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Ovoidinium
From Williams et al., 2017:
[Ovoidinium, Davey, 1970, p. 351; Emendations: Lentin and Williams, 1976, p. 103-104; Duxbury, 1983, p. 61, 63
Tax. jr. syn. of Ascodinium Cookson and Eisenack, 1960, according to Helenes, 1983, and Lentin and Williams, 1985. Bujak and Davies, 1983, and Lentin and Williams, 1989, retained Ovoidinium as a separate genus.
tax. sr. syn. of Craspedodinium Cookson and Eisenack, 1974, according to Lentin and Williams, 1976. Stover and Evitt, 1978, retained Craspedodinium as a separate genus.
Type species: originally as Ascodinium verrucosum, Cookson and Hughes, 1964 (pl.5, fig.4)] ; Ovoidinium verrucosum, Davey, 1970
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Original description: [Davey, 1970]:
Diagnosis:
Bicavate dinoflagellate cyst, possessing one or two antapical horns and typically an apical horn. Periphragm and endophragm only in contact medially. Inner body subspherical, smooth or granular, commonly possessing a cingulum. Periphragm smooth or granular, forming sulcus. Tabulation absent.
Archaeopyle apical with slightly angular margin.
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Emended description:
Lentin and Williams, 1976:
Description:
Shape: Pericyst: Ambitus ovoidal to elongate pentagonal, produced into a short acuminate to rounded apical horn and one eccentrically located or two symmetrically located unequal antapial horns. When there are two antapical horns, the right is either reduced or vestigial. Maximum width in vicinity of pericingulum, epipericyst and hypopericyst of more or less equal size.
Endocyst: Ambitus circular to ovoidal. In contact with the pericyst, except apically and antapically.
Pericoels: An apical and an antapical pericoel.
Phragma: Periphragm: Surface laevigate, scabrate, granulate, verrucate, rugulate or tuberculate.
Endophragm: Surface laevigate, scabrate, granulate or verrucate.
Paratabulation: Pericyst: Paratabulation indeterminate other than three anterior intercalaries present.
Pericingulum: Generally present, may be delineated by a raised anterior and posterior parasuture. Planar or slightly helicoidal. Not always visible.
Perisulcus: barely discernible, more developed on the hypocyst than on the epicyst.
Endocyst: Paratabulation unknown.
Archaeopyle: Combination simple archaeopyle including all apical and all the anterior intercalary paraplates. The operculum may be completely detached or remain attached along parasuture 1`-anterior sulcal. the endophragm and periphragm are appressed in the vicinity of the archaeopyle other than immediately below the apical horn. There is no separation of the endoperculum and perioperculum so that effectively there is one archaeopyle and one operculum.
Archaeopyle fomula: 4A3I (1`-4`+1a-3a).
Hypopericyst opening: A second opening with attached "operculum" may be present in the perisulcal or ventral posterior region of the hypopericyst. The opening appears to result from separation along the antapical parasuture of the perisulcus, the flap or "operculum" remaining attached along the anterioir margin. The function of this opening is unknown. there is no observable ventral opening in the hypoendocyst.
Affinities:
Ovoidinium can be readily distinguished from Ascodinium, which according to Evitt (1967, p.50) possesses a periarcheopyle which is a circular opening occupying an eccentrically apical position, extending farther towards the pericingulum dorsally than ventrally.
Senoniasphaera Clarke and Verdier, 1967, differs in having the endocyst separated from the pericyst laterally and possesses an apical archeopyle.
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Duxbury, 1983:
Diagnosis:
Peridiniacean dinoflagellate cysts which are distinctly bi-layered and which are most variable in the degree of body layer separation. The endophragm is smooth to very finely granular and forms an ovoidal to spheroidal endocyst which may be dorso-ventrally flattened. The periphragm may be smooth or may be variously ornamented and the pericyst may be closely appressed to the endocyst with separations being confined to a small apical and a small left antapical horn. However, separation of the body layers into apical and antapical pericoels is usually observed and the degree of cavation is most variable. In the extreme, cysts adopt a deflandroid shape with the apical and antapical pericoels forming a well-developed apical and two well-developed antapical horns, respectively. Often, only the left antapical is formed.
Some indication of the paracingulum and parasulcus is usually observed, indicated by folding or by surface ornament alignment.
The archaeopyle is of the tAtI type and the operculum may remain attached or may be lost.
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Modified description:
Stover and Evitt 1978, p. 216-217:
Synopsis:
Cysts proximate, bicavate, compressed peridinioid with a short apical horn; antapical horns commonly reduced; combination archeopyle, Type tAtI.
Description:
Shape: Compressed peridinioid, outline generally rounded; apical horn short, antapical horns commonly reduced and unequally developed; antapical margin often obliquely truncate.
Wall relationships: Cysts bicavate.
Wall features: Parasutural features weakly expressed or absent. Periphragm smooth or bears generally scattered granulae; an opening may be present on the ventral hypophragm.
Paratabulation: Generally indicated by archeopyle and paracingulum, other indications vague and inconsistent; probably peridiniacean; complete formula unknown.
Archeopyle: Combination, Type tAtI, without accessory archeopyle sutures; operculum free or adherent, commonly dislodged; constituent paraplate boundaries generally not indicated.
Paracingulum: Indicated by parallel, transverse, parasutural ridges or folds. Parasulcus: Expressed as a weakly developed midventral, depressed, and commonly folded area on the hypocyst, or not indicated at all.
Size: Intermediate to large.
Affinities:
Ovoidinium differs from Ascodinium in being bicavate rather than circumcavate. Although the archeopyle is interpreted as Type tAtI, on the species it is nearly circular and occupies an eccentrically apical position extending further towards the paracingulum on the dorsal than on the ventral surface.
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Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Ovoidinium Davey, 1970, emend. Lentin and Williams, 1976, emend. Duxbury, 1983. Ovoidinium was emended by Duxbury (1983, p.61-62) as follows. Peridiniacean dinoflagellate cysts which are distinctly bilayered and which are most variable in the degree of body layer separation. The endophragm is smooth to very finely granular and forms an ovoidal to spheroidal endocyst which may be dorso-ventrally flattened. The periphragm may be smooth or may be variously ornamented and the pericyst may be closely appressed to the endocyst with separations being confined to a small apical and a small left antapical horn. However, separation of the body layers into apical and antapical pericoels is usually observed and the degree of cavation is most variable. In the extreme, cysts adopt a deflandreoid shape with the apical and antapical pericoels forming a well-developed apical and two well-developed antapical horns, respectively. Often, only the left antapical is formed. Some indication of the paracingulum and parasulcus is usually observed, indicated by folding or by surface ornament alignment. The archeopyle is of the (tAtI) type and the operculum may remain attached or may be lost.
[Ovoidinium, Davey, 1970, p. 351; Emendations: Lentin and Williams, 1976, p. 103-104; Duxbury, 1983, p. 61, 63
Tax. jr. syn. of Ascodinium Cookson and Eisenack, 1960, according to Helenes, 1983, and Lentin and Williams, 1985. Bujak and Davies, 1983, and Lentin and Williams, 1989, retained Ovoidinium as a separate genus.
tax. sr. syn. of Craspedodinium Cookson and Eisenack, 1974, according to Lentin and Williams, 1976. Stover and Evitt, 1978, retained Craspedodinium as a separate genus.
Type species: originally as Ascodinium verrucosum, Cookson and Hughes, 1964 (pl.5, fig.4)] ; Ovoidinium verrucosum, Davey, 1970
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Davey, 1970]:
Diagnosis:
Bicavate dinoflagellate cyst, possessing one or two antapical horns and typically an apical horn. Periphragm and endophragm only in contact medially. Inner body subspherical, smooth or granular, commonly possessing a cingulum. Periphragm smooth or granular, forming sulcus. Tabulation absent.
Archaeopyle apical with slightly angular margin.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Lentin and Williams, 1976:
Description:
Shape: Pericyst: Ambitus ovoidal to elongate pentagonal, produced into a short acuminate to rounded apical horn and one eccentrically located or two symmetrically located unequal antapial horns. When there are two antapical horns, the right is either reduced or vestigial. Maximum width in vicinity of pericingulum, epipericyst and hypopericyst of more or less equal size.
Endocyst: Ambitus circular to ovoidal. In contact with the pericyst, except apically and antapically.
Pericoels: An apical and an antapical pericoel.
Phragma: Periphragm: Surface laevigate, scabrate, granulate, verrucate, rugulate or tuberculate.
Endophragm: Surface laevigate, scabrate, granulate or verrucate.
Paratabulation: Pericyst: Paratabulation indeterminate other than three anterior intercalaries present.
Pericingulum: Generally present, may be delineated by a raised anterior and posterior parasuture. Planar or slightly helicoidal. Not always visible.
Perisulcus: barely discernible, more developed on the hypocyst than on the epicyst.
Endocyst: Paratabulation unknown.
Archaeopyle: Combination simple archaeopyle including all apical and all the anterior intercalary paraplates. The operculum may be completely detached or remain attached along parasuture 1`-anterior sulcal. the endophragm and periphragm are appressed in the vicinity of the archaeopyle other than immediately below the apical horn. There is no separation of the endoperculum and perioperculum so that effectively there is one archaeopyle and one operculum.
Archaeopyle fomula: 4A3I (1`-4`+1a-3a).
Hypopericyst opening: A second opening with attached "operculum" may be present in the perisulcal or ventral posterior region of the hypopericyst. The opening appears to result from separation along the antapical parasuture of the perisulcus, the flap or "operculum" remaining attached along the anterioir margin. The function of this opening is unknown. there is no observable ventral opening in the hypoendocyst.
Affinities:
Ovoidinium can be readily distinguished from Ascodinium, which according to Evitt (1967, p.50) possesses a periarcheopyle which is a circular opening occupying an eccentrically apical position, extending farther towards the pericingulum dorsally than ventrally.
Senoniasphaera Clarke and Verdier, 1967, differs in having the endocyst separated from the pericyst laterally and possesses an apical archeopyle.
--------------------------------------------
Duxbury, 1983:
Diagnosis:
Peridiniacean dinoflagellate cysts which are distinctly bi-layered and which are most variable in the degree of body layer separation. The endophragm is smooth to very finely granular and forms an ovoidal to spheroidal endocyst which may be dorso-ventrally flattened. The periphragm may be smooth or may be variously ornamented and the pericyst may be closely appressed to the endocyst with separations being confined to a small apical and a small left antapical horn. However, separation of the body layers into apical and antapical pericoels is usually observed and the degree of cavation is most variable. In the extreme, cysts adopt a deflandroid shape with the apical and antapical pericoels forming a well-developed apical and two well-developed antapical horns, respectively. Often, only the left antapical is formed.
Some indication of the paracingulum and parasulcus is usually observed, indicated by folding or by surface ornament alignment.
The archaeopyle is of the tAtI type and the operculum may remain attached or may be lost.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified description:
Stover and Evitt 1978, p. 216-217:
Synopsis:
Cysts proximate, bicavate, compressed peridinioid with a short apical horn; antapical horns commonly reduced; combination archeopyle, Type tAtI.
Description:
Shape: Compressed peridinioid, outline generally rounded; apical horn short, antapical horns commonly reduced and unequally developed; antapical margin often obliquely truncate.
Wall relationships: Cysts bicavate.
Wall features: Parasutural features weakly expressed or absent. Periphragm smooth or bears generally scattered granulae; an opening may be present on the ventral hypophragm.
Paratabulation: Generally indicated by archeopyle and paracingulum, other indications vague and inconsistent; probably peridiniacean; complete formula unknown.
Archeopyle: Combination, Type tAtI, without accessory archeopyle sutures; operculum free or adherent, commonly dislodged; constituent paraplate boundaries generally not indicated.
Paracingulum: Indicated by parallel, transverse, parasutural ridges or folds. Parasulcus: Expressed as a weakly developed midventral, depressed, and commonly folded area on the hypocyst, or not indicated at all.
Size: Intermediate to large.
Affinities:
Ovoidinium differs from Ascodinium in being bicavate rather than circumcavate. Although the archeopyle is interpreted as Type tAtI, on the species it is nearly circular and occupies an eccentrically apical position extending further towards the paracingulum on the dorsal than on the ventral surface.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Ovoidinium Davey, 1970, emend. Lentin and Williams, 1976, emend. Duxbury, 1983. Ovoidinium was emended by Duxbury (1983, p.61-62) as follows. Peridiniacean dinoflagellate cysts which are distinctly bilayered and which are most variable in the degree of body layer separation. The endophragm is smooth to very finely granular and forms an ovoidal to spheroidal endocyst which may be dorso-ventrally flattened. The periphragm may be smooth or may be variously ornamented and the pericyst may be closely appressed to the endocyst with separations being confined to a small apical and a small left antapical horn. However, separation of the body layers into apical and antapical pericoels is usually observed and the degree of cavation is most variable. In the extreme, cysts adopt a deflandreoid shape with the apical and antapical pericoels forming a well-developed apical and two well-developed antapical horns, respectively. Often, only the left antapical is formed. Some indication of the paracingulum and parasulcus is usually observed, indicated by folding or by surface ornament alignment. The archeopyle is of the (tAtI) type and the operculum may remain attached or may be lost.