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Conosphaeridium norfolkense
Conosphaeridium norfolkense, Pearce, M. A., 2018, p. 79-80
Holotype: Pearce, M. A., 2018, Pl. 3, figs. 1–3.
Type locality and horizon: Upper Chalk (Burnham Chalk Formation)
Stratigraphic range: Lower Coniacian
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Original description: [Pearce, M. A., 2018]:
Diagnosis:
A species of Conosphaeridium with a smooth to only very weakly striate periphragm.
Description:
Medium-sized proximochorate dinoflagellate with a globular sub-spherical central body.
The wall is two-layered, comprised of a thin, smooth endophragm and smooth to very weakly striate periphragm that forms hollow intratabular processes.
The processes are relatively squat, rounded-lagenate and typically open distally.
The archaeopyle is precingular, Type P3′′ , the operculum may be attached, but more usually detached.
Dimensions:
Holotype: central body diameter = 60 μm, maximum processes length = 17 μm.
Paratype: central body diameter = 51 μm, maximum processes length = 12 μm.
Range central body diameter = 44(54)65 μm, maximum processes length = 8(12)17 μm
Six specimens measured
Affinities/Comparison:
Both Conosphaeridium abbreviatum Wilson, 1984 and C. striatoconum (Deflandre and Cookson, 1955) Cookson and Eisenack, 1969 differ by possessing strong ribs on the processes; the former also has a much larger central body size (holotype body diameter 95 × 81 μm). Brideaux and McIntyre (1975, pl. 7, figs. 17–18) figured a specimen as Conosphaeridium sp. A from the Middle Albian of northern Canada that is similar to C. norfolkense in possessing a very weakly striate periphragm, but which differs in the shape of the processes that are tubular and narrow distally with a truncated distal margin. The specimen figured as Conosphaeridium cf. striatoconus by Benson (1976) from the undifferentiated Upper Cretaceous of Maryland, USA, is considered here synonymous with C. norfolkense sp. Nov.
Holotype: Pearce, M. A., 2018, Pl. 3, figs. 1–3.
Type locality and horizon: Upper Chalk (Burnham Chalk Formation)
Stratigraphic range: Lower Coniacian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Pearce, M. A., 2018]:
Diagnosis:
A species of Conosphaeridium with a smooth to only very weakly striate periphragm.
Description:
Medium-sized proximochorate dinoflagellate with a globular sub-spherical central body.
The wall is two-layered, comprised of a thin, smooth endophragm and smooth to very weakly striate periphragm that forms hollow intratabular processes.
The processes are relatively squat, rounded-lagenate and typically open distally.
The archaeopyle is precingular, Type P3′′ , the operculum may be attached, but more usually detached.
Dimensions:
Holotype: central body diameter = 60 μm, maximum processes length = 17 μm.
Paratype: central body diameter = 51 μm, maximum processes length = 12 μm.
Range central body diameter = 44(54)65 μm, maximum processes length = 8(12)17 μm
Six specimens measured
Affinities/Comparison:
Both Conosphaeridium abbreviatum Wilson, 1984 and C. striatoconum (Deflandre and Cookson, 1955) Cookson and Eisenack, 1969 differ by possessing strong ribs on the processes; the former also has a much larger central body size (holotype body diameter 95 × 81 μm). Brideaux and McIntyre (1975, pl. 7, figs. 17–18) figured a specimen as Conosphaeridium sp. A from the Middle Albian of northern Canada that is similar to C. norfolkense in possessing a very weakly striate periphragm, but which differs in the shape of the processes that are tubular and narrow distally with a truncated distal margin. The specimen figured as Conosphaeridium cf. striatoconus by Benson (1976) from the undifferentiated Upper Cretaceous of Maryland, USA, is considered here synonymous with C. norfolkense sp. Nov.