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Senoniasphaera jurassica
Senoniasphaera jurassica (Gitmez and Sarjeant, 1972) Lentin and Williams, 1976; emend. Poulsen and Riding, 1992
Originally Hexagonifera, subsequently (and now) Senoniasphaera, thirdly Ambonosphaera. Fensome, 1979 transferred this species to Ambonosphaera Fensome, 1979; however, Lentin and Williams, 1981 retained it in Senoniasphaera.
Possible taxonimic junior synonym of Meiourogonyaulax staffinensis Gitmez, 1970, according to Riley, 1979
Taxonomic senior synonym: Meiourogonyaulax (now Lithodinia?) staffinensis, according to Williams et al. (1993, p.32) — however, elsewhere in the same publication, Williams et al. (1993, p.56) retained Hexagonifera (now Senoniasphaera) jurassica.
Holotype: Gitmez and Sarjeant, 1972, pl. 14, fig. 5
Stratum typicum: Middle Kimmeridgian
Locus typicus: Warlingham, England
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Senoniasphaera jurassica (Gitmez and Sarjeant, 1972) Lentin and Williams, 1976, emend. Poulsen and Riding, 1992. Emendation from Poulsen and Riding (1992, p.28), proximate, circumcavate, lenticular dinoflagellate cysts, with an elongate ovoidal to subpentagonal ambitus. Endocyst consistently ovoidal, formed of relatively thick, scabrate to granulate endophragm. Pericyst formed into a short, rounded, hollow apical projection; antapex flat to concave. Specimens with a concave antapex may exhibit an antapical claustrum in the relatively thin, smooth periphragm. Gonyaulacacean paratabulation partially indicated by low, smooth, parasutural ridges on the periphragm. Paracingulum consistently delineated. Epicyst and hypocyst equal in length or the hypocyst is slightly longer than the epicyst. The remaining paraplate series may be indicated by complete or discontinuous parasutural ridges. Kofoidian formula ?pr, 4', 6", ?6c, 6"’, 1p, 1"”, sexiform gonyaulacacean configuration with an apparently L-type parasulcus, which has a parasulcal notch offset to the left. Archeopyle apical type (4A), operculum free. Size: overall length including operculum 63.5-105 µm, overall width 51-91.5 µm, endocyst length 62.5-87 µm, width 53-74 µm.
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Original diagnosis: Gitmez and Sarjeant, 1972, p. 240-241: Hexagonifera jurassica.
A species of Hexagonifera with broadly ovoidal to elongate cyst. The periblast has a blunt, hollow apical projection formed by the periphragm only. The surface of the periblast is delicate, smooth or minutely granular: the endoblast, in contrast, is thick-walled and densely granular, with occasional tubercles. A circular cingulum divides the periblast almost equally; sometimes the epitract is slightly smaller than the hypotract. There is no definite indication of tabulation or of a sulcus. An apical archaeopyle is typically developed.
Dimensions: Holotype overall length 85 µm, breadth 72 µm, endoblast length 73 µm, breadth 66 µm. Paratype: overall length (apex lacking) 46 µm, breadth 50 µm, endoblast length (apex lacking) 40 µm, breadth 42 µm. according to measurements, the Lower Kimmeridgian specimens are smaller than those from the Middle and Upper Kimmeridgian. (There is only a slight size difference between the Middle and Upper Kimmeridgian specimens). No dimensional difference was observable between the English and French specimens.
Original description: Gitmez and Sarjeant, 1972, p. 240-241: Hexagonifera jurassica.
The subsperical to ovoidal endoblast is completely enclosed by the delicate periblast. The epitract of the periblast is conical, with no apical projection superimposed on the cone shape. The epitract of the endoblast is rounded and dome-shaped. The antapex of both periblast and endoblast is rounded. A polygonal apical archaeopyle is usually present; generally the operculum remains attached to the shell. The tabulation is generally indeterminable, but the dorsal tabulation could be distinguished with difficulty on some specimens: two apical, three precingular, three postcingular and one antapical plate were recognised.
Remarks: This new species is distinguished from previously described species of the genus by the presence of a cingulum and poorly developed tabulation. These specimens are similar to H. chlamydata Cookson and Eisenack, (1952) in having a granular endoblast, but it is impossible to compare the periblast since it is usually badly preserved or not preserved at all. The presence of a slight apical prominence, a cingulum and poorly developed tabulation distinguish this species form H. chlamydata.
Emended diagnosis: Poulson and Riding, 1992, p. 28
Proximate, circumcavate, lenticular dinoflagellate cysts, with an elongate ovoidal to subpentagonal ambitus. Endocyst consistently ovoidal, formed of relatively thick, scabrate to granulate endophragm. Pericyst formed into a short, rounded, hollow apical projection; antapex flat to concave. Specimens with a concave antapex may exhibit an antapical claustrum in the relatively thin, smooth periphragm. Gonyaulacacean paratabulation partially indicated by low, smooth parasutural ridges on the periphragm. Paracingulum consistently delineated; epicyst and hypocyst equal in length or the hypocyst is slightly longer than the epicyst. The remaining paraplate series may be indicated by complete or discontinuous parasutural ridges. Kofoidian formula: ?pr, 4', 6", ?6c, 6''', 1p, 1'''', sexiform gonyaulacacean configuration with an apparently L-type parasulcus, which has a parasulcal notch offset to the left. Archeopyle apical, type (4A), operculum free.
Emended description: Poulsen and Riding, 1992, p. 28
A species of Senoniasphaera which is proximate, circumcavate, strongly lenticular, and of intermediate size (63 to 105 µm in length). The dorsoventral outline is elongate ovoidal to subpentangular. The periphragm is thin, smooth and forms a short, rounded apical horn; the antapex is flat to concave, with the periphragm of concave specimens frequently exhibiting a round antapical claustrum flanked by two small protrusions. The endophragm is relatively thick (up to 1.5 µm) and scabrate to granulate, forming an elongate ovoidal endocyst. Low, distally smooth ridges on the periphragm partially indicate a sexiform gonyaulacacean paratabulation. The parasulcal notch is markedly offset to the left of the median line (see Evitt, 1985, text-figs. 5.15D, 10.1,10.2) and the parasulcus appears to be longitudinal (L-type); Kofoidian paratabulation is interpreted as ?pr, 4', 6", ?6c, 6''', 1p, 1''''. The laevorotatory paracingulum is displaced by up to twice its height. The hypocystal paraplate series may be partially delineated, the parasutural ridges are often discontinuous. The principal archeopyle suture indicates the position of the parasulcus and the anterior and posterior sides of the precingular and apical paraplate series respectively (see Text-Figure 3). The archeopyle is apical, type (4A), with a free operculum. Rarely, the operculum may remain adherent.
Dimensions:
minimum mean maximum
Overall cyst length: 63.5 84.5 105.0 (including operculum)
Overall cyst width: 51.0 73.5 91.5
Endocyst length: 62.5 75.5 87.0 (including operculum)
Endocyst width: 53.0 67.5 74.0
Originally Hexagonifera, subsequently (and now) Senoniasphaera, thirdly Ambonosphaera. Fensome, 1979 transferred this species to Ambonosphaera Fensome, 1979; however, Lentin and Williams, 1981 retained it in Senoniasphaera.
Possible taxonimic junior synonym of Meiourogonyaulax staffinensis Gitmez, 1970, according to Riley, 1979
Taxonomic senior synonym: Meiourogonyaulax (now Lithodinia?) staffinensis, according to Williams et al. (1993, p.32) — however, elsewhere in the same publication, Williams et al. (1993, p.56) retained Hexagonifera (now Senoniasphaera) jurassica.
Holotype: Gitmez and Sarjeant, 1972, pl. 14, fig. 5
Stratum typicum: Middle Kimmeridgian
Locus typicus: Warlingham, England
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Senoniasphaera jurassica (Gitmez and Sarjeant, 1972) Lentin and Williams, 1976, emend. Poulsen and Riding, 1992. Emendation from Poulsen and Riding (1992, p.28), proximate, circumcavate, lenticular dinoflagellate cysts, with an elongate ovoidal to subpentagonal ambitus. Endocyst consistently ovoidal, formed of relatively thick, scabrate to granulate endophragm. Pericyst formed into a short, rounded, hollow apical projection; antapex flat to concave. Specimens with a concave antapex may exhibit an antapical claustrum in the relatively thin, smooth periphragm. Gonyaulacacean paratabulation partially indicated by low, smooth, parasutural ridges on the periphragm. Paracingulum consistently delineated. Epicyst and hypocyst equal in length or the hypocyst is slightly longer than the epicyst. The remaining paraplate series may be indicated by complete or discontinuous parasutural ridges. Kofoidian formula ?pr, 4', 6", ?6c, 6"’, 1p, 1"”, sexiform gonyaulacacean configuration with an apparently L-type parasulcus, which has a parasulcal notch offset to the left. Archeopyle apical type (4A), operculum free. Size: overall length including operculum 63.5-105 µm, overall width 51-91.5 µm, endocyst length 62.5-87 µm, width 53-74 µm.
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Original diagnosis: Gitmez and Sarjeant, 1972, p. 240-241: Hexagonifera jurassica.
A species of Hexagonifera with broadly ovoidal to elongate cyst. The periblast has a blunt, hollow apical projection formed by the periphragm only. The surface of the periblast is delicate, smooth or minutely granular: the endoblast, in contrast, is thick-walled and densely granular, with occasional tubercles. A circular cingulum divides the periblast almost equally; sometimes the epitract is slightly smaller than the hypotract. There is no definite indication of tabulation or of a sulcus. An apical archaeopyle is typically developed.
Dimensions: Holotype overall length 85 µm, breadth 72 µm, endoblast length 73 µm, breadth 66 µm. Paratype: overall length (apex lacking) 46 µm, breadth 50 µm, endoblast length (apex lacking) 40 µm, breadth 42 µm. according to measurements, the Lower Kimmeridgian specimens are smaller than those from the Middle and Upper Kimmeridgian. (There is only a slight size difference between the Middle and Upper Kimmeridgian specimens). No dimensional difference was observable between the English and French specimens.
Original description: Gitmez and Sarjeant, 1972, p. 240-241: Hexagonifera jurassica.
The subsperical to ovoidal endoblast is completely enclosed by the delicate periblast. The epitract of the periblast is conical, with no apical projection superimposed on the cone shape. The epitract of the endoblast is rounded and dome-shaped. The antapex of both periblast and endoblast is rounded. A polygonal apical archaeopyle is usually present; generally the operculum remains attached to the shell. The tabulation is generally indeterminable, but the dorsal tabulation could be distinguished with difficulty on some specimens: two apical, three precingular, three postcingular and one antapical plate were recognised.
Remarks: This new species is distinguished from previously described species of the genus by the presence of a cingulum and poorly developed tabulation. These specimens are similar to H. chlamydata Cookson and Eisenack, (1952) in having a granular endoblast, but it is impossible to compare the periblast since it is usually badly preserved or not preserved at all. The presence of a slight apical prominence, a cingulum and poorly developed tabulation distinguish this species form H. chlamydata.
Emended diagnosis: Poulson and Riding, 1992, p. 28
Proximate, circumcavate, lenticular dinoflagellate cysts, with an elongate ovoidal to subpentagonal ambitus. Endocyst consistently ovoidal, formed of relatively thick, scabrate to granulate endophragm. Pericyst formed into a short, rounded, hollow apical projection; antapex flat to concave. Specimens with a concave antapex may exhibit an antapical claustrum in the relatively thin, smooth periphragm. Gonyaulacacean paratabulation partially indicated by low, smooth parasutural ridges on the periphragm. Paracingulum consistently delineated; epicyst and hypocyst equal in length or the hypocyst is slightly longer than the epicyst. The remaining paraplate series may be indicated by complete or discontinuous parasutural ridges. Kofoidian formula: ?pr, 4', 6", ?6c, 6''', 1p, 1'''', sexiform gonyaulacacean configuration with an apparently L-type parasulcus, which has a parasulcal notch offset to the left. Archeopyle apical, type (4A), operculum free.
Emended description: Poulsen and Riding, 1992, p. 28
A species of Senoniasphaera which is proximate, circumcavate, strongly lenticular, and of intermediate size (63 to 105 µm in length). The dorsoventral outline is elongate ovoidal to subpentangular. The periphragm is thin, smooth and forms a short, rounded apical horn; the antapex is flat to concave, with the periphragm of concave specimens frequently exhibiting a round antapical claustrum flanked by two small protrusions. The endophragm is relatively thick (up to 1.5 µm) and scabrate to granulate, forming an elongate ovoidal endocyst. Low, distally smooth ridges on the periphragm partially indicate a sexiform gonyaulacacean paratabulation. The parasulcal notch is markedly offset to the left of the median line (see Evitt, 1985, text-figs. 5.15D, 10.1,10.2) and the parasulcus appears to be longitudinal (L-type); Kofoidian paratabulation is interpreted as ?pr, 4', 6", ?6c, 6''', 1p, 1''''. The laevorotatory paracingulum is displaced by up to twice its height. The hypocystal paraplate series may be partially delineated, the parasutural ridges are often discontinuous. The principal archeopyle suture indicates the position of the parasulcus and the anterior and posterior sides of the precingular and apical paraplate series respectively (see Text-Figure 3). The archeopyle is apical, type (4A), with a free operculum. Rarely, the operculum may remain adherent.
Dimensions:
minimum mean maximum
Overall cyst length: 63.5 84.5 105.0 (including operculum)
Overall cyst width: 51.0 73.5 91.5
Endocyst length: 62.5 75.5 87.0 (including operculum)
Endocyst width: 53.0 67.5 74.0