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Oligosphaeridium junctum
Oligosphaeridium ?junctum Bailey and Loy, 1997, p.159,162, pl.1, figs.1–4; pl.2, figs.1–4; text-fig.2.
Holotype: Bailey and Loy, 1997, pl.1, figs.1–3.
Originally Oligosphaeridium, subsequently (and now) Oligosphaeridium?.
Questionable assignment: Fauconnier and Cornu in Fauconnier and Masure (2004, p.402).
Age: early–late Hauterivian.
Original description (Bailey & Loy, 1997)
Derivation of name. Latin junctus, a connection; with reference to the distally linked processes of this species.
Diagnosis. Chorate gonyaulacoid cyst with a subspherical body and plate centred tubiform processes on the apical, precingular, postcingular and antapical paraplates. Endophragm and periphragm more or less smooth and closely appressed, except where the periphragm separates to form the processes. Processes expanded distally, with complex terminations, comprising elongated, flexuose spines which thin to thread-like trabeculae
that often link adjacent processes. Apical archaeopyle, type (tA).
Holotype. Slide EH1(2). England finder reference E37. Plate 1, figs 1- 3.
Type locality. Conoco Well 15/29b-4Z, 14636 feet (from RKB).
Dimensions. Inner body 43(52)61 μm (12 specimens measured), overall diameter 78(91)104μm (12 specimens measured). Dimensions of holotype; inner body 48 μm, overall diameter 96 μm. Specimens measured from samples EHi and EH2.
Remarks. The process formula corresponds to that of the type species 0. complex. the distal trabecula are thin and irregular, sometimes branching and often connecting with adjacent processes. However, they are very delicate and prone to breakage and often do not interconnect. Distally, the main trunk of some of the larger processes may be deeply furcate (see text Fig. 2).
Comparison. Of species published to date O. junctum is most similar to the type species, O. complex (White) Davey & Williams, 1966, which lacks distal trabecula and has generally less complicated process terminations. Oligosphaeridium trabeculosum Singh, 1983 has narrower processes and thicker trabeculae, which do not link pre- and post-cingular processes. Furthermore, the hypocyst processes of O. trabeculosum are longer than those on the epicyst, whilst there is no such distinction in O. junctum.
The authors feel that this new species belongs to the genus Oligosphaeridium rather than Rigaudella Below, 1982, even though the processes are ditally linked by trabecula. Rigaudella exhibits both solid and hollow processes and has an undifferentiated autophragm.
Occurrence. Oligosphaeridium junctum is stratigraphically restricted to Hauterivian-aged sediments in the l 5/29b-4Z well. it has also been recorded from Hauterivian strata of the Danish central trough by Heilmann-Clausen ( 1987). The present authors have also observed O. junctum in the Hauterivian of numerous North Sea wells.
Holotype: Bailey and Loy, 1997, pl.1, figs.1–3.
Originally Oligosphaeridium, subsequently (and now) Oligosphaeridium?.
Questionable assignment: Fauconnier and Cornu in Fauconnier and Masure (2004, p.402).
Age: early–late Hauterivian.
Original description (Bailey & Loy, 1997)
Derivation of name. Latin junctus, a connection; with reference to the distally linked processes of this species.
Diagnosis. Chorate gonyaulacoid cyst with a subspherical body and plate centred tubiform processes on the apical, precingular, postcingular and antapical paraplates. Endophragm and periphragm more or less smooth and closely appressed, except where the periphragm separates to form the processes. Processes expanded distally, with complex terminations, comprising elongated, flexuose spines which thin to thread-like trabeculae
that often link adjacent processes. Apical archaeopyle, type (tA).
Holotype. Slide EH1(2). England finder reference E37. Plate 1, figs 1- 3.
Type locality. Conoco Well 15/29b-4Z, 14636 feet (from RKB).
Dimensions. Inner body 43(52)61 μm (12 specimens measured), overall diameter 78(91)104μm (12 specimens measured). Dimensions of holotype; inner body 48 μm, overall diameter 96 μm. Specimens measured from samples EHi and EH2.
Remarks. The process formula corresponds to that of the type species 0. complex. the distal trabecula are thin and irregular, sometimes branching and often connecting with adjacent processes. However, they are very delicate and prone to breakage and often do not interconnect. Distally, the main trunk of some of the larger processes may be deeply furcate (see text Fig. 2).
Comparison. Of species published to date O. junctum is most similar to the type species, O. complex (White) Davey & Williams, 1966, which lacks distal trabecula and has generally less complicated process terminations. Oligosphaeridium trabeculosum Singh, 1983 has narrower processes and thicker trabeculae, which do not link pre- and post-cingular processes. Furthermore, the hypocyst processes of O. trabeculosum are longer than those on the epicyst, whilst there is no such distinction in O. junctum.
The authors feel that this new species belongs to the genus Oligosphaeridium rather than Rigaudella Below, 1982, even though the processes are ditally linked by trabecula. Rigaudella exhibits both solid and hollow processes and has an undifferentiated autophragm.
Occurrence. Oligosphaeridium junctum is stratigraphically restricted to Hauterivian-aged sediments in the l 5/29b-4Z well. it has also been recorded from Hauterivian strata of the Danish central trough by Heilmann-Clausen ( 1987). The present authors have also observed O. junctum in the Hauterivian of numerous North Sea wells.