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Gonyaulacysta jurassica ssp. desmos
Gonyaulacysta jurassica subsp. desmos Poulsen, 1991, p.213-214, pl.1, figs.3-6.
Holotype: Poulsen, 1991, pl.1, fig.3.
Age: Early Oxfordian.
Original description (Poulsen, 1991)
Derivation of Name. Greek oc.crμos (desmos), link, (transitional form).
Diagnosis. A subspecies of Gonyaulacysta jurassica which exhibits only partial development of the hypopericoel,
i.e., there is a marginal separation of the hypoperiphragm and hypoendophragm, whereas the two wall layers
are in contact at the mid-antapical region.
Holotype. Oxford Clay ( 1 m below the Lower Calcareous Grit Formation) Cayton Bay, Yorkshire, DGU Catalogue
No.: 1989-NEP-l.Para type. Oxford Clay (27 m below the Lower Calcareous Grit Formation) Cayton Bay, Yorkshire, DGU CatalogueNo.: 1989-NEP-2.
Occurrence. Praecordatum, Bukowskii and Costicardia ammonite subzones of the early Oxfordian in England.
Discussion. Gonyaulacysta jurassica desmos subsp. nov. appears to be a transitional form between the subspecies
G.jurassica adecta, which has an acavate hypocyst, and the subspecies G.jurassicajurassica which has a well developed hypopericoel. The new subspecies of G. jurassica is proposed because it is morphologically distinct and
it has potential stratigraphic significance. All three subspecies occur together in the early Oxfordian.
Holotype: Poulsen, 1991, pl.1, fig.3.
Age: Early Oxfordian.
Original description (Poulsen, 1991)
Derivation of Name. Greek oc.crμos (desmos), link, (transitional form).
Diagnosis. A subspecies of Gonyaulacysta jurassica which exhibits only partial development of the hypopericoel,
i.e., there is a marginal separation of the hypoperiphragm and hypoendophragm, whereas the two wall layers
are in contact at the mid-antapical region.
Holotype. Oxford Clay ( 1 m below the Lower Calcareous Grit Formation) Cayton Bay, Yorkshire, DGU Catalogue
No.: 1989-NEP-l.Para type. Oxford Clay (27 m below the Lower Calcareous Grit Formation) Cayton Bay, Yorkshire, DGU CatalogueNo.: 1989-NEP-2.
Occurrence. Praecordatum, Bukowskii and Costicardia ammonite subzones of the early Oxfordian in England.
Discussion. Gonyaulacysta jurassica desmos subsp. nov. appears to be a transitional form between the subspecies
G.jurassica adecta, which has an acavate hypocyst, and the subspecies G.jurassicajurassica which has a well developed hypopericoel. The new subspecies of G. jurassica is proposed because it is morphologically distinct and
it has potential stratigraphic significance. All three subspecies occur together in the early Oxfordian.