalary for D. albertii in Sarjeant’s (1966) opinion. However, the published detailed morphological studies support the presence of intercalary plates in representatives of the genus Dingodinium and their presence in the combination archeopyle of composite type (Stover and Helby, 1987a; Pestchevitskaya, 2010). As a result, within the same species, the archeopyle can look intercalary (when only intercalary plates are lost), apical (when all are lost), or combination (when plates are not completely torn off and it is possible to establish the detailed morphology of the operculum). A review of the morphology of the Jurassic and Early Cretaceous members of the genus Dingodinium shows that D. minutum is readily distinguished by the presence of a relatively deep cingular notch and by the specific ornamentation of the endocyst (Fig. 3), whereas forms with a short apical horn and isometric cyst and a wide pericoel should be assigned to D. albertii. Another debatable issue is the separation of the species D. albertii and D. jurassicum. The presence in some specimens with a wide pericoel and isometric shape of peri- and endocyst of a very short and weakly expressed apical horn led some authors (Riding et al., 1999, 2017) to assign those specimens to the latter species. However, the study of a new material showed that it possible to construct a series of intermediate forms from these morphotypes to the typical representatives of D. albertii (Pl. 8, figs. 1–6, 15–17, 19; Fig. 4a). Note that a series of intermediate forms from these morphotypes to the typical representatives of D. jurassicum with an ellipsoid endocyst and pericyst with no apical horn was not observed.