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Kiokansium prolatum
Kiokansium prolatum Duxbury, 1983; emend. Masure, 1986
Holotype: Duxbury, 1983, pl.6, fig.8
Locus typicus: Sandrock Series, Isle of Wight, England
Stratum typicum: Late Aptian-Early Albian
Original diagnosis: Duxbury, 1983, p.49-50
An elongate ellipsoidal, thin-walled, chorate dinoflagellate cyst. It has 19 slender, solid processes which are proximally flared and distally produced into several flat, tapering, recurved spines. Each process is paraplate centred and a gonyaulacacean paratabulation pattern of the formula 4", 6"", ?c, 6""", 1p, 1p.v., 1"""" may be inferred. The paracingulum is devoid of processes. The pre- and postcingular processes are longer than elsewhere, so that the length to breadth ratio of the entire cyst is considerably smaller than that of the main body. The archeopyle is two-paraplate precingular.
Observed dimensions: holotype 78x55 Ám. Overall 89(69)61x78(53)41 Ám. Main Body 61(45)38x38(27)20 Ám.
Affinities:
Duxbury, 1983, p. 50: The elongate shape of this species, particularly of the main body, renders it most distinctive. The most closely comparable taxon is Hystrichosphaeridium? phoenix Duxbury, 1980, a species which bears very similar processes to K prolatum, both numerically and morphologically. H. ?phoenix, however, has a spheroidal main body with processes of equal length, whereas K. prolatum is elongate with pre- and postcingular processes longer than processes elsewhere.
The specimen figured by Singh (1971, pl. 56, fig. 4) and referred to Oligosphaeridium prolixispinosum Davey and Williams, 1966 is here considered an example of Kiokansium prolatum. Singh"s illustration shows well the elongate ellipsoidal shape, variability in process length and, more particularly, the distinctive process terminations of K. prolatum.
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Emendation by Masure, 1986 (translated from French):
Emended diagnosis: Skolochorate dinoflagellate cyst with an ellipsoidal central body, elongated vertically, extending at the apex into a rounded protrusion. Non-fibrous, compact wall formed by a closely adjacent periphragm and endophragm. Solid, intratabular processes (one in the center of some paraplates), with a distal end terminating in a rosette of branched, very sharp spines. Paracingulate and parasulcal areas devoid of processes.
Paratabulation formula of processes: pr?, 4', 6", Oc, 6"', 1"", 1p, ? s.
Deduced paratabulation: gonyaulacoid type.
Precingulate archaeopyle 2P formed by the loss of the 3" and 4" paraplates according to Kofoid. Taylor-Evitt formula of the acheopyle: 2P 4-5.
Opercular parts free.
Dimensions (according to Duxbury): Holotype: 78-55 µm.
Note: The assignment of this species to the genus Kiokansium is debatable. Indeed, a species possessing intratabular processes, one in the center of the paraplates, cannot be definitively assigned to a genus characterized by non-tabular processes.
Holotype: Duxbury, 1983, pl.6, fig.8
Locus typicus: Sandrock Series, Isle of Wight, England
Stratum typicum: Late Aptian-Early Albian
Original diagnosis: Duxbury, 1983, p.49-50
An elongate ellipsoidal, thin-walled, chorate dinoflagellate cyst. It has 19 slender, solid processes which are proximally flared and distally produced into several flat, tapering, recurved spines. Each process is paraplate centred and a gonyaulacacean paratabulation pattern of the formula 4", 6"", ?c, 6""", 1p, 1p.v., 1"""" may be inferred. The paracingulum is devoid of processes. The pre- and postcingular processes are longer than elsewhere, so that the length to breadth ratio of the entire cyst is considerably smaller than that of the main body. The archeopyle is two-paraplate precingular.
Observed dimensions: holotype 78x55 Ám. Overall 89(69)61x78(53)41 Ám. Main Body 61(45)38x38(27)20 Ám.
Affinities:
Duxbury, 1983, p. 50: The elongate shape of this species, particularly of the main body, renders it most distinctive. The most closely comparable taxon is Hystrichosphaeridium? phoenix Duxbury, 1980, a species which bears very similar processes to K prolatum, both numerically and morphologically. H. ?phoenix, however, has a spheroidal main body with processes of equal length, whereas K. prolatum is elongate with pre- and postcingular processes longer than processes elsewhere.
The specimen figured by Singh (1971, pl. 56, fig. 4) and referred to Oligosphaeridium prolixispinosum Davey and Williams, 1966 is here considered an example of Kiokansium prolatum. Singh"s illustration shows well the elongate ellipsoidal shape, variability in process length and, more particularly, the distinctive process terminations of K. prolatum.
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Emendation by Masure, 1986 (translated from French):
Emended diagnosis: Skolochorate dinoflagellate cyst with an ellipsoidal central body, elongated vertically, extending at the apex into a rounded protrusion. Non-fibrous, compact wall formed by a closely adjacent periphragm and endophragm. Solid, intratabular processes (one in the center of some paraplates), with a distal end terminating in a rosette of branched, very sharp spines. Paracingulate and parasulcal areas devoid of processes.
Paratabulation formula of processes: pr?, 4', 6", Oc, 6"', 1"", 1p, ? s.
Deduced paratabulation: gonyaulacoid type.
Precingulate archaeopyle 2P formed by the loss of the 3" and 4" paraplates according to Kofoid. Taylor-Evitt formula of the acheopyle: 2P 4-5.
Opercular parts free.
Dimensions (according to Duxbury): Holotype: 78-55 µm.
Note: The assignment of this species to the genus Kiokansium is debatable. Indeed, a species possessing intratabular processes, one in the center of the paraplates, cannot be definitively assigned to a genus characterized by non-tabular processes.