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Manumiella bertodano
Manumiella bertodano Thorn et al., 2009, p.439,441, pl.1, figs.1–3,5,6.
Holotype: Thorn et al., 2009, pl.1, figs.5–6.
Age: latest Maastrichtian.
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Original description (Thorn et al., 2009):
Manumiella bertodano sp. nov. (Plate I, figs. 1–3, 5, 6)
“Manumiella” n. sp. 2 Askin 1988a pars, fig. 9.4 (not 9.5).
“Manumiella” n. sp. 2 of Askin 1988a. Pirrie et al., 1991, figs. 7f, 7j.
“Manumiella” n. sp. 2 of Askin 1988a. Riding et al., 1992, pl. 2, fig. 10.
“Manumiella” n. sp. 2 of Askin 1988a. Roncaglia et al., 1999, fig. 16.9.
Holotype: Plate I, figs. 5, 6; specimen from slide D5.1237.1A, England Finder coordinate L40-4. Pericyst length 163 μm; pericyst width 88 μm (length to width ratio 1: 1.85). Endocyst length 68 μm; endocyst width 80 μm. Mesophragm present.
Repository: British Antarctic Survey, Cambridge, United Kingdom, collection number D5.1237.1A, L40-4.
Type locality: López de Bertodano Formation composite section, Marambio Group, Seymour Island, Antarctic Peninsula.
Stratigraphical horizon: Stratigraphical level 959 m in López de Bertodano Formation composite section (equivalent to the 10 m level in sub-section D5.222), Marambio Group, Seymour Island, Antarctic Peninsula, latest Maastrichtian. Isabelidinium korojonense Range Zone to Manumiella druggii Interval Zone (Helby et al., 1987).
Etymology: From the López de Bertodano Formation, from which this species was first illustrated by Askin (1988a) from material from Seymour Island.
Description: Deflandreoid dinoflagellate cyst with an elongate, subpentagonal outline in dorsoventral view. Periphragm relatively thin, smooth, microscabrate to finely granular in surface texture. Circumcavate cyst organisation. Epicyst and hypocyst approximately equal in size. Smooth, relatively thin mesophragm present in some specimens, occupying varying amounts of the pericoel and closely following the internal surface of the periphragm (commonly adjacent to it) for most of its outline. The mesophragm does not normally reach into the extremities of the horns. Equatorial folding in the periphragm often suggests vague paracingulum development. However, there are no unequivocal traces of paratabulation other than the archeopyle, which is intercalary, monoplacoid, periarcheopyle (Type I/−/−). The archeopyle is bilaterally symmetrical, iso- to lati-deltaform hexa 2a, subrounded; free operculum. Prominent, sharply distally-tapering apical horn with a pointed or rounded tip. Two asymmetrical antapical horns are present; the left antapical horn is more prominent, and is typically distally pointed. The left antapical horn is shorter than the apical horn, but is significantly longer than the right antapical horn, which is typically reduced and forms a bulge. Endocyst smooth, relatively thick and prominent, ovoid in outline, infrequently folded.
Discussion and comparisons: Manumiella bertodano sp. nov. is distinguished by the following: a prominent endocyst; an elongate, subpentagonal outline; a consistently prominent distally-pointed apical horn; a large, distally-pointed left antapical horn; and a reduced typically rounded (bulge-like) right antapical horn. Specimens of Manumiella bertodano sp. nov. occur within the uppermost López de Bertodano Formation on Seymour Island from 969 to 834 m, except for rare probably reworked specimens up to 995 m, in the section (Fig. 3). These rare forms are interpreted as probably being reworked due to their scarcity, and their sporadic presence stratigraphically above the consistent occurrences of this species. Askin (1988a, fig. 9.4) first illustrated M. bertodano sp. nov. as “Manumiella” n. sp. 2, but it was not formally described. Manumiella bertodano sp. nov. was also illustrated by Pirrie et al. (1991), Riding et al. (1992) and Roncaglia et al. (1999) from the late Maastrictian of Vega Island, Antarctica and New Zealand. The specimen of Manumiella sp. 2 of Askin 1988 in Mohr and Mao (1997, pl. 1, fig. 7) from the Maastrichtian of the Maud Rise off the coast of East Antarctica is bicavate, and hence cannot be referable to Manumiella. Furthermore, it has a short endocyst, a narrow antapical area, lacks a particularly prominent apical horn and is relatively small, hence is not conspecific with M. bertodano sp. nov. Transitional forms possessing most, but not all, of the characteristic features were observed by Askin (1988a, figs. 9.3, 9.5) and herein; examples of these are Manumiella sp. (Plate I, figs. 4, 7, 8). Marenssi et al. (2004, fig. 6F) figured a specimen that appears to be transitional between M. bertodano sp. nov. and M. seelandica. This is within the “Manumiella complex” from the Calafate Formation of southern Patagonia, Argentina. This specimen would here be designated Manumiella sp. because it does not directly satisfy the criteria for either of these two species.
Dimensions: Pericyst length 97(136)172 μm, standard deviation (sd) 19.4; pericyst width 68(91)112 μm, sd 11.3; pericyst length to width ratio 1:0.65 to 1:0.70. Endocyst length 37(68)88 μm, sd 10.8 μm; endocyst width 32(76)95 μm, sd 13.4. The range of apical horn length is not stated due to the difficulty of consistent measurement between specimens with no sharp break in slope at the ‘base’ of the horn. Thirty specimens were measured.
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Holotype: Thorn et al., 2009, pl.1, figs.5–6.
Age: latest Maastrichtian.
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Original description (Thorn et al., 2009):
Manumiella bertodano sp. nov. (Plate I, figs. 1–3, 5, 6)
“Manumiella” n. sp. 2 Askin 1988a pars, fig. 9.4 (not 9.5).
“Manumiella” n. sp. 2 of Askin 1988a. Pirrie et al., 1991, figs. 7f, 7j.
“Manumiella” n. sp. 2 of Askin 1988a. Riding et al., 1992, pl. 2, fig. 10.
“Manumiella” n. sp. 2 of Askin 1988a. Roncaglia et al., 1999, fig. 16.9.
Holotype: Plate I, figs. 5, 6; specimen from slide D5.1237.1A, England Finder coordinate L40-4. Pericyst length 163 μm; pericyst width 88 μm (length to width ratio 1: 1.85). Endocyst length 68 μm; endocyst width 80 μm. Mesophragm present.
Repository: British Antarctic Survey, Cambridge, United Kingdom, collection number D5.1237.1A, L40-4.
Type locality: López de Bertodano Formation composite section, Marambio Group, Seymour Island, Antarctic Peninsula.
Stratigraphical horizon: Stratigraphical level 959 m in López de Bertodano Formation composite section (equivalent to the 10 m level in sub-section D5.222), Marambio Group, Seymour Island, Antarctic Peninsula, latest Maastrichtian. Isabelidinium korojonense Range Zone to Manumiella druggii Interval Zone (Helby et al., 1987).
Etymology: From the López de Bertodano Formation, from which this species was first illustrated by Askin (1988a) from material from Seymour Island.
Description: Deflandreoid dinoflagellate cyst with an elongate, subpentagonal outline in dorsoventral view. Periphragm relatively thin, smooth, microscabrate to finely granular in surface texture. Circumcavate cyst organisation. Epicyst and hypocyst approximately equal in size. Smooth, relatively thin mesophragm present in some specimens, occupying varying amounts of the pericoel and closely following the internal surface of the periphragm (commonly adjacent to it) for most of its outline. The mesophragm does not normally reach into the extremities of the horns. Equatorial folding in the periphragm often suggests vague paracingulum development. However, there are no unequivocal traces of paratabulation other than the archeopyle, which is intercalary, monoplacoid, periarcheopyle (Type I/−/−). The archeopyle is bilaterally symmetrical, iso- to lati-deltaform hexa 2a, subrounded; free operculum. Prominent, sharply distally-tapering apical horn with a pointed or rounded tip. Two asymmetrical antapical horns are present; the left antapical horn is more prominent, and is typically distally pointed. The left antapical horn is shorter than the apical horn, but is significantly longer than the right antapical horn, which is typically reduced and forms a bulge. Endocyst smooth, relatively thick and prominent, ovoid in outline, infrequently folded.
Discussion and comparisons: Manumiella bertodano sp. nov. is distinguished by the following: a prominent endocyst; an elongate, subpentagonal outline; a consistently prominent distally-pointed apical horn; a large, distally-pointed left antapical horn; and a reduced typically rounded (bulge-like) right antapical horn. Specimens of Manumiella bertodano sp. nov. occur within the uppermost López de Bertodano Formation on Seymour Island from 969 to 834 m, except for rare probably reworked specimens up to 995 m, in the section (Fig. 3). These rare forms are interpreted as probably being reworked due to their scarcity, and their sporadic presence stratigraphically above the consistent occurrences of this species. Askin (1988a, fig. 9.4) first illustrated M. bertodano sp. nov. as “Manumiella” n. sp. 2, but it was not formally described. Manumiella bertodano sp. nov. was also illustrated by Pirrie et al. (1991), Riding et al. (1992) and Roncaglia et al. (1999) from the late Maastrictian of Vega Island, Antarctica and New Zealand. The specimen of Manumiella sp. 2 of Askin 1988 in Mohr and Mao (1997, pl. 1, fig. 7) from the Maastrichtian of the Maud Rise off the coast of East Antarctica is bicavate, and hence cannot be referable to Manumiella. Furthermore, it has a short endocyst, a narrow antapical area, lacks a particularly prominent apical horn and is relatively small, hence is not conspecific with M. bertodano sp. nov. Transitional forms possessing most, but not all, of the characteristic features were observed by Askin (1988a, figs. 9.3, 9.5) and herein; examples of these are Manumiella sp. (Plate I, figs. 4, 7, 8). Marenssi et al. (2004, fig. 6F) figured a specimen that appears to be transitional between M. bertodano sp. nov. and M. seelandica. This is within the “Manumiella complex” from the Calafate Formation of southern Patagonia, Argentina. This specimen would here be designated Manumiella sp. because it does not directly satisfy the criteria for either of these two species.
Dimensions: Pericyst length 97(136)172 μm, standard deviation (sd) 19.4; pericyst width 68(91)112 μm, sd 11.3; pericyst length to width ratio 1:0.65 to 1:0.70. Endocyst length 37(68)88 μm, sd 10.8 μm; endocyst width 32(76)95 μm, sd 13.4. The range of apical horn length is not stated due to the difficulty of consistent measurement between specimens with no sharp break in slope at the ‘base’ of the horn. Thirty specimens were measured.
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