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Isabelia
From Fensome et al., 2019:
"Isabelia", Lentin and Williams, 1976, p.56.
Name illegitimate -- senior homonym: Isabelia BarbosaRodrigues, 1877.
Substitute name: Isabelidinium.
Type: Cookson and Eisenack, 1958, pl.4, fig.10, as Deflandrea korojonensis.
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Original description: [Lentin and Williams, 1976]: (taken from Stover and Evitt, 1978, p. 108; major headings deleted and paragraphing modified)
Description:
Pericyst: Ambitus commonly pentagonal, elongated in an anteroposterior direction, rarely rhomboidal or rectangular. Apex prolonged into a broad short apical horn which may merge imperceptibly into the epipericyst, or be developed into shoulders. Antapex produced into two symmetrically located short antapical horns, usually of unequal length. The left antapical horn is always the longer, the right is reduced or vestigial. The apical and two antapical horns sometimes reduced. There is usually a slight to prominent equatorial bulge in ambital view. Compression dorsoventral.
Endocyst: Ambitus ovoidal with longest axis equatorially aligned to circular, to elongate ovoidal. May be equatorially in contact with endocyst. Pericoels: When endocyst and pericyst are appressed in precingular, cingular and postcingular regions, they are separated apically and antapically by a large apical and a large antapical pericoel, respectively. Alternatively the apical and antapical pericoels may be united by an ambital pericoel. Compression dorsoventral, may be negligible.
Periphragm: Usually of constant thickness. Surface levigate, scabrate, granulate or verrucate. Ornamentation nontabular.
Endophragm: Surface levigate to scabrate to granulate.
Pericyst: Paratabulation indeterminate other than in the vicinity of the periarcheopyle.
Pericingulum: Almost always absent or rudimentary and never complete, occasionally visible on the ambitus as an indentation.
Perisulcus: Not observed.
Endocyst: Paratabulation unknown.
Periarcheopyle: Omegaform intercalary resulting from the partial detachment of the second anterior intercalary paraplate, 2a, with perioperculum usually remaining attached along parasuture H4. Transverse periarcheopyle index is 0.33-0.55. Transverse archeopyle ratio is 0.50-1.25.
Endoarcheopyle: Where observable appears to result from the loss of the second anterior intercalary paraplate (2a), or all three anterior intercalaries.
Archeopyle Formula: I/I (2a/2a) or I/3I (2a/1-3a).
Affinities:
Isabelia closely resembles Chatangiella in possessing an omegaform periarchaeopyle which seems to be related to the outline of the epipericyst, which in such taxa is commonly widest in the vicinity of the archaeopyle. However, Chatangiella has a hepta/pentapartite pericingulum and frequently penetabular ornamentation.
Alterbia differs in possessing a pericingulum and a standard to attenuated hexa periarchaeopyle. The apical horn and left antapical horn also tend to be more prominent in Alterbia.
Amphidiadema which lacks a pericingulum differs from Isabelia in having a standard hexa or attenuated hexa periarchaeopyle, and apical and antapical regions devoid of horns.
Trithyrodinium has the distinctive 3I (1-3a) periarchaeopyle.
"Isabelia", Lentin and Williams, 1976, p.56.
Name illegitimate -- senior homonym: Isabelia BarbosaRodrigues, 1877.
Substitute name: Isabelidinium.
Type: Cookson and Eisenack, 1958, pl.4, fig.10, as Deflandrea korojonensis.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Lentin and Williams, 1976]: (taken from Stover and Evitt, 1978, p. 108; major headings deleted and paragraphing modified)
Description:
Pericyst: Ambitus commonly pentagonal, elongated in an anteroposterior direction, rarely rhomboidal or rectangular. Apex prolonged into a broad short apical horn which may merge imperceptibly into the epipericyst, or be developed into shoulders. Antapex produced into two symmetrically located short antapical horns, usually of unequal length. The left antapical horn is always the longer, the right is reduced or vestigial. The apical and two antapical horns sometimes reduced. There is usually a slight to prominent equatorial bulge in ambital view. Compression dorsoventral.
Endocyst: Ambitus ovoidal with longest axis equatorially aligned to circular, to elongate ovoidal. May be equatorially in contact with endocyst. Pericoels: When endocyst and pericyst are appressed in precingular, cingular and postcingular regions, they are separated apically and antapically by a large apical and a large antapical pericoel, respectively. Alternatively the apical and antapical pericoels may be united by an ambital pericoel. Compression dorsoventral, may be negligible.
Periphragm: Usually of constant thickness. Surface levigate, scabrate, granulate or verrucate. Ornamentation nontabular.
Endophragm: Surface levigate to scabrate to granulate.
Pericyst: Paratabulation indeterminate other than in the vicinity of the periarcheopyle.
Pericingulum: Almost always absent or rudimentary and never complete, occasionally visible on the ambitus as an indentation.
Perisulcus: Not observed.
Endocyst: Paratabulation unknown.
Periarcheopyle: Omegaform intercalary resulting from the partial detachment of the second anterior intercalary paraplate, 2a, with perioperculum usually remaining attached along parasuture H4. Transverse periarcheopyle index is 0.33-0.55. Transverse archeopyle ratio is 0.50-1.25.
Endoarcheopyle: Where observable appears to result from the loss of the second anterior intercalary paraplate (2a), or all three anterior intercalaries.
Archeopyle Formula: I/I (2a/2a) or I/3I (2a/1-3a).
Affinities:
Isabelia closely resembles Chatangiella in possessing an omegaform periarchaeopyle which seems to be related to the outline of the epipericyst, which in such taxa is commonly widest in the vicinity of the archaeopyle. However, Chatangiella has a hepta/pentapartite pericingulum and frequently penetabular ornamentation.
Alterbia differs in possessing a pericingulum and a standard to attenuated hexa periarchaeopyle. The apical horn and left antapical horn also tend to be more prominent in Alterbia.
Amphidiadema which lacks a pericingulum differs from Isabelia in having a standard hexa or attenuated hexa periarchaeopyle, and apical and antapical regions devoid of horns.
Trithyrodinium has the distinctive 3I (1-3a) periarchaeopyle.