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Kleithriasphaeridium porosispinum
Kleithriasphaeridium porosispinum Davey, 1982
Originally (and now) Kleithriasphaeridium, subsequently Tityrosphaeridium.
Norris and Jux, 1984, transferred this species to Tityrosphaeridium Sarjeant, 1981. Lentin and Williams, 1985, retained it in Kleithriasphaeridium.
Holotype: Davey 1982: Pl. 10, fig. 10-12
Locus typicus: Bed J (Arkell 1933, Cherty Series, Tilly Whim Caves, Dorset,
England. Portlandian, kerberus Zone
Age: Portlandian-Ryazanian
Original Diagnosis: Davey 1982, p. 29-30
Shape: The body is of ovoidal shape with only minor dorsoventral flattening.
Wall: The wall is apparently two-layered and of moderate thickness. The periphragm is extremely fibrous and alone forms the processes. Fibres radiate from the bases of the processes over the body and the surface region between processes may be fibrous or strongly to weakly reticulate.
Processes: These are tubiform and terminate with a smooth, or slightly to strongly serrate margin. Rarely they bifurcate medially or distally. Usually two of the apical processes are linked by a crest. The width and length of the processes vary according to their position on the cyst; the largest are dorsal hypocystal and antapical in position and the smallest are the parasulcals. The apical and paracingular processes are intermediate in size. The process formula appears to be lpr, 4", 6", 6c, 5"", lp, 1"" plus xs. Fewer processes sometimes occur apparently resulting from a reduction in the number of processes in and around the parasulcal region.
Archaeopyle: Precingular, Type P (3" only) with free operculum.
DimensionsHolotype (Ám)Range (Ám)
Pericyst diameter (excluding processes)40x4832 (44) 57
Length of processes+11-2010-24
Maximum length of processes 2016 (21) 26
Remarks. K. porosispinum sp. nov. is characterised, and distinguished from other members of the genus Kleithriasphaeridium, by the presence of highly fibrous processes. There appears to be a difference in the degree of ornamentation between the onshore English specimens and those recovered from Denmark. Whereas the surface of the cyst is strongly fibro-reticulate on the English specimens, the Danish specimens tend to be smooth to slightly reticulate.
Occurrence. This species is common (5%) in the kerberus ("giganteus") Zone of Dorset and has been reported down to the pectinatus Zone (late Kimmeridgian). In eastern England it has a definite range of stenomphalus Zone (late Ryazanian) to the anguiformis - okusensis (formerly giganteus) Zones. It has been reported from the latest Ryazanian and early Valanginian here but these rare occurrences may be due to reworking. In the Haldager No. 1 borehole it occurs from 2866"-76" (late Ryazanian) to the base of the examined section.
synonyms:
1979: Kleithriasphaeridium sp. A Davey, p. 61, pl. 11, figs. 10,11
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Originally (and now) Kleithriasphaeridium, subsequently Tityrosphaeridium.
Norris and Jux, 1984, transferred this species to Tityrosphaeridium Sarjeant, 1981. Lentin and Williams, 1985, retained it in Kleithriasphaeridium.
Holotype: Davey 1982: Pl. 10, fig. 10-12
Locus typicus: Bed J (Arkell 1933, Cherty Series, Tilly Whim Caves, Dorset,
England. Portlandian, kerberus Zone
Age: Portlandian-Ryazanian
Original Diagnosis: Davey 1982, p. 29-30
Shape: The body is of ovoidal shape with only minor dorsoventral flattening.
Wall: The wall is apparently two-layered and of moderate thickness. The periphragm is extremely fibrous and alone forms the processes. Fibres radiate from the bases of the processes over the body and the surface region between processes may be fibrous or strongly to weakly reticulate.
Processes: These are tubiform and terminate with a smooth, or slightly to strongly serrate margin. Rarely they bifurcate medially or distally. Usually two of the apical processes are linked by a crest. The width and length of the processes vary according to their position on the cyst; the largest are dorsal hypocystal and antapical in position and the smallest are the parasulcals. The apical and paracingular processes are intermediate in size. The process formula appears to be lpr, 4", 6", 6c, 5"", lp, 1"" plus xs. Fewer processes sometimes occur apparently resulting from a reduction in the number of processes in and around the parasulcal region.
Archaeopyle: Precingular, Type P (3" only) with free operculum.
DimensionsHolotype (Ám)Range (Ám)
Pericyst diameter (excluding processes)40x4832 (44) 57
Length of processes+11-2010-24
Maximum length of processes 2016 (21) 26
Remarks. K. porosispinum sp. nov. is characterised, and distinguished from other members of the genus Kleithriasphaeridium, by the presence of highly fibrous processes. There appears to be a difference in the degree of ornamentation between the onshore English specimens and those recovered from Denmark. Whereas the surface of the cyst is strongly fibro-reticulate on the English specimens, the Danish specimens tend to be smooth to slightly reticulate.
Occurrence. This species is common (5%) in the kerberus ("giganteus") Zone of Dorset and has been reported down to the pectinatus Zone (late Kimmeridgian). In eastern England it has a definite range of stenomphalus Zone (late Ryazanian) to the anguiformis - okusensis (formerly giganteus) Zones. It has been reported from the latest Ryazanian and early Valanginian here but these rare occurrences may be due to reworking. In the Haldager No. 1 borehole it occurs from 2866"-76" (late Ryazanian) to the base of the examined section.
synonyms:
1979: Kleithriasphaeridium sp. A Davey, p. 61, pl. 11, figs. 10,11
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