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Impagidinium detroitense
Impagidinium detroitense sp. nov., Zorzi, C. et al., 264, 24–37, 2019
Holotype: Zorzi, C. et al., 2019, Sample ODP 882A-26H3W, Plate I, 1–8
Age: Pliocene
Stratigraphic range: Early Pliocene through Late Pliocene, from 5.27 to 2.70 Ma.
Original description: Zorzi, C. et al., 2019: Impagidinium detroitense sp. nov.:
Diagnosis:
A proximochorate and suturocavate species of the genus Impagidinium with a spheroidal to broadly ovoidal central body, and tabulation formula 3–4′, 6′′, 6c, 5′′′, 1p, 1′′′′, ps expressed mostly by cavate septa that are appressed distally to form solid crests. The surfaces of the central body and septa are finely granulate. Septa are higher at the
antapex than apex. The ratio of the central body maximum diameter to antapical crest height is around 0.11 to 0.27. Plate 6′′ is strongly sub-triangular and narrowly contacts apical plates (1′ + 4′), which are often not clearly separated. Plate 6c narrows towards the sulcus, its anterior margin displaced downwards by plate 6′′. Dorsal tabulation shows approximately neutral torsion. The archeopyle, formed by loss of plate 3′′, has well defined angles and corresponds closely to the bounding septa.
Description:
Cyst: proximochorate and suturocavate, with a spheroidal to broadly ovoidal central body, sometimes bearing a small apical protuberance up to about 1.0 μm high
Central body wall: away from the sutures is ~0.5–0.8 μm thick and stratification is indistinguishable under light microscopy, surface of the central body and sutures is finely granulate, with adjacent granules sometimes fused to form an incomplete microreticulation. Septa are mostly cavate, becoming distally appressed to form solid crests
that are usually slightly undulating. Septa are systematically higher at the antapex than apex, and they may tend to rise slightly towards plate junctions.
Tabulation: Septa indicate an S-type ventral organization, and follow the formula 3–4′, 6′′, 6c, 5′′′, 1 p, 1′′′′, ps. Apical plates 2′ and 3′ are large, and 1′ and 4′ are often not clearly separated from one another. Plate 6′′ is strongly sub-triangular and narrowly contacts apical plate 4′ (or 1′ + 4′), whereas the contact between plates 5′′ and 4′ or the merged 4′ + 1′ plate is broad and distinctive. The cingular plates are discernible individually, and plate 6c narrows towards the sulcus, its anterior margin distinctly displaced downwards by plate 6′′. The cingulum may narrow at the 2c/3c, 3c/4c, and 4c/5c boundaries. Individual sulcal plates are usually not expressed, with the exception that the ps plate is well defined. Plate 1′′′ is not observed and presumably is small and located within the sulcus. Dorsal tabulation shows approximately neutral torsion.
Archeopyle: formed by the loss of plate 3′′, has well-defined angles, and corresponds closely to the bounding septa.
Color: slightly brownish
Dimensions:
Holotype: central body maximum diameter: 36 μm; apical crest height: 5 μm; antapical crest height: 8 μm; apical/antapical crest height ratio: 0.63; central body maximum diameter/antapical crest height ratio: 0.22.
Range based on Hole 882A - 16 specimens measured: central body maximum diameter: 31 (37.0) 43 μm; apical crest height: 2.5 (4.13) 5.5 μm; antapical crest height: 4.0 (6.57) 11.0 μm; apical/antapical crest height ratio: 0.36 (0.642) 0.77; central body maximum diameter/antapical crest height ratio: 0.11 (0.178) 0.26
Range based on Hole 887C - 26 specimens measured: central body maximum diameter: 30 (36.2) 44 μm; apical crest height: 3 (4.3) 7 μm; antapical crest height: 5 (6.9) 11 μm; apical/antapical crest height ratio: 0.43 (0.636) 0.73; central body maximum diameter/antapical crest height ratio: 0.14 (0.187) 0.27
Affinities:
Impagidinium detroitense sp. nov. is characterized by spheroidal to broadly ovoidal central body, well expressed tabulation, well-developed sutural crests that are higher at the antapex than apex, and slightly brownish color.
Impagidinium cantabrigiense (De Schepper and Head, 2008) is similar to Impagidinium detroitense as both are suturocavate and have crests that are higher at the antapex than apex. However, Impagidinium cantabrigiense has a somewhat smaller central body maximum diameter (25–36 vs. 30–44 μm) and relatively higher crests both apically (4–8 vs. 2.5–7.0 μm) and antapically (9–15 vs. 4–11 μm), and the central body maximum diameter/antapical crest height ratio is greater (0.33–0.48 vs. 0.11–0.27), although the apical/antapical crest height ratio is similar in both species (0.29–0.67 vs. 0.36–0.77). The tabulation is less well expressed in Impagidinium cantabrigiense, especially in the sulcal and surrounding areas and the torsion can be slightly sinistral, unlike in Impagidinium detroitense, where the dorsal surface has approximately neutral torsion.
Pentadinium netangei and Impagidinium cantabrigiense (probably conspecific) have a funnel-like antapical structure, which is absent from Impagidinium detroitense. The holotype of Pentadinium netangei has a central body maximum diameter/antapical crest height ratio of 0.44 which is outside of the range of Impagidinium detroitense. The height of antapical crests relative to the central body maximum diameter is higher for Impagidinium cantabrigiense and Pentadinium netangei and lower for
Impagidinium detroitense sp. nov.
Impagidinium japonicum (Matsuoka, 1983) is described as autophragmal and crucially lacks the pronounced suturocavation of Impagidinium detroitense sp. nov. The holotype shows somewhat more completely expressed tabulation in the sulcal area. The presence of a long narrow plate 1′′′ in Impagidinium japonicum is not seen in Impagidinium detroitense sp. nov., and a schematic tabulation in Matsuoka (1983, text-Fig. 13B) shows the 3c/4c boundary aligned with the 3′′/4′′ boundary whereas in
Impagidinium detroitense sp. nov. this boundary aligns with the midpoint of 3′′. No cingular boundary aligns with the 3′′/4′′ boundary in Impagidinium detroitense sp. nov.
Impagidinium velorum (Bujak, 1984) is distinguished from Impagidinium detroitense sp. nov. by its relatively small, thin-walled central body (length 17–33 μm), high (maximum 19–25 μm) membranous crests, and its cingulum marked by a single crest.
Holotype: Zorzi, C. et al., 2019, Sample ODP 882A-26H3W, Plate I, 1–8
Age: Pliocene
Stratigraphic range: Early Pliocene through Late Pliocene, from 5.27 to 2.70 Ma.
Original description: Zorzi, C. et al., 2019: Impagidinium detroitense sp. nov.:
Diagnosis:
A proximochorate and suturocavate species of the genus Impagidinium with a spheroidal to broadly ovoidal central body, and tabulation formula 3–4′, 6′′, 6c, 5′′′, 1p, 1′′′′, ps expressed mostly by cavate septa that are appressed distally to form solid crests. The surfaces of the central body and septa are finely granulate. Septa are higher at the
antapex than apex. The ratio of the central body maximum diameter to antapical crest height is around 0.11 to 0.27. Plate 6′′ is strongly sub-triangular and narrowly contacts apical plates (1′ + 4′), which are often not clearly separated. Plate 6c narrows towards the sulcus, its anterior margin displaced downwards by plate 6′′. Dorsal tabulation shows approximately neutral torsion. The archeopyle, formed by loss of plate 3′′, has well defined angles and corresponds closely to the bounding septa.
Description:
Cyst: proximochorate and suturocavate, with a spheroidal to broadly ovoidal central body, sometimes bearing a small apical protuberance up to about 1.0 μm high
Central body wall: away from the sutures is ~0.5–0.8 μm thick and stratification is indistinguishable under light microscopy, surface of the central body and sutures is finely granulate, with adjacent granules sometimes fused to form an incomplete microreticulation. Septa are mostly cavate, becoming distally appressed to form solid crests
that are usually slightly undulating. Septa are systematically higher at the antapex than apex, and they may tend to rise slightly towards plate junctions.
Tabulation: Septa indicate an S-type ventral organization, and follow the formula 3–4′, 6′′, 6c, 5′′′, 1 p, 1′′′′, ps. Apical plates 2′ and 3′ are large, and 1′ and 4′ are often not clearly separated from one another. Plate 6′′ is strongly sub-triangular and narrowly contacts apical plate 4′ (or 1′ + 4′), whereas the contact between plates 5′′ and 4′ or the merged 4′ + 1′ plate is broad and distinctive. The cingular plates are discernible individually, and plate 6c narrows towards the sulcus, its anterior margin distinctly displaced downwards by plate 6′′. The cingulum may narrow at the 2c/3c, 3c/4c, and 4c/5c boundaries. Individual sulcal plates are usually not expressed, with the exception that the ps plate is well defined. Plate 1′′′ is not observed and presumably is small and located within the sulcus. Dorsal tabulation shows approximately neutral torsion.
Archeopyle: formed by the loss of plate 3′′, has well-defined angles, and corresponds closely to the bounding septa.
Color: slightly brownish
Dimensions:
Holotype: central body maximum diameter: 36 μm; apical crest height: 5 μm; antapical crest height: 8 μm; apical/antapical crest height ratio: 0.63; central body maximum diameter/antapical crest height ratio: 0.22.
Range based on Hole 882A - 16 specimens measured: central body maximum diameter: 31 (37.0) 43 μm; apical crest height: 2.5 (4.13) 5.5 μm; antapical crest height: 4.0 (6.57) 11.0 μm; apical/antapical crest height ratio: 0.36 (0.642) 0.77; central body maximum diameter/antapical crest height ratio: 0.11 (0.178) 0.26
Range based on Hole 887C - 26 specimens measured: central body maximum diameter: 30 (36.2) 44 μm; apical crest height: 3 (4.3) 7 μm; antapical crest height: 5 (6.9) 11 μm; apical/antapical crest height ratio: 0.43 (0.636) 0.73; central body maximum diameter/antapical crest height ratio: 0.14 (0.187) 0.27
Affinities:
Impagidinium detroitense sp. nov. is characterized by spheroidal to broadly ovoidal central body, well expressed tabulation, well-developed sutural crests that are higher at the antapex than apex, and slightly brownish color.
Impagidinium cantabrigiense (De Schepper and Head, 2008) is similar to Impagidinium detroitense as both are suturocavate and have crests that are higher at the antapex than apex. However, Impagidinium cantabrigiense has a somewhat smaller central body maximum diameter (25–36 vs. 30–44 μm) and relatively higher crests both apically (4–8 vs. 2.5–7.0 μm) and antapically (9–15 vs. 4–11 μm), and the central body maximum diameter/antapical crest height ratio is greater (0.33–0.48 vs. 0.11–0.27), although the apical/antapical crest height ratio is similar in both species (0.29–0.67 vs. 0.36–0.77). The tabulation is less well expressed in Impagidinium cantabrigiense, especially in the sulcal and surrounding areas and the torsion can be slightly sinistral, unlike in Impagidinium detroitense, where the dorsal surface has approximately neutral torsion.
Pentadinium netangei and Impagidinium cantabrigiense (probably conspecific) have a funnel-like antapical structure, which is absent from Impagidinium detroitense. The holotype of Pentadinium netangei has a central body maximum diameter/antapical crest height ratio of 0.44 which is outside of the range of Impagidinium detroitense. The height of antapical crests relative to the central body maximum diameter is higher for Impagidinium cantabrigiense and Pentadinium netangei and lower for
Impagidinium detroitense sp. nov.
Impagidinium japonicum (Matsuoka, 1983) is described as autophragmal and crucially lacks the pronounced suturocavation of Impagidinium detroitense sp. nov. The holotype shows somewhat more completely expressed tabulation in the sulcal area. The presence of a long narrow plate 1′′′ in Impagidinium japonicum is not seen in Impagidinium detroitense sp. nov., and a schematic tabulation in Matsuoka (1983, text-Fig. 13B) shows the 3c/4c boundary aligned with the 3′′/4′′ boundary whereas in
Impagidinium detroitense sp. nov. this boundary aligns with the midpoint of 3′′. No cingular boundary aligns with the 3′′/4′′ boundary in Impagidinium detroitense sp. nov.
Impagidinium velorum (Bujak, 1984) is distinguished from Impagidinium detroitense sp. nov. by its relatively small, thin-walled central body (length 17–33 μm), high (maximum 19–25 μm) membranous crests, and its cingulum marked by a single crest.