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Apteodinium crassum
Apteodinium crassum, Slimani and Louwye, 2013, p. 13, pl.1, figs.1–16.
Holotype: Slimani and Louwye, 2013, pl.1, figs.1–4.
Type locality: Turnhout, Antwerp province, northern Belgium, well no. 17E225 (S120) of the Geological Survey of Belgium.
Stratigraphic horizon: Upper part of the Upper Campanian, Turnhout borehole, 931.50 m depth.
Stratigraphic range: Upper part of the Upper Campanian of Turnhout in northern Belgium (Slimani, 1995).
Age: late Campanian.
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Original description: [Slimani and Louwye, 2013]:
Diagnosis:
A spheroidal to ovoidal species of Apteodinium characterized by a very thick and finely spongeous single-layered wall. The cingulum is absent or faintly indicated by very low ridges.
The archaeopyle is formed by the release of the precingular plate 3″ and is in most cases the sole indication of tabulation. The operculum is mostly free, occasionally in place.
Description:
The dinoflagellate cyst of intermediate size has a spheroidal to ovoidal shape and bears a small subtriangular and bulbous apical horn (4–7 µm length) with a nipple-like tip.
The cyst wall consists of a very thick (6–8 µm) and finely spongeous autophragm. The thickness of the autophragm is constant on a single specimen.
The tabulation pattern is indicated by the archaeopyle and occasionally by a discrete cingulum.
The cingulum is then expressed by an unsegmented transverse depression faintly bordered by two parallel low ridges. The cingulum is slightly laevorotatory and has a maximum width of 4 µm. A few specimens present small circular to oval alveoles (0.5–6 µm diameter), which are often located deeply within the innermost half of the spongeous autophragm.
The precingular archaeopyle (type P) has a pentagonal outline and is mostly free, or occasionally adherent.
Affinities/Discussion:
The very thick and finely spongeous autophragm, together with the bulbous apical horn with a nipple-like tip, distinguishes Apteodinium crassus sp. nov. from all other Apteodinium species. Apteodinium granulatum Eisenack, 1958, Apteodinium maculatum subsp. maculatum Eisenack and Cookson, 1960 and Apteodinium thelium Sarjeant, 1985 have at first glance a slightly similar wall structure, but differ, however, by their spongeous-granulated and much thinner walls that possess a variable thickness on a single specimen. Furthermore, the apical horns of the latter species are longer. Apteodinium spongiosum McIntyre and Brideaux, 1980, differs distinctly from A. crassus sp. nov. in possessing a complex scrollwork-like structure on the cyst wall, rather than a finely spongeous autophragm with constant thickness on a single specimen. The new species is conspecific with Apteodinium sp. A of Slimani (1995) and is associated with species of Samlandia Eisenack, 1954 in the upper Upper Campanian (Beutenaken Member) in the Turnhout borehole.
Dimensions of measured specimens:
Length 62(67)77 µm, width 60(64)68 µm. 12 specimens measured.
Holotype: Slimani and Louwye, 2013, pl.1, figs.1–4.
Type locality: Turnhout, Antwerp province, northern Belgium, well no. 17E225 (S120) of the Geological Survey of Belgium.
Stratigraphic horizon: Upper part of the Upper Campanian, Turnhout borehole, 931.50 m depth.
Stratigraphic range: Upper part of the Upper Campanian of Turnhout in northern Belgium (Slimani, 1995).
Age: late Campanian.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Slimani and Louwye, 2013]:
Diagnosis:
A spheroidal to ovoidal species of Apteodinium characterized by a very thick and finely spongeous single-layered wall. The cingulum is absent or faintly indicated by very low ridges.
The archaeopyle is formed by the release of the precingular plate 3″ and is in most cases the sole indication of tabulation. The operculum is mostly free, occasionally in place.
Description:
The dinoflagellate cyst of intermediate size has a spheroidal to ovoidal shape and bears a small subtriangular and bulbous apical horn (4–7 µm length) with a nipple-like tip.
The cyst wall consists of a very thick (6–8 µm) and finely spongeous autophragm. The thickness of the autophragm is constant on a single specimen.
The tabulation pattern is indicated by the archaeopyle and occasionally by a discrete cingulum.
The cingulum is then expressed by an unsegmented transverse depression faintly bordered by two parallel low ridges. The cingulum is slightly laevorotatory and has a maximum width of 4 µm. A few specimens present small circular to oval alveoles (0.5–6 µm diameter), which are often located deeply within the innermost half of the spongeous autophragm.
The precingular archaeopyle (type P) has a pentagonal outline and is mostly free, or occasionally adherent.
Affinities/Discussion:
The very thick and finely spongeous autophragm, together with the bulbous apical horn with a nipple-like tip, distinguishes Apteodinium crassus sp. nov. from all other Apteodinium species. Apteodinium granulatum Eisenack, 1958, Apteodinium maculatum subsp. maculatum Eisenack and Cookson, 1960 and Apteodinium thelium Sarjeant, 1985 have at first glance a slightly similar wall structure, but differ, however, by their spongeous-granulated and much thinner walls that possess a variable thickness on a single specimen. Furthermore, the apical horns of the latter species are longer. Apteodinium spongiosum McIntyre and Brideaux, 1980, differs distinctly from A. crassus sp. nov. in possessing a complex scrollwork-like structure on the cyst wall, rather than a finely spongeous autophragm with constant thickness on a single specimen. The new species is conspecific with Apteodinium sp. A of Slimani (1995) and is associated with species of Samlandia Eisenack, 1954 in the upper Upper Campanian (Beutenaken Member) in the Turnhout borehole.
Dimensions of measured specimens:
Length 62(67)77 µm, width 60(64)68 µm. 12 specimens measured.