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Satyrodinium bengalense
Satyrodinium benegalense Lentin and Manum, 1986
Holotype: Lentin and Manum, 1986, 1986, pl.1, figs.1-3
Paratypes: Lentin and Manum, 1986
Locus typicus: Bay of Benegal, DSDP 217-31-2
Stratum typicum: Campanian
Original description: Lentin and Manum, 1986, p.114
Shape compressed, elongate rectangular with two lateral apical horns, which tend to recurve towards the apex. When seen in lateral view these horns are distally notched or forked giving the appearance of four apical prominences. In addition, a low mid-apical horn may also occur. Dorsal and ventral lateral fold-like ridges normally extend from each lateral prominence towards the antapex. The area between the horns may be raised to create a central apical horn or it may be depressed; a ventral apical pore-like structure is usually present. Two narrow, pointed, antapical horns recurve towards the midline, the right antapical horn may be reduced; a third, much smaller antapical horn may be developed centrally on the dorsal side between the right and left horns; an appendage is developed ventrally, on the inside of the left antapical horn. A mid-dorsal bulge results in folding towards the lateral margins, and this folding often causes the posterior archeopyle margin to appear angled in the direction of the fold. Cysts bicavate; endocyst oblate, extremely thin and difficult to see; parasutural features lacking; periphragm and endophragm smooth and thin. Paratabulation indicated by the archeopyle only; intercalary, type I (2a only): standard hexa, operculum attached along the 2a-4" margin; no opening observed on the endocyst. No indication of a paracingulum or a parasulcus.
Size. Holotype overall, 112 x 78 µm. Other measured specimens 105 (128) 157 µm total length and 63 (77) 100 µm in width, lateral apical horns average 11 µm in length and the main antapical horns average 23 µm in length, apical pore 3-4 µm in diameter. Fourteen specimens measured, 22 specimens observed.
Discussion. This species displays considerable morphological variability, particularly at the apex. The lateral apical horns are sometimes reduced (Plate 1, fig. 7). If the lateral apical horns are well developed the mid-apical area is flat; if they are not well developed the mid-apical horn is usually developed. The shape of the paraplates in the apical and intercalary series is difficult to reconstruct because there are few observable features to use as a foundation. The shape of the archeopyle can be used as a basis of reconstruction because the joint boundaries between the intercalary paraplates are very long, which suggests that the 1a and 3a are very large. The fork in the lateral apical horns may be the reflection of a plate boundary and if so, this logically would be the boundary between the 1a-2" and the 3a-4" on the epicyst and the 1"""-2""" and 4"""-5""" paraplates on the hypocyst (see Text-Figure 2). Because the apical pore-like structure is ventrally located on the apex, the boundaries between the 2"-3" and 3"-4" paraplates are probably also ventral.
Affinities:
Lentin and Manum, 1986, p.115: A tendency for modification in the shape and size of the intercalary paraplates is not unusual in the Late Cretaceous, but such extreme development as suggested for Satyrodinium is not known from Australian sediments. However, high, wide "shoulders" resulting from an increase in the size of the intercalary series are found in Chatangiella coronata (McIntyre 1975) Lentin & Williams 1976 from the McIntyre Floral Province (Lentin and Williams, 1980; an area including Arctic Canada and the Western Interior of Canada and the U.S., and probably parts of the U.S.S.R.). However, C. coronata has a tripartite paracingulum. Among those forms with developed "shoulders" and no paracingular features, Isabelidinium korojonense (Cookson & Eisenack 1958) Lentin & Williams 1977 from the Campanian to early Maastrichtian of Australia is the only known species that could be considered similar to species of Satyrodinium.
I. korojonense is bicavate with an omegaform archeopyle and has square "shoulders" and a low apical horn, which appears in the illustration of the holotype (Cookson and Eisenack, 1958, pl. 4, fig. 10) to have an apical pore-like structure, although it is not described. In this species the antapex is quite flat with antapical horns rarely developed.
Amphidiadema rectangularis (Cookson & Eisenack 1962) Lentin & Williams 1976 from the Senonian of Australia is also bicavate, has a standard hexa archeopyle and is almost perfectly rectangular in outline without the development of apical or antapical horns. It also has an apical pore-like structure which is not described.
Holotype: Lentin and Manum, 1986, 1986, pl.1, figs.1-3
Paratypes: Lentin and Manum, 1986
Locus typicus: Bay of Benegal, DSDP 217-31-2
Stratum typicum: Campanian
Original description: Lentin and Manum, 1986, p.114
Shape compressed, elongate rectangular with two lateral apical horns, which tend to recurve towards the apex. When seen in lateral view these horns are distally notched or forked giving the appearance of four apical prominences. In addition, a low mid-apical horn may also occur. Dorsal and ventral lateral fold-like ridges normally extend from each lateral prominence towards the antapex. The area between the horns may be raised to create a central apical horn or it may be depressed; a ventral apical pore-like structure is usually present. Two narrow, pointed, antapical horns recurve towards the midline, the right antapical horn may be reduced; a third, much smaller antapical horn may be developed centrally on the dorsal side between the right and left horns; an appendage is developed ventrally, on the inside of the left antapical horn. A mid-dorsal bulge results in folding towards the lateral margins, and this folding often causes the posterior archeopyle margin to appear angled in the direction of the fold. Cysts bicavate; endocyst oblate, extremely thin and difficult to see; parasutural features lacking; periphragm and endophragm smooth and thin. Paratabulation indicated by the archeopyle only; intercalary, type I (2a only): standard hexa, operculum attached along the 2a-4" margin; no opening observed on the endocyst. No indication of a paracingulum or a parasulcus.
Size. Holotype overall, 112 x 78 µm. Other measured specimens 105 (128) 157 µm total length and 63 (77) 100 µm in width, lateral apical horns average 11 µm in length and the main antapical horns average 23 µm in length, apical pore 3-4 µm in diameter. Fourteen specimens measured, 22 specimens observed.
Discussion. This species displays considerable morphological variability, particularly at the apex. The lateral apical horns are sometimes reduced (Plate 1, fig. 7). If the lateral apical horns are well developed the mid-apical area is flat; if they are not well developed the mid-apical horn is usually developed. The shape of the paraplates in the apical and intercalary series is difficult to reconstruct because there are few observable features to use as a foundation. The shape of the archeopyle can be used as a basis of reconstruction because the joint boundaries between the intercalary paraplates are very long, which suggests that the 1a and 3a are very large. The fork in the lateral apical horns may be the reflection of a plate boundary and if so, this logically would be the boundary between the 1a-2" and the 3a-4" on the epicyst and the 1"""-2""" and 4"""-5""" paraplates on the hypocyst (see Text-Figure 2). Because the apical pore-like structure is ventrally located on the apex, the boundaries between the 2"-3" and 3"-4" paraplates are probably also ventral.
Affinities:
Lentin and Manum, 1986, p.115: A tendency for modification in the shape and size of the intercalary paraplates is not unusual in the Late Cretaceous, but such extreme development as suggested for Satyrodinium is not known from Australian sediments. However, high, wide "shoulders" resulting from an increase in the size of the intercalary series are found in Chatangiella coronata (McIntyre 1975) Lentin & Williams 1976 from the McIntyre Floral Province (Lentin and Williams, 1980; an area including Arctic Canada and the Western Interior of Canada and the U.S., and probably parts of the U.S.S.R.). However, C. coronata has a tripartite paracingulum. Among those forms with developed "shoulders" and no paracingular features, Isabelidinium korojonense (Cookson & Eisenack 1958) Lentin & Williams 1977 from the Campanian to early Maastrichtian of Australia is the only known species that could be considered similar to species of Satyrodinium.
I. korojonense is bicavate with an omegaform archeopyle and has square "shoulders" and a low apical horn, which appears in the illustration of the holotype (Cookson and Eisenack, 1958, pl. 4, fig. 10) to have an apical pore-like structure, although it is not described. In this species the antapex is quite flat with antapical horns rarely developed.
Amphidiadema rectangularis (Cookson & Eisenack 1962) Lentin & Williams 1976 from the Senonian of Australia is also bicavate, has a standard hexa archeopyle and is almost perfectly rectangular in outline without the development of apical or antapical horns. It also has an apical pore-like structure which is not described.