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Bitectatodinium heistense
Bitectatodinium heistense, Louwye, 2001, p.127,129, fig.5, nos.1–7; text-fig.6.
Holotype: Louwye, 2001, fig.5, nos.1–4; text-fig.6.
Type locality: Zonderschot (hamlet of the city of Heist-op-denBerg, Antwerp Province, northern Belgium), temporary outcrop at x = 176.520; y = 194.600 (Lambert coordinates) (Hnyghebaert and Nolf 1979).
Type stratum: Zonderschot Sands, Berchem Formation, Miocene.
Age: early-middle Miocene.
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Original description: [Louwye, 2001]:
Diagnosis:
Small, proximate to proximochorate cyst with spherical to subspherical ambitus. The cyst comprises a thin, solid pedium bearing septa with an average height of about one tenth of the total cyst diameter. Many septa are connected laterally and thus form an incomplete and irregular sinuous reticulate pattern with relatively large lumina.
The large archeopyle is formed by the release of two precingular plates, probably 3" and 4". The archeopyle is the only indication of a tabulation. The operculum is free.
Description:
The cyst is slightly dorso-ventrally compressed. The thickness of the pedium and septa are comparable and reaches about 0.3 µm. The nontabular narrow septa are sparsely ornamented with discrete linear thickenings, barely visible under the light microscope. The crest of the septa is smooth and slightly undulating. The size of the irregular lumina formed by the septa which are laterally connected, is highly variable on an individual and ranges from 3 to 7 µm. The margins of the large precingular archeopyle, probably involving plates 3" and 4", are slightly irregular (Fig. 6). It is not known whether the operculum is compound or not. No accessory sutures were observed.
Dimensions:
Holotype: diameter including septa: 44 µm, height septa: ca. 4.5 µm.
Range: diameter including septa: 30 (41.5) 45 µm, height septa: ca. 4-6 µm. Number of specimens measured: 6.
Affinities/Comparison:
According to the study by Head (1994), Bitectatodinium tepikiense WILSON, 1973 has a wall structure composed of a complex arrangement of occasionally branched lamellae arising from raised bases. Furthermore, the average overall diameter appears to be larger (46 (53) 60 µm). Bitectatodinium raedwaldii HEAD, 1997 has a pedium from which terminally fused pili arise. Bitectatodinium ? serratum (HEAD et al. 1989) has a smooth, faintly granulate or faintly granulorugulate surface and a finely serrate archeopyle margin. The reticulate ornament of Filisphaera microornata (HEAD et al. 1989) consists of fine, sinuous muri and resembles the ornamentation of Bitectatodinium heistense nov. sp. However, the reticulate ornamentation of the new species is highly incomplete since the septa do not always interconnect laterally. Furthermore, Bitectatodinium heistense nov. sp. has a 2P archeopyle formed by the release of plates 3" and 4". This feature is not consistently observed on Filisphaera microornata or on other species attributed to this genus.
Holotype: Louwye, 2001, fig.5, nos.1–4; text-fig.6.
Type locality: Zonderschot (hamlet of the city of Heist-op-denBerg, Antwerp Province, northern Belgium), temporary outcrop at x = 176.520; y = 194.600 (Lambert coordinates) (Hnyghebaert and Nolf 1979).
Type stratum: Zonderschot Sands, Berchem Formation, Miocene.
Age: early-middle Miocene.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Louwye, 2001]:
Diagnosis:
Small, proximate to proximochorate cyst with spherical to subspherical ambitus. The cyst comprises a thin, solid pedium bearing septa with an average height of about one tenth of the total cyst diameter. Many septa are connected laterally and thus form an incomplete and irregular sinuous reticulate pattern with relatively large lumina.
The large archeopyle is formed by the release of two precingular plates, probably 3" and 4". The archeopyle is the only indication of a tabulation. The operculum is free.
Description:
The cyst is slightly dorso-ventrally compressed. The thickness of the pedium and septa are comparable and reaches about 0.3 µm. The nontabular narrow septa are sparsely ornamented with discrete linear thickenings, barely visible under the light microscope. The crest of the septa is smooth and slightly undulating. The size of the irregular lumina formed by the septa which are laterally connected, is highly variable on an individual and ranges from 3 to 7 µm. The margins of the large precingular archeopyle, probably involving plates 3" and 4", are slightly irregular (Fig. 6). It is not known whether the operculum is compound or not. No accessory sutures were observed.
Dimensions:
Holotype: diameter including septa: 44 µm, height septa: ca. 4.5 µm.
Range: diameter including septa: 30 (41.5) 45 µm, height septa: ca. 4-6 µm. Number of specimens measured: 6.
Affinities/Comparison:
According to the study by Head (1994), Bitectatodinium tepikiense WILSON, 1973 has a wall structure composed of a complex arrangement of occasionally branched lamellae arising from raised bases. Furthermore, the average overall diameter appears to be larger (46 (53) 60 µm). Bitectatodinium raedwaldii HEAD, 1997 has a pedium from which terminally fused pili arise. Bitectatodinium ? serratum (HEAD et al. 1989) has a smooth, faintly granulate or faintly granulorugulate surface and a finely serrate archeopyle margin. The reticulate ornament of Filisphaera microornata (HEAD et al. 1989) consists of fine, sinuous muri and resembles the ornamentation of Bitectatodinium heistense nov. sp. However, the reticulate ornamentation of the new species is highly incomplete since the septa do not always interconnect laterally. Furthermore, Bitectatodinium heistense nov. sp. has a 2P archeopyle formed by the release of plates 3" and 4". This feature is not consistently observed on Filisphaera microornata or on other species attributed to this genus.