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Alterbidinium
From Fensome et al., 2019:
Alterbidinium, Lentin and Williams, 1985, p.14. Substitute name for Albertia Vozzhennikova, 1967, p.150–151 (an illegitimate name) and Alterbia Lentin and Williams, 1976, p.47–48 (an illegitimate name).
Emendations: Khowaja-Ateequzzaman et al., 1991, p.38; Fensome et al., 2016b, p.24.
Originally Albertia (name illegitimate), subsequently Alterbia (name illegitimate), thirdly (and now) Alterbidinium.
Type: Vozzhennikova, 1967, pl.77, fig.2, as Albertia recticornis (see discussion under Alterbidinium recticorne).
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Original description Albertia: [Vozzhennikova, 1967]: (Translation: Lees in Sarjeant (ed.), 1971, p. 47)
Description:
Theca pentagonal, rhomboid, subdivided into almost equal parts. Epitheca bell-shaped, triangular with a small apical horn. Hypotheca with one or two unequal antapical horns. Transverse furrow equatorial, annulate; longitudinal furrow situated on hypotheca and extends to the antapex. Internal body has the same outline as that of the theca. Pylome triangular with rounded or truncated angles, thus appearing somewhat trapeziform.
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Emended description Alterbia:
Lentin and Williams, 1976:
Description
Pericyst: Ambitus rhomboidal to subpentagonal, elongated in an anterior-posterior direction. Pericyst prolonged into one apical and two symmetrically placed antapical horns, the right antapical generally reduced or vestigial. The pericyst attains its greatest width in the region of the pericingulum. Compression dorso-ventral.
Endocyst: Ambitus circular to ovoidal to rhomboidal. Frequently there is a slight apical protuberance. May be in contact with pericyst in precingular, cingular and postcingular regions.
Pericoels: Apical pericoel always present, antapical pericoel commonly present. The apical and antapical pericoels may be united by an ambital pericoel.
Periphragm: Thickness variable but usually ca. 1 µm. Surface generally laevigate, occasionally scabrate, granulate, or verrucate.
Endophragm: Rarely exceeding 1 µm and of constant thickness. Surface generally laevigate, may be granulate or striate.
Pericyst: Paratabulation indeterminate except in the vicinity of the archeopyle.
Pericingulum: Frequently well developed, planar or slightly elicoidal, with anterior parasuture only, or anterior and posterior parasuture as a slightly raised ridge or border, with smooth or denticulate margins.
Perisulcus: Rarely determinable; when visible largely restricted to the hypopericyst. Occasionally flagellar scar visible.
Endocyst: No observable paratabulation, other than in the vicinity of the endoarcheopyle.
Periarcheopyle: Attenuated hexa to standard hexa intercalary resulting from the loss of the second anterior intercalary paraplate, 2a. Perioperculum free or remaining attached along parasuture H4. The attenuated hexa archeopyle usually has a free operculum, the standard archeopyle is usually an attached operculum. Transverse periarcheopyle index 0.16-0.46. Transverse periarcheopyle ratio 0.20-0.88.
Endoarcheopyle: Often difficult to discern. When observed is intercalary resulting from the loss of the second anterior intercalary paraplate (2a).
Archeopyle Formula: I/I (2a/2a)
Pericyst: Length 23-192 µm, breadth 19-152 µm.
Endocyst: Length ?22-118 µm, breadth ?18-118 µm.
Affinities:
Fossil dinoflagellate species which are included in Alterbia differ from species of Deflandrea in possessing an attenuated hexa to standard hexa 2a intercalary archaeopyle, an archaeopyle index of 0.3-0.5 and almost invariably a reduced right antapical horn. The presence in the species Alterbia distincta (Wilson, 1967) and A. dilwynensis (Cookson and Eisenack, 1965) of such Deflandrea like features as a thicker endophragm and larger overall size suggest that they constitute a morphological lineage from which some of the ancestral species of Deflandrea evolved.
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Modified description Alterbia:
Stover and Evitt, 1978, p. 92-93:
Synopsis:
Cysts proximate, circumcavate, compressed, elongate ellipsoidal to nearly biconical, with an apical and a generally prominent left antapical horn; right antapical horn reduced or absent; outline of endocyst elliptical and generally approximates that of pericyst except at bases of horns; paratabulation indicated by archeopyle, occasionally also by paracingulum; archeopyle intercalary, Types I or la; archeopyle index about 0.3.
Description:
Shape: Compressed, elongate ellipsoidal to nearly biconical; apical and left antapical horns normally well developed, right antapical horn reduced or absent.
Wall relationships: Cysts circumcavate; endocyst outline subcircular to elliptical, generally approximating that of pericyst except at bases of horns.
Wall features: No parasutural features. Periphragm smooth or faintly ornamented.
Paratabulation: Indicated generally by archeopyle only, occasionally by archeopyle and paracingulum.
Archeopyle: Intercalary, Types l or la (2a only); archeopyle index generally about 0.3; operculum free.
Paracingulum: Not indicated, or expressed weakly by low transverse equatorial folds, or by concavities along lateral margins.
Parasulcus: Generally not indicated, or expressed as a poorly defined depression on the hypocyst.
Size: Intermediate to large.
Affinities:
Alterbia differs from Senegalinium in that its epipericoel is in communication with the exterior through the archeopyle and in having a reduced or absent right antapical horn instead of two nearly equally developed antapical horns. Eucladinium, like Alterbia, has a reduced right antapical horn, but the former is mainly epicavate rather than circumcavate.
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Emended description Alterbidinium:
Khowaja-Ateequzzaman et al., 1991:
Diagnosis:
Cyst proximate, dorsoventrally compressed, circumcavate; pericyst ambitus pentagonal to subpenyagonal with an apical and two unequal antapical horns, right antapical horn reduced; endocyst subspherical to broadly pentagonal; periphragm and endophragm smooth or with ornamentation of low relief; periparacingulum generally present, annulate; paratabulation present or absent; archaeopyle intercalary, independently developed on periphragm and endophragm, dissimilar in shape; periaechaeopyle hexa 2a, steno/iso-deltaform, perioperculum free or adnate; endoarchaeopyle hexa 2a, eury-deltaform, endoperculum adnate.
Alterbidinium, Lentin and Williams, 1985, p.14. Substitute name for Albertia Vozzhennikova, 1967, p.150–151 (an illegitimate name) and Alterbia Lentin and Williams, 1976, p.47–48 (an illegitimate name).
Emendations: Khowaja-Ateequzzaman et al., 1991, p.38; Fensome et al., 2016b, p.24.
Originally Albertia (name illegitimate), subsequently Alterbia (name illegitimate), thirdly (and now) Alterbidinium.
Type: Vozzhennikova, 1967, pl.77, fig.2, as Albertia recticornis (see discussion under Alterbidinium recticorne).
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Original description Albertia: [Vozzhennikova, 1967]: (Translation: Lees in Sarjeant (ed.), 1971, p. 47)
Description:
Theca pentagonal, rhomboid, subdivided into almost equal parts. Epitheca bell-shaped, triangular with a small apical horn. Hypotheca with one or two unequal antapical horns. Transverse furrow equatorial, annulate; longitudinal furrow situated on hypotheca and extends to the antapex. Internal body has the same outline as that of the theca. Pylome triangular with rounded or truncated angles, thus appearing somewhat trapeziform.
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Emended description Alterbia:
Lentin and Williams, 1976:
Description
Pericyst: Ambitus rhomboidal to subpentagonal, elongated in an anterior-posterior direction. Pericyst prolonged into one apical and two symmetrically placed antapical horns, the right antapical generally reduced or vestigial. The pericyst attains its greatest width in the region of the pericingulum. Compression dorso-ventral.
Endocyst: Ambitus circular to ovoidal to rhomboidal. Frequently there is a slight apical protuberance. May be in contact with pericyst in precingular, cingular and postcingular regions.
Pericoels: Apical pericoel always present, antapical pericoel commonly present. The apical and antapical pericoels may be united by an ambital pericoel.
Periphragm: Thickness variable but usually ca. 1 µm. Surface generally laevigate, occasionally scabrate, granulate, or verrucate.
Endophragm: Rarely exceeding 1 µm and of constant thickness. Surface generally laevigate, may be granulate or striate.
Pericyst: Paratabulation indeterminate except in the vicinity of the archeopyle.
Pericingulum: Frequently well developed, planar or slightly elicoidal, with anterior parasuture only, or anterior and posterior parasuture as a slightly raised ridge or border, with smooth or denticulate margins.
Perisulcus: Rarely determinable; when visible largely restricted to the hypopericyst. Occasionally flagellar scar visible.
Endocyst: No observable paratabulation, other than in the vicinity of the endoarcheopyle.
Periarcheopyle: Attenuated hexa to standard hexa intercalary resulting from the loss of the second anterior intercalary paraplate, 2a. Perioperculum free or remaining attached along parasuture H4. The attenuated hexa archeopyle usually has a free operculum, the standard archeopyle is usually an attached operculum. Transverse periarcheopyle index 0.16-0.46. Transverse periarcheopyle ratio 0.20-0.88.
Endoarcheopyle: Often difficult to discern. When observed is intercalary resulting from the loss of the second anterior intercalary paraplate (2a).
Archeopyle Formula: I/I (2a/2a)
Pericyst: Length 23-192 µm, breadth 19-152 µm.
Endocyst: Length ?22-118 µm, breadth ?18-118 µm.
Affinities:
Fossil dinoflagellate species which are included in Alterbia differ from species of Deflandrea in possessing an attenuated hexa to standard hexa 2a intercalary archaeopyle, an archaeopyle index of 0.3-0.5 and almost invariably a reduced right antapical horn. The presence in the species Alterbia distincta (Wilson, 1967) and A. dilwynensis (Cookson and Eisenack, 1965) of such Deflandrea like features as a thicker endophragm and larger overall size suggest that they constitute a morphological lineage from which some of the ancestral species of Deflandrea evolved.
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Modified description Alterbia:
Stover and Evitt, 1978, p. 92-93:
Synopsis:
Cysts proximate, circumcavate, compressed, elongate ellipsoidal to nearly biconical, with an apical and a generally prominent left antapical horn; right antapical horn reduced or absent; outline of endocyst elliptical and generally approximates that of pericyst except at bases of horns; paratabulation indicated by archeopyle, occasionally also by paracingulum; archeopyle intercalary, Types I or la; archeopyle index about 0.3.
Description:
Shape: Compressed, elongate ellipsoidal to nearly biconical; apical and left antapical horns normally well developed, right antapical horn reduced or absent.
Wall relationships: Cysts circumcavate; endocyst outline subcircular to elliptical, generally approximating that of pericyst except at bases of horns.
Wall features: No parasutural features. Periphragm smooth or faintly ornamented.
Paratabulation: Indicated generally by archeopyle only, occasionally by archeopyle and paracingulum.
Archeopyle: Intercalary, Types l or la (2a only); archeopyle index generally about 0.3; operculum free.
Paracingulum: Not indicated, or expressed weakly by low transverse equatorial folds, or by concavities along lateral margins.
Parasulcus: Generally not indicated, or expressed as a poorly defined depression on the hypocyst.
Size: Intermediate to large.
Affinities:
Alterbia differs from Senegalinium in that its epipericoel is in communication with the exterior through the archeopyle and in having a reduced or absent right antapical horn instead of two nearly equally developed antapical horns. Eucladinium, like Alterbia, has a reduced right antapical horn, but the former is mainly epicavate rather than circumcavate.
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Emended description Alterbidinium:
Khowaja-Ateequzzaman et al., 1991:
Diagnosis:
Cyst proximate, dorsoventrally compressed, circumcavate; pericyst ambitus pentagonal to subpenyagonal with an apical and two unequal antapical horns, right antapical horn reduced; endocyst subspherical to broadly pentagonal; periphragm and endophragm smooth or with ornamentation of low relief; periparacingulum generally present, annulate; paratabulation present or absent; archaeopyle intercalary, independently developed on periphragm and endophragm, dissimilar in shape; periaechaeopyle hexa 2a, steno/iso-deltaform, perioperculum free or adnate; endoarchaeopyle hexa 2a, eury-deltaform, endoperculum adnate.