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Chatangiella scheii
Chatangiella? scheii, (Manum, 1963), Lentin and Williams, 1976
Now Arvalidinium. Originally Deflandrea, subsequently Cooksoniella, thirdly Chatangiella?, fourthly (and now) Arvalidinium.
Lentin and Williams, 1976, questionably included this species in Chatangiella.
Holotype: Manum, 1963, pl.1, figs.1-4;text-fig.1
Age: Middle Cretaceous
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Original description as Deflandrea scheii: [Manum 1963, p. 56-58]:
Diagnosis:
Thecal in dorsoventral view roughly pentagonal, slightly convex in the equatorial region, and divided into nearly equal parts by a slightly spiral, laevo-rotatory girdle bordered by ridges with more or less prominent discontinuities. Apical horn short and blunt, antapex with a short and blunt horn on the left-hand side and a rudimentary one on the right-hand side.
A tabulation is marked by low ridges, formula 4', 3a, 7", 5"', ?"".
Archeopyle (2a) almost equilaterally hexagonal.
Theca-membrane smooth or with scattered knob-like projections which also occur along the girdle and the sutures. A capsulel of circular outline occupies the central part of the theca.
Description:
The capsule lies on to the theca in the equatorial region. Above the upper limit of the capsule the epitheca bulges moderately before tapering towards the apical horn. The hypotheca narrows gradually towards the broad and often somewhat obliquely truncate antapex. The horn on the left-hand side is usually distinct, while the one on the right-hand side is only suggested and sometimes not apparent. The girdle is always clear, but certain parts of the ridges by which it is bordered are usually markedly less prominent than others, giving it a discontinuous appearance. The prominent parts are usually composed of small, knob-like projections closely arranged in a line (Pl. I figs. 5, 15), but in some specimens the ridges are inconspicuous and the interruptions not apparent. The most prominent interruptions occur on the dorsal side at some distance on either side of the midline, less prominent ones occur on the ventral side not far from the lateral margins of the theca. Knobs similar to those along the girdle, but less prominent and more widely spaced, occur along the sutures and are scattered elsewhere on the shell, particularly on the plates 4" and 3"'. Furthermore, there is a marked variation in the number and prominence of the knobs, the general appearance in some specimens being that the membrane is smooth. In profile the knobs appear as small outward bulges from the theca-membrane. Each is penetrated by a fine tubule which in surface view is seen as a bright spot in the center. The tabulation varies considerably in distinctness. Plate 2a (the archeopyle) is always distinct and plate 4" nearly always so. The intercalary plates la and 3a, and the other precingular plates are usually clear, except that the delimitation of plates 1" and 7" towards plate 1' have not been clearly seen in any of the specimens. In general, the sutures between the apical plates and the precingular ones are faint and often indistinguishable. The postcingular plates on the dorsal side are usually delineated by clear longitudinal sutures which can be traced for short distances from the girdle and then fade out. No antapical plates could be distinguished. For the greater part the outline of the shell usually coincides with sutures, particularly of the precingular and postcingular plates. The borders of the postcingular plates towards the longitudinal furrow have not been clear. More or less prominent folds usually extend from the ventral ends of the girdle towards the antapex. Approximately midway between these folds and the lateral outline of the shell similar folds occur. These pairs of folds (in text-fig. 1 marked by closely dotted lines), together with the usually thickened borders of the girdle, outline two narrow triangles, one on either side of the longitudinal furrow. These triangles often appear as conspicuously raised parts of the theca-membrane and could be taken for plates, in which case the number of postcingular plates would be seven. However, in specimens where the folds are lacking, sutures could not be distinguished. The theca-membrane is less than 1 µm thick, the wall of the capsule is usually slightly thicker, between 1 and 2 µm, and finely granular.
Dimensions:
Holotype: 94x62 µm.
Range: length 82-116 µm, width 57-81 µm; average of 24 specimens 98x67 µm.
Affinities/Remarks:
The shape in D. scheii somewhat resembles that of D. phosphoritica EISENACK (1954), but its general appearance is slightly more elongate and there is only one prominent antapical horn. The shape together with the tabulation and scattered ornamentation distinguish D. scheii from other species of Deflandrea. Even when the tabulation is not clear, the species can be recognized by the regular shape of the archeopyle (2a) and the precingular plate below it (4") which is almost invariably indicated, together with the overall shape of the theca. The specific name is given in memory of PER SCHEI, geologist with the 2nd "Fram"-expedition, who collected the sample from which the present fossils have been obtained.
Now Arvalidinium. Originally Deflandrea, subsequently Cooksoniella, thirdly Chatangiella?, fourthly (and now) Arvalidinium.
Lentin and Williams, 1976, questionably included this species in Chatangiella.
Holotype: Manum, 1963, pl.1, figs.1-4;text-fig.1
Age: Middle Cretaceous
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Deflandrea scheii: [Manum 1963, p. 56-58]:
Diagnosis:
Thecal in dorsoventral view roughly pentagonal, slightly convex in the equatorial region, and divided into nearly equal parts by a slightly spiral, laevo-rotatory girdle bordered by ridges with more or less prominent discontinuities. Apical horn short and blunt, antapex with a short and blunt horn on the left-hand side and a rudimentary one on the right-hand side.
A tabulation is marked by low ridges, formula 4', 3a, 7", 5"', ?"".
Archeopyle (2a) almost equilaterally hexagonal.
Theca-membrane smooth or with scattered knob-like projections which also occur along the girdle and the sutures. A capsulel of circular outline occupies the central part of the theca.
Description:
The capsule lies on to the theca in the equatorial region. Above the upper limit of the capsule the epitheca bulges moderately before tapering towards the apical horn. The hypotheca narrows gradually towards the broad and often somewhat obliquely truncate antapex. The horn on the left-hand side is usually distinct, while the one on the right-hand side is only suggested and sometimes not apparent. The girdle is always clear, but certain parts of the ridges by which it is bordered are usually markedly less prominent than others, giving it a discontinuous appearance. The prominent parts are usually composed of small, knob-like projections closely arranged in a line (Pl. I figs. 5, 15), but in some specimens the ridges are inconspicuous and the interruptions not apparent. The most prominent interruptions occur on the dorsal side at some distance on either side of the midline, less prominent ones occur on the ventral side not far from the lateral margins of the theca. Knobs similar to those along the girdle, but less prominent and more widely spaced, occur along the sutures and are scattered elsewhere on the shell, particularly on the plates 4" and 3"'. Furthermore, there is a marked variation in the number and prominence of the knobs, the general appearance in some specimens being that the membrane is smooth. In profile the knobs appear as small outward bulges from the theca-membrane. Each is penetrated by a fine tubule which in surface view is seen as a bright spot in the center. The tabulation varies considerably in distinctness. Plate 2a (the archeopyle) is always distinct and plate 4" nearly always so. The intercalary plates la and 3a, and the other precingular plates are usually clear, except that the delimitation of plates 1" and 7" towards plate 1' have not been clearly seen in any of the specimens. In general, the sutures between the apical plates and the precingular ones are faint and often indistinguishable. The postcingular plates on the dorsal side are usually delineated by clear longitudinal sutures which can be traced for short distances from the girdle and then fade out. No antapical plates could be distinguished. For the greater part the outline of the shell usually coincides with sutures, particularly of the precingular and postcingular plates. The borders of the postcingular plates towards the longitudinal furrow have not been clear. More or less prominent folds usually extend from the ventral ends of the girdle towards the antapex. Approximately midway between these folds and the lateral outline of the shell similar folds occur. These pairs of folds (in text-fig. 1 marked by closely dotted lines), together with the usually thickened borders of the girdle, outline two narrow triangles, one on either side of the longitudinal furrow. These triangles often appear as conspicuously raised parts of the theca-membrane and could be taken for plates, in which case the number of postcingular plates would be seven. However, in specimens where the folds are lacking, sutures could not be distinguished. The theca-membrane is less than 1 µm thick, the wall of the capsule is usually slightly thicker, between 1 and 2 µm, and finely granular.
Dimensions:
Holotype: 94x62 µm.
Range: length 82-116 µm, width 57-81 µm; average of 24 specimens 98x67 µm.
Affinities/Remarks:
The shape in D. scheii somewhat resembles that of D. phosphoritica EISENACK (1954), but its general appearance is slightly more elongate and there is only one prominent antapical horn. The shape together with the tabulation and scattered ornamentation distinguish D. scheii from other species of Deflandrea. Even when the tabulation is not clear, the species can be recognized by the regular shape of the archeopyle (2a) and the precingular plate below it (4") which is almost invariably indicated, together with the overall shape of the theca. The specific name is given in memory of PER SCHEI, geologist with the 2nd "Fram"-expedition, who collected the sample from which the present fossils have been obtained.