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Tetranguladinium conspicuum
Tetranguladinium conspicuum Yu Jingxian et al., 1983 ex Chen et al., 1988
The name Tetranguladinium conspicuum was not validly published in Yu Jingxian et al., 1983 since these authors did not designate a holotype.
Batten and Lister, 1988 considered this to be a dinoflagellate species.
Holotype: Yu Jingxian et al., 1983, pl.30, fig.2 (designated by Chen et al. 1988)
Locus typicus:
Stratum typicum: Cretaceous
Supplemental description: Batten and Lister, 1988, p.358-359
Large cavate cyst. Pericyst thin ( < 1 µm), smooth, hyaline, without ornamentation, often extensively wrinkled and folded; maximum diameter 90(152)195 µm (11 specimens). Outline approximately "H"shaped, consisting of a basically rhomboidal to square central area extended at corners into four broad ( > 32 µm), hollow, tubular horns, sometimes of similar dimensions but usually unequal in length; one can be much longer than the others (c. > 100 µm) or two diagonally opposite horns can be longer than the other two, or all four may be only weakly developed as bulges at corners. Width of horns usually more or less constant throughout their length, occasionally slightly expanded distally and resembling elongate sacks; distal ends closed, truncate or bluntly rounded when inflated and with a terminal suture (not always clearly visible).
Distinct to faint traces of transverse or longitudinal ridge-like thickenings, occasionally quite complex in organization, may be present on periphragm. Sometimes they appear to extend along each horn and may connect with one or two centrally positioned transverse ridges or folds. One specimen displays a relatively small, approximately central, oblong "paraplate" 10 µm wide with three or four ridges extending from it towards corners of cyst. Paracingulum appears to be suggested in one or two specimens by traces of a shallow, transverse furrow bordered by weak, parallel ridges 5-6 µm wide which may form a rim enclosing a small, semicircular to bean-shaped depression c.5 µm in diameter located in a median position offset to one side of pericyst; this could be a flagellar scar, or an impression left by an accumulation body. A small, solid, bean-shaped body 7 µm in diameter was noted in a similar location in one individual.
Endocyst rounded to ovoidal or rarely slightly rhomboidal, maximum diameter 37(47)70 x 30(40)55 µm (12 specimens), contained within central area of pericyst, usually surrounded by an extensive pericoel without supporting structures connecting it to periphragm. Sometimes pericyst appears less voluminous because it is crumpled against inner body; hence pericoel is much reduced. Endocyst thin-walled ( < 1 µm), smooth to finely granular, cryptotabulate and occasionally darker than pericyst.
Endoarcheopyle commonly undeveloped but a split may be present at one pole which is assumed to be apical. In one specimen endocyst has opened somewhat irregularly along what appear to be paraplate boundaries showing an attached flap-like operculum with a smooth, curved outline at apical pole, a series of elongate, rectanguloid paraplates on body, and a single, angular, antapical paraplate. In another specimen archeopyle margin is indicated by one geniculate, and rectilinear paraplate boundaries; a pronounced accessory suture is developed between the camerate and adjacent planate paraplates. This cyst has an adherent (?adnate) operculum, which might indicate a simple apical/intercalary or apical/precingular combination-type archeopyle.
No clear indication of an excystment aperture was noted in pericyst, although it is frequently ruptured at the base of a horn.
Remarks: Pericysts occasionally lack endocysts and one presumed isolated endocyst having a slightly rhomboidal ambitus displays a very faint, paracingular depression with a complex series of breakages immediately anterior to it and in the apical region. This provides further support for the possibility of archeopyle formation involving both precingular and apical paraplates with an adnate operculum.
The name Tetranguladinium conspicuum was not validly published in Yu Jingxian et al., 1983 since these authors did not designate a holotype.
Batten and Lister, 1988 considered this to be a dinoflagellate species.
Holotype: Yu Jingxian et al., 1983, pl.30, fig.2 (designated by Chen et al. 1988)
Locus typicus:
Stratum typicum: Cretaceous
Supplemental description: Batten and Lister, 1988, p.358-359
Large cavate cyst. Pericyst thin ( < 1 µm), smooth, hyaline, without ornamentation, often extensively wrinkled and folded; maximum diameter 90(152)195 µm (11 specimens). Outline approximately "H"shaped, consisting of a basically rhomboidal to square central area extended at corners into four broad ( > 32 µm), hollow, tubular horns, sometimes of similar dimensions but usually unequal in length; one can be much longer than the others (c. > 100 µm) or two diagonally opposite horns can be longer than the other two, or all four may be only weakly developed as bulges at corners. Width of horns usually more or less constant throughout their length, occasionally slightly expanded distally and resembling elongate sacks; distal ends closed, truncate or bluntly rounded when inflated and with a terminal suture (not always clearly visible).
Distinct to faint traces of transverse or longitudinal ridge-like thickenings, occasionally quite complex in organization, may be present on periphragm. Sometimes they appear to extend along each horn and may connect with one or two centrally positioned transverse ridges or folds. One specimen displays a relatively small, approximately central, oblong "paraplate" 10 µm wide with three or four ridges extending from it towards corners of cyst. Paracingulum appears to be suggested in one or two specimens by traces of a shallow, transverse furrow bordered by weak, parallel ridges 5-6 µm wide which may form a rim enclosing a small, semicircular to bean-shaped depression c.5 µm in diameter located in a median position offset to one side of pericyst; this could be a flagellar scar, or an impression left by an accumulation body. A small, solid, bean-shaped body 7 µm in diameter was noted in a similar location in one individual.
Endocyst rounded to ovoidal or rarely slightly rhomboidal, maximum diameter 37(47)70 x 30(40)55 µm (12 specimens), contained within central area of pericyst, usually surrounded by an extensive pericoel without supporting structures connecting it to periphragm. Sometimes pericyst appears less voluminous because it is crumpled against inner body; hence pericoel is much reduced. Endocyst thin-walled ( < 1 µm), smooth to finely granular, cryptotabulate and occasionally darker than pericyst.
Endoarcheopyle commonly undeveloped but a split may be present at one pole which is assumed to be apical. In one specimen endocyst has opened somewhat irregularly along what appear to be paraplate boundaries showing an attached flap-like operculum with a smooth, curved outline at apical pole, a series of elongate, rectanguloid paraplates on body, and a single, angular, antapical paraplate. In another specimen archeopyle margin is indicated by one geniculate, and rectilinear paraplate boundaries; a pronounced accessory suture is developed between the camerate and adjacent planate paraplates. This cyst has an adherent (?adnate) operculum, which might indicate a simple apical/intercalary or apical/precingular combination-type archeopyle.
No clear indication of an excystment aperture was noted in pericyst, although it is frequently ruptured at the base of a horn.
Remarks: Pericysts occasionally lack endocysts and one presumed isolated endocyst having a slightly rhomboidal ambitus displays a very faint, paracingular depression with a complex series of breakages immediately anterior to it and in the apical region. This provides further support for the possibility of archeopyle formation involving both precingular and apical paraplates with an adnate operculum.