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Membranigonyaulax wilsonii
From Fensome et al., 2019:
Membranigonyaulax wilsonii Slimani, 1994, p.22–23, pl.2, figs.10–12,17–18,36–37; text-figs.5A–B. Holotype: Slimani, 1994, pl.2, figs.17–18; text-figs.5A–B. Taxonomic junior synonyms: Meiourogonyaulax membranacea (name not validly published), according to Slimani (2001a, p.193); Microdinium? sincfalense, according to Slimani and Louwye (2012, p.110,113). Age: early Campanian–early Maastrichtian.
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Original description (Slimani, 1994):
Membranigonyaulax wilsonii sp. nov. (P1.2, Fig.10-12,17,18,36,37; Text-fig.5)
Name Derivation: In honor of Dr. Graeme Wilson, who first described this type of cyst in his unpublished Ph.D. work.
Holotype: Turnhout -864.60 m, preparation 7, E.F. coord. J41/3 - K41/1.
Paratype: Turnhout -933 m, preparation 5, E.F. coord. 034/3.
Type locality: Turnhout -864.60 m.
Type horizon: Campanian
Synonymy:
1974: Meiourogonyaulax? membranácea sp. nov. in Wilson, pp. 274-275, pl. 13, fig. 10-12
?1992: Phanerodinium sp. 1 - MARHEINECKE, p. lll.pl. 25, fig. 7-8.
Diagnosis: Membranigonyaulax cyst with a subcircular to oval outline. The endocyst is separated from the thin, fragile ectophragm by a narrow ectocoel. The ectophragm is supported by smooth parasutural ridges with a height between 1/12 and 1/5 of the total diameter of the cyst and by intratabular structures often expressed by a single central process per plate. The paratabulation is of the gonyaulacoid type and conforms to the following formula: 4', 6", 6c, 5"', 1 p, 1 pv, 1"".
Dimensions:
Holotype: Length with operculum: 66 µm, width: 54 µm
Variations: pericyst; length without operculum: 44-54 µm, length with operculum: 42-66 µm, width: 42-58 µm.
Number of specimens measured: 15
Material: 50 specimens.
Description: The epicyst is slightly smaller than the hypocyst. The endophragm and periphragm are smooth and perfectly in contact. The parasutural ridges (4-9 µm high) are membranous and smooth. The central intratabular structures (6-10 µm long) are often represented by a single process per plate, solid or hollow and flared distally. The quinqueform arrangement of the hypocystal paraplates is constantly observed. The paracingulum is strongly laevorotatory, segmented and devoid of intratabular structures. The parasulcus is indicated by a narrow, polygonal, unsegmented surface extending from the base of the sulcal notch towards the antapex. The archaeopyle is apical type (4A), 26-34 µm wide with a hexagonal rim and a deep sulcal notch. The operculum is free or attached.
Comparison: Membranigonyaulax wilsonii sp. nov. is comparable to Meiourogonyaulax? membranácea in WILSON (1974) and has the same appearances as the cyst of Phanerodinium sp. 1 in MARHEINECKE (1992). It is distinguished from Microdinium cretaceum sp. nov. (in this work) by its broader archaeopyle of type (4A) with a deep sulcal notch, by its unsegmented parasulcus and by its less broad paracingulum. Membranigonyaulax wilsonii differs from Membranigonyaulax promineseptatum sp. nov. by its lower parasutural ridges and by the absence of intratabular ridges, it differs from Membranigonyaulax granulatum sp. nov. by its smooth endocyst, by the presence of one or two intratabular processes per plate and by the absence of intratabular ridges.
Stratigraphic distribution: Beutenaken: sample. 1 to 20, Halembaye: scale. 1 to 31; Lower Campanian - Maastrichtian inf. (Zone with G. quadrata - Zone with B. lanceolata). Turnhout: -978 to -836.95 m, Upper Campanian- Lower Maastrichtian. In WILSON (1974), Campanian sup. and Maastrichtian inf. (mucronata Zone - lanceolata zone), Maastricht region and Denmark. MARHEINECKE (1992), Maastrichtien inf., Hemmoor, Germany.
Membranigonyaulax wilsonii Slimani, 1994, p.22–23, pl.2, figs.10–12,17–18,36–37; text-figs.5A–B. Holotype: Slimani, 1994, pl.2, figs.17–18; text-figs.5A–B. Taxonomic junior synonyms: Meiourogonyaulax membranacea (name not validly published), according to Slimani (2001a, p.193); Microdinium? sincfalense, according to Slimani and Louwye (2012, p.110,113). Age: early Campanian–early Maastrichtian.
---------------------------------------------------------------------------------------------------
Original description (Slimani, 1994):
Membranigonyaulax wilsonii sp. nov. (P1.2, Fig.10-12,17,18,36,37; Text-fig.5)
Name Derivation: In honor of Dr. Graeme Wilson, who first described this type of cyst in his unpublished Ph.D. work.
Holotype: Turnhout -864.60 m, preparation 7, E.F. coord. J41/3 - K41/1.
Paratype: Turnhout -933 m, preparation 5, E.F. coord. 034/3.
Type locality: Turnhout -864.60 m.
Type horizon: Campanian
Synonymy:
1974: Meiourogonyaulax? membranácea sp. nov. in Wilson, pp. 274-275, pl. 13, fig. 10-12
?1992: Phanerodinium sp. 1 - MARHEINECKE, p. lll.pl. 25, fig. 7-8.
Diagnosis: Membranigonyaulax cyst with a subcircular to oval outline. The endocyst is separated from the thin, fragile ectophragm by a narrow ectocoel. The ectophragm is supported by smooth parasutural ridges with a height between 1/12 and 1/5 of the total diameter of the cyst and by intratabular structures often expressed by a single central process per plate. The paratabulation is of the gonyaulacoid type and conforms to the following formula: 4', 6", 6c, 5"', 1 p, 1 pv, 1"".
Dimensions:
Holotype: Length with operculum: 66 µm, width: 54 µm
Variations: pericyst; length without operculum: 44-54 µm, length with operculum: 42-66 µm, width: 42-58 µm.
Number of specimens measured: 15
Material: 50 specimens.
Description: The epicyst is slightly smaller than the hypocyst. The endophragm and periphragm are smooth and perfectly in contact. The parasutural ridges (4-9 µm high) are membranous and smooth. The central intratabular structures (6-10 µm long) are often represented by a single process per plate, solid or hollow and flared distally. The quinqueform arrangement of the hypocystal paraplates is constantly observed. The paracingulum is strongly laevorotatory, segmented and devoid of intratabular structures. The parasulcus is indicated by a narrow, polygonal, unsegmented surface extending from the base of the sulcal notch towards the antapex. The archaeopyle is apical type (4A), 26-34 µm wide with a hexagonal rim and a deep sulcal notch. The operculum is free or attached.
Comparison: Membranigonyaulax wilsonii sp. nov. is comparable to Meiourogonyaulax? membranácea in WILSON (1974) and has the same appearances as the cyst of Phanerodinium sp. 1 in MARHEINECKE (1992). It is distinguished from Microdinium cretaceum sp. nov. (in this work) by its broader archaeopyle of type (4A) with a deep sulcal notch, by its unsegmented parasulcus and by its less broad paracingulum. Membranigonyaulax wilsonii differs from Membranigonyaulax promineseptatum sp. nov. by its lower parasutural ridges and by the absence of intratabular ridges, it differs from Membranigonyaulax granulatum sp. nov. by its smooth endocyst, by the presence of one or two intratabular processes per plate and by the absence of intratabular ridges.
Stratigraphic distribution: Beutenaken: sample. 1 to 20, Halembaye: scale. 1 to 31; Lower Campanian - Maastrichtian inf. (Zone with G. quadrata - Zone with B. lanceolata). Turnhout: -978 to -836.95 m, Upper Campanian- Lower Maastrichtian. In WILSON (1974), Campanian sup. and Maastrichtian inf. (mucronata Zone - lanceolata zone), Maastricht region and Denmark. MARHEINECKE (1992), Maastrichtien inf., Hemmoor, Germany.