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Hystrichosphaerina sarjeantii
Hystrichosphaerina sarjeantii (Gitmez, 1970) Duxbury, 1980
NOW Emmetrocysta. Originally Polystephanephorus, subsequently (and now) Emmetrocysta, thirdly Hystrichosphaerina, fourthly Stiphrosphaeridium.
Lentin and Williams, 1989, accepted the transfer of this species to Hystrichosphaerina, preferring to disagree with Lentin and Williams, 1981.
Stancliffe and Sarjeant, 1990, listed this as an accepted species of Hystrichosphaerina.
Holotype: Gitmez, 1970, pl.11, fig.4; text-fig.25; Fauconnier and Masure, 2004, pl.26, fig.7.
Age: Early Kimmeridgian
Original (Gitmez, 1970):
Derivation of the name: Named in honour of Dr. William A. S. Sarjeant, who established the genus.
Diagnosis: Polystephanephorus having a spherical to subspherical shell, bearing 14 groups of processes together with 2 single processes. There is no connection between the adjacent groups. All processes of each group are connected distally by a ring trabecula. The number of the processes in the groups is variable, between 2 and 6. Reflected tabulation: ?’, 6’’, 6’’’, 1p, 2s and 1’’’’. Surface of the shell smooth and transparent. Apical Archeopyle developed.
Holotype: BM(NH) Slide V.52792(2).Shally clay from the base of the Kimmeridge Clay, Liostrea delta Bed, Osmington Mills, Dorset.
Dimensions. Holotype: shell length 40 µ, breadth 45 µ ; process length 20-25 µ. Range of the English specimens (10 specimens measured): shell length 40-70 µ, breadth 35-60 µ ; process length 20-28 µ. French specimens (6 measured) : shell length 42-60 µ, breadth 40-55 µ ; process length 22-28 µm.
Description: Central body subspherical or spherical in shape, with groups of complicated processes. In addition to the groups of the processes, two single processes were observed, which are foliate and furcate towards their distal ends. All the processes of each group separately rise up from the central body and are subsequently connected by bridge-like strands ; near to their tips, they are foliate and fenestrate ; at their tips, they ate connected by a ring of trabecula with denticulate edges. All the processes are solid. The surface of the shell appears smooth and transparent ; because of their transparency, identification of the processes was extremely difficult. An apical Archeopyle, slightly polygonal in shape, was seen in some of the specimens studied.
Remarks: This new species of the genus Polystephanephorus differs from the previously described species in its more complicated processes. The processes are not connected proximally, as in P. urnaformis, and the branches are longer than the branches of P. calathus and P. paracalathus ; they are not directed parallel to the shell surface ; however the processes are linked by a ring trabecula as the other species of the genus. P. sarjeantii is similar to Adnatosphaeridium caulleryi, but the arrangement and the manner of linkage of the processes are different. This new species was observed in moderate number in the assemblages from Dorset and the Boulonnais, but none from Scotland.
NOW Emmetrocysta. Originally Polystephanephorus, subsequently (and now) Emmetrocysta, thirdly Hystrichosphaerina, fourthly Stiphrosphaeridium.
Lentin and Williams, 1989, accepted the transfer of this species to Hystrichosphaerina, preferring to disagree with Lentin and Williams, 1981.
Stancliffe and Sarjeant, 1990, listed this as an accepted species of Hystrichosphaerina.
Holotype: Gitmez, 1970, pl.11, fig.4; text-fig.25; Fauconnier and Masure, 2004, pl.26, fig.7.
Age: Early Kimmeridgian
Original (Gitmez, 1970):
Derivation of the name: Named in honour of Dr. William A. S. Sarjeant, who established the genus.
Diagnosis: Polystephanephorus having a spherical to subspherical shell, bearing 14 groups of processes together with 2 single processes. There is no connection between the adjacent groups. All processes of each group are connected distally by a ring trabecula. The number of the processes in the groups is variable, between 2 and 6. Reflected tabulation: ?’, 6’’, 6’’’, 1p, 2s and 1’’’’. Surface of the shell smooth and transparent. Apical Archeopyle developed.
Holotype: BM(NH) Slide V.52792(2).Shally clay from the base of the Kimmeridge Clay, Liostrea delta Bed, Osmington Mills, Dorset.
Dimensions. Holotype: shell length 40 µ, breadth 45 µ ; process length 20-25 µ. Range of the English specimens (10 specimens measured): shell length 40-70 µ, breadth 35-60 µ ; process length 20-28 µ. French specimens (6 measured) : shell length 42-60 µ, breadth 40-55 µ ; process length 22-28 µm.
Description: Central body subspherical or spherical in shape, with groups of complicated processes. In addition to the groups of the processes, two single processes were observed, which are foliate and furcate towards their distal ends. All the processes of each group separately rise up from the central body and are subsequently connected by bridge-like strands ; near to their tips, they are foliate and fenestrate ; at their tips, they ate connected by a ring of trabecula with denticulate edges. All the processes are solid. The surface of the shell appears smooth and transparent ; because of their transparency, identification of the processes was extremely difficult. An apical Archeopyle, slightly polygonal in shape, was seen in some of the specimens studied.
Remarks: This new species of the genus Polystephanephorus differs from the previously described species in its more complicated processes. The processes are not connected proximally, as in P. urnaformis, and the branches are longer than the branches of P. calathus and P. paracalathus ; they are not directed parallel to the shell surface ; however the processes are linked by a ring trabecula as the other species of the genus. P. sarjeantii is similar to Adnatosphaeridium caulleryi, but the arrangement and the manner of linkage of the processes are different. This new species was observed in moderate number in the assemblages from Dorset and the Boulonnais, but none from Scotland.