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Cryptarchaeodinium calcaratum
Cryptarchaeodinium calcaratum Deflandre, 1939; emend. Gitmez, 1970
Holotype: Deflandre, 1939, pl.6, fig.6
Locus typicus: Orbagnoux, Jura Mountains, france
Stratum typicum: Kimmeridgian
Original diagnosis: Deflandre, 1939, p.145
Emended diagnosis: Gitmez, 1970, p.246
A Cryptarchaeodinium having a small, almost spherical shell, without either an apical or antapical process. Tabulation 4, 6", 6c, 7""", 2p, 1"""". Plate boundaries bear short spiny crests. Cingulum almost equatorial, strongly spiral, laevorotatory. Shell wall thin, surface granular. Large precingular archaeopyle formed by loss of plate 3".
Dimensions: Holotype: overall length 40 Ám, breadth 40 Ám; length of the spines 3 Ám. Figured specimen: overall length 34 Ám, breadth 33 Ám; spines length 2-3 Ám.
Description: Gitmez, 1970, p.247
Theca almost spherical, but having a somewhat polygonal appearance because of the angularly set spine rows on the plate boundaries. Four apical plates are present. Plate 1" is the largest; the boundary between plates 1" and 4" was not clear. The six precingular plates, together with the apical plates form the epitract; there is no anterior intercalary plate. Plate 1" is reduced to accommodate of plate 2". Plates 2", 3", 4" and 5" are more or less uniform in size and shape, but plate 6" is different in shape because of the broadening sulcus.
The cingulum is occupied by six plates of moderate size. The sulcus extends onto the epitract and the hypotract, from apex to antapex; it is narrow in its middle portion, being broad in its anterior and posterior portions.
Seven postcingular plates of variable size and shape are present. Plates 1""" 6""" and 7""" are small, whereas plate 4""" is largest of all the plates of the shell. Two posterior intercalary plates are located on the two sides of the posterior end of the sulcus. The single antapical plate 1"""" is a rather small plate.
Affinities:
Gitmez, 1970, p.247-248: The diagnosis of C. calcaratum is emended to include the presence of the archaeopyle and the detail of the tabulation. This study was based on a single but excellently preserved specimen from the Kimmeridge Clay of Stretham.
Deflandre first observed C. calcaratum in the assemblages from Orbagnoux in 1939 a fuller diagnosis was given in 1941. The Stretham specimen corresponds closely to the holotype, differing only in the number of the apical plates, which are hesitantly mentioned as 4 in number by Deflandre (1941), and in the presence of the precingular archaeopyle.
In 1957, Downie observed a very similar specimen in the Kimmeridge Clay of Dorset, which he mentioned and figured as Cryptarchaeodinium sp. Although it was similar in many respects to this genus, it differed in the presence of an anterior intercalary plate ra and of several very small plates between the plates Ia and 6". The position of the antapical plate 1"""" and the sutures were also different. Eisenack incorrectly cited Downie"s species as C. calcaratum in his " Katalog der Fossilen Dinoflagellaten, Hystrichospharen und verwandten Mikrofossilen" in 1964. On the basis of Downie"s figure and description, this is unjustified.
Holotype: Deflandre, 1939, pl.6, fig.6
Locus typicus: Orbagnoux, Jura Mountains, france
Stratum typicum: Kimmeridgian
Original diagnosis: Deflandre, 1939, p.145
Emended diagnosis: Gitmez, 1970, p.246
A Cryptarchaeodinium having a small, almost spherical shell, without either an apical or antapical process. Tabulation 4, 6", 6c, 7""", 2p, 1"""". Plate boundaries bear short spiny crests. Cingulum almost equatorial, strongly spiral, laevorotatory. Shell wall thin, surface granular. Large precingular archaeopyle formed by loss of plate 3".
Dimensions: Holotype: overall length 40 Ám, breadth 40 Ám; length of the spines 3 Ám. Figured specimen: overall length 34 Ám, breadth 33 Ám; spines length 2-3 Ám.
Description: Gitmez, 1970, p.247
Theca almost spherical, but having a somewhat polygonal appearance because of the angularly set spine rows on the plate boundaries. Four apical plates are present. Plate 1" is the largest; the boundary between plates 1" and 4" was not clear. The six precingular plates, together with the apical plates form the epitract; there is no anterior intercalary plate. Plate 1" is reduced to accommodate of plate 2". Plates 2", 3", 4" and 5" are more or less uniform in size and shape, but plate 6" is different in shape because of the broadening sulcus.
The cingulum is occupied by six plates of moderate size. The sulcus extends onto the epitract and the hypotract, from apex to antapex; it is narrow in its middle portion, being broad in its anterior and posterior portions.
Seven postcingular plates of variable size and shape are present. Plates 1""" 6""" and 7""" are small, whereas plate 4""" is largest of all the plates of the shell. Two posterior intercalary plates are located on the two sides of the posterior end of the sulcus. The single antapical plate 1"""" is a rather small plate.
Affinities:
Gitmez, 1970, p.247-248: The diagnosis of C. calcaratum is emended to include the presence of the archaeopyle and the detail of the tabulation. This study was based on a single but excellently preserved specimen from the Kimmeridge Clay of Stretham.
Deflandre first observed C. calcaratum in the assemblages from Orbagnoux in 1939 a fuller diagnosis was given in 1941. The Stretham specimen corresponds closely to the holotype, differing only in the number of the apical plates, which are hesitantly mentioned as 4 in number by Deflandre (1941), and in the presence of the precingular archaeopyle.
In 1957, Downie observed a very similar specimen in the Kimmeridge Clay of Dorset, which he mentioned and figured as Cryptarchaeodinium sp. Although it was similar in many respects to this genus, it differed in the presence of an anterior intercalary plate ra and of several very small plates between the plates Ia and 6". The position of the antapical plate 1"""" and the sutures were also different. Eisenack incorrectly cited Downie"s species as C. calcaratum in his " Katalog der Fossilen Dinoflagellaten, Hystrichospharen und verwandten Mikrofossilen" in 1964. On the basis of Downie"s figure and description, this is unjustified.