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Areoligera barskii
Derivation of name
Named after palaeontologist Marcin Barski (Warsaw University), who introduced me to dinocysts and was my BSc supervisor.
Diagnosis
A species of Areoligera with proximochorate ornamentation. The surface of the cyst is smooth or microreticulate. The dorsoventral outline is subspherical, often asymmetrical and usually more pronounced on the left side. Intratabular or nontabular processes are distally free, sometimes connected basally. Processes are tapering often of various length but are generally not longer than 12 μm and are distally capitate but can also be bifurcate, acuminate, oblate and digitate. The sulcal area and the central part of the antapical plate (10000) are free from ornamentation. Except for the archeopyle margin, there is no tabulation on the ventral surface.
Holotype
Well 11/10-1, depth 533.40mb.s.f. or 1750 ft b.s.f., slide ? 1=40; England Finder Coordinates (EFCs) O26 (Plate 8A–
C). Palynological slides are stored at the Norwegian Petroleum Directorate in Stavanger, Norway.
Paratype
Well 11/10-1, depth 533.40mb.s.f. or 1750 ft, slide ? 1/4’,
EFC M32/1 (Plate 8F, G); depth 640.10mb.s.f. or
2100 ft b.s.f., slide ? 1/4’, EFC S60/1 (Plate 8H, I). Palynological
slides are stored at the Norwegian Petroleum Directorate
in Stavanger, Norway.
Material
Ditch cutting samples from an industrial Syracuse Oils Norge A/S well 11/10-1.
Locality and horizon
So far the taxon has only been observed in Rupelian strata in the North Sea basin in well 11/10-1 (the interval between 823 and 412mb.s.f.).
Age: Rupelian.
Description
The cyst is dorsoventrally flattened, with a convex dorsal side and a concave ventral side (Plate 8D and E). The welldeveloped sulcal notch is strongly offset to the left (Plate 8A– C). The autophragm can be up to 3 μm thick. On the ventral side the processes are often single but are usually arranged in soleate or arcuate complexes. The sulcal area is devoid of processes. The cingulum from the ventral side appears to be free of processes. The dorsal surface is more densely covered with processes, but their arrangement is not clearly seen. The outline of the cyst is circular (Plate 8L and M) or subcircular, with one or two antapical lobes. Antapex can have either a moderately sized (Plate 8J–K) or pronounced (Plate 8F–I) left antapical lobe or a minute horn (Plate 8J–M). The outline of the central body is similar to other species of Areoligera, e.g. Areoligera campoensis. The antapical lobe or horn can carry processes (Plate 8F–IL and M). The archeopyle is apical and tetratabular. The operculum is free.
Dimensions
Holotype: 84 66 μm (w l). Paratype: 79 62:5 μm (w l). Average dimensions (n D 10): width 77.13 μm (62.50– 91 μm), length 63.00 μm (57–69 μm). The length does not include the operculum. The height of the antapical lobe or horn is up to 7.5 μm. Maximum length of processes 12 μm.
Stratigraphic range and occurrence
The LO of Areoligera? barskii sp. nov. occurs at 412mb.s.f., the same depth as the LOs of Rhombodinium draco and Enneadocysta pectinifromis at 412mb.s.f. The LO of A.? barskii sp. nov. (note that this may not be in situ but may be an effect of caving) is at the same level as the LO of Glaphyrocysta semitecta at 823.0mb.s.f. Areoligera.? barskii is rare (< 1% of the total dinocyst assemblage) to abundant (> 50% of the total dinocyst assemblage).
Genus assignment
The species is questionably included in the genus Areoligera. It differs from Canningia, which has an autophragm and an ectophragm and is uniformly ornamented. Cerbia is clearly paratabulate, and both mid-dorsal and mid-ventral areas are essentially devoid of ornament. Furthermore, Cerbia has usually low lateral projections and clearly defined, significantly shorter processes. Cyclonephelium has linear ornamentation, and, like Chiropteridium, the ornamentation is reduced or lacking on both mid-ventral and mid-dorsal areas. Glaphyrocysta also differs in having distally connected processes.
Remarks
Areoligera? barskii sp. nov. is distinguished from other species of the genus by the length of the processes, which are on average only 15 %–20% of the cyst width. The central body outline of Areoligera? barskii and the short length of the processes may resemble Areoligera guembelii, but processes in A. guembelii are only capitate and bifurcate and are arranged in pronounced annulate complexes. Actually, all known species of Areoligera are characterised by rather broad processes (process complexes) and rising soleate or arcuate ridges on their dorsal side (Williams and Downie, 1966). Since ridges are not clearly developed in Areoligera? barskii sp. nov., the taxon is only questionably assigned to the genus.
Named after palaeontologist Marcin Barski (Warsaw University), who introduced me to dinocysts and was my BSc supervisor.
Diagnosis
A species of Areoligera with proximochorate ornamentation. The surface of the cyst is smooth or microreticulate. The dorsoventral outline is subspherical, often asymmetrical and usually more pronounced on the left side. Intratabular or nontabular processes are distally free, sometimes connected basally. Processes are tapering often of various length but are generally not longer than 12 μm and are distally capitate but can also be bifurcate, acuminate, oblate and digitate. The sulcal area and the central part of the antapical plate (10000) are free from ornamentation. Except for the archeopyle margin, there is no tabulation on the ventral surface.
Holotype
Well 11/10-1, depth 533.40mb.s.f. or 1750 ft b.s.f., slide ? 1=40; England Finder Coordinates (EFCs) O26 (Plate 8A–
C). Palynological slides are stored at the Norwegian Petroleum Directorate in Stavanger, Norway.
Paratype
Well 11/10-1, depth 533.40mb.s.f. or 1750 ft, slide ? 1/4’,
EFC M32/1 (Plate 8F, G); depth 640.10mb.s.f. or
2100 ft b.s.f., slide ? 1/4’, EFC S60/1 (Plate 8H, I). Palynological
slides are stored at the Norwegian Petroleum Directorate
in Stavanger, Norway.
Material
Ditch cutting samples from an industrial Syracuse Oils Norge A/S well 11/10-1.
Locality and horizon
So far the taxon has only been observed in Rupelian strata in the North Sea basin in well 11/10-1 (the interval between 823 and 412mb.s.f.).
Age: Rupelian.
Description
The cyst is dorsoventrally flattened, with a convex dorsal side and a concave ventral side (Plate 8D and E). The welldeveloped sulcal notch is strongly offset to the left (Plate 8A– C). The autophragm can be up to 3 μm thick. On the ventral side the processes are often single but are usually arranged in soleate or arcuate complexes. The sulcal area is devoid of processes. The cingulum from the ventral side appears to be free of processes. The dorsal surface is more densely covered with processes, but their arrangement is not clearly seen. The outline of the cyst is circular (Plate 8L and M) or subcircular, with one or two antapical lobes. Antapex can have either a moderately sized (Plate 8J–K) or pronounced (Plate 8F–I) left antapical lobe or a minute horn (Plate 8J–M). The outline of the central body is similar to other species of Areoligera, e.g. Areoligera campoensis. The antapical lobe or horn can carry processes (Plate 8F–IL and M). The archeopyle is apical and tetratabular. The operculum is free.
Dimensions
Holotype: 84 66 μm (w l). Paratype: 79 62:5 μm (w l). Average dimensions (n D 10): width 77.13 μm (62.50– 91 μm), length 63.00 μm (57–69 μm). The length does not include the operculum. The height of the antapical lobe or horn is up to 7.5 μm. Maximum length of processes 12 μm.
Stratigraphic range and occurrence
The LO of Areoligera? barskii sp. nov. occurs at 412mb.s.f., the same depth as the LOs of Rhombodinium draco and Enneadocysta pectinifromis at 412mb.s.f. The LO of A.? barskii sp. nov. (note that this may not be in situ but may be an effect of caving) is at the same level as the LO of Glaphyrocysta semitecta at 823.0mb.s.f. Areoligera.? barskii is rare (< 1% of the total dinocyst assemblage) to abundant (> 50% of the total dinocyst assemblage).
Genus assignment
The species is questionably included in the genus Areoligera. It differs from Canningia, which has an autophragm and an ectophragm and is uniformly ornamented. Cerbia is clearly paratabulate, and both mid-dorsal and mid-ventral areas are essentially devoid of ornament. Furthermore, Cerbia has usually low lateral projections and clearly defined, significantly shorter processes. Cyclonephelium has linear ornamentation, and, like Chiropteridium, the ornamentation is reduced or lacking on both mid-ventral and mid-dorsal areas. Glaphyrocysta also differs in having distally connected processes.
Remarks
Areoligera? barskii sp. nov. is distinguished from other species of the genus by the length of the processes, which are on average only 15 %–20% of the cyst width. The central body outline of Areoligera? barskii and the short length of the processes may resemble Areoligera guembelii, but processes in A. guembelii are only capitate and bifurcate and are arranged in pronounced annulate complexes. Actually, all known species of Areoligera are characterised by rather broad processes (process complexes) and rising soleate or arcuate ridges on their dorsal side (Williams and Downie, 1966). Since ridges are not clearly developed in Areoligera? barskii sp. nov., the taxon is only questionably assigned to the genus.