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Aprobolocysta extrema
From Fensome et al., 2019:
Aprobolocysta extrema, Duxbury, 2001, p.99, fig.2, nos.1–4.
Holotype: Duxbury, 2001, fig.2, no.1.
Age: early Valanginian.
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Original description: [Duxbury, 2001]:
Aprobolocysta extrema n. sp.
Holotype: Figure 2.1.
Type Locality: Well 13/30-1 at 7333.67 ft (core), Early Valanginian, E.F. N36.0.
Derivation of Name: From the Latin extremus, extreme, utmost – in reference to the very high reticulum.
Diagnosis: A fairly large, very distinctive dinoflagellate cyst. The endocyst is elongate ovoidal, and low, distally closed and rounded projections
may be present at both poles. A high, reticulate structure is formed entirely from the periphragm layer; this is delicate, often distorted and its height approximates half the width of the endocyst. The archeopyle is apical, and the operculum is usually detached, and a deep sulcal notch, typical of the genus, is observed on opercular detachment. No paratabulation has been discerned other than around the archeopyle margin.
Dimensions: Holotype (operculum detached): Endocyst -- 60 x 41 μm
Overall -- 76 x65 μm
Complete specimens: Endocyst -- 66 (65) 64 x 36 (33) 30 μm
Overall -- 94 (93) 92 x 54 (49) 44 μm
Specimens measured -- 2
Operculum detached: Endocyst -- 60 (58) 56 x 41 (37) 29 μm
Overall -- 79 (74) 68 x 66 (64) 61 μm
Specimens measured -- 3
Comments: Aprobolocysta extrema n. sp. differs from all other species of this genus in possessing a high, reticulate structure formed entirely from the periphragm layer. The delicate nature of this species often causes cyst distortion. Poorly preserved specimens are reminiscent of the genus Valensiella EISENACK, 1963, although the deep sulcal notch and low polar projections are typical of the genus Aprobolocysta DUXBURY, 1977.
This very distinctive species is restricted to the Early Valanginian, and is a valuable, although rare, indicator of that Sub-stage.
In addition to the U.K.C.S., this species has been recorded from the North Sea Norwegian and Dutch sectors, where its stratigraphic range appears to be equally restricted.
Aprobolocysta extrema, Duxbury, 2001, p.99, fig.2, nos.1–4.
Holotype: Duxbury, 2001, fig.2, no.1.
Age: early Valanginian.
---------------------------------------------------------------------------------------------------
Original description: [Duxbury, 2001]:
Aprobolocysta extrema n. sp.
Holotype: Figure 2.1.
Type Locality: Well 13/30-1 at 7333.67 ft (core), Early Valanginian, E.F. N36.0.
Derivation of Name: From the Latin extremus, extreme, utmost – in reference to the very high reticulum.
Diagnosis: A fairly large, very distinctive dinoflagellate cyst. The endocyst is elongate ovoidal, and low, distally closed and rounded projections
may be present at both poles. A high, reticulate structure is formed entirely from the periphragm layer; this is delicate, often distorted and its height approximates half the width of the endocyst. The archeopyle is apical, and the operculum is usually detached, and a deep sulcal notch, typical of the genus, is observed on opercular detachment. No paratabulation has been discerned other than around the archeopyle margin.
Dimensions: Holotype (operculum detached): Endocyst -- 60 x 41 μm
Overall -- 76 x65 μm
Complete specimens: Endocyst -- 66 (65) 64 x 36 (33) 30 μm
Overall -- 94 (93) 92 x 54 (49) 44 μm
Specimens measured -- 2
Operculum detached: Endocyst -- 60 (58) 56 x 41 (37) 29 μm
Overall -- 79 (74) 68 x 66 (64) 61 μm
Specimens measured -- 3
Comments: Aprobolocysta extrema n. sp. differs from all other species of this genus in possessing a high, reticulate structure formed entirely from the periphragm layer. The delicate nature of this species often causes cyst distortion. Poorly preserved specimens are reminiscent of the genus Valensiella EISENACK, 1963, although the deep sulcal notch and low polar projections are typical of the genus Aprobolocysta DUXBURY, 1977.
This very distinctive species is restricted to the Early Valanginian, and is a valuable, although rare, indicator of that Sub-stage.
In addition to the U.K.C.S., this species has been recorded from the North Sea Norwegian and Dutch sectors, where its stratigraphic range appears to be equally restricted.