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Impagidinium cornutum
Impagidinium cornutum Matsuoka and Bujak, 1988
Holotype: Matsuoka and Bujak, 1988, pl.6,fig.1a-c; text-fig.9
Paratype: Matsuoka and Bujak, 1988
Locus typicus: Norton Sound COST No. 1 Well, Norton Sound, Bering Sea
Stratum typicum: Hystrichophaeropsis variabile Zone; Late Miocene
Original diagnosis: Matsuoka and Bujak, 1988, p.52
Small to intermediate proximate cyst with an ovoidal to roundly hexagonal shape. Epicyst roundly triangular in dorso-ventral view, slightly larger than hypocyst and bearing a distinctive small apical horn; hypocyst trapezoidal in dorso-ventral view and lacking an antapical horn. Cyst wall comprising a smooth periphragm and endophragm. Parasutures membranous, sometimes perforated, mostly low but distinct and representing the paratabulation as 4", 6", 6c, 6""", 1p, 1"""" and xs. Paraplate 4" similar to the 1" in shape and size; 6" narrowly triangular; 1""" longitudinally narrow. Paracingulum displaced by twice of its width; slightly helicoidal; anterior and posterior sulcal paraplates present, but others obscure. Archeopyle precingular (3" ); operculum detached.
Original description: Matsuoka and Bujak, 1988, p.52-53
The cyst body varies from ovoidal to roundly polygonal with a hypocyst that is usually trapezoidal in dorso-ventral view. The epicyst varies from trapezoidal to roundly triangular in dorso-ventral view and forms a short, conical, hollow horn that is distally closed and sometimes truncated. The distinct parasutures are membranous and sometimes perforated. The paratabulation indicated by the parasutural septa is 4", 6", 6c, 6""", 1p, 1"""", xc, although the boundary between the first and fourth apical paraplates is usually strongly reduced. The 3" paraplate does not contact the 6" paraplate which is smaller and typically triangular. All of the precingular paraplates except for the sixth have distinct parasutures. All six cingular paraplates are developed and are transversely rectangular, and the paracingulum is laevorotary and displaced by approximately one to two paracingular width. Paraplate 1""" is reduced and the lp paraplate is located below the 2""" paraplate. The parasulcus is slightly curved and extends onto the epicyst but does not reach the centre of the hypocyst. The precingular archeopyle is slightly reduced and is formed by the loss of paraplate 3".
Dimensions: Holotype; length of cyst 52 µm, width 44 µm, length of apical horn 6 µm, height of parasutures ca. 3 µm. Range: length of cyst 45-52 µm, width 39-44 Ám, length of apical horn 5-7 µm, hight of parasutures 3-4 µm. Number of specimens measured: 6.
Thecal affinities: Impagidinium cornutum may be related to the modern Gonyaulacaceae based on its paratabulation and archeopyle type.
Affinities:
Matsuoka and Bujak, 1988, p.53: Impagidinium cornutum is similar to I. japonicum Matsuoka in having distinctive parasutures and a complete set of paracingular plates. However, the characteristic apical horn and perforated parasutural septa distinguish I. cornutum from this species and other species of Impagidinium.
I. cornutum resembles Psaligonyaulax cf. simplica (Cookson and Eisenack) recorded from the middle to late Eocene of the Norwegian-Greenland Sea by Manum (1976, pl. 2, fig. 5, 6), but differs in possessing a shorter and more spherical cyst body and a less well-developed hypocystal pericoel. Wiggins (1986) recorded the Impagidinium sp. which is probably conspecific with I. cornutum from core material of the Navarin Basin in the Bering Sea.
Holotype: Matsuoka and Bujak, 1988, pl.6,fig.1a-c; text-fig.9
Paratype: Matsuoka and Bujak, 1988
Locus typicus: Norton Sound COST No. 1 Well, Norton Sound, Bering Sea
Stratum typicum: Hystrichophaeropsis variabile Zone; Late Miocene
Original diagnosis: Matsuoka and Bujak, 1988, p.52
Small to intermediate proximate cyst with an ovoidal to roundly hexagonal shape. Epicyst roundly triangular in dorso-ventral view, slightly larger than hypocyst and bearing a distinctive small apical horn; hypocyst trapezoidal in dorso-ventral view and lacking an antapical horn. Cyst wall comprising a smooth periphragm and endophragm. Parasutures membranous, sometimes perforated, mostly low but distinct and representing the paratabulation as 4", 6", 6c, 6""", 1p, 1"""" and xs. Paraplate 4" similar to the 1" in shape and size; 6" narrowly triangular; 1""" longitudinally narrow. Paracingulum displaced by twice of its width; slightly helicoidal; anterior and posterior sulcal paraplates present, but others obscure. Archeopyle precingular (3" ); operculum detached.
Original description: Matsuoka and Bujak, 1988, p.52-53
The cyst body varies from ovoidal to roundly polygonal with a hypocyst that is usually trapezoidal in dorso-ventral view. The epicyst varies from trapezoidal to roundly triangular in dorso-ventral view and forms a short, conical, hollow horn that is distally closed and sometimes truncated. The distinct parasutures are membranous and sometimes perforated. The paratabulation indicated by the parasutural septa is 4", 6", 6c, 6""", 1p, 1"""", xc, although the boundary between the first and fourth apical paraplates is usually strongly reduced. The 3" paraplate does not contact the 6" paraplate which is smaller and typically triangular. All of the precingular paraplates except for the sixth have distinct parasutures. All six cingular paraplates are developed and are transversely rectangular, and the paracingulum is laevorotary and displaced by approximately one to two paracingular width. Paraplate 1""" is reduced and the lp paraplate is located below the 2""" paraplate. The parasulcus is slightly curved and extends onto the epicyst but does not reach the centre of the hypocyst. The precingular archeopyle is slightly reduced and is formed by the loss of paraplate 3".
Dimensions: Holotype; length of cyst 52 µm, width 44 µm, length of apical horn 6 µm, height of parasutures ca. 3 µm. Range: length of cyst 45-52 µm, width 39-44 Ám, length of apical horn 5-7 µm, hight of parasutures 3-4 µm. Number of specimens measured: 6.
Thecal affinities: Impagidinium cornutum may be related to the modern Gonyaulacaceae based on its paratabulation and archeopyle type.
Affinities:
Matsuoka and Bujak, 1988, p.53: Impagidinium cornutum is similar to I. japonicum Matsuoka in having distinctive parasutures and a complete set of paracingular plates. However, the characteristic apical horn and perforated parasutural septa distinguish I. cornutum from this species and other species of Impagidinium.
I. cornutum resembles Psaligonyaulax cf. simplica (Cookson and Eisenack) recorded from the middle to late Eocene of the Norwegian-Greenland Sea by Manum (1976, pl. 2, fig. 5, 6), but differs in possessing a shorter and more spherical cyst body and a less well-developed hypocystal pericoel. Wiggins (1986) recorded the Impagidinium sp. which is probably conspecific with I. cornutum from core material of the Navarin Basin in the Bering Sea.