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Hapsocysta susanae
Hapsocysta susanae Duxbury, 2002, p.78-80, pl.1, figs.1-6,9; text-figs.3-5. Holotype: Duxbury, 2002, pl.1, figs.1-2; text-fig.3. Age: Early-Mid Albian.
Original description
Hapsocysta susanae n. sp.
(Pl. 1, figs 1–6, 9; figs 3–5)
Derivation. After my wife, Susan, in recognition of her continuing and necessary patience with the author.
Diagnosis. A spheroidal dinocyst species which consists mainly of an open parasutural network. Individual parasutures are V-shaped in cross-section, composed of a thickened, linear base and two smooth, ribbon-like flanges. A gonyaulacacean paratabulation of the form acl., aa, 4', 6'', as, 6c, pras, ras, las, 6''', rs, ls, ps, 1p, 1'''' is outlined by trifurcation of the parasutures. The width of individual parasutures varies between 0.8 µm and 2.8 µm, with the more slender ones bordering the smaller paraplates. A short apical projection, composed entirely of parasutural material, is observed in lateral orientation, and a small, very thin-walled, wrinkled endocyst is observed in the minority of specimens.
Holotype. Plate 1, figs 1, 2; fig. 3.
Paratype. Plate 1, fig. 4; fig. 4.
Locality & horizon. Holotype: well 14/29a-5 at 8399.0 ft (sidewall core), Middle Albian (E.F. K43.0). Paratype: well 14/29a-5 at 8420.0 ft (sidewall core), Middle Albian (E.F. S42.4).
Dimensions. Holotype: 70 × 70 µm. Paratype: 71 × 68 µm. Overall: 78 (70) 60 × 73 (65) 50 µm, 15 specimens measured. Endocyst: 34 (33) 30 × 28 (27) 26 µm, 3 specimens measured.
Remarks. This species has been placed in Hapsocysta Davey, 1979 because it is essentially an open meshwork, composed of narrow strands, outlining the paratabulation and surrounding an endocyst. Unfortunately, the paratabulation of the genus Hapsocysta has not been formally reported, and no direct comparisons may be made. However, Davey (1979) described, ‘large, basically pentagonal, preand postcingular, and antapical areas, elongate paracingular areas and small, subcircular parasulcal areas’.
An endocyst is observed only in the minority of specimens of Hapsocysta susanae, and no clear attachment to the parasutural framework has been discerned. The absence of an endocyst from the majority of specimens may be due to its easy detachment and small size; it is presumably easily detached and typically lost through the wide mesh of the encircling framework.
Close comparisons may be made between H. susanae and the type species, Hapsocysta peridictya (Eisenack & Cookson, 1960) Davey, 1979, which occurs at the same stratigraphic level in the study area (although the last species has a significantly longer range). Specimens of H. peridictya (Eisenack & Cookson, 1960) Davey, 1979 illustrated and described by Morgan (1980) are particularly reminiscent of H. susanae, including specimens which, ‘lack an endophragm’.
H. susanae differs from H. peridictya (Eisenack & Cookson, 1960) Davey, 1979 in having a more rigid parasutural framework with broader individual elements, in its significantly smaller overall size and in the smaller size of the endocyst relative to the parasutural network. The last feature may account for the characteristic loss of the endocyst in H. susanae.
In addition, H. susanae has an apical projection, a feature absent from H. peridictya (Eisenack & Cookson, 1960) Davey, 1979, and no specimens of H. susanae have yet displayed, ‘a continuous ectophragm joining the trabeculae’, as described for some specimens of H. peridictya by Morgan (1980).
The structure of H. susanae is very reminiscent of the genera Evittosphaerula Manum, 1979 and Chaenosphaerula Damassa, 1997. These are monotypic, morphologically very similar, and the type species, Evittosphaerula paratabulata Manum, 1979 and Chaenosphaerula magnifica Damassa, 1997 were described from the Lower Miocene and Upper Oligocene respectively. However, H. susanae differs from both of these in possessing an apical projection and an endocyst (although this is usually lost).
Detailed comparison may be made of the paratabulation of H. susanae (figured here) with illustrations in Damassa (1997, figs 2, 3 and 6) of apical–ventral paratabulation patterns for E. paratabulata Manum, 1979 and C. magnifica Damassa, 1997. In particular, the configuration of paraplate quartet {5'', 4', as, 6''} is most similar to that in C. magnifica and to most species of Impagidinium Stover & Evitt, 1978. However, the multi-paraplate sulcal arrangement in H. susanae is very similar to that of E. paratabulata.
The structure of H. susanae also bears some resemblance to the genus Cannosphaeropsis Wetzel, 1933, although the trabecular network of the latter genus bears short, distally bi- or trifurcate spines (see Duxbury, 1980; Marheinecke, 1992), a feature absent from H. susanae.
The stratigraphic range of H. susanae is short, restricted to the Early to Middle Albian, palyzones LKP33.1 to LKP34 of Duxbury (2001), where it can be common. In the study area, its inception is within the upper Carrack Formation, and its extinction is within the lower Rødby Formation.
Original description
Hapsocysta susanae n. sp.
(Pl. 1, figs 1–6, 9; figs 3–5)
Derivation. After my wife, Susan, in recognition of her continuing and necessary patience with the author.
Diagnosis. A spheroidal dinocyst species which consists mainly of an open parasutural network. Individual parasutures are V-shaped in cross-section, composed of a thickened, linear base and two smooth, ribbon-like flanges. A gonyaulacacean paratabulation of the form acl., aa, 4', 6'', as, 6c, pras, ras, las, 6''', rs, ls, ps, 1p, 1'''' is outlined by trifurcation of the parasutures. The width of individual parasutures varies between 0.8 µm and 2.8 µm, with the more slender ones bordering the smaller paraplates. A short apical projection, composed entirely of parasutural material, is observed in lateral orientation, and a small, very thin-walled, wrinkled endocyst is observed in the minority of specimens.
Holotype. Plate 1, figs 1, 2; fig. 3.
Paratype. Plate 1, fig. 4; fig. 4.
Locality & horizon. Holotype: well 14/29a-5 at 8399.0 ft (sidewall core), Middle Albian (E.F. K43.0). Paratype: well 14/29a-5 at 8420.0 ft (sidewall core), Middle Albian (E.F. S42.4).
Dimensions. Holotype: 70 × 70 µm. Paratype: 71 × 68 µm. Overall: 78 (70) 60 × 73 (65) 50 µm, 15 specimens measured. Endocyst: 34 (33) 30 × 28 (27) 26 µm, 3 specimens measured.
Remarks. This species has been placed in Hapsocysta Davey, 1979 because it is essentially an open meshwork, composed of narrow strands, outlining the paratabulation and surrounding an endocyst. Unfortunately, the paratabulation of the genus Hapsocysta has not been formally reported, and no direct comparisons may be made. However, Davey (1979) described, ‘large, basically pentagonal, preand postcingular, and antapical areas, elongate paracingular areas and small, subcircular parasulcal areas’.
An endocyst is observed only in the minority of specimens of Hapsocysta susanae, and no clear attachment to the parasutural framework has been discerned. The absence of an endocyst from the majority of specimens may be due to its easy detachment and small size; it is presumably easily detached and typically lost through the wide mesh of the encircling framework.
Close comparisons may be made between H. susanae and the type species, Hapsocysta peridictya (Eisenack & Cookson, 1960) Davey, 1979, which occurs at the same stratigraphic level in the study area (although the last species has a significantly longer range). Specimens of H. peridictya (Eisenack & Cookson, 1960) Davey, 1979 illustrated and described by Morgan (1980) are particularly reminiscent of H. susanae, including specimens which, ‘lack an endophragm’.
H. susanae differs from H. peridictya (Eisenack & Cookson, 1960) Davey, 1979 in having a more rigid parasutural framework with broader individual elements, in its significantly smaller overall size and in the smaller size of the endocyst relative to the parasutural network. The last feature may account for the characteristic loss of the endocyst in H. susanae.
In addition, H. susanae has an apical projection, a feature absent from H. peridictya (Eisenack & Cookson, 1960) Davey, 1979, and no specimens of H. susanae have yet displayed, ‘a continuous ectophragm joining the trabeculae’, as described for some specimens of H. peridictya by Morgan (1980).
The structure of H. susanae is very reminiscent of the genera Evittosphaerula Manum, 1979 and Chaenosphaerula Damassa, 1997. These are monotypic, morphologically very similar, and the type species, Evittosphaerula paratabulata Manum, 1979 and Chaenosphaerula magnifica Damassa, 1997 were described from the Lower Miocene and Upper Oligocene respectively. However, H. susanae differs from both of these in possessing an apical projection and an endocyst (although this is usually lost).
Detailed comparison may be made of the paratabulation of H. susanae (figured here) with illustrations in Damassa (1997, figs 2, 3 and 6) of apical–ventral paratabulation patterns for E. paratabulata Manum, 1979 and C. magnifica Damassa, 1997. In particular, the configuration of paraplate quartet {5'', 4', as, 6''} is most similar to that in C. magnifica and to most species of Impagidinium Stover & Evitt, 1978. However, the multi-paraplate sulcal arrangement in H. susanae is very similar to that of E. paratabulata.
The structure of H. susanae also bears some resemblance to the genus Cannosphaeropsis Wetzel, 1933, although the trabecular network of the latter genus bears short, distally bi- or trifurcate spines (see Duxbury, 1980; Marheinecke, 1992), a feature absent from H. susanae.
The stratigraphic range of H. susanae is short, restricted to the Early to Middle Albian, palyzones LKP33.1 to LKP34 of Duxbury (2001), where it can be common. In the study area, its inception is within the upper Carrack Formation, and its extinction is within the lower Rødby Formation.