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Trithyrodinium sabulum
Trithyrodinium sabulum Mao Shaozhi and Norris, 1988
Holotype: Mao Shaozhi and Norris, 1988, pl.12, fig.4; text-fig.16
Paratype: Mao Shaozhi and Norris, 1988
Locus typicus: Tarim Basin, Xinjiang Province, China
Stratum typicum: Late Cretaceous
Original diagnosis: Mao Shaozhi and Norris, 1988, p.43-44
Cyst proximate, cornucavate, subspherical to elliptical with an apical horn, and with or without two poorly developed, unequal antapical horns appearing as angular bulges, the left one usually being longer. Wall layers thin (less than 1 Ám), folded. Periphragm transparent and delicate, smooth or with scattered granules; endophragm granulate, thicker than periphragm. Archeopyle intercalary, more clearly indicated in endoblast than in periblast, type 3I/3I. Operculum compound, typically dislodged or la and 3a detached and 2a attached posteriorly.
Original description: Mao Shaozhi and Norris, 1988, p.44
Cyst transversely to longitudinally broad, elliptical in ambital view. Apical horn present, small, bluntly pointed or nipplelike, 4 to 7 Ám long, formed usually by periphragm. Antapex rounded or stretched out to two angular bulges. Periphragm very thin, easily folded, transparent, lightly coloured or not easily stained. Periphragm sometimes lost, leaving endoblast free. Endophragm thin, thicker than periphragm, typically densely granulate; diameter of granules varying, commonly less than 1 Ám. Intercalary 3I archeopyle compound and linteloid. When the archeopyle not fully developed and the periphragm not removed, plates 1 to 3a recognizable by slightly open sutures; in that case (18 of 38 specimens observed) the posterior suture of 2a absent (Text-Fig. 16). When periphragm completely lost (18 of 38 specimens), plates la and 3a detached, plate 2a remaining attached along its posterior margin (Text-Fig. 17); rarely (2 of 38 specimens observed), three opercular pieces totally free. Therefore, plate 2a may have stronger connection with endoblast than plates 1a and 3a, because it is removed after the other two. Plate 2a standard hexa, plates 1a and 3a pentagonal in shape. Indications of tabulation, other than archeopyle, absent.
Dimensions: Length 45 to 65 Ám (holotype 54 Ám), width 35 to 53 Ám (holotype 44 Ám); 38 specimens measured.
Affinities:
Mao Shaozhi and Norris, 1988, p.44: This species differs from Trithyrodinium evittii in that (1) its three opercular plates do not function as a unit, (2) the cingulum is typically not indicated, and (3) the endophragm is granulate rather than psilate. It differs from T. suspectum (Manum and Cookson, 1964) in having thinner wall layers; the wall layers of T. suspectum are composed of rod-shaped elements of unequal length, such structures being completely absent in T. sabulum.
Holotype: Mao Shaozhi and Norris, 1988, pl.12, fig.4; text-fig.16
Paratype: Mao Shaozhi and Norris, 1988
Locus typicus: Tarim Basin, Xinjiang Province, China
Stratum typicum: Late Cretaceous
Original diagnosis: Mao Shaozhi and Norris, 1988, p.43-44
Cyst proximate, cornucavate, subspherical to elliptical with an apical horn, and with or without two poorly developed, unequal antapical horns appearing as angular bulges, the left one usually being longer. Wall layers thin (less than 1 Ám), folded. Periphragm transparent and delicate, smooth or with scattered granules; endophragm granulate, thicker than periphragm. Archeopyle intercalary, more clearly indicated in endoblast than in periblast, type 3I/3I. Operculum compound, typically dislodged or la and 3a detached and 2a attached posteriorly.
Original description: Mao Shaozhi and Norris, 1988, p.44
Cyst transversely to longitudinally broad, elliptical in ambital view. Apical horn present, small, bluntly pointed or nipplelike, 4 to 7 Ám long, formed usually by periphragm. Antapex rounded or stretched out to two angular bulges. Periphragm very thin, easily folded, transparent, lightly coloured or not easily stained. Periphragm sometimes lost, leaving endoblast free. Endophragm thin, thicker than periphragm, typically densely granulate; diameter of granules varying, commonly less than 1 Ám. Intercalary 3I archeopyle compound and linteloid. When the archeopyle not fully developed and the periphragm not removed, plates 1 to 3a recognizable by slightly open sutures; in that case (18 of 38 specimens observed) the posterior suture of 2a absent (Text-Fig. 16). When periphragm completely lost (18 of 38 specimens), plates la and 3a detached, plate 2a remaining attached along its posterior margin (Text-Fig. 17); rarely (2 of 38 specimens observed), three opercular pieces totally free. Therefore, plate 2a may have stronger connection with endoblast than plates 1a and 3a, because it is removed after the other two. Plate 2a standard hexa, plates 1a and 3a pentagonal in shape. Indications of tabulation, other than archeopyle, absent.
Dimensions: Length 45 to 65 Ám (holotype 54 Ám), width 35 to 53 Ám (holotype 44 Ám); 38 specimens measured.
Affinities:
Mao Shaozhi and Norris, 1988, p.44: This species differs from Trithyrodinium evittii in that (1) its three opercular plates do not function as a unit, (2) the cingulum is typically not indicated, and (3) the endophragm is granulate rather than psilate. It differs from T. suspectum (Manum and Cookson, 1964) in having thinner wall layers; the wall layers of T. suspectum are composed of rod-shaped elements of unequal length, such structures being completely absent in T. sabulum.