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Occisucysta echinata
Occisucysta? echinata Duxbury, 1983; emend. Jan du Chene et al., 1986
Duxbury, 1983, questionably included this species in Occisucysta.
Holotype: Duxbury, 1983, pl.4, figs.12-13; Jan du Chene et al., 1986(a), pl.77, figs.10-12; Jan du Chene et al., 1986(b), pl.8, figs.1-6
Locus typicus: Redcliff section, Isle of Wight.
Stratum typicum: Aptian
Translation Jan du Chene et al, 1986: LPP
Original diagnosis Duxbury, 1983, p.51:
A proximate to proximo-cavate dinoflagellate cyst species which is spheroidal to ovoidal in shape and which is surmounted by a prominent, notably cavate apical horn. A crude reticulum, in the form of low, punctate muri, extends over the whole body surface. Numerous spines arise from the reticulum and these may be proximally vacuolate to such a degree that localised or extensive cavation may result. An ectophragm covers the reticulum but leaves the distal ends of the spines free. The ectophragm bears low paracingular and parasutural crests which are perforate, finely denticulate distally and which mark out a typically gonyaulacacean paratabulation pattern. Some small grana and/or coni may be present on the ectophragm surface. The archeopyle is formed by detachment of paraplates 2" and 3".
Observed dimensions: Holotype - 81 x 90 µm Overall - 81 (75) 70 x 90 (73) 61 µm.
Specimens measured - 7.
Emended description: Jan du Chene et al., 1986, p. 18
Diagnosis: Cyst proximocavate, subsphaerical to ovoidal, with a distinct apical horn formed by the periphragm only. The gonyaulacoid paratabulation, 1-?2pr, 4", 6"", 6c, 5s, 6""", 1p, 1"""", is expressed by parasutural septa of which the crests are irregularly ornamented with spines. These parasutural septa are sometimes difficult to discern due to a dense intratabular ornamentation. The periphragm and endophragm are interconnected by a network of solid, sometimes laterally connected muri, which may form a more or less regular reticulum. The periphagm supports a dense intratabular spinous ornamentation. The archaeopyle is formed by the detachment of paraplates 2"" and 3"". The operculum is free, composite.
Description: Proximate to proximocavate cyst, subspherical to ovoidal, with a distinct apical horn formed by the periphragm only. The endophragm seems slightly thicker than the periphragm with which it is connected by a network of irregularly arranged, sometimes laterally interconnected, solid muri, which may form a more or less regular reticulum. The periphragm supports a dense, spinous intratabular ornamentation. It is irregularly perforate. The gonyaulacoid paratabulation (1-?2pr, 4", 6"", 6c, 5s, 6""", 1p, 1"""") is expressed by continuous parasutural septa with irregularly spinous crests. These parasutural septa are sometimes difficult to discern in transmitted light due to the densely spinous intratabulae ornamentation and the presence of the muri connecting the endophragm and periphragm. The paracingulum is slightly helicoidal, laevorotatory. The parasulcus is composed of 5 sulcal paraplates, only slightly individualized, not ornamented. The archaeopyle is precingular, formed by the detachment of paraplates 2"" and 3"". The operculum is composite, free.
Affinities:
Duxbury, 1983, p.51:
This species is most distinctive, particularly in being an extremely spinose Occisucysta-type cyst with a clearly marked reticulum between the body layers. The variation in the degree of development of the vacuoles at the proximal ends of the spines results in some specimens being largely proximate whilst others are almost entirely cavate. No other species of Occisucysta demonstrates this last feature and for this reason the assignment of echinata to Occisucysta may be only tentative.
Jan du Chene et al., 1986, p. 18
O.? echinata differs from all known Occisucysta species in the wall structure. The presence of a 2P(2""+3"") archaeopyle does not allow this species to be attributed to the genus Aldorfia.
Duxbury, 1983, questionably included this species in Occisucysta.
Holotype: Duxbury, 1983, pl.4, figs.12-13; Jan du Chene et al., 1986(a), pl.77, figs.10-12; Jan du Chene et al., 1986(b), pl.8, figs.1-6
Locus typicus: Redcliff section, Isle of Wight.
Stratum typicum: Aptian
Translation Jan du Chene et al, 1986: LPP
Original diagnosis Duxbury, 1983, p.51:
A proximate to proximo-cavate dinoflagellate cyst species which is spheroidal to ovoidal in shape and which is surmounted by a prominent, notably cavate apical horn. A crude reticulum, in the form of low, punctate muri, extends over the whole body surface. Numerous spines arise from the reticulum and these may be proximally vacuolate to such a degree that localised or extensive cavation may result. An ectophragm covers the reticulum but leaves the distal ends of the spines free. The ectophragm bears low paracingular and parasutural crests which are perforate, finely denticulate distally and which mark out a typically gonyaulacacean paratabulation pattern. Some small grana and/or coni may be present on the ectophragm surface. The archeopyle is formed by detachment of paraplates 2" and 3".
Observed dimensions: Holotype - 81 x 90 µm Overall - 81 (75) 70 x 90 (73) 61 µm.
Specimens measured - 7.
Emended description: Jan du Chene et al., 1986, p. 18
Diagnosis: Cyst proximocavate, subsphaerical to ovoidal, with a distinct apical horn formed by the periphragm only. The gonyaulacoid paratabulation, 1-?2pr, 4", 6"", 6c, 5s, 6""", 1p, 1"""", is expressed by parasutural septa of which the crests are irregularly ornamented with spines. These parasutural septa are sometimes difficult to discern due to a dense intratabular ornamentation. The periphragm and endophragm are interconnected by a network of solid, sometimes laterally connected muri, which may form a more or less regular reticulum. The periphagm supports a dense intratabular spinous ornamentation. The archaeopyle is formed by the detachment of paraplates 2"" and 3"". The operculum is free, composite.
Description: Proximate to proximocavate cyst, subspherical to ovoidal, with a distinct apical horn formed by the periphragm only. The endophragm seems slightly thicker than the periphragm with which it is connected by a network of irregularly arranged, sometimes laterally interconnected, solid muri, which may form a more or less regular reticulum. The periphragm supports a dense, spinous intratabular ornamentation. It is irregularly perforate. The gonyaulacoid paratabulation (1-?2pr, 4", 6"", 6c, 5s, 6""", 1p, 1"""") is expressed by continuous parasutural septa with irregularly spinous crests. These parasutural septa are sometimes difficult to discern in transmitted light due to the densely spinous intratabulae ornamentation and the presence of the muri connecting the endophragm and periphragm. The paracingulum is slightly helicoidal, laevorotatory. The parasulcus is composed of 5 sulcal paraplates, only slightly individualized, not ornamented. The archaeopyle is precingular, formed by the detachment of paraplates 2"" and 3"". The operculum is composite, free.
Affinities:
Duxbury, 1983, p.51:
This species is most distinctive, particularly in being an extremely spinose Occisucysta-type cyst with a clearly marked reticulum between the body layers. The variation in the degree of development of the vacuoles at the proximal ends of the spines results in some specimens being largely proximate whilst others are almost entirely cavate. No other species of Occisucysta demonstrates this last feature and for this reason the assignment of echinata to Occisucysta may be only tentative.
Jan du Chene et al., 1986, p. 18
O.? echinata differs from all known Occisucysta species in the wall structure. The presence of a 2P(2""+3"") archaeopyle does not allow this species to be attributed to the genus Aldorfia.