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Operculodinium megagranum
Operculodinium megagranum Head in Head and Westphal, 1999, p.13,15, fig.10, nos.14–15; fig.12, nos.1–9.
Questionable assignment: Head and Westphal (1999, p.13).
Holotype: Head and Westphal, 1999, fig.12, nos.1–3.
Age: late late Pliocene.
Original description (Head & Westphal, 1999):
Operculodinium? Megagranum Head, new species Figures 10.14, 10.15, 12.1-12.9
Operculodinium sp. A. Wrenn and Kokinos, 1986, pl. 10, fig. 6-7, pl. 20, fig. 1.
? cf. Pyxidiella sp. Jan du Chêne, 1977, p. 112, text-fig. 4.9, pl. 1, fig. 12.
Diagnosis.-Egg-shaped gonyaulacacean cyst with small, rounded apical protuberance. Wall consists of pedium whose surface has a dense cover of small granules along with sparse, irregular distribution of larger elements represented by grana, blunt spines, and bacula. Archeopyle precingular Type IP (3") with smooth margins and well-developed angles; operculum free. No other indications of tabulation. Description.-Apical protuberance varies between 0.5 and 3.0 µm in height. Pedium moderately thick (ca. 0.5 µm or less), surface bearing dense cover of small (less than 0.5 µm) granules along with sparse, irregular distribution of larger elements consisting of grana, blunt spines, and bacula. These larger elements (up to ca. 3 µm high) often have irregular shapes, may appear to be composed of aggregations of granules, and often have constricted bases. They may be evenly distributed over entire cyst, but are often larger and more concentrated on ventral and antapical surfaces.
Dimensions.-Holotype: length, 49 µm; thickness, 47 mm. Range: maximum diameter, 47(52.4)59 µm, standard deviation 3.12. Twenty-one specimens measured.
Etymology.-Named with reference to the large, irregular grana that occur on the surface of this species.
Holotype.-Fig. 12.1-12.3. Sample CUS M8, slide 4; England Finder reference S31/3. ROM 53433. Clino core, 255.88 m (839.5 ft) below mud pit; upper upper Pliocene.
Comparison.- Cf. Pyxidiella sp. of Jan du Chine (1977) is similar but a pronounced apical protuberance is not indicated. Previous records.-Upper Miocene through upper lower Pleistocene (ca. 0.8-0.9 Ma; as Operculodinium sp. A in Wrenn and Kokinos, 1986; Aubry, 1993). Possibly recorded from the upper Miocene of Spain (as cf. Pyxidiella sp. in Jan du Chene, 1977. Discussion.-The generic assignation is tentative owing to the lack of fibrous processes, presence of a nonfibrous wall, angular archeopyle margin, and apical protuberance. Operculodinium centrocarpum, the type of the genus, differs in all these features.
Questionable assignment: Head and Westphal (1999, p.13).
Holotype: Head and Westphal, 1999, fig.12, nos.1–3.
Age: late late Pliocene.
Original description (Head & Westphal, 1999):
Operculodinium? Megagranum Head, new species Figures 10.14, 10.15, 12.1-12.9
Operculodinium sp. A. Wrenn and Kokinos, 1986, pl. 10, fig. 6-7, pl. 20, fig. 1.
? cf. Pyxidiella sp. Jan du Chêne, 1977, p. 112, text-fig. 4.9, pl. 1, fig. 12.
Diagnosis.-Egg-shaped gonyaulacacean cyst with small, rounded apical protuberance. Wall consists of pedium whose surface has a dense cover of small granules along with sparse, irregular distribution of larger elements represented by grana, blunt spines, and bacula. Archeopyle precingular Type IP (3") with smooth margins and well-developed angles; operculum free. No other indications of tabulation. Description.-Apical protuberance varies between 0.5 and 3.0 µm in height. Pedium moderately thick (ca. 0.5 µm or less), surface bearing dense cover of small (less than 0.5 µm) granules along with sparse, irregular distribution of larger elements consisting of grana, blunt spines, and bacula. These larger elements (up to ca. 3 µm high) often have irregular shapes, may appear to be composed of aggregations of granules, and often have constricted bases. They may be evenly distributed over entire cyst, but are often larger and more concentrated on ventral and antapical surfaces.
Dimensions.-Holotype: length, 49 µm; thickness, 47 mm. Range: maximum diameter, 47(52.4)59 µm, standard deviation 3.12. Twenty-one specimens measured.
Etymology.-Named with reference to the large, irregular grana that occur on the surface of this species.
Holotype.-Fig. 12.1-12.3. Sample CUS M8, slide 4; England Finder reference S31/3. ROM 53433. Clino core, 255.88 m (839.5 ft) below mud pit; upper upper Pliocene.
Comparison.- Cf. Pyxidiella sp. of Jan du Chine (1977) is similar but a pronounced apical protuberance is not indicated. Previous records.-Upper Miocene through upper lower Pleistocene (ca. 0.8-0.9 Ma; as Operculodinium sp. A in Wrenn and Kokinos, 1986; Aubry, 1993). Possibly recorded from the upper Miocene of Spain (as cf. Pyxidiella sp. in Jan du Chene, 1977. Discussion.-The generic assignation is tentative owing to the lack of fibrous processes, presence of a nonfibrous wall, angular archeopyle margin, and apical protuberance. Operculodinium centrocarpum, the type of the genus, differs in all these features.