Back
Corrudinium regulare
Corrudinium regulare Clowes and Wilson, 2006, p.402, figs.3G–L,4A–C.
Holotype: Clowes and Wilson, 2006, figs.3G–I.
Age: Lutetian–Rupelian.
Original description (Clowes & Wilson, 2006)
DERIVATION OF NAME: Latin, regula, meaning principle or rule; with reference to the regular shape and even reticulum.
HOLOTYPE: Specimen L8947/SM4886, Fig. 3G-I; sample I44/f080, Burnside Formation, Abbotts Hill Road, Dunedin, New Zealand, grid ref. I44/11407675; Bortonian Stage (Bartonian).
DESCRIPTION: Cysts of intermediate size, proximate, spherical, lacking horns; the episome and hyposome roughly equal in size. Cyst wall single layered; thick and robust, so that the cysts are most commonly found either fully spherical or else fractured rather than distorted. Archeopyle precingular, type P(3 ); operculum free. Processes lacking; ornament comprising low parasutural and intratabular septa, the latter forming an incomplete reticulum with
features on a scale of c. 3 µm; the cyst wall appears smooth within the lacunae. Parasutural septa low, rarely very low, forming a well defined gonyaulacacean paratabulation, ?4 , 0a, 6 , 6c, 6 , 1p, 1 ; hyposome sexiform, S-type ventral organisation (Fig. 3I), torsion neutral (Fig. 3G). Paracingulum and parasulcus clearly expressed
by the parasutural septa; paracingulum with strong laevorotatory offset; parasulcus exhibiting considerable obliquity between contact with the cingular paraplates.
SIZE RANGE: Holotype 54 μm length × 54 μm breadth; range of 20 specimens 48 (54) 65 µm in maximum overall diameter.
DISTRIBUTION: Table 3 lists known occurrences of Corrudinium regulare, which is locally common in the Bortonian—Runangan (Lutetian-Priabonian) interval of New Zealand. Similar forms also occur in the Browns Creek Clays of southwest Victoria, Australia (Alan Partridge pers. comm.) and in middle Eocene to early Oligocene samples from DSDP sites in the Tasman Sea and on the Falkland Plateau, southwest Atlantic Ocean.
REMARKS: Corrudinium regulare, as defined here, exhibits a range of variation from relatively smooth (Fig. 4A) to deeply sculptured, like C. otagoense (Fig. 4B). Compared to C. incompositum the present species is distinctly larger, more spherical, and more robust; the intratabular areas are more densely ornamented; and the intratabular septa distinctly lower than the parasutural features (on C. incompositum they have a very similar appearance and so are less readily distinguished). It differs from C. otagoense, typically, in possessing lower septa, and consistently in displaying a distinct paratabulation, even in variants where the intratabular ornament is abnormally high (e.g., Fig. 4B,C).
Holotype: Clowes and Wilson, 2006, figs.3G–I.
Age: Lutetian–Rupelian.
Original description (Clowes & Wilson, 2006)
DERIVATION OF NAME: Latin, regula, meaning principle or rule; with reference to the regular shape and even reticulum.
HOLOTYPE: Specimen L8947/SM4886, Fig. 3G-I; sample I44/f080, Burnside Formation, Abbotts Hill Road, Dunedin, New Zealand, grid ref. I44/11407675; Bortonian Stage (Bartonian).
DESCRIPTION: Cysts of intermediate size, proximate, spherical, lacking horns; the episome and hyposome roughly equal in size. Cyst wall single layered; thick and robust, so that the cysts are most commonly found either fully spherical or else fractured rather than distorted. Archeopyle precingular, type P(3 ); operculum free. Processes lacking; ornament comprising low parasutural and intratabular septa, the latter forming an incomplete reticulum with
features on a scale of c. 3 µm; the cyst wall appears smooth within the lacunae. Parasutural septa low, rarely very low, forming a well defined gonyaulacacean paratabulation, ?4 , 0a, 6 , 6c, 6 , 1p, 1 ; hyposome sexiform, S-type ventral organisation (Fig. 3I), torsion neutral (Fig. 3G). Paracingulum and parasulcus clearly expressed
by the parasutural septa; paracingulum with strong laevorotatory offset; parasulcus exhibiting considerable obliquity between contact with the cingular paraplates.
SIZE RANGE: Holotype 54 μm length × 54 μm breadth; range of 20 specimens 48 (54) 65 µm in maximum overall diameter.
DISTRIBUTION: Table 3 lists known occurrences of Corrudinium regulare, which is locally common in the Bortonian—Runangan (Lutetian-Priabonian) interval of New Zealand. Similar forms also occur in the Browns Creek Clays of southwest Victoria, Australia (Alan Partridge pers. comm.) and in middle Eocene to early Oligocene samples from DSDP sites in the Tasman Sea and on the Falkland Plateau, southwest Atlantic Ocean.
REMARKS: Corrudinium regulare, as defined here, exhibits a range of variation from relatively smooth (Fig. 4A) to deeply sculptured, like C. otagoense (Fig. 4B). Compared to C. incompositum the present species is distinctly larger, more spherical, and more robust; the intratabular areas are more densely ornamented; and the intratabular septa distinctly lower than the parasutural features (on C. incompositum they have a very similar appearance and so are less readily distinguished). It differs from C. otagoense, typically, in possessing lower septa, and consistently in displaying a distinct paratabulation, even in variants where the intratabular ornament is abnormally high (e.g., Fig. 4B,C).