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Andalusiella guersteiniae
From Fensome et al., 2019:
Andalusiella guersteiniae, Ottone et al., 2018, p.344–346, fig.3, nos.1–4.
Holotype Ottone et al., 2018, p.344–346, fig.3, no.1.
Age: late Campanian to early Maastrichtian.
Type locality: Bahía Blanca, Colorado Basin
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Original description: [Ottone, E. G. et al., 2018]:
Diagnosis:
Proximate, acrocavate organic-walled dinoflagellate cyst, with a rhomboidal to ellipsoidal central body lengthened by a long apical horn and a single undivided antapical horn. Wall composed of a periphragm and an endophragm, the latter extends into the horns. A peridinioid
paratabulation is suggested by the intercalary 2a hexa iso-deltaform archeopyle and a paracingulum. Parasulcus with a flagellar scar.
Description:
Long cyst with a rhomboidal to ellipsoidal central body. The apical horn is longer than the single undivided antapical horn which is the left one. The periphragm is smooth to chagrinate and markedly thinner than the endophragm. The endophragm develops thickenings in horn areas. The wall of the endophragm is smooth. The periphragm and the endophragm are closely pressed on the central body. The paracingulum is currently bordered by folds. The parasulcus bears a flagellar scar.
Archeopyle: Intercalary, 2a hexa, iso-deltaform
Operculum: is adherent or free
Dimensions:
19 specimens measured: Overall length 185 (196) 208 μm, overall width 70 (81) 91 μm, apical horn 41–67 μm, antapical horn 36–38 μm, overall length/wide ratio ≈ 2.5–2.8, endophragm length/wide ratio ≈ 1.2–1.6, apical/antapical horns ratio ≈ 1.1–1.7, archeopyle ratio (AR) ≈ 1, archeopyle
signum (AS) = 0.3–0.6, transverse archeopyle index = 0.5, longitudinal archeopyle index = 0.7.
Affinities/Comparison:
Andalusiella guersteiniae sp. nov. is distinguishable from most species that have two or divided antapical horns as described by Masure et al. (1996) and Srivastava (1995). In contrast, Andalusiella guersteiniae sp. nov. should be compared to species that only have a single undivided antapical horn as: A. rhomboides, A. spinosa and A. basita. All these species have shorter horns that are proportional to the central body, however, A. rhomboides and A. spinosa show an ornamented periphragm, verrucose in A. rhomboides, spiny in A. spinosa. Andalusiella guersteiniae sp. nov. differs from A. basita by virtue of its much more thickened endophragm, its apical and antapical horns of unequal
length, the presence of a paracingulum and of a distinct flagellar scar, and by reaching a markedly larger size. Close comparison of A. guersteiniae sp. nov. with specimens from the Campanian of offshore Mauritania, referred to as A. polymorpha by Malloy (1972) is hindered by the fact that the African material has not been described.
Andalusiella guersteiniae, Ottone et al., 2018, p.344–346, fig.3, nos.1–4.
Holotype Ottone et al., 2018, p.344–346, fig.3, no.1.
Age: late Campanian to early Maastrichtian.
Type locality: Bahía Blanca, Colorado Basin
---------------------------------------------------------------------------------------------------
Original description: [Ottone, E. G. et al., 2018]:
Diagnosis:
Proximate, acrocavate organic-walled dinoflagellate cyst, with a rhomboidal to ellipsoidal central body lengthened by a long apical horn and a single undivided antapical horn. Wall composed of a periphragm and an endophragm, the latter extends into the horns. A peridinioid
paratabulation is suggested by the intercalary 2a hexa iso-deltaform archeopyle and a paracingulum. Parasulcus with a flagellar scar.
Description:
Long cyst with a rhomboidal to ellipsoidal central body. The apical horn is longer than the single undivided antapical horn which is the left one. The periphragm is smooth to chagrinate and markedly thinner than the endophragm. The endophragm develops thickenings in horn areas. The wall of the endophragm is smooth. The periphragm and the endophragm are closely pressed on the central body. The paracingulum is currently bordered by folds. The parasulcus bears a flagellar scar.
Archeopyle: Intercalary, 2a hexa, iso-deltaform
Operculum: is adherent or free
Dimensions:
19 specimens measured: Overall length 185 (196) 208 μm, overall width 70 (81) 91 μm, apical horn 41–67 μm, antapical horn 36–38 μm, overall length/wide ratio ≈ 2.5–2.8, endophragm length/wide ratio ≈ 1.2–1.6, apical/antapical horns ratio ≈ 1.1–1.7, archeopyle ratio (AR) ≈ 1, archeopyle
signum (AS) = 0.3–0.6, transverse archeopyle index = 0.5, longitudinal archeopyle index = 0.7.
Affinities/Comparison:
Andalusiella guersteiniae sp. nov. is distinguishable from most species that have two or divided antapical horns as described by Masure et al. (1996) and Srivastava (1995). In contrast, Andalusiella guersteiniae sp. nov. should be compared to species that only have a single undivided antapical horn as: A. rhomboides, A. spinosa and A. basita. All these species have shorter horns that are proportional to the central body, however, A. rhomboides and A. spinosa show an ornamented periphragm, verrucose in A. rhomboides, spiny in A. spinosa. Andalusiella guersteiniae sp. nov. differs from A. basita by virtue of its much more thickened endophragm, its apical and antapical horns of unequal
length, the presence of a paracingulum and of a distinct flagellar scar, and by reaching a markedly larger size. Close comparison of A. guersteiniae sp. nov. with specimens from the Campanian of offshore Mauritania, referred to as A. polymorpha by Malloy (1972) is hindered by the fact that the African material has not been described.