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Tenua magna
From Fensome et al., 2019:
(Duxbury, 2001, p.101–102, fig.4, nos.1–4) Fensome et al., 2019a, p.49. Holotype: Duxbury, 2001, fig.4, no.3; Fensome et al., 2019a, fig.18H. Originally Cerbia, subsequently (and now) Tenua Eisenack. Age: late Barremian.
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Original description (Duxbury, 2001):
Cerbia magna n. sp.
1995 Canninginopsis intermedia MORGAN, 1980 in HELMANN-CLAUSEN & THOMSEN, 1995, pl. 2, fig. 14 only.
Holotype: Figure 4.3.
Type Locality: Well 13/30b-5 at 4819.0 ft (sidewall core), Late Barremian, E.F. Q29.2.
Derivation of Name: From the Latin nagnus, large - in reference to the particularly large size of this species.
Diagnosis: A large, thin-walled, dorso-ventrally flattened, proximate dinoflagellate cyst with a sub-circular outline. Low apical, lateral and antapical proections are present, and short spines are distributed over the surface of the cyst. These spines are variable in their distribution, often essentially penitabular, but sometimes more densely arranged.
Paratabulation appears to be typical for the genus. The archeopyle is apical, with a zig zag margin; the operculum is usually detached.
Dimensions: Holotype (operculum detached): Length – 117 μm.
Width - 127 μm
Overall (operculum detached): Length - 135 (123) 94 μm
Width 145 (124) 109 μm
Specimens Measured - 15
Comments: Cerbia magna n. sp. differs from all other species of this genus in its large size and in a distinct angularity of outline caused by the presence of low apical, lateral and antapical projections. The thin-walled nature of this species often causes folding or breakage of the cyst.
This very distinctive species is restricted to the Late Barremian, where it can be superabundant, and it is a valuable indicator of that Sub-stage. The specimen figured by HEILMANN-CLAUSEN & THOMSEN (1995, pl. 2, fig. 14) is very similar to the holotype of Cerbia magna n.sp., and is included here.
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Comments Fensome et al., 2019a:
In erecting this species, Duxbury (2001, p. 101) stated:
"Low apical, lateral and antapical projections are present, and short spines are distributed over the surface of the cyst. These spines are variable in their distribution, often essentially penitabular, but sometimes more densely arranged."
Thus, penitabular features are not clearcut and ornament covers most or all of the surface: hence we transfer this species to Tenua.
Stratigraphical occurrence. Duxbury (2001) described this species from the upper Barremian of the North Sea.
(Duxbury, 2001, p.101–102, fig.4, nos.1–4) Fensome et al., 2019a, p.49. Holotype: Duxbury, 2001, fig.4, no.3; Fensome et al., 2019a, fig.18H. Originally Cerbia, subsequently (and now) Tenua Eisenack. Age: late Barremian.
---------------------------------------------------------------------------------------------------
Original description (Duxbury, 2001):
Cerbia magna n. sp.
1995 Canninginopsis intermedia MORGAN, 1980 in HELMANN-CLAUSEN & THOMSEN, 1995, pl. 2, fig. 14 only.
Holotype: Figure 4.3.
Type Locality: Well 13/30b-5 at 4819.0 ft (sidewall core), Late Barremian, E.F. Q29.2.
Derivation of Name: From the Latin nagnus, large - in reference to the particularly large size of this species.
Diagnosis: A large, thin-walled, dorso-ventrally flattened, proximate dinoflagellate cyst with a sub-circular outline. Low apical, lateral and antapical proections are present, and short spines are distributed over the surface of the cyst. These spines are variable in their distribution, often essentially penitabular, but sometimes more densely arranged.
Paratabulation appears to be typical for the genus. The archeopyle is apical, with a zig zag margin; the operculum is usually detached.
Dimensions: Holotype (operculum detached): Length – 117 μm.
Width - 127 μm
Overall (operculum detached): Length - 135 (123) 94 μm
Width 145 (124) 109 μm
Specimens Measured - 15
Comments: Cerbia magna n. sp. differs from all other species of this genus in its large size and in a distinct angularity of outline caused by the presence of low apical, lateral and antapical projections. The thin-walled nature of this species often causes folding or breakage of the cyst.
This very distinctive species is restricted to the Late Barremian, where it can be superabundant, and it is a valuable indicator of that Sub-stage. The specimen figured by HEILMANN-CLAUSEN & THOMSEN (1995, pl. 2, fig. 14) is very similar to the holotype of Cerbia magna n.sp., and is included here.
---------------------------------------------------------------------------------------------------
Comments Fensome et al., 2019a:
In erecting this species, Duxbury (2001, p. 101) stated:
"Low apical, lateral and antapical projections are present, and short spines are distributed over the surface of the cyst. These spines are variable in their distribution, often essentially penitabular, but sometimes more densely arranged."
Thus, penitabular features are not clearcut and ornament covers most or all of the surface: hence we transfer this species to Tenua.
Stratigraphical occurrence. Duxbury (2001) described this species from the upper Barremian of the North Sea.