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Operculodinium aquinawense
Operculodinium aquinawense Marret and Kim, 2009, p.128,130,132,136, pl.1, figs.1–12; pl.2, figs.1–12; pl.3, figs.1–9; pl.4, fig.1; pl.5, figs.1–4,6.
Holotype: Marret and Kim, 2009, pl.1, figs.1–8.
Age: late Pleistocene–Holocene.
Original description (Marret & Kim, 2009):
Operculodinium aguinawense Marret sp. nov. Plate 1, figs. 1-12, Plate 2, figs. 1-12, Plate 3, figs. 1-9, Plate 4, fig. 1, Plate 5, figs. 1-4, 6.
Operculodinium sp.n, Marret, 1994b,p. 198,pl.4,figs.7-8.
Operculodinium? sp. II, Marret, 1994a, pi. II, figs. 5-6.
Holotype. Slide M16865-1, England Finder coordinate Q39/2, NHM catalog number PM FD 803(1) (Plate 1, figs. 1-8).
Repository of holotype. Natural History Museum, London, U.K.
Reference material. Recent marine sediments collected at 2°40.3'N, 6°03.3'E, water depth 2492 m, off the Niger River Mouth, Gulf of Guinea.
Derivation of name. From the Gulf of Guinea (originally called aguinaw), with reference to the location of the type material.
Diagnosis. Egg-shaped to spherical, chorate cyst made up of closely adpressed endophragm and periphragm. Wall is thin (up to 1.5 µm), and has a fibroreticulate surface. Processes are about 1/3 of the cyst diameter, cylindrical, solid with fibrous conical bases and a multifurcate distal termination. Paratabulation is only expressed by the loss of a precingular, iso-deltaform camerate paraplate (3").
Description. A chorate cyst of egg-shaped to spherical shape, that consists of two adpressed layers, the endophragm and periphragm. The cyst wall is relatively thin (1.0-1.5 µm); its surface appears strongly fibroreticulate (Plate 1, figs. 6-7, Plate 2, fig. 2) in transmitted light. Scanning electron microscopy shows that the surface is randomly perforate, with wider perforations at the bases of the processes (Plate 5, figs. 2—4,6), giving the impression of a fibroreticulate texture when observed in transmitted light. The processes appear randomly inserted, about 5 ^m apart, although some processes are close or joined (Plate 1, figs. 2,12). On some specimens, a parallel arrangement of two rows of processes is observed below the paracingular region (Plate 3, figs. 1-4). Processes are solid, cylindrical, distally-tapering with a conical and perforated base (Plate 2, fig. 2, about 3 (µm in diameter), and have tetrafurcate to multifurcate tips (Plate 2, figs. 7-8, Plate 4, figs 1,7, Plate 5, figs.4,6). Processes are mostly flexible, although some specimens bear stout processes; their length is uniform on a single specimen. The ratio between the size of the cyst body and the length of the processes appears to be proportional according to the measurements shown in Text-Figure 2A, the processes averaging one-third of the body. Paratabulation is only expressed by the loss of paraplate 3', of iso-deltaform camerate shape. No opercula have been observed.
Dimensions. Holotype: cyst body diameter 45 µm; process length 11 µm; wall thickness 1 µm. Range in surface sediment samples (79 specimens measured): cyst body diameter range 37-69 µm; process length 8.0-16.7 µm; wall thickness 1.0-1.5 µm. Range in core material (core GeoB4905-4, depths 55 and 75 cm (43 specimens measured): cyst body diameter range 34.5-48.8 µm; process length 9.5-13.8 µm; wall thickness 1.0-1.5 µm.
Stratigraphic range. Late Pleistocene to Holocene.
Comparison. Table 1 summarizes the main morphologic characteristics of the species most closely resembling Operculodinium aguinawense sp. nov. Plots in Text-Figure 2 also document the range in diameter size versus process length for the most similar species. This highlights a distinct range for Operculodinium aguinawense sp. nov., differing from the cysts of Protoceratium reticulatum (=Operculodinium centrocarpum sensu Wall and Dale, 1966) in particular. The wall surface is similar only to one specimen of Operculodinium centrocarpum sensu Wall and Dale (1966), with the exception of the base of the processes which show pronounced fibroreticulation in Operculodinium aguinawense sp. nov. Processes are very distinct, being broader and cylindrical with multifurcate tips (Plate 2, fig. 7, Plate 4, fig. 1, Plate 5, figs. 4, 6) compared to the slender processes of Operculodinium centrocarpum (Plate 4, fig. 3). Operculodinium aguinawense sp. nov. also differs from Operculodinium israelianum (Rossignol 1962) Wall 1967 by having longer and less numerous processes, and an overall smaller body size (Text-Figure 2A, Plate 3, fig. 10, Plate 5, fig. 5). Operculodinium aguinawense sp. nov. superficially resembles Operculodinium crassum Harland 1979 (Plate 4, figs. 4-6) but has a thinner wall, a smaller body, and more flexuous and longer processes. Operculodinium aguinawense sp. nov. is distinguished from Operculodinium wallii Matsuoka 1983 by having a smaller cyst diameter and overall shorter processes with multifurcate distal tips.
Holotype: Marret and Kim, 2009, pl.1, figs.1–8.
Age: late Pleistocene–Holocene.
Original description (Marret & Kim, 2009):
Operculodinium aguinawense Marret sp. nov. Plate 1, figs. 1-12, Plate 2, figs. 1-12, Plate 3, figs. 1-9, Plate 4, fig. 1, Plate 5, figs. 1-4, 6.
Operculodinium sp.n, Marret, 1994b,p. 198,pl.4,figs.7-8.
Operculodinium? sp. II, Marret, 1994a, pi. II, figs. 5-6.
Holotype. Slide M16865-1, England Finder coordinate Q39/2, NHM catalog number PM FD 803(1) (Plate 1, figs. 1-8).
Repository of holotype. Natural History Museum, London, U.K.
Reference material. Recent marine sediments collected at 2°40.3'N, 6°03.3'E, water depth 2492 m, off the Niger River Mouth, Gulf of Guinea.
Derivation of name. From the Gulf of Guinea (originally called aguinaw), with reference to the location of the type material.
Diagnosis. Egg-shaped to spherical, chorate cyst made up of closely adpressed endophragm and periphragm. Wall is thin (up to 1.5 µm), and has a fibroreticulate surface. Processes are about 1/3 of the cyst diameter, cylindrical, solid with fibrous conical bases and a multifurcate distal termination. Paratabulation is only expressed by the loss of a precingular, iso-deltaform camerate paraplate (3").
Description. A chorate cyst of egg-shaped to spherical shape, that consists of two adpressed layers, the endophragm and periphragm. The cyst wall is relatively thin (1.0-1.5 µm); its surface appears strongly fibroreticulate (Plate 1, figs. 6-7, Plate 2, fig. 2) in transmitted light. Scanning electron microscopy shows that the surface is randomly perforate, with wider perforations at the bases of the processes (Plate 5, figs. 2—4,6), giving the impression of a fibroreticulate texture when observed in transmitted light. The processes appear randomly inserted, about 5 ^m apart, although some processes are close or joined (Plate 1, figs. 2,12). On some specimens, a parallel arrangement of two rows of processes is observed below the paracingular region (Plate 3, figs. 1-4). Processes are solid, cylindrical, distally-tapering with a conical and perforated base (Plate 2, fig. 2, about 3 (µm in diameter), and have tetrafurcate to multifurcate tips (Plate 2, figs. 7-8, Plate 4, figs 1,7, Plate 5, figs.4,6). Processes are mostly flexible, although some specimens bear stout processes; their length is uniform on a single specimen. The ratio between the size of the cyst body and the length of the processes appears to be proportional according to the measurements shown in Text-Figure 2A, the processes averaging one-third of the body. Paratabulation is only expressed by the loss of paraplate 3', of iso-deltaform camerate shape. No opercula have been observed.
Dimensions. Holotype: cyst body diameter 45 µm; process length 11 µm; wall thickness 1 µm. Range in surface sediment samples (79 specimens measured): cyst body diameter range 37-69 µm; process length 8.0-16.7 µm; wall thickness 1.0-1.5 µm. Range in core material (core GeoB4905-4, depths 55 and 75 cm (43 specimens measured): cyst body diameter range 34.5-48.8 µm; process length 9.5-13.8 µm; wall thickness 1.0-1.5 µm.
Stratigraphic range. Late Pleistocene to Holocene.
Comparison. Table 1 summarizes the main morphologic characteristics of the species most closely resembling Operculodinium aguinawense sp. nov. Plots in Text-Figure 2 also document the range in diameter size versus process length for the most similar species. This highlights a distinct range for Operculodinium aguinawense sp. nov., differing from the cysts of Protoceratium reticulatum (=Operculodinium centrocarpum sensu Wall and Dale, 1966) in particular. The wall surface is similar only to one specimen of Operculodinium centrocarpum sensu Wall and Dale (1966), with the exception of the base of the processes which show pronounced fibroreticulation in Operculodinium aguinawense sp. nov. Processes are very distinct, being broader and cylindrical with multifurcate tips (Plate 2, fig. 7, Plate 4, fig. 1, Plate 5, figs. 4, 6) compared to the slender processes of Operculodinium centrocarpum (Plate 4, fig. 3). Operculodinium aguinawense sp. nov. also differs from Operculodinium israelianum (Rossignol 1962) Wall 1967 by having longer and less numerous processes, and an overall smaller body size (Text-Figure 2A, Plate 3, fig. 10, Plate 5, fig. 5). Operculodinium aguinawense sp. nov. superficially resembles Operculodinium crassum Harland 1979 (Plate 4, figs. 4-6) but has a thinner wall, a smaller body, and more flexuous and longer processes. Operculodinium aguinawense sp. nov. is distinguished from Operculodinium wallii Matsuoka 1983 by having a smaller cyst diameter and overall shorter processes with multifurcate distal tips.