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Operculodinium antwerpense
Operculodinium antwerpense Louwye, 1999, p.115–117, pl.2, figs.1–9.
Taxonomic senior synonym: Operculodinium tegillatum, according to Louwye and de Schepper (2010, p.767).
Taxonomic junior synonym: Operculodinium? pontis (name not validly published), according to Louwye (1999, p.115).
Holotype: Louwye, 1999, pl.2, figs.1–6.
Age: late Miocene.
Original description (Louwye, 1999):
Operculodinium antwerpensis Louwye, sp. nov. (Plate II, 1–9)
Holotype: Slide Kalmthout 82(1), England Finder reference J49/3 ( Plate II, 1–6).
Repository: Collection of the ‘Institut Royal des Sciences Naturelles' (Brussels), catalogue number IRScN b3656.
Type locality: Kalmthout (Antwerp province, Belgium), well no. 6E110 of the Geological Survey of Belgium, 82 m below core top.
Type stratum: Diest Formation, Upper Miocene.
Etymology: Named for the Antwerp province, Belgium, in which the type locality Kalmthout is located.
Diagnosis: Small, proximochorate cyst with an elliptical to spherical ambitus. The endophragm is ornamented with granules or small, solid rods supporting a thin smooth and continuous periphragm. The periphragm forms short and solid, tapering processes, distally blunt to minutely platformed and with hollow expanded bases. The processes are isolated or proximally to medially joined. The distribution of the processes is non-tabular. Large precingular archeopyle, type P(3″) with free operculum.
Description: The thickness of the cyst wall varies between 0.8 and 2.5 μm and consists of an endophragm and hyaline periphragm. Both have a thickness of less than 0.3 μm and are separated by granules or solid rods. The length of the processes on a cyst is usually uniform. The simple processes can proximally be 2 to 5 times wider than distally which gives the simple process the appearance of a steep, truncated pyramid. No alignment of the processes was observed, the archeopyle is the only reflection of a tabulation.
Dimensions: Holotype: length of central body, 36 μm; width (equatorial) of central body, 34 μm; length of processes 5–7 μm. Range: length of central body, 32(36)42 μm; width (equatorial) of central body, 29(34)39 μm; length of processes 2(5)8 μm. Number of specimens measured: 12.
Comparison: The periphragm of Operculodinium tegillatum Head, 1997 is clearly reticulate to perforate, while the periphragm of the new species is continuous. Furthermore, proximally to medially joined processes are observed on every specimen of Operculodinium antwerpensis, a feature apparently not shared with Operculodinium tegillatum Head, 1997. Operculodinium antwerpenis differs from all other Operculodinium species by the architecture of the bilayered wall and the presence of granules or small, solid rods between the wall layers.
Occurrence: Upper Miocene (Diest Formation) of northern Belgium (this study); Upper Miocene (Diest Formation) and Pliocene (Kattendijk and Lillo formations) of northern Belgium as `Operculodinium pontis'? Zevenboom and Santarelli (ms name) in Zevenboom (1995) and Louwye and Laga (1998).
Taxonomic senior synonym: Operculodinium tegillatum, according to Louwye and de Schepper (2010, p.767).
Taxonomic junior synonym: Operculodinium? pontis (name not validly published), according to Louwye (1999, p.115).
Holotype: Louwye, 1999, pl.2, figs.1–6.
Age: late Miocene.
Original description (Louwye, 1999):
Operculodinium antwerpensis Louwye, sp. nov. (Plate II, 1–9)
Holotype: Slide Kalmthout 82(1), England Finder reference J49/3 ( Plate II, 1–6).
Repository: Collection of the ‘Institut Royal des Sciences Naturelles' (Brussels), catalogue number IRScN b3656.
Type locality: Kalmthout (Antwerp province, Belgium), well no. 6E110 of the Geological Survey of Belgium, 82 m below core top.
Type stratum: Diest Formation, Upper Miocene.
Etymology: Named for the Antwerp province, Belgium, in which the type locality Kalmthout is located.
Diagnosis: Small, proximochorate cyst with an elliptical to spherical ambitus. The endophragm is ornamented with granules or small, solid rods supporting a thin smooth and continuous periphragm. The periphragm forms short and solid, tapering processes, distally blunt to minutely platformed and with hollow expanded bases. The processes are isolated or proximally to medially joined. The distribution of the processes is non-tabular. Large precingular archeopyle, type P(3″) with free operculum.
Description: The thickness of the cyst wall varies between 0.8 and 2.5 μm and consists of an endophragm and hyaline periphragm. Both have a thickness of less than 0.3 μm and are separated by granules or solid rods. The length of the processes on a cyst is usually uniform. The simple processes can proximally be 2 to 5 times wider than distally which gives the simple process the appearance of a steep, truncated pyramid. No alignment of the processes was observed, the archeopyle is the only reflection of a tabulation.
Dimensions: Holotype: length of central body, 36 μm; width (equatorial) of central body, 34 μm; length of processes 5–7 μm. Range: length of central body, 32(36)42 μm; width (equatorial) of central body, 29(34)39 μm; length of processes 2(5)8 μm. Number of specimens measured: 12.
Comparison: The periphragm of Operculodinium tegillatum Head, 1997 is clearly reticulate to perforate, while the periphragm of the new species is continuous. Furthermore, proximally to medially joined processes are observed on every specimen of Operculodinium antwerpensis, a feature apparently not shared with Operculodinium tegillatum Head, 1997. Operculodinium antwerpenis differs from all other Operculodinium species by the architecture of the bilayered wall and the presence of granules or small, solid rods between the wall layers.
Occurrence: Upper Miocene (Diest Formation) of northern Belgium (this study); Upper Miocene (Diest Formation) and Pliocene (Kattendijk and Lillo formations) of northern Belgium as `Operculodinium pontis'? Zevenboom and Santarelli (ms name) in Zevenboom (1995) and Louwye and Laga (1998).