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Chatangiella granulifera
Chatangiella granulifera, (Manum, 1963), Lentin and Williams, 1976
Originally Deflandrea, subsequently Australiella, thirdly (and now) Chatangiella.
Tax. sr. synonym of Chatangiella vnigrii (Vozzhennikova, 1967) Lentin and Williams, 1976, according to Lentin and Vozzhennikova, 1990.
Wheeler and Sarjeant, 1990, retained Chatangiella vnigrii as a separate species. Lentin and Vozzhennikova, 1990, appeared one month later than Wheeler and Sarjeant, 1990.
Holotype: 243: Manum 1963: Pl. III, figs. 5, 6
Locus typicus: Graham Island, Arctic Canada
Stratum typicum: Cretaceous
Age: Senonian
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Original description as Deflandrea granulifera: [Manum 1963, p. 61-64]:
Diagnosis:
Theca in dorsoventral view elongate, divided into nearly equal parts by a slightly spiral, laevo-rotatory girdle. Equatorial region convex; epitheca widened in the upper part, apex slightly rounded with a blunt horn; hypotheca obliquely truncate to slightly concave, with a short, pointed horn on the left-hand side and a suggestion of one on the right-hand side.
Intercalary archeopyle rounded hexagonal in shape.
Theca-membrane up to 1µm thick, with a delicate granulation. Girdle bordered by ridges with conspicuous discontinuities. Central portion of the theca occupied by a capsule of circular outline.
Description:
The widened upper portion of the epitheca forms rounded "shoulders". The apical horn is c. 11 µm long. The sides of the lower portion of the hypotheca may be parallel, slightly divergent or convergent. The antapical horn on the left-hand side is either distinct with a triangular outline, or it is only indicated by the acute angle of the obliquely truncate antapex. The shape of the archeopyle is clearly hexagonal and almost equilateral in some specimens, but usually it is rounded and sometimes almost circular. The granulation of the theca-membrane varies in distinctness. In surface view it is usually seen as a fairly dense pattern of dark dots less than 0.5 µm in diameter, and in optical section of the membrane as distinct, delicate projections which sometimes are slightly longer than broad. In some specimens the dotted surface pattern is less distinct and even faint, and in the optical section of the membrane projections are not apparent. Such specimens usually have a very thin membrane, while in the more distinctly granular ones its thickness may go up to 1 µm. The density of the granulation is constant all over the theca. The girdle is "broken" in exactly the same positions as in D. verrucosa. Longitudinal folds in the ventral hypotheca indicate a longitudinal furrow. The capsule usually reaches the lateral walls of the theca. The wall of the capsule is usually about 2 µm thick and sometimes clearly two-layered with the inner layer solid and the outer one of granular composition; the granulation is denser and coarser than that on the theca. In a few specimens the wall of the capsule is not appreciably thicker than that of the theca and a distinct granulation is lacking. The mode of opening of the capsule is similar to that in D. verrucosa, including the lateral breaks.
Dimensions:
Holotype: length 112 µm, width 70 µm.
Range: length 95-124 µm, width 60-84 µm; average of 19 specimens 112.5x79.5 µm.
Affinities/Remarks:
As indicated in the description, some of the specimens included in D. granulifera are quite smooth (although dotted on the surface) and the capsule is thin-walled, smooth, and does not extend to the lateral margins of the theca. It appears possible that these specimens represent a separate species, distinct from the typical specimens of D. granulifera in which the capsule entirely fills the middle portion of the theca and has a granular wall c. 2 µm thick. However, since the distinction would depend largely on the characters of the capsule, the diagnostic value of which is as yet uncertain, D. granulifera has been made broad enough to include the entire range in this respect. The specimens of D. granulifera with a smooth, thin-walled capsule not extending to the lateral margins of the theca show certain resemblances to D. spectabilis ALBERTI (1959 P. 99). The latter has a finely dotted theca-membrane, rounded hexagonal, intercalary archeopyle, and a girdle that is often bordered by interrupted ridges. The position of these interruptions are not mentioned in ALBERTI'S description, but his figures suggest that they correspond to those in D. granulifera and the other species described herein. The theca in D. spectabilis is somewhat similar in shape to that of D. granulifera, but it narrows gradually from the equator towards both apices and lacks the typical epithecal shoulders. In D. spectabilis the range in length of the theca is 10-15 µm less than in D. granulifera. D. granulifera is closely similar in shape and size to D. verrucosa. The most reliable distinguishing character is the ornamentation, but sometimes the use of a high power oil immersion lens is necessary for the recognition. Heavily warty specimens of D. verrucosa are easily distinguished, but under a low power lens prominently granular specimens of D. granulifera may be confused with the less coarsely and heavily ornamented specimens of D. verrucosa. However, under high power D. granulifera is seen to have a fine, dotted pattern of granules evenly distributed over the theca and warts are never present, while in D. verrucosa warts are always present, at least equatorially, and the granules which may occur towards the apex and antapex are scattered and never form a pattern of evenly distributed dots over the whole surface of the theca. The two species also differ in the shape of the theca, but in this respect there is some overlapping of the characters. In D. granulifera the "shoulders" are rounded, whereas in typical examples of D. verrucosa they are angular with a flat upper limit. The apical horn in D. granulifera is fairly narrow and blunt and usually with somewhat concave sides, while in D. verrucosa it is broader and usually more distinctly triangular in outline. The size-ranges in the two species also overlap but measurements of a number of specimens distinguished by the ornamentation show that there is a distinct difference in the mean size of the two species (cp. diagram in text-fig. 4). Furthermore, D. granulifera is closely similar to D. tripartita in its extended description and illustration by COOKSON & EISENACK (1961 P. 70, text-fig. 1).
The shape of the theca comes close to D. granulifera and the girdle is broken in the same manner. However, in D. tripartita sensu C. & E. (1961) the ornamentation is coarser and the projections more sparse, and the apical horn is longer in relation to the length of the theca and with a much broader base. Furthermore, D. tripartita sensu C. & E. (1961) is on the average smaller than D. granulifera although their size-ranges overlap. In 51 examples of D. tripartita from the Belfast Mudstone, Victoria, the range of the length was 76-116 µm, and of the width 49-73 µm, the arithmetical mean was 98.0x59.5 µm (Text-fig. 4). D. granulifera also resembles D. micracantha COOKSON & EISENACK (1960 p. 3). The ornamentation in D. micracantha is similar to that of D. granulifera in its closeness in the equatorial region, however, it is not constant all over the theca and the very fine rods or spinules are 1.0-1.5 µm long. The shapes of the thecae are roughly similar, but in D. micracantha it is broader in the middle portion and has less pronounced shoulders. It is interesting to note that in D. micracantha linearly arranged spinules suggest a tabulation as mentioned in the original description; it corresponds to that observed in D. scheii and D. sverdrupiana. Furthermore, the girdle is laevo-rotatory, and it is broken, although not so distinctly as in D. tripartita (sensu C. & E. 1961) and D. granulifera. The resemblances noted between D. granulifera, D. micracantha, D. spectabilis, D. tripartita sensu C. & E. (1961), and D. verrucosa indicate close relationship between these species.
Originally Deflandrea, subsequently Australiella, thirdly (and now) Chatangiella.
Tax. sr. synonym of Chatangiella vnigrii (Vozzhennikova, 1967) Lentin and Williams, 1976, according to Lentin and Vozzhennikova, 1990.
Wheeler and Sarjeant, 1990, retained Chatangiella vnigrii as a separate species. Lentin and Vozzhennikova, 1990, appeared one month later than Wheeler and Sarjeant, 1990.
Holotype: 243: Manum 1963: Pl. III, figs. 5, 6
Locus typicus: Graham Island, Arctic Canada
Stratum typicum: Cretaceous
Age: Senonian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Deflandrea granulifera: [Manum 1963, p. 61-64]:
Diagnosis:
Theca in dorsoventral view elongate, divided into nearly equal parts by a slightly spiral, laevo-rotatory girdle. Equatorial region convex; epitheca widened in the upper part, apex slightly rounded with a blunt horn; hypotheca obliquely truncate to slightly concave, with a short, pointed horn on the left-hand side and a suggestion of one on the right-hand side.
Intercalary archeopyle rounded hexagonal in shape.
Theca-membrane up to 1µm thick, with a delicate granulation. Girdle bordered by ridges with conspicuous discontinuities. Central portion of the theca occupied by a capsule of circular outline.
Description:
The widened upper portion of the epitheca forms rounded "shoulders". The apical horn is c. 11 µm long. The sides of the lower portion of the hypotheca may be parallel, slightly divergent or convergent. The antapical horn on the left-hand side is either distinct with a triangular outline, or it is only indicated by the acute angle of the obliquely truncate antapex. The shape of the archeopyle is clearly hexagonal and almost equilateral in some specimens, but usually it is rounded and sometimes almost circular. The granulation of the theca-membrane varies in distinctness. In surface view it is usually seen as a fairly dense pattern of dark dots less than 0.5 µm in diameter, and in optical section of the membrane as distinct, delicate projections which sometimes are slightly longer than broad. In some specimens the dotted surface pattern is less distinct and even faint, and in the optical section of the membrane projections are not apparent. Such specimens usually have a very thin membrane, while in the more distinctly granular ones its thickness may go up to 1 µm. The density of the granulation is constant all over the theca. The girdle is "broken" in exactly the same positions as in D. verrucosa. Longitudinal folds in the ventral hypotheca indicate a longitudinal furrow. The capsule usually reaches the lateral walls of the theca. The wall of the capsule is usually about 2 µm thick and sometimes clearly two-layered with the inner layer solid and the outer one of granular composition; the granulation is denser and coarser than that on the theca. In a few specimens the wall of the capsule is not appreciably thicker than that of the theca and a distinct granulation is lacking. The mode of opening of the capsule is similar to that in D. verrucosa, including the lateral breaks.
Dimensions:
Holotype: length 112 µm, width 70 µm.
Range: length 95-124 µm, width 60-84 µm; average of 19 specimens 112.5x79.5 µm.
Affinities/Remarks:
As indicated in the description, some of the specimens included in D. granulifera are quite smooth (although dotted on the surface) and the capsule is thin-walled, smooth, and does not extend to the lateral margins of the theca. It appears possible that these specimens represent a separate species, distinct from the typical specimens of D. granulifera in which the capsule entirely fills the middle portion of the theca and has a granular wall c. 2 µm thick. However, since the distinction would depend largely on the characters of the capsule, the diagnostic value of which is as yet uncertain, D. granulifera has been made broad enough to include the entire range in this respect. The specimens of D. granulifera with a smooth, thin-walled capsule not extending to the lateral margins of the theca show certain resemblances to D. spectabilis ALBERTI (1959 P. 99). The latter has a finely dotted theca-membrane, rounded hexagonal, intercalary archeopyle, and a girdle that is often bordered by interrupted ridges. The position of these interruptions are not mentioned in ALBERTI'S description, but his figures suggest that they correspond to those in D. granulifera and the other species described herein. The theca in D. spectabilis is somewhat similar in shape to that of D. granulifera, but it narrows gradually from the equator towards both apices and lacks the typical epithecal shoulders. In D. spectabilis the range in length of the theca is 10-15 µm less than in D. granulifera. D. granulifera is closely similar in shape and size to D. verrucosa. The most reliable distinguishing character is the ornamentation, but sometimes the use of a high power oil immersion lens is necessary for the recognition. Heavily warty specimens of D. verrucosa are easily distinguished, but under a low power lens prominently granular specimens of D. granulifera may be confused with the less coarsely and heavily ornamented specimens of D. verrucosa. However, under high power D. granulifera is seen to have a fine, dotted pattern of granules evenly distributed over the theca and warts are never present, while in D. verrucosa warts are always present, at least equatorially, and the granules which may occur towards the apex and antapex are scattered and never form a pattern of evenly distributed dots over the whole surface of the theca. The two species also differ in the shape of the theca, but in this respect there is some overlapping of the characters. In D. granulifera the "shoulders" are rounded, whereas in typical examples of D. verrucosa they are angular with a flat upper limit. The apical horn in D. granulifera is fairly narrow and blunt and usually with somewhat concave sides, while in D. verrucosa it is broader and usually more distinctly triangular in outline. The size-ranges in the two species also overlap but measurements of a number of specimens distinguished by the ornamentation show that there is a distinct difference in the mean size of the two species (cp. diagram in text-fig. 4). Furthermore, D. granulifera is closely similar to D. tripartita in its extended description and illustration by COOKSON & EISENACK (1961 P. 70, text-fig. 1).
The shape of the theca comes close to D. granulifera and the girdle is broken in the same manner. However, in D. tripartita sensu C. & E. (1961) the ornamentation is coarser and the projections more sparse, and the apical horn is longer in relation to the length of the theca and with a much broader base. Furthermore, D. tripartita sensu C. & E. (1961) is on the average smaller than D. granulifera although their size-ranges overlap. In 51 examples of D. tripartita from the Belfast Mudstone, Victoria, the range of the length was 76-116 µm, and of the width 49-73 µm, the arithmetical mean was 98.0x59.5 µm (Text-fig. 4). D. granulifera also resembles D. micracantha COOKSON & EISENACK (1960 p. 3). The ornamentation in D. micracantha is similar to that of D. granulifera in its closeness in the equatorial region, however, it is not constant all over the theca and the very fine rods or spinules are 1.0-1.5 µm long. The shapes of the thecae are roughly similar, but in D. micracantha it is broader in the middle portion and has less pronounced shoulders. It is interesting to note that in D. micracantha linearly arranged spinules suggest a tabulation as mentioned in the original description; it corresponds to that observed in D. scheii and D. sverdrupiana. Furthermore, the girdle is laevo-rotatory, and it is broken, although not so distinctly as in D. tripartita (sensu C. & E. 1961) and D. granulifera. The resemblances noted between D. granulifera, D. micracantha, D. spectabilis, D. tripartita sensu C. & E. (1961), and D. verrucosa indicate close relationship between these species.