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Prionodinium alveolatum
Prionodinium alvelatum Leffingwell and Morgan 1977
Holotype: Leffingwell and Morgan 1977, pl.1, fig.4a-b; Jan du Chêne et al., 1986, pl.84, figs. 4-9
Age: Late Neocomian
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Original description (Leffingwell and Morgan, 1977):
PRIONODINIUM ALVEOLATUM n. sp. Pl. 1, figs. 4-6; Pl. 2, figs. 6-8; Text-fig. 5
Type locality. Unnamed formation of late Neocomian (Hauterivian-Barremian) age described by Jones & Detterman ( 1966), located at the headwaters of an unnamed tributary east of the ·south Fork of the Kamishak River, Lat. 58° 49'N, Long. 154° 03'W (Text-fig. 3).
Type stratum.-The holotype is from sample H69-1121, taken 85 feet above the contact of the unnamed formation and the underlying Naknek Formation of Late Jurassic age. The paratypes (Pl. 1, figs. 5,6) are from sample 7 3RCW34, taken 17 5 feet above the base of the unnamed formation.
Types .-See Plate Explanations for designations and descriptions of types.
Description. -Oval-elongate proximate cysts with an apical horn formed by the junction of the four apical crests; dorsoventrally flattened; cyst length-width ratio approximately 2; wall layers closely appressed, endophragm 0.8 μm thick, periphragm less than 0.5 μm thick; tabulation clearly reflected by high sutural crests; tabulation: 4', 6", 6c, 5- 6"', Ip, (ps), 1"", an antapically-widening postsulcal plate sometimes delineated in sulcal area by a narrow, transverse septum (Pl. 2, figs. 7 ,8); subtriangular 6" plate smaller than other precingulars; 1' and 4' plates narrow and elongate and the 2' and 3' plates larger and equidimensional; sutural crests approximately 8 μm high, and lace-like in appearance due to various sized perforations which are round to elongate; crests slightly denticulate on distal margin; cingulum is offset at sulcus by about one cingulum width; sulcus extends onto epitract, wall finely scabrate with scattered, superimposed pustules; maximum length of projections c. 5 µm; precingular (3") archeopyle, operculum free; size (exclusive of crests) 60—85 μm x 33-43 μm (25 specimens); average size (exclusive of crests) 71.6 x 38.6 μm.
Remarks .-There is a slight indication on three specimens that a reduced 1 '" plate is incorporated into the sulcus. The lower margin of the cingulum below the 1" plate extends into the sulcus as shown on Plate 2, figures 6b,7,8, and a longitudinal row of granules in figure 8 may represent the plate boundary between the sulcus and the 1 "' plate. If this is so, this species has six rather than five postcingular plates, a possibility which has been acknowledged in the tabulation formula. We have seen no evidence of a reduced 1 "' plate in P. alaskense .
Comparison with other species .- This species differs from P. alaskense Leffingwell & Morgan n. sp. in apical horn type and in possessing higher and densely perforate sutural crests.
Stratigraphic and geographic range.-Thus far, known only from rocks of late Neocomian age, Alaska.
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Supplemental description: Brideaux, 1977, p. 9-10
Shape: Pericyst outline distinctly longer than broad; maximum width at the latitude of the pericingulum; tapering little at apices; apical and antapical horns absent.
Endocyst outline as for the pericyst; pericoel absent; slight dorso-ventral compression.
Phragma: Periphragm smooth, thin, +/-1 µm thick, projecting to form parasutural septa; septa up to 10µm high with entire, serrate or strongly denticulate margins, perforated, the lumina varying from 1-5 µm in maximum diameter and of irregular shape; confluence of septa in apical region producing an apical prominence but no
true apical horn. Endophragm smooth, thin, about 1 µm thick, closely appressed to periphragm; no pericoel developed.
Paratabulation: Parasutural septa denote a paratabulation of ?4", 6", 6c, 5"""-?6""", 1p, 1""""; precingular and postcingular paraplates elongate; folding of septa in apical region obscures apical paraplate series. Evidence of paratabulation on endocyst not noted. Archeopyle/operculum. Peri- and endarcheopyle formed by the loss of the precingular paraplate 3". Peri- and endoperculum simple and free, Horseshoe-shaped, the layers separating as a unit. Formula P.
Pericingulum/perisulcus: Pericingulum 6-8 µm wide, outlined by perforated parasutres displaced from one and one-half to two pericingular widths; six cingular paraplates. Perisulcus extending from the middle of the epicyst, terminating near the antapex; narrow anteriorly, widening posteriorly, assuming a sigmoid outline inclined to the left; bounded by perforated septa. Dimensions - Pericyst length, 62-69 µm; pericyst width, 36-40 µm.
Affinities:
Brideaux, 1977, p. 10: Carpodinium granuIatum Cookson and Eisenack, 1962a, p. 489, Plate 1, figures 6-10 and C. obliquicostatum Cookson and Hughes, 1964, p. 48,
Plate 6, figures 1-6 differ in possessing granular or grooved intratabular ornamentation respectively. Both species possess a pronounced apical prominence
and neither species possesses perforated parasutural crests. Clathroctenocystis elegans Wiggins, 1972, p. 303, Plate 2A-C, Plate 3A-D, and Figure 3 possesses
an apical horn and apical archeopyle.
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Holotype: Leffingwell and Morgan 1977, pl.1, fig.4a-b; Jan du Chêne et al., 1986, pl.84, figs. 4-9
Age: Late Neocomian
--------------------------------------
Original description (Leffingwell and Morgan, 1977):
PRIONODINIUM ALVEOLATUM n. sp. Pl. 1, figs. 4-6; Pl. 2, figs. 6-8; Text-fig. 5
Type locality. Unnamed formation of late Neocomian (Hauterivian-Barremian) age described by Jones & Detterman ( 1966), located at the headwaters of an unnamed tributary east of the ·south Fork of the Kamishak River, Lat. 58° 49'N, Long. 154° 03'W (Text-fig. 3).
Type stratum.-The holotype is from sample H69-1121, taken 85 feet above the contact of the unnamed formation and the underlying Naknek Formation of Late Jurassic age. The paratypes (Pl. 1, figs. 5,6) are from sample 7 3RCW34, taken 17 5 feet above the base of the unnamed formation.
Types .-See Plate Explanations for designations and descriptions of types.
Description. -Oval-elongate proximate cysts with an apical horn formed by the junction of the four apical crests; dorsoventrally flattened; cyst length-width ratio approximately 2; wall layers closely appressed, endophragm 0.8 μm thick, periphragm less than 0.5 μm thick; tabulation clearly reflected by high sutural crests; tabulation: 4', 6", 6c, 5- 6"', Ip, (ps), 1"", an antapically-widening postsulcal plate sometimes delineated in sulcal area by a narrow, transverse septum (Pl. 2, figs. 7 ,8); subtriangular 6" plate smaller than other precingulars; 1' and 4' plates narrow and elongate and the 2' and 3' plates larger and equidimensional; sutural crests approximately 8 μm high, and lace-like in appearance due to various sized perforations which are round to elongate; crests slightly denticulate on distal margin; cingulum is offset at sulcus by about one cingulum width; sulcus extends onto epitract, wall finely scabrate with scattered, superimposed pustules; maximum length of projections c. 5 µm; precingular (3") archeopyle, operculum free; size (exclusive of crests) 60—85 μm x 33-43 μm (25 specimens); average size (exclusive of crests) 71.6 x 38.6 μm.
Remarks .-There is a slight indication on three specimens that a reduced 1 '" plate is incorporated into the sulcus. The lower margin of the cingulum below the 1" plate extends into the sulcus as shown on Plate 2, figures 6b,7,8, and a longitudinal row of granules in figure 8 may represent the plate boundary between the sulcus and the 1 "' plate. If this is so, this species has six rather than five postcingular plates, a possibility which has been acknowledged in the tabulation formula. We have seen no evidence of a reduced 1 "' plate in P. alaskense .
Comparison with other species .- This species differs from P. alaskense Leffingwell & Morgan n. sp. in apical horn type and in possessing higher and densely perforate sutural crests.
Stratigraphic and geographic range.-Thus far, known only from rocks of late Neocomian age, Alaska.
--------------------------------------
Supplemental description: Brideaux, 1977, p. 9-10
Shape: Pericyst outline distinctly longer than broad; maximum width at the latitude of the pericingulum; tapering little at apices; apical and antapical horns absent.
Endocyst outline as for the pericyst; pericoel absent; slight dorso-ventral compression.
Phragma: Periphragm smooth, thin, +/-1 µm thick, projecting to form parasutural septa; septa up to 10µm high with entire, serrate or strongly denticulate margins, perforated, the lumina varying from 1-5 µm in maximum diameter and of irregular shape; confluence of septa in apical region producing an apical prominence but no
true apical horn. Endophragm smooth, thin, about 1 µm thick, closely appressed to periphragm; no pericoel developed.
Paratabulation: Parasutural septa denote a paratabulation of ?4", 6", 6c, 5"""-?6""", 1p, 1""""; precingular and postcingular paraplates elongate; folding of septa in apical region obscures apical paraplate series. Evidence of paratabulation on endocyst not noted. Archeopyle/operculum. Peri- and endarcheopyle formed by the loss of the precingular paraplate 3". Peri- and endoperculum simple and free, Horseshoe-shaped, the layers separating as a unit. Formula P.
Pericingulum/perisulcus: Pericingulum 6-8 µm wide, outlined by perforated parasutres displaced from one and one-half to two pericingular widths; six cingular paraplates. Perisulcus extending from the middle of the epicyst, terminating near the antapex; narrow anteriorly, widening posteriorly, assuming a sigmoid outline inclined to the left; bounded by perforated septa. Dimensions - Pericyst length, 62-69 µm; pericyst width, 36-40 µm.
Affinities:
Brideaux, 1977, p. 10: Carpodinium granuIatum Cookson and Eisenack, 1962a, p. 489, Plate 1, figures 6-10 and C. obliquicostatum Cookson and Hughes, 1964, p. 48,
Plate 6, figures 1-6 differ in possessing granular or grooved intratabular ornamentation respectively. Both species possess a pronounced apical prominence
and neither species possesses perforated parasutural crests. Clathroctenocystis elegans Wiggins, 1972, p. 303, Plate 2A-C, Plate 3A-D, and Figure 3 possesses
an apical horn and apical archeopyle.
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