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Operculodinium crassum
Operculodinium crassum Harland, 1979
Tax. jr. synonym of Operculodinium israelianum (Rossignol, 1962) Wall, 1967, according to Edwards and Andrle, 1992.
Taxonomic senior synonym: Hystrichosphaeridium (as Operculodinium) israelianum, according to Harland in Head and Wrenn (1992, p.20) and Edwards and Andrle (1992) — however, Head (1996b, p.1231) provisionally retained Operculodinium crassum. Williams et al. (1998, p.441) incorrectly indicated that Head (1996b, p.1231) questioned the assignment of this species to Operculodinium.
Holotype: Harland, 1979, pl.2, figs.12-14
Age: Late Miocene-Pleistocene
Original description (Harland, 1979):
Operculodinium crassum sp. nov. (Plate 2, Figures 12-14)
Derivation of Name: Latin—crassus, thick, with reference to the thick wall of this species.
Diagnosis: Spherical chorate cyst made up of two closely adpressed wall layers. Wall is thick (up to 4.0 µm), with the bulk of it being periphragm. Surface ornament microgranulate or micropunctate, but in optical section the wall layer appears spongy. Processes short (Vs-Vs cyst diameter), numerous, conical with a flared distal tip. Archeopyle pre-cingular presumably formed by the loss of plate 3".
Holotype: MPK 1642 (Plate 2, Figures 12-14). Type Locality: Bay of Biscay, Sample 400A-12-3, 60-62 cm.
Dimensions: Holotype: Length, exclusive of processes, 62.0 µm; breadth 62.0 µm; maximum process length 8.0 µm; wall thickness 4.0 µm. Range: Length, 54.0-74.0 µm; breadth 50.0-68.0 µm; process length 8.0- 11.0 µm; wall thickness 2.0-4.0 µm. Seven specimens measured.
Description: A species of Operculodinium with a characteristically thick wall layer, at least twice the thickness of any previously described species (Plate 2, Figure 13). The exact nature of the wall structure and ornament is difficult to see and would benefit from study with a transmission and scanning electron microscope. The processes carry the same microgranulation and punctation on their shafts as seen on the cyst body and have bifid or flared tips.
Remarks: This species is most similar to Operculodinium israelianum (Rossignol) Wall from which it differs in possessing a thick wall. The process structure of the two species is similar, being short and conical, but O. crassum differs in that the process morphology is variable and not so consistent as in O. israelianum (Wall, 1967). This species is probably cospecific with Operculodinium sp. I of Manum (1976).
Occurrence: Observed in late Miocene to early Pleistocene sediments from Hole 400A.
Tax. jr. synonym of Operculodinium israelianum (Rossignol, 1962) Wall, 1967, according to Edwards and Andrle, 1992.
Taxonomic senior synonym: Hystrichosphaeridium (as Operculodinium) israelianum, according to Harland in Head and Wrenn (1992, p.20) and Edwards and Andrle (1992) — however, Head (1996b, p.1231) provisionally retained Operculodinium crassum. Williams et al. (1998, p.441) incorrectly indicated that Head (1996b, p.1231) questioned the assignment of this species to Operculodinium.
Holotype: Harland, 1979, pl.2, figs.12-14
Age: Late Miocene-Pleistocene
Original description (Harland, 1979):
Operculodinium crassum sp. nov. (Plate 2, Figures 12-14)
Derivation of Name: Latin—crassus, thick, with reference to the thick wall of this species.
Diagnosis: Spherical chorate cyst made up of two closely adpressed wall layers. Wall is thick (up to 4.0 µm), with the bulk of it being periphragm. Surface ornament microgranulate or micropunctate, but in optical section the wall layer appears spongy. Processes short (Vs-Vs cyst diameter), numerous, conical with a flared distal tip. Archeopyle pre-cingular presumably formed by the loss of plate 3".
Holotype: MPK 1642 (Plate 2, Figures 12-14). Type Locality: Bay of Biscay, Sample 400A-12-3, 60-62 cm.
Dimensions: Holotype: Length, exclusive of processes, 62.0 µm; breadth 62.0 µm; maximum process length 8.0 µm; wall thickness 4.0 µm. Range: Length, 54.0-74.0 µm; breadth 50.0-68.0 µm; process length 8.0- 11.0 µm; wall thickness 2.0-4.0 µm. Seven specimens measured.
Description: A species of Operculodinium with a characteristically thick wall layer, at least twice the thickness of any previously described species (Plate 2, Figure 13). The exact nature of the wall structure and ornament is difficult to see and would benefit from study with a transmission and scanning electron microscope. The processes carry the same microgranulation and punctation on their shafts as seen on the cyst body and have bifid or flared tips.
Remarks: This species is most similar to Operculodinium israelianum (Rossignol) Wall from which it differs in possessing a thick wall. The process structure of the two species is similar, being short and conical, but O. crassum differs in that the process morphology is variable and not so consistent as in O. israelianum (Wall, 1967). This species is probably cospecific with Operculodinium sp. I of Manum (1976).
Occurrence: Observed in late Miocene to early Pleistocene sediments from Hole 400A.