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Dichadogonyaulax cristata
Dichadogonyaulax cristata (Horowitz, 1975, p.25, pl.1, fig.8) Fensome and Sarjeant, 1982, p.56. Emendation: Wheeler and Sarjeant, 1990, p.306–307, as Dichadogonyaulax cristata. Holotype: Horowitz, 1975, pl.1, fig.8; Fensome et al., 1995, fig.1
— p.1479; lost according to Sarjeant (1988, p.177). Neotype: Wheeler and Sarjeant, 1990, pl.8, fig.4; text-figs.10a– b; Fensome et al., 1995, fig.1 — p.1479; designated by Wheeler and Sarjeant (1992, p.382). Originally Brotzenia, subsequently Ctenidodinium?, thirdly (and now) Dichadogonyaulax. Taxonomic senior synonym: Ctenidodinium ornatum, according to Woollam (1983, p.190) — however, Sarjeant (1988, p.180) retained Dichadogonyaulax cristata. Age: Late Triassic (probably not in place).
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Original description (Horowitz, 1975) Not yet translated from French
Holotype: Slide P 426, Zohar 8 Well, depth 1893 m, Upper Triassic, Southern Israel.
Description: Identical to the genus.
Average dimensions: 10 x 50 l, 20 specimens.
Name origin: Based on the crested appearance of the cyst sutures.
Genus description: Diagnosis: Proximate dinoflagellate cyst. Ovoid to hemispherical, ellipsoidal shape. Clear, slightly helical equatorial cingulum. Very distinct tabulation, sutures bearing a crest approximately 4-5 l in width.
Note: Brotzenia is distinguished by its broad, low-lying shape. No other known genus of dinoflagellates appears to bear a close resemblance to it. Type species: Brotzenia cristata n.sp., Upper Triassic, Israel.
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Emendation (Wheeler and Sarjeant, 1990):
Emended Diagnosis: A species of Dichadogonyaulax with a broadly subspherical central body, commonly seen as polar views of the isolated hypotractor, more rarely, epitract. Surface of phragma finely scabrate. Parasutural ornament highly variable; on many specimens there is little indication of paratabulation, especially on the epitract, but the opposite extreme is seen in specimens having crests of, low to moderate height and displaying a wide range of morphologies, including undulate to echinate or acanthate types and reaching extremes in which the echinae are very high and narrow (1 um x 10 um). Cingulum weakly laevoro tatory. Sulcus conined to the hypotract.
Paratabulation gonyaulacoid; formula 1pr, 4', 2a, 6", 6c?, 6'", 1p, 1pv, 1"", Paraplate 1'" is small and elongate, 1p short and broad, and 6'" broad and polygonal.
Anterior and posterior margins of cingulum generally both marked by crests giving rise irregularly to broad-based, acuminate spines; however, the crest on the anterior margin may be less pronouncedly developed than that on the posterior margin. Paraplate boundaries against the sulcus marked only by lines. Archaeopyie epitractal, Type tAtP; line of schism immediately anterior to the cingulum. Material: 112 specimens, all from the Dalichai Formation, found in samples 1265, 1266 and 1267. Particularly abundant in 1265.
Remarks: Horowitz described the new genus Brotzenia (p. 25) which contained the single species B. cristata. Stover and Evitt (1978, p. 204) considered the genus Brotzenia to be a junior synonym of Ctenidodinium and provisionally transferred its type species to that genus; subsequently, Fensome and Sarjeant (1982, p. 56) placed it firmly in Dichadogonyaulax. Lentin and Williams (1985, p. 41, 82, 105) considered
alternative generic placements but expressed no clear judgement. Later (1985, p. 105) they returned it doubtfully to Ctenidodinium; however, following Woollam's revision (1983, p. 193) of that genus, such a placement is clearly inappropriate. Horowitz's figure of the holotype, now lost (see Sarjeant, 1988, p. 177), shows an isolated hypotract (incorrectly oriented). Although found in a borehole assemblage from the Upper Triassic of southern Israel, it is believed not to be indigenous, but to represent contamination from a Middle Jurassic source. Consequently, since the type horizon cannot be determined, we consider it acceptable to choose neotypes from an entirely different locality within the same, very broad geographic area.
Dichadogonyaulax chondra (Drugg, 1978) Courtinat, 1989 is comparable, but has only lines of granules to mark septa between paraplates. The paratabulation of its hypotract has not been fully determined, but appears similar. It may well prove to fall within the range of variation of D. cristata and to merit treatment 'as a junior synonym.
D. cristata differs from D. norrisii (Pocock, 1972) Sarjeant, 1974 in the proportionately larger size of the apical and antapical paraplates, the smaller size and more elongate shape of paraplate 1'", the presence of a posterior ventral plate, the lack of accessory Sutures (though Jansonius, 1986, p. 206, states these are not prominent)
and the more complex crest ornamentation. It differs from D. sellwoodi Sarjeant, 1974, in being subspheroidal rather than polygonal in shape and in the smaller size of its antapical paraplate (that of D. sellwoodii being unusually large and almost square). It is likely that D. cristata forms the central member of a plexus of variation in which D. pocockii and D. sellwoodii are morphologically more extreme members. However, since the precise stratigraphical relationships of these species are not yet clear, their evolutionary relationships must remain a matter for speculation.
— p.1479; lost according to Sarjeant (1988, p.177). Neotype: Wheeler and Sarjeant, 1990, pl.8, fig.4; text-figs.10a– b; Fensome et al., 1995, fig.1 — p.1479; designated by Wheeler and Sarjeant (1992, p.382). Originally Brotzenia, subsequently Ctenidodinium?, thirdly (and now) Dichadogonyaulax. Taxonomic senior synonym: Ctenidodinium ornatum, according to Woollam (1983, p.190) — however, Sarjeant (1988, p.180) retained Dichadogonyaulax cristata. Age: Late Triassic (probably not in place).
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Original description (Horowitz, 1975) Not yet translated from French
Holotype: Slide P 426, Zohar 8 Well, depth 1893 m, Upper Triassic, Southern Israel.
Description: Identical to the genus.
Average dimensions: 10 x 50 l, 20 specimens.
Name origin: Based on the crested appearance of the cyst sutures.
Genus description: Diagnosis: Proximate dinoflagellate cyst. Ovoid to hemispherical, ellipsoidal shape. Clear, slightly helical equatorial cingulum. Very distinct tabulation, sutures bearing a crest approximately 4-5 l in width.
Note: Brotzenia is distinguished by its broad, low-lying shape. No other known genus of dinoflagellates appears to bear a close resemblance to it. Type species: Brotzenia cristata n.sp., Upper Triassic, Israel.
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Emendation (Wheeler and Sarjeant, 1990):
Emended Diagnosis: A species of Dichadogonyaulax with a broadly subspherical central body, commonly seen as polar views of the isolated hypotractor, more rarely, epitract. Surface of phragma finely scabrate. Parasutural ornament highly variable; on many specimens there is little indication of paratabulation, especially on the epitract, but the opposite extreme is seen in specimens having crests of, low to moderate height and displaying a wide range of morphologies, including undulate to echinate or acanthate types and reaching extremes in which the echinae are very high and narrow (1 um x 10 um). Cingulum weakly laevoro tatory. Sulcus conined to the hypotract.
Paratabulation gonyaulacoid; formula 1pr, 4', 2a, 6", 6c?, 6'", 1p, 1pv, 1"", Paraplate 1'" is small and elongate, 1p short and broad, and 6'" broad and polygonal.
Anterior and posterior margins of cingulum generally both marked by crests giving rise irregularly to broad-based, acuminate spines; however, the crest on the anterior margin may be less pronouncedly developed than that on the posterior margin. Paraplate boundaries against the sulcus marked only by lines. Archaeopyie epitractal, Type tAtP; line of schism immediately anterior to the cingulum. Material: 112 specimens, all from the Dalichai Formation, found in samples 1265, 1266 and 1267. Particularly abundant in 1265.
Remarks: Horowitz described the new genus Brotzenia (p. 25) which contained the single species B. cristata. Stover and Evitt (1978, p. 204) considered the genus Brotzenia to be a junior synonym of Ctenidodinium and provisionally transferred its type species to that genus; subsequently, Fensome and Sarjeant (1982, p. 56) placed it firmly in Dichadogonyaulax. Lentin and Williams (1985, p. 41, 82, 105) considered
alternative generic placements but expressed no clear judgement. Later (1985, p. 105) they returned it doubtfully to Ctenidodinium; however, following Woollam's revision (1983, p. 193) of that genus, such a placement is clearly inappropriate. Horowitz's figure of the holotype, now lost (see Sarjeant, 1988, p. 177), shows an isolated hypotract (incorrectly oriented). Although found in a borehole assemblage from the Upper Triassic of southern Israel, it is believed not to be indigenous, but to represent contamination from a Middle Jurassic source. Consequently, since the type horizon cannot be determined, we consider it acceptable to choose neotypes from an entirely different locality within the same, very broad geographic area.
Dichadogonyaulax chondra (Drugg, 1978) Courtinat, 1989 is comparable, but has only lines of granules to mark septa between paraplates. The paratabulation of its hypotract has not been fully determined, but appears similar. It may well prove to fall within the range of variation of D. cristata and to merit treatment 'as a junior synonym.
D. cristata differs from D. norrisii (Pocock, 1972) Sarjeant, 1974 in the proportionately larger size of the apical and antapical paraplates, the smaller size and more elongate shape of paraplate 1'", the presence of a posterior ventral plate, the lack of accessory Sutures (though Jansonius, 1986, p. 206, states these are not prominent)
and the more complex crest ornamentation. It differs from D. sellwoodi Sarjeant, 1974, in being subspheroidal rather than polygonal in shape and in the smaller size of its antapical paraplate (that of D. sellwoodii being unusually large and almost square). It is likely that D. cristata forms the central member of a plexus of variation in which D. pocockii and D. sellwoodii are morphologically more extreme members. However, since the precise stratigraphical relationships of these species are not yet clear, their evolutionary relationships must remain a matter for speculation.