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Ctenidodinium stauromatos
Ctenidodinium stauromatos (Sarjeant, 1976) Stover and Evitt, 1978
Originally Dichadogonyaulax, subsequently Ctenidodinium, thirdly Ctenidodinium?.
Tax. jr. synonym of Ctenidodinium (as Dichadogonyaulax) sellwoodii (Sarjeant, 1975) Stover and Evitt, 1978, according to Riley and Fenton, 1982. Sarjeant in Lentin and Williams, 1989, retained Ctenidodinium? (as Dichadogonyaulax) stauromatos as a separate species. 1990, agreed with Riley and Fenton, 1982.
Probable tax. jr. synonym of Ctenidodinium? rotundum Dodekova, 1975, according to Dodekova, 1990.
Questionable tax. jr. synonym of Ctenidodinium tenellum Deflandre, 1938, according to Woollam, 1980.
Questionable tax. jr. synonym of Ctenidodinium sellwoodii (Sarjeant, 1975) Stover and Evitt, 1978, according to Woollam, 1980).
Tax. jr. synonym of Ctenidodinium tenellum Deflandre, 1938, according to Courtinat, 1989. Lentin and Williams, 1989, following the advice of Sarjeant (pers. comm.), retained Ctenidodinium (as Dichadogonyaulax) stauromatos as a separate species.
Lentin and Williams, 1993, agreed with Sarjeant, 1978, that the name Ctenidodinium tenellum should be allowed to fall into disuse.
Benson, 1985, questionably retained this species in Ctenidodinium.
Holotype: Sarjeant, 1976, pl.2, fig.4
Locus typicus: Great Oolite Limestone, 2 metres above base. Ketton Grange Quarry, Ketton, Lincolnshire, England
Stratum typicum: Bathonian
Original diagnosis: Sarjeant, 1976, p. 10: Dichadogonyaulax stauromatos
Proximate dinoflagellate cysts of splleroidal to ovoidal shape, with a short apical prominence (not readily visible in many orientations). Reflected tabulation: 1 preapical, 4", 2-?4a, 6", ?c, 6""", 1p, 1""""; sulcus apparently not subdivided. Cingulum helicoid, laevo-rotatory; sulcus broad, extending from apex to antapex. Crests bounding plate-areas marked by low ridges bearing quite long spines. especially at crest nodes. Surface of cyst elaborLltely patterlled (as illustrated in text-fig. 1c). Archaeopyle epitractal, formed by schism at the anterior margin of the cingulum; the epitract. however, frequently breaks up by further schism along plate-area boundaries.
Original description: Sarjeant, 1976, p. 10: Dichadogonyaulax stauromatos
The apical horn is inconspicuous, apparently having the form of a blunt pyramid; it arises from a single small preapical plate-area. Plate-area 1" occupies the anterior prolongation of the sulcus; plate-areas 2" and 3" are larger and form the dorsal section of the apex. A tiny anterior intercalary plate of almost triangular shape (2a on text-fig.1A ) is present between the junction of the two latter plates and the anterior boulldary of platearea 3", Plate-area 4" is roughly quadrate in shape. Six precingular plate-areas are present.
All these features were seen on the paratype alld on other, less well-displayed epitracts (such as that of the holotype). However, only one complete, detached epitract--the paratype--was encountered and it is on this- specimen only that interpretation of the remaining features of the epitractal tabulatioll, as shown in Text-fig.1A, is based. There appear to be four anterior intercalary plates; one situated in the familiar position to the right of the cingulum (plate 6" being reduced in size to accommodate it) and one, already mentioned, on the dorsal surface. The other two anterior intercalary plate-areas are situated, respectively, between plate-area 1" and the apical series and between plate-areas 5"" and 6" and the apical series. Since such positions are unusual, the number of anterior intercalary plate-areas is only tentatively quoted in the diagnosis for this species, pending confirmation from other specimens of the constant presence of these two later plate-areas.
The cingulum appears to be moderately broad, though the schism along it makes this uncertain: the number of cingular plate-areas was not determined. The sulcus is broad and, in its hypotractal portion, distinctly sunken: it extends from apex to antapex and shows no exidence of subdivision into plate-areas.
The hypotract has the form of a truncated cone. Six postcingular plate-areas are developed; plateareas 1""" and 2""" are very much reduced to accommodate the posterior intercalary plate-area, plateareas 3""" and 5""" all very large, plate-area 6"" somewhat smaller. The single antapical plate-area is large, larger than that of D. norrisii (Pocock, 1970) Sarjeant, 1975b, but somewhat smaller than that typical of D. sellwoodii Sarjeant; the notch in its ventral margin, at intersection with the sulcus, is more marked than in either of those species.
The crest spines are of variable length. On the epitract in particular, spines at crest nodes are markedly longer, in some cases (e.g. the paratype) up to twice as long as those arising between nodes. On the hypotract this disparity in length is less evident, all spines being proportionately longer that the shorter epitractal spine. Spines are reduced or lacking on the margins of the sulcus. The spines are typically simple, acuminate or blunttipped: rarely they are knobbed or briefly bifurcate.
The ornamentation of the cyst surface resembles a negative infrareticulation, but there is no coherent pattern: instead, the elements consist of irregular, very narrow grooves, sometimes forming, rough ovoids or polygons which may or may not be interlinked (see Text-fig. IC). The cyst wall is of moderate thickness; the crests and spines are formed from the periphragm only.
Dimensions: Holotype: dorso-ventral cross-measurement on hypotract 39 Ám, lateral cross-measurement 41 Ám, spine length up to 5 Ám. Paratype (epitract): dorso-ventral cross measurement 41 Ám, lateral cross-measurement 43 Ám, nodal spines up to 6 Ám, internodal spines up to 3 Ám in length.
Range: Cross-measurements of hemicysts 34-43 Ám, length of spines c. 2-7 Ám.
Originally Dichadogonyaulax, subsequently Ctenidodinium, thirdly Ctenidodinium?.
Tax. jr. synonym of Ctenidodinium (as Dichadogonyaulax) sellwoodii (Sarjeant, 1975) Stover and Evitt, 1978, according to Riley and Fenton, 1982. Sarjeant in Lentin and Williams, 1989, retained Ctenidodinium? (as Dichadogonyaulax) stauromatos as a separate species. 1990, agreed with Riley and Fenton, 1982.
Probable tax. jr. synonym of Ctenidodinium? rotundum Dodekova, 1975, according to Dodekova, 1990.
Questionable tax. jr. synonym of Ctenidodinium tenellum Deflandre, 1938, according to Woollam, 1980.
Questionable tax. jr. synonym of Ctenidodinium sellwoodii (Sarjeant, 1975) Stover and Evitt, 1978, according to Woollam, 1980).
Tax. jr. synonym of Ctenidodinium tenellum Deflandre, 1938, according to Courtinat, 1989. Lentin and Williams, 1989, following the advice of Sarjeant (pers. comm.), retained Ctenidodinium (as Dichadogonyaulax) stauromatos as a separate species.
Lentin and Williams, 1993, agreed with Sarjeant, 1978, that the name Ctenidodinium tenellum should be allowed to fall into disuse.
Benson, 1985, questionably retained this species in Ctenidodinium.
Holotype: Sarjeant, 1976, pl.2, fig.4
Locus typicus: Great Oolite Limestone, 2 metres above base. Ketton Grange Quarry, Ketton, Lincolnshire, England
Stratum typicum: Bathonian
Original diagnosis: Sarjeant, 1976, p. 10: Dichadogonyaulax stauromatos
Proximate dinoflagellate cysts of splleroidal to ovoidal shape, with a short apical prominence (not readily visible in many orientations). Reflected tabulation: 1 preapical, 4", 2-?4a, 6", ?c, 6""", 1p, 1""""; sulcus apparently not subdivided. Cingulum helicoid, laevo-rotatory; sulcus broad, extending from apex to antapex. Crests bounding plate-areas marked by low ridges bearing quite long spines. especially at crest nodes. Surface of cyst elaborLltely patterlled (as illustrated in text-fig. 1c). Archaeopyle epitractal, formed by schism at the anterior margin of the cingulum; the epitract. however, frequently breaks up by further schism along plate-area boundaries.
Original description: Sarjeant, 1976, p. 10: Dichadogonyaulax stauromatos
The apical horn is inconspicuous, apparently having the form of a blunt pyramid; it arises from a single small preapical plate-area. Plate-area 1" occupies the anterior prolongation of the sulcus; plate-areas 2" and 3" are larger and form the dorsal section of the apex. A tiny anterior intercalary plate of almost triangular shape (2a on text-fig.1A ) is present between the junction of the two latter plates and the anterior boulldary of platearea 3", Plate-area 4" is roughly quadrate in shape. Six precingular plate-areas are present.
All these features were seen on the paratype alld on other, less well-displayed epitracts (such as that of the holotype). However, only one complete, detached epitract--the paratype--was encountered and it is on this- specimen only that interpretation of the remaining features of the epitractal tabulatioll, as shown in Text-fig.1A, is based. There appear to be four anterior intercalary plates; one situated in the familiar position to the right of the cingulum (plate 6" being reduced in size to accommodate it) and one, already mentioned, on the dorsal surface. The other two anterior intercalary plate-areas are situated, respectively, between plate-area 1" and the apical series and between plate-areas 5"" and 6" and the apical series. Since such positions are unusual, the number of anterior intercalary plate-areas is only tentatively quoted in the diagnosis for this species, pending confirmation from other specimens of the constant presence of these two later plate-areas.
The cingulum appears to be moderately broad, though the schism along it makes this uncertain: the number of cingular plate-areas was not determined. The sulcus is broad and, in its hypotractal portion, distinctly sunken: it extends from apex to antapex and shows no exidence of subdivision into plate-areas.
The hypotract has the form of a truncated cone. Six postcingular plate-areas are developed; plateareas 1""" and 2""" are very much reduced to accommodate the posterior intercalary plate-area, plateareas 3""" and 5""" all very large, plate-area 6"" somewhat smaller. The single antapical plate-area is large, larger than that of D. norrisii (Pocock, 1970) Sarjeant, 1975b, but somewhat smaller than that typical of D. sellwoodii Sarjeant; the notch in its ventral margin, at intersection with the sulcus, is more marked than in either of those species.
The crest spines are of variable length. On the epitract in particular, spines at crest nodes are markedly longer, in some cases (e.g. the paratype) up to twice as long as those arising between nodes. On the hypotract this disparity in length is less evident, all spines being proportionately longer that the shorter epitractal spine. Spines are reduced or lacking on the margins of the sulcus. The spines are typically simple, acuminate or blunttipped: rarely they are knobbed or briefly bifurcate.
The ornamentation of the cyst surface resembles a negative infrareticulation, but there is no coherent pattern: instead, the elements consist of irregular, very narrow grooves, sometimes forming, rough ovoids or polygons which may or may not be interlinked (see Text-fig. IC). The cyst wall is of moderate thickness; the crests and spines are formed from the periphragm only.
Dimensions: Holotype: dorso-ventral cross-measurement on hypotract 39 Ám, lateral cross-measurement 41 Ám, spine length up to 5 Ám. Paratype (epitract): dorso-ventral cross measurement 41 Ám, lateral cross-measurement 43 Ám, nodal spines up to 6 Ám, internodal spines up to 3 Ám in length.
Range: Cross-measurements of hemicysts 34-43 Ám, length of spines c. 2-7 Ám.