Back
Gardodinium attenuatum
Gardodinium attenuatum Stover and Helby, 1987, p.107-109
Holotype: Stover and Helby, 1987a, figs.5A–C; Helby et al., 1987, figs.27F–G; Fensome et al., 1996, figs.1–3 — p.2051.
Paratypes: Stover and Helby, 1987
Locus typicus: Exmouth Plateau, Australia
Stratum typicum: Valanginian
Original description: Stover and Helby, 1987, p. 107
Cysts proximate, holocavate elongate ellipsoidal, with prominent apical horn formed by the ectophragm. Anteriorly, the ellipsoidal autocyst narrowly rounded and may be extended somewhat apically to form a blunt protrusion, more broadly rounded posteriorly. Autophragm smooth, approximately 1 µm thick, with numerous, intratabular processes apparently confined within fields defined by penitabular alignment (Fig.5A,D,H,J). Intratabular processes cylindrical or slightly tapered distally, hollow for about one third to one half their length, and solid distally. Processes relatively short in precingular and postcingular areas (2.5-4 µm in length), only slightly longer on the pole and along the borders of the paracingulum (5-6.5 µm), do not extend into distal part of apical horn. Elsewhere, tips of processes merge with a smooth, continuous ectophragm which is thinner than the autophragm. Archeopyle apical, type [tA]; principal suture angular, accessory sutures between precingular paraplates short, when present. Operculum free or adherent. Paracingulum nearer antapical than apical end, indicated by 2, parallel rows of processes marginally longer than adjacent ones. Ends of paracingulum offset by about the width of the paracingulum. Parasulcus not discernible.
Overall length 71(78)95 µm, width 38(45)55 µm, length of opercula 23(27.5)32 µm.
The paratabulation is expressed by the paracingulum and the archeopyle, with the principal and accessory sutures of the latter indicating 4 apical and 6 precingular paraplates. Additional indications of paratabulation are commonly lacking or vague, however, processes on the anterior edge of the precingular paraplates and on both sides of accessory sutures may be aligned in penitabular rows. The alignment is most evident near the archeopyle margin and may become obscure towards the paracingulum. We found only rare indications of paratabulation on the hypocyst. The anterior extremity of the apical horn is characterized by a small, stopper-like.
Affinities:
Stover and Helby, 1987, p. 109: Gardodinium attenuatum differs from C. Iowii Backhouse this memoir, in having a shorter apical horn, fewer, wider, and generally longer processes between the wall layers and a less apically protrusive autophragm. In G. Iowii, the autophragm extends into the horn for about one-half or more of its length. Gardodinium attenuatum, G. Iowii and an unnamed Chlamydophorella species comprise a useful mid Valanginian to Hauterivian lineage (Fig.6). Some specimens identified as G. eisenackii by Vozzhennikova (1967, pl.99, figs 3a,b, 4a) from the Valanginian of the U.S.S.R. may be conspecific with G. attenuatum. Other species of Cardodinium (G. albertii Neale & Sarjeant 1962, C. ordinale Davey 1974, G. pyriforme Vozzhennikova 1967 and G. trabeculosum) are not as elongate as G. attenuatum and their apical horns may be open anteriorly.
Holotype: Stover and Helby, 1987a, figs.5A–C; Helby et al., 1987, figs.27F–G; Fensome et al., 1996, figs.1–3 — p.2051.
Paratypes: Stover and Helby, 1987
Locus typicus: Exmouth Plateau, Australia
Stratum typicum: Valanginian
Original description: Stover and Helby, 1987, p. 107
Cysts proximate, holocavate elongate ellipsoidal, with prominent apical horn formed by the ectophragm. Anteriorly, the ellipsoidal autocyst narrowly rounded and may be extended somewhat apically to form a blunt protrusion, more broadly rounded posteriorly. Autophragm smooth, approximately 1 µm thick, with numerous, intratabular processes apparently confined within fields defined by penitabular alignment (Fig.5A,D,H,J). Intratabular processes cylindrical or slightly tapered distally, hollow for about one third to one half their length, and solid distally. Processes relatively short in precingular and postcingular areas (2.5-4 µm in length), only slightly longer on the pole and along the borders of the paracingulum (5-6.5 µm), do not extend into distal part of apical horn. Elsewhere, tips of processes merge with a smooth, continuous ectophragm which is thinner than the autophragm. Archeopyle apical, type [tA]; principal suture angular, accessory sutures between precingular paraplates short, when present. Operculum free or adherent. Paracingulum nearer antapical than apical end, indicated by 2, parallel rows of processes marginally longer than adjacent ones. Ends of paracingulum offset by about the width of the paracingulum. Parasulcus not discernible.
Overall length 71(78)95 µm, width 38(45)55 µm, length of opercula 23(27.5)32 µm.
The paratabulation is expressed by the paracingulum and the archeopyle, with the principal and accessory sutures of the latter indicating 4 apical and 6 precingular paraplates. Additional indications of paratabulation are commonly lacking or vague, however, processes on the anterior edge of the precingular paraplates and on both sides of accessory sutures may be aligned in penitabular rows. The alignment is most evident near the archeopyle margin and may become obscure towards the paracingulum. We found only rare indications of paratabulation on the hypocyst. The anterior extremity of the apical horn is characterized by a small, stopper-like.
Affinities:
Stover and Helby, 1987, p. 109: Gardodinium attenuatum differs from C. Iowii Backhouse this memoir, in having a shorter apical horn, fewer, wider, and generally longer processes between the wall layers and a less apically protrusive autophragm. In G. Iowii, the autophragm extends into the horn for about one-half or more of its length. Gardodinium attenuatum, G. Iowii and an unnamed Chlamydophorella species comprise a useful mid Valanginian to Hauterivian lineage (Fig.6). Some specimens identified as G. eisenackii by Vozzhennikova (1967, pl.99, figs 3a,b, 4a) from the Valanginian of the U.S.S.R. may be conspecific with G. attenuatum. Other species of Cardodinium (G. albertii Neale & Sarjeant 1962, C. ordinale Davey 1974, G. pyriforme Vozzhennikova 1967 and G. trabeculosum) are not as elongate as G. attenuatum and their apical horns may be open anteriorly.