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Prionodinium alaskense
Prionodinium alaskense Leffingwell and Morgan, 1977
Holotype: Leffingwell and Morgan 1977, pl.1, fig.2a-b; Jan du Chêne et al., 1986, pl.84, figs.10-15
Paratypes: Leffingwell and Morgan, 1977
Locus typicus: Headwaters of unnamed tributary east of the South Fork of the Kamishak River, Alaska, U.S.A. (latitude 58¦49"N, longitude 154¦03"W); 215" above the contact between the unnamed formation of Jones and Detterman (1966) and the underlying Naknek Formation
Stratum typicum: Hauterivian-Barremian
Original description: Leffingwell and Morgan, 1977, p.295
Oval-elongate proximate cysts with a short, apical horn, 5Ám high or less, formed by modification of the apical crests into a bifid projection whose axis of projection is oriented dorsoventrally; cysts not dorsoventrally flattened; cyst length-width ratio approximately 2; double-layered wall closely appressed, endophragm 0.8 µm thick, periphragm less than 0.5 µm thick; tabulation clearly reflected by sutural crests; tabulation: 4", 6", 6c, 5""", 1p, (ps), 1""""; large rectangular postsulcal plate delineated by horizontal septum ([Leffingwell and Morgan, 1977] Pl. 2, fig. 2); posterior intercalary plate large and trapezoidal; precingular plates elongate except for 6", which is reduced in height and subtriangular; 1", 4" plates are elongate and narrow, the 2", 3" are large and equidimensional; sutural crests are faintly striated, 3-5 µm high and are slightly denticulate on their distal margins; cingulum is offset by approximately one cingulum width; sulcus extends onto epitract; wall finely scabrate with scattered superimposed pustules; precingular (3") archeopyle, operculum free; size (exclusive of crests) 47-74 µm x 25-35 µm (25 specimens); average size (exclusive of crests) 57.5 x 31.9 µm.
Supplemental description: Brideaux, 1977, p. 8
Shape: Pericyst ovoid, the length twice the width, the maximum width at the latitude of the paracingulum; apical and antapical horns absent. Endocyst shape as above, closely appressed to pericyst, no development of pericoel; lateral compression.
Phragma: Periphragm thin, about 0.5 µm thick; smooth to microrugulate intratabularly, forming parasutural crests 3-5 µm high; crests distally serrate, occasionally ragged and often bearing discrete spinules up to 1.0 µm long, surface of crests microgranulate to microrugulate. Endophragm smooth, about 1.0 thick.
Paratabulation: Parasutural crests denote a paratabulation of 4", 6", 6c, 5""", 1p, 1""""; of the apical paraplates, 1" is diamond-shaped and 2" is the largest; of the precingular paraplates, 1" is triangular and 3" is tongue-shaped and twice as long as broad; other precingular and postcingular paraplates are elongate, with 5""" being smaller and trapezoidal; paraplate 1p is quadrate.
Endophragm shows no evidence of paratabulation.
Archeopyle/operculum: Archeopyle formed by the loss of the third precingular paraplate. Operculum simple, free; tongue-shaped, occasionally found in endocoel; the two layers closely appressed and separating as a unit. Formula P.
Pericingulum/perisulcus: Helicoid pericingulum from 4-6 µm wide and offset one width, with six cingular paraplates; perisulcus long and narrow, extending anteriorly halfway up the epicyst and posteriorly the length of the hypocyst; the lateral compression precluding observation of perisulcal details.
Affinities:
Leffingwell and Morgan (1977, p.295) compared Prionodinium alaskense with Prionodinium alveolatum Leffingwell and Morgan, 1977. Jan du Chene et al. (1986, table 57 - p.263) tabulated the diagnostic features of Prionodinium alaskense and Prionodinium alveolatum (Fensome et al., 1993, p.892).
Brideaux, 1977, p. 9: Prionodinium alaskense is superficially similar to Herendeenia pisciformis (Cookson and Eisenack) Wiggins, 1969 but lacks the apical horn of that species and differs in possessing four apical paraplates, six precingular paraplates and five postcingular paraplates. Prionodinium alaskense differs from another superficially similar form, Clathroctenocystis elegans Wiggins, 1972, p. 303, Plate II, figures A-C, Plate III, figures A-D, and Figure 3, in possession of a precingular archeopyle and absence of an apical horn.
Holotype: Leffingwell and Morgan 1977, pl.1, fig.2a-b; Jan du Chêne et al., 1986, pl.84, figs.10-15
Paratypes: Leffingwell and Morgan, 1977
Locus typicus: Headwaters of unnamed tributary east of the South Fork of the Kamishak River, Alaska, U.S.A. (latitude 58¦49"N, longitude 154¦03"W); 215" above the contact between the unnamed formation of Jones and Detterman (1966) and the underlying Naknek Formation
Stratum typicum: Hauterivian-Barremian
Original description: Leffingwell and Morgan, 1977, p.295
Oval-elongate proximate cysts with a short, apical horn, 5Ám high or less, formed by modification of the apical crests into a bifid projection whose axis of projection is oriented dorsoventrally; cysts not dorsoventrally flattened; cyst length-width ratio approximately 2; double-layered wall closely appressed, endophragm 0.8 µm thick, periphragm less than 0.5 µm thick; tabulation clearly reflected by sutural crests; tabulation: 4", 6", 6c, 5""", 1p, (ps), 1""""; large rectangular postsulcal plate delineated by horizontal septum ([Leffingwell and Morgan, 1977] Pl. 2, fig. 2); posterior intercalary plate large and trapezoidal; precingular plates elongate except for 6", which is reduced in height and subtriangular; 1", 4" plates are elongate and narrow, the 2", 3" are large and equidimensional; sutural crests are faintly striated, 3-5 µm high and are slightly denticulate on their distal margins; cingulum is offset by approximately one cingulum width; sulcus extends onto epitract; wall finely scabrate with scattered superimposed pustules; precingular (3") archeopyle, operculum free; size (exclusive of crests) 47-74 µm x 25-35 µm (25 specimens); average size (exclusive of crests) 57.5 x 31.9 µm.
Supplemental description: Brideaux, 1977, p. 8
Shape: Pericyst ovoid, the length twice the width, the maximum width at the latitude of the paracingulum; apical and antapical horns absent. Endocyst shape as above, closely appressed to pericyst, no development of pericoel; lateral compression.
Phragma: Periphragm thin, about 0.5 µm thick; smooth to microrugulate intratabularly, forming parasutural crests 3-5 µm high; crests distally serrate, occasionally ragged and often bearing discrete spinules up to 1.0 µm long, surface of crests microgranulate to microrugulate. Endophragm smooth, about 1.0 thick.
Paratabulation: Parasutural crests denote a paratabulation of 4", 6", 6c, 5""", 1p, 1""""; of the apical paraplates, 1" is diamond-shaped and 2" is the largest; of the precingular paraplates, 1" is triangular and 3" is tongue-shaped and twice as long as broad; other precingular and postcingular paraplates are elongate, with 5""" being smaller and trapezoidal; paraplate 1p is quadrate.
Endophragm shows no evidence of paratabulation.
Archeopyle/operculum: Archeopyle formed by the loss of the third precingular paraplate. Operculum simple, free; tongue-shaped, occasionally found in endocoel; the two layers closely appressed and separating as a unit. Formula P.
Pericingulum/perisulcus: Helicoid pericingulum from 4-6 µm wide and offset one width, with six cingular paraplates; perisulcus long and narrow, extending anteriorly halfway up the epicyst and posteriorly the length of the hypocyst; the lateral compression precluding observation of perisulcal details.
Affinities:
Leffingwell and Morgan (1977, p.295) compared Prionodinium alaskense with Prionodinium alveolatum Leffingwell and Morgan, 1977. Jan du Chene et al. (1986, table 57 - p.263) tabulated the diagnostic features of Prionodinium alaskense and Prionodinium alveolatum (Fensome et al., 1993, p.892).
Brideaux, 1977, p. 9: Prionodinium alaskense is superficially similar to Herendeenia pisciformis (Cookson and Eisenack) Wiggins, 1969 but lacks the apical horn of that species and differs in possessing four apical paraplates, six precingular paraplates and five postcingular paraplates. Prionodinium alaskense differs from another superficially similar form, Clathroctenocystis elegans Wiggins, 1972, p. 303, Plate II, figures A-C, Plate III, figures A-D, and Figure 3, in possession of a precingular archeopyle and absence of an apical horn.