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Geonettia clineae
Geonettia clineae, de Verteuil and Norris, 1996b, pp. 263-284
Gonettia clineae gen. et sp. nov.
Characterization: resting cyst having fields that all routinely dissociate, revealing a tabulation most similar to fossil Eocladopyxis peniculata and living Pyrodinium bahamense;
proximate luxuriae composed of fibrilar, knobby and anastomosing structural elements that form an even microreticulate network about the cyst; virgae, crests and ridges are absent. Selective angles of most fields have small acute projections that intercalate with angular re-entrants in adjacent fields.
Description:
Cysts: proximate, spherical to subspherical
wall: comprises thin homogenous pedium, less than 0.25 µm thick, bearing anastomosing strands ca. 0.2µm in diameter that form a microreticulate labyrinth of spaces and fibrils up to ca. 1.25 µm thick; appears puncto-reticulate under TLM
lumina: irregular, ca 0.5 to 1.5 µm across
dinosporin strands bear scattered microgranules ca. 0.1 µm across
Tabulation: quinqueform, L-type, with narrow cingulum ca. 3 to 5 µm wide and gently laevorotatory having about one width displacement;
distal-most field of the cingulum partly within the sulcus as defined by the small, stenoform fields surrounding the two flagella scars; anterior flagella scar is about level with the proximal end of the cingulum; sulcus: not noticeably recessed and ca. 8 to 12 µm wide between the ends of the cingulum, on hypocyst it is inclined slightly to right, towards contact with 2p in the posterior-most ventral region of hypocyst; two sulcal fields forming this contact termed right and left sulcal fields (Is and rs), no anterior margin observed for fields where their mutual boundary is offset; angular groove formed at the posterior shared ls rs contact as consistent feature of tabulation; it and the larger one formed at the contact of Is and lp intercalate with acute projections on the contacting margin of 2p; antapical field: extends onto posterior dorsal surface, rectilinear third postcingular (inferred *4") < geniculate second and fourth postcingulars (inferred *3"' and *5"); centers of 3" and 1"" are slightly to right of the sulcal plane, sinistral torsion of hypotabulation; third precingular field: middorsally positioned but the 3c/4c contact lies to the left of the sulcal plane; sixth precingular field: irregularly steno-camerate, long 6'71'boundary; first apical field: omegaform, widens from narrow l`/as boundary, forming convex arching l`/l`` contact, imparting distinctive geometry to latiform l"; presence of a Q-field; all four climactals contact apical pore field and are strict Kofoid apicals; P-field: tear-drop shaped, narrow end ventrally directed; the outer convex margin contacts latiform second apical field; labyrinthose luxuriae obscure external cyst expression of apical pore structure; inner surface P-field: complex-appearing aperture, analogous to apical pore, disrupts smooth pedium; one or potentially two Q-fields present: larger and more ventral is rounded triangular, nestled against inner convex margin of P, contacting 4' and l'; second Q-field ca. 3 µm across, rounded triangular, positioned at apex anterior, to the right of P, contacts 3' and 4' ;adcingular fields: small, dorsally directed, acute projections
precingular series: adcingular fields present on 1 ", 2 ", 4", 5" and 6" where they meet cingulum, are absent from 3"; postcingular series: dosally pointing acute projections occur on fields 5"', 4"', 2"' and 1 "', not on 3"'; Excystment: appears to occur via disintegration of much of the cyst along field boundaries, most often involving loss of the apical series and rupture of the dorsal surface.
Size: intermediate
Stratigraphic range: upper middle Miocene - upper upper Miocene in the western north Atlantic
Gonettia clineae gen. et sp. nov.
Characterization: resting cyst having fields that all routinely dissociate, revealing a tabulation most similar to fossil Eocladopyxis peniculata and living Pyrodinium bahamense;
proximate luxuriae composed of fibrilar, knobby and anastomosing structural elements that form an even microreticulate network about the cyst; virgae, crests and ridges are absent. Selective angles of most fields have small acute projections that intercalate with angular re-entrants in adjacent fields.
Description:
Cysts: proximate, spherical to subspherical
wall: comprises thin homogenous pedium, less than 0.25 µm thick, bearing anastomosing strands ca. 0.2µm in diameter that form a microreticulate labyrinth of spaces and fibrils up to ca. 1.25 µm thick; appears puncto-reticulate under TLM
lumina: irregular, ca 0.5 to 1.5 µm across
dinosporin strands bear scattered microgranules ca. 0.1 µm across
Tabulation: quinqueform, L-type, with narrow cingulum ca. 3 to 5 µm wide and gently laevorotatory having about one width displacement;
distal-most field of the cingulum partly within the sulcus as defined by the small, stenoform fields surrounding the two flagella scars; anterior flagella scar is about level with the proximal end of the cingulum; sulcus: not noticeably recessed and ca. 8 to 12 µm wide between the ends of the cingulum, on hypocyst it is inclined slightly to right, towards contact with 2p in the posterior-most ventral region of hypocyst; two sulcal fields forming this contact termed right and left sulcal fields (Is and rs), no anterior margin observed for fields where their mutual boundary is offset; angular groove formed at the posterior shared ls rs contact as consistent feature of tabulation; it and the larger one formed at the contact of Is and lp intercalate with acute projections on the contacting margin of 2p; antapical field: extends onto posterior dorsal surface, rectilinear third postcingular (inferred *4") < geniculate second and fourth postcingulars (inferred *3"' and *5"); centers of 3" and 1"" are slightly to right of the sulcal plane, sinistral torsion of hypotabulation; third precingular field: middorsally positioned but the 3c/4c contact lies to the left of the sulcal plane; sixth precingular field: irregularly steno-camerate, long 6'71'boundary; first apical field: omegaform, widens from narrow l`/as boundary, forming convex arching l`/l`` contact, imparting distinctive geometry to latiform l"; presence of a Q-field; all four climactals contact apical pore field and are strict Kofoid apicals; P-field: tear-drop shaped, narrow end ventrally directed; the outer convex margin contacts latiform second apical field; labyrinthose luxuriae obscure external cyst expression of apical pore structure; inner surface P-field: complex-appearing aperture, analogous to apical pore, disrupts smooth pedium; one or potentially two Q-fields present: larger and more ventral is rounded triangular, nestled against inner convex margin of P, contacting 4' and l'; second Q-field ca. 3 µm across, rounded triangular, positioned at apex anterior, to the right of P, contacts 3' and 4' ;adcingular fields: small, dorsally directed, acute projections
precingular series: adcingular fields present on 1 ", 2 ", 4", 5" and 6" where they meet cingulum, are absent from 3"; postcingular series: dosally pointing acute projections occur on fields 5"', 4"', 2"' and 1 "', not on 3"'; Excystment: appears to occur via disintegration of much of the cyst along field boundaries, most often involving loss of the apical series and rupture of the dorsal surface.
Size: intermediate
Stratigraphic range: upper middle Miocene - upper upper Miocene in the western north Atlantic