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Impagidinium crouchiae
Impagidinium crouchiae Willumsen, 2011, p.220,222, figs.9A,D.
Holotype: Willumsen, 2011, fig.9A.
Age: late Maastrichtian–early Paleocene.
Original description (Willumsen, 2011):
Impagidinium crouchiae sp. nov. (Fig. 9A, D)
Types. Holotype, Mead Stream, P30/f989, slide L18511/4, 16 mm, EG: V26,1/V25,2 (Fig. 9A). Paratype, Tangaruhe Stream, U24/f591, L19196/1, 16 mm, EF: G50,3 (Fig. 9D).
Type unit and locality. Mead Hill Formation, Mead Stream section, Clarence Valley, Marlborough, New Zealand.
Etymology. After Dr Erica Crouch who recorded this species in a study of the Tawanui and Te Uri Stream sections, Wairarapa, North Island, New Zealand (Crouch 1993).
Diagnosis. A circular Impagidinium species with a smooth surface covered by very low, uniform, hyaline sutural ridges ca 1– 2 µm high that partly indicate the paratabulation of the cyst.
Description. A small circular proximate cyst. Cyst surface is smooth with low hyaline parasutural ridges of 1–2 µm average height indicating the tabulation of the cyst apart from the sulcus, where paratabulation is not evident. Ridges in the gonal area are not expanded. Diameter 44(47)60 µm [10 specimens measured].
Remarks. Impagidinium crouchiae sp. nov. differs from I. aspinatum Cookson & Eisenack, 1974 by not having an apical protrusion and from I. celineae Jan du Chêne, 1988 by not having finely denticulate or serrate parasutural septa. Impagidinium antecarcerum, de Verteuil & Norris, 1996 differs from I. crouchiae by having alveolate wall structure and limbate septa. Impagidinium cristatum May, 1980 has more strongly developed septa in the gonal areas compared with I. crouchiae. Impagidinium crouchiae is half the size of I. victorianum Cookson & Eisenack, 1965, whereas I. elegans Cookson & Eisenack, 1965 differs by its finely granular surface ornamentation on the cyst. Impagidinium rigidaseptatum and I. scabrosum Slimani, 1994 differ from I. crouchiae by having much more expanded septa (10–20 µm high).
Age and distribution. The FO of Impagidinium crouchiae is below the sampled section, but the LO of I. crouchiae is correlated to the Paleocene radiolarian zone RP2 or lowermost part of RP3, which corresponds to an interval from ca 64.6–64.7 Ma. Impagidinium crouchiae is rare to common in the sections studied at Branch Stream, Fairfield Quarry, Grey River, Mead Stream, mid-Waipara River, Tawanui Stream and Wharanui Point (Willumsen 2003). Crouch (1993) recorded high relative abundances of I. crouchiae from Paleocene strata in the Te Uri Stream, Southern Hawkes Bay, North Island (Impagidinium sp. 1; Crouch 1993, p. 70). This species is also common in a sample from the Tangaruhe Stream section, southern Hawkes Bay, North Island (Sample U24/f591).
Holotype: Willumsen, 2011, fig.9A.
Age: late Maastrichtian–early Paleocene.
Original description (Willumsen, 2011):
Impagidinium crouchiae sp. nov. (Fig. 9A, D)
Types. Holotype, Mead Stream, P30/f989, slide L18511/4, 16 mm, EG: V26,1/V25,2 (Fig. 9A). Paratype, Tangaruhe Stream, U24/f591, L19196/1, 16 mm, EF: G50,3 (Fig. 9D).
Type unit and locality. Mead Hill Formation, Mead Stream section, Clarence Valley, Marlborough, New Zealand.
Etymology. After Dr Erica Crouch who recorded this species in a study of the Tawanui and Te Uri Stream sections, Wairarapa, North Island, New Zealand (Crouch 1993).
Diagnosis. A circular Impagidinium species with a smooth surface covered by very low, uniform, hyaline sutural ridges ca 1– 2 µm high that partly indicate the paratabulation of the cyst.
Description. A small circular proximate cyst. Cyst surface is smooth with low hyaline parasutural ridges of 1–2 µm average height indicating the tabulation of the cyst apart from the sulcus, where paratabulation is not evident. Ridges in the gonal area are not expanded. Diameter 44(47)60 µm [10 specimens measured].
Remarks. Impagidinium crouchiae sp. nov. differs from I. aspinatum Cookson & Eisenack, 1974 by not having an apical protrusion and from I. celineae Jan du Chêne, 1988 by not having finely denticulate or serrate parasutural septa. Impagidinium antecarcerum, de Verteuil & Norris, 1996 differs from I. crouchiae by having alveolate wall structure and limbate septa. Impagidinium cristatum May, 1980 has more strongly developed septa in the gonal areas compared with I. crouchiae. Impagidinium crouchiae is half the size of I. victorianum Cookson & Eisenack, 1965, whereas I. elegans Cookson & Eisenack, 1965 differs by its finely granular surface ornamentation on the cyst. Impagidinium rigidaseptatum and I. scabrosum Slimani, 1994 differ from I. crouchiae by having much more expanded septa (10–20 µm high).
Age and distribution. The FO of Impagidinium crouchiae is below the sampled section, but the LO of I. crouchiae is correlated to the Paleocene radiolarian zone RP2 or lowermost part of RP3, which corresponds to an interval from ca 64.6–64.7 Ma. Impagidinium crouchiae is rare to common in the sections studied at Branch Stream, Fairfield Quarry, Grey River, Mead Stream, mid-Waipara River, Tawanui Stream and Wharanui Point (Willumsen 2003). Crouch (1993) recorded high relative abundances of I. crouchiae from Paleocene strata in the Te Uri Stream, Southern Hawkes Bay, North Island (Impagidinium sp. 1; Crouch 1993, p. 70). This species is also common in a sample from the Tangaruhe Stream section, southern Hawkes Bay, North Island (Sample U24/f591).