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Xandarodinium variabile
From Fensome et al., 2019:
Xandarodinium variabile Bujak, 1984, p.194–195, pl.4, figs.7–10; text-fig.3.
Holotype: Bujak, 1984, pl.4, fig.8; Head, 1994b, pl.11, figs.4–5,7–8; text-fig.3.
NOW Trinovantedinium. Originally Xandarodinium, subsequently (and now) Trinovantedinium.
Paratypes: Bujak, 1984, pl.4, fig.7
Locus typicus: Bering Sea
Stratum typicum: Late Miocene-Early Pleistocene
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Original description: Bujak, 1984, p. 194-195
Diagnosis: Single-walled protoperidiniacean cysts, typically dorsoventrally compressed with circular to oval outline, or occasionally compressed along polar axis with circular to reniform outline. One apical and two antapical lobes weakly developed or absent. Cyst wall light brown with smooth to shagrinate surface bearing processes. Cingulum marked by rows of processes and sometimes by folds, or not delineated. Sulcus shallow, sometimes with row of processes along each lateral margin on hypocyst. Processes variable in shape; usually hollow and slender with flared aculeate terminations, or less commonly irregularly branched. Process number and distribution variable; processes often concentrated on ambital periphery of cyst and along cingulum. Archeopyle hexa 2a, typically symmetrically located along dorsal midline.
Dimensions: Cyst length (excluding processes) 42 to 65 µm, breadth (excluding processes) 42 to 63 µm; maximum process length 7 to 15 µm, 20 specimens measured.
Description (annotated): The most variable features shown by this species are the number, distribution, and morphology of the processes. Processes are always present near the ambital periphery of the cyst seen in dorsoventral view and generally also along the cingulum. Processes may be present or absent from the middorsal and midventral precingular areas and are usually present on the middorsal postcingular area. They are absent from the sulcal area, but a row often marks each lateral margin of the sulcus. Processes are concentrated on some specimens near the apex, with longer or more complexly branched processes typically present on the left antapical lobe and sometimes also on the right antapical lobe. A long, pointed left antapical process is occasionally present and its length is such that it could be designated as a left antapical horn.
The morphology of the processes is highly variable. On most specimens examined the processes are unbranched and slender with proximal and distal expansion, a circular cross section, and are distally aculeate. Other specimens bear a variety of processes as shown in text-fig. 3. These always include the relatively simple processes described above, plus a variety of irregularly branched processes. When complexly branched, the processes are taeniate in cross section.
Affinities:
Bujak, 1984, p. 447
Xandarodinium xanthum, described by Reid (1977) from Recent intertidal sediments of the British Isles differs X. variabile in having broader processes. Multispinula quanta, described by Bradford (1975) form Recent sediments of the Persian Gulf, differs from X. variabile in having solid, pointed processes.
Xandarodinium variabile Bujak, 1984, p.194–195, pl.4, figs.7–10; text-fig.3.
Holotype: Bujak, 1984, pl.4, fig.8; Head, 1994b, pl.11, figs.4–5,7–8; text-fig.3.
NOW Trinovantedinium. Originally Xandarodinium, subsequently (and now) Trinovantedinium.
Paratypes: Bujak, 1984, pl.4, fig.7
Locus typicus: Bering Sea
Stratum typicum: Late Miocene-Early Pleistocene
----------------------------------------------------------------------------------------------------------------------------------
Original description: Bujak, 1984, p. 194-195
Diagnosis: Single-walled protoperidiniacean cysts, typically dorsoventrally compressed with circular to oval outline, or occasionally compressed along polar axis with circular to reniform outline. One apical and two antapical lobes weakly developed or absent. Cyst wall light brown with smooth to shagrinate surface bearing processes. Cingulum marked by rows of processes and sometimes by folds, or not delineated. Sulcus shallow, sometimes with row of processes along each lateral margin on hypocyst. Processes variable in shape; usually hollow and slender with flared aculeate terminations, or less commonly irregularly branched. Process number and distribution variable; processes often concentrated on ambital periphery of cyst and along cingulum. Archeopyle hexa 2a, typically symmetrically located along dorsal midline.
Dimensions: Cyst length (excluding processes) 42 to 65 µm, breadth (excluding processes) 42 to 63 µm; maximum process length 7 to 15 µm, 20 specimens measured.
Description (annotated): The most variable features shown by this species are the number, distribution, and morphology of the processes. Processes are always present near the ambital periphery of the cyst seen in dorsoventral view and generally also along the cingulum. Processes may be present or absent from the middorsal and midventral precingular areas and are usually present on the middorsal postcingular area. They are absent from the sulcal area, but a row often marks each lateral margin of the sulcus. Processes are concentrated on some specimens near the apex, with longer or more complexly branched processes typically present on the left antapical lobe and sometimes also on the right antapical lobe. A long, pointed left antapical process is occasionally present and its length is such that it could be designated as a left antapical horn.
The morphology of the processes is highly variable. On most specimens examined the processes are unbranched and slender with proximal and distal expansion, a circular cross section, and are distally aculeate. Other specimens bear a variety of processes as shown in text-fig. 3. These always include the relatively simple processes described above, plus a variety of irregularly branched processes. When complexly branched, the processes are taeniate in cross section.
Affinities:
Bujak, 1984, p. 447
Xandarodinium xanthum, described by Reid (1977) from Recent intertidal sediments of the British Isles differs X. variabile in having broader processes. Multispinula quanta, described by Bradford (1975) form Recent sediments of the Persian Gulf, differs from X. variabile in having solid, pointed processes.