Back
Costacysta bucina
Costacysta *bucina Heilmann-Clausen and Van Simaeys, 2005, p.160, pl.2, figs.13–16.
Holotype: Heilmann-Clausen and Van Simaeys, 2005, pl.2, fig.15.
Age: middle Eocene.
Original description (Heilmann-Clausen and Van Simaeys, 2005)
Description. As for the genus, with the following additional features. The endophragm is thick, 1 to 3 µm, and varies from almost smooth, through finely granular, to irregularly verrucate–gemmate. The periphragm is thin, less than 0.5 µm, and hyaline. The periphragm bulges inwards at the margins of the archeopyle, and is here fused to the endocyst. Holes of variable size (2 to 8 µm) are usually present in parts of the periphragm, in particular adjacent to the archeopyle margin and in parts of the ventral surface.
Derivation of name. From Latin, bucina meaning shepherd's horn, from the appearance of the antapical columella.
Designation of holotype. Plate 2, fig. 15, Slide 2653 H3, England Finder coordinates U56/1. MGUH 27765. Kysing-4 borehole, sample 2653, Middle Eocene. Specimen dimensions: Pericyst length 105 µm; pericyst breadth 81 µm; endocyst length 75 µm; endocyst breadth 65 µm; length of antapical columella 12 µm; thickness of endophragm 2 µm.
Designation of paratype. Paratype 1. Plate 2, fig. 16, Slide 2653 H1, England Finder coordinates C47/2. MGUH 27766. Kysing-4 borehole, sample 2653, Middle Eocene. Specimen dimensions: Pericyst length 108 µm; pericyst breadth 75 µm; endocyst length 78 µm; endocyst breadth 60 µm; length of antapical columella 18 µm; thickness of endophragm 2 µm. Paratype 2. Plate 2, fig. 14, Slide 482 G1, England Finder coordinates P54. MGUH 27767. LB 38 borehole, sample chc92 at 19.4 m, Søvind Marl Formation, Middle Eocene. Paratype 3. Plate 2, fig. 13, Slide 1805 G2, England Finder coordinates L40. MGUH 27768. Pøt Strand borehole 1991, sample at 7.8–8.0 m, Søvind Marl Formation, Middle Eocene.
Dimensions of measured specimens. Pericyst length 84 (100) 114 µm. Pericyst breadth 64 (79) 90 µm. Endocyst length 62 (71) 78 µm. Endocyst breadth 49 (59) 67 µm. Length of antapical columella 11 (16) 26 µm. Thickness of endophragm 1.5–3 µm. (18 specimens measured).
Variation. The crater-like ring structure on the ventral surface of the endocyst may be small and nearly invisible, or larger, approaching the shape and size of the antapical columella.
Holotype: Heilmann-Clausen and Van Simaeys, 2005, pl.2, fig.15.
Age: middle Eocene.
Original description (Heilmann-Clausen and Van Simaeys, 2005)
Description. As for the genus, with the following additional features. The endophragm is thick, 1 to 3 µm, and varies from almost smooth, through finely granular, to irregularly verrucate–gemmate. The periphragm is thin, less than 0.5 µm, and hyaline. The periphragm bulges inwards at the margins of the archeopyle, and is here fused to the endocyst. Holes of variable size (2 to 8 µm) are usually present in parts of the periphragm, in particular adjacent to the archeopyle margin and in parts of the ventral surface.
Derivation of name. From Latin, bucina meaning shepherd's horn, from the appearance of the antapical columella.
Designation of holotype. Plate 2, fig. 15, Slide 2653 H3, England Finder coordinates U56/1. MGUH 27765. Kysing-4 borehole, sample 2653, Middle Eocene. Specimen dimensions: Pericyst length 105 µm; pericyst breadth 81 µm; endocyst length 75 µm; endocyst breadth 65 µm; length of antapical columella 12 µm; thickness of endophragm 2 µm.
Designation of paratype. Paratype 1. Plate 2, fig. 16, Slide 2653 H1, England Finder coordinates C47/2. MGUH 27766. Kysing-4 borehole, sample 2653, Middle Eocene. Specimen dimensions: Pericyst length 108 µm; pericyst breadth 75 µm; endocyst length 78 µm; endocyst breadth 60 µm; length of antapical columella 18 µm; thickness of endophragm 2 µm. Paratype 2. Plate 2, fig. 14, Slide 482 G1, England Finder coordinates P54. MGUH 27767. LB 38 borehole, sample chc92 at 19.4 m, Søvind Marl Formation, Middle Eocene. Paratype 3. Plate 2, fig. 13, Slide 1805 G2, England Finder coordinates L40. MGUH 27768. Pøt Strand borehole 1991, sample at 7.8–8.0 m, Søvind Marl Formation, Middle Eocene.
Dimensions of measured specimens. Pericyst length 84 (100) 114 µm. Pericyst breadth 64 (79) 90 µm. Endocyst length 62 (71) 78 µm. Endocyst breadth 49 (59) 67 µm. Length of antapical columella 11 (16) 26 µm. Thickness of endophragm 1.5–3 µm. (18 specimens measured).
Variation. The crater-like ring structure on the ventral surface of the endocyst may be small and nearly invisible, or larger, approaching the shape and size of the antapical columella.