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Aidelocysta
From Williams et al., 2017:
[Aidelocysta, Riding, Helby and Stevens in Riding and Helby, 2001g, p. 178-179, 181
Type species: Aidelocysta clavata, Riding and Helby, 2001g (figs.1I–L)]
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Original description: [Riding and Helby, 2001g]:
Diagnosis:
Small, acavate cysts with an equatorial constriction. The hypocyst and epicyst each comprise two prominent rounded lobes or protuberances in dorsoventral view. The cysts are elongate ellipsoidal in lateral view. The autophragm bears predominantly nontabular low relief ornamentation, which may be distally connected to form an ectophragm. The autophragm may also be differentiated. Occasionally, short, discontinuous lineations of ornamentation may be parasutural or penitabular.
Archeopyle anterior intercalary, type I(2a), eury-deltaform in shape; the operculum is normally free. The archaeopyle is situated close to the apex (i.e. subpolar). The hexagonal outline of the principal archaeopyle suture may be distorted into an ellipsoidal shape.
Paratabulation not developed except at the principal archaeopyle suture, and occasional alignment of ornament.
Paracingulum indicated by the equatorial constriction and possibly lack of ornamentation.
The parasulcus is marked by a narrow, midventral, linear depression and by reduced ornamentation.
Remarks:
Aidelocysta is a distinctive, small, quadrilobate genus with a subpolar, anterior intercalary archeopyle. Distortion may alter the outline of the archaeopyle from hexagonal to ellipsoidal. Due to the high position of the archaeopyle on the epicyst, the hexagonal shape may not be observable in poorly preserved or oriented material. The shape of the archeopyle is hexagonal and is eury-deltaform of Bujak & Davies (1983). This genus is, therefore, peridiniacean and Aidelocysta appears to be one of he oldest representatives of the suborder Peridiniineae (order Peridiniales) of Fensome et al. (1993). Previously, the oldest known peridiniacean was the Tithonian calcareous dinoflagellate cyst Pirumella multistrata (Pflaumann & Krasheninnikov 1978) Lentin & Williams 1993 forma carteri (Bolli 1974) Williams et al. 1998. However, the oldest unequivocal dinosporin peridinacean species is Subtilisphaera terrula (Davey 1974) Lentin & Williams 1976, the earliest occurrence of which is Hauterivian (Duxbury, 1977, fig. 21). Pyxidiella pandora Cookson & Eisenack 1958, from the Upper Jurassic (Tithonian) Dngo Siltstone of Western Australia (Cookson & Eisenack, 1958) is older (Callovian to Berriasian), but its anterior intercalary archaeopyle appears to be seven-sided, suggesting an affinity with the Family Heterocapsaceae. There are also two possible species of Subtilisphaera; S? inaffecta (Drugg 1978) Bujak & Davies 1983 and S? paeminosa (Drugg 1978) Bujak & Davies 1983, in the Late Jurassic (Kimmeridgian) of Europe. However, the peridiniacean affinities of these species are uncertain (Riding & Thomas, 1988). Aidelocysta is unusual among peridinioid genera in lacking polar horns and not being cavate.
Affinities:
Aidelocysta resembles several other small proximate genera, but is the only quadrilobate genus to have an anterior intercalary archaeopyle of peridiniacean type. Hexagonifera Cookson & Eisenack 1961 emend. Stover & Evitt 1978 resembles Aidelocysta in being an acavate peridiniineacean genus which lacks polar horns and has a subpolar type I archeopyle. However, Hexagonifera is subsphearical to ellipsoidal in outline, is not holocavate and lacks an equatorial constriction. Pycidiella Cookson & Eisenack 1958 differs from Aidelocysta in being elongate ellipsoidal, exclusively acavate, paratabulate and not constricted in the paracingular region. Members of the 'Parvocysta suite' of Riding (1984) resemble Aidelocysta in having lobate epicysts and hypocysts. This complex includes Parvocysta Bjaerke 1980, Reutlingia Drugg 1978 emend. Below 1987 and Susadinium Dörhöfer & Davies. However, members of the 'Parvocysta suite' usually have apical horns and therefore are subpentagonal is outline. Moreover, the anterior intercalary archaeopyles are longitudinally elongate and have geniculate anterior and posterior margins. Stenopyxinium Deflandre 1968 is a lobate genus, but is extremely small, spinose and probably has a epicystal rather than a intercalary archaeopyle. Of the genera with apical archaeopyles, the most similar to Aidelocysta are the quadrilobate forms Horologinella Cookson & Eisenack 1962 emend. Backhouse 1988. However, Horologinellahas an unusual paratabulation indicated by parasutural ridges and an apical archaeopyle with a subcircular principal archaeopyle suture (Blackhouse 1988). Tetrachacysta is small, quadrilobate, has no indications of paratabulation other than the angular, apical principal archaeopyle suture (Blackhouse, 1988, fig. 32) and accessory archaeopyle sutures. Ampulladinium gen. nov. varies from being acavate to holocavate and sometimes has a differentiated autophragm. However, Apulladiniumis trilobate and has an apical archaeopyle. Tringadinium Riding & Helby (this volume) and Woodinia Riding & Helby (this volume) are also somewhat similar to Aidelocysta. Tringadinium is lobate and has an equatorial constriction, but is exclusively acavate and has a gonyalacalean paratabulation indicated by intratabular protuberances. Woodinia is elongate, sometimes trilobate, has intratabular ornamentation and an extremely small epicyst. Both Tringadinium and Woodinia have apical archaeopyles.
[Aidelocysta, Riding, Helby and Stevens in Riding and Helby, 2001g, p. 178-179, 181
Type species: Aidelocysta clavata, Riding and Helby, 2001g (figs.1I–L)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Riding and Helby, 2001g]:
Diagnosis:
Small, acavate cysts with an equatorial constriction. The hypocyst and epicyst each comprise two prominent rounded lobes or protuberances in dorsoventral view. The cysts are elongate ellipsoidal in lateral view. The autophragm bears predominantly nontabular low relief ornamentation, which may be distally connected to form an ectophragm. The autophragm may also be differentiated. Occasionally, short, discontinuous lineations of ornamentation may be parasutural or penitabular.
Archeopyle anterior intercalary, type I(2a), eury-deltaform in shape; the operculum is normally free. The archaeopyle is situated close to the apex (i.e. subpolar). The hexagonal outline of the principal archaeopyle suture may be distorted into an ellipsoidal shape.
Paratabulation not developed except at the principal archaeopyle suture, and occasional alignment of ornament.
Paracingulum indicated by the equatorial constriction and possibly lack of ornamentation.
The parasulcus is marked by a narrow, midventral, linear depression and by reduced ornamentation.
Remarks:
Aidelocysta is a distinctive, small, quadrilobate genus with a subpolar, anterior intercalary archeopyle. Distortion may alter the outline of the archaeopyle from hexagonal to ellipsoidal. Due to the high position of the archaeopyle on the epicyst, the hexagonal shape may not be observable in poorly preserved or oriented material. The shape of the archeopyle is hexagonal and is eury-deltaform of Bujak & Davies (1983). This genus is, therefore, peridiniacean and Aidelocysta appears to be one of he oldest representatives of the suborder Peridiniineae (order Peridiniales) of Fensome et al. (1993). Previously, the oldest known peridiniacean was the Tithonian calcareous dinoflagellate cyst Pirumella multistrata (Pflaumann & Krasheninnikov 1978) Lentin & Williams 1993 forma carteri (Bolli 1974) Williams et al. 1998. However, the oldest unequivocal dinosporin peridinacean species is Subtilisphaera terrula (Davey 1974) Lentin & Williams 1976, the earliest occurrence of which is Hauterivian (Duxbury, 1977, fig. 21). Pyxidiella pandora Cookson & Eisenack 1958, from the Upper Jurassic (Tithonian) Dngo Siltstone of Western Australia (Cookson & Eisenack, 1958) is older (Callovian to Berriasian), but its anterior intercalary archaeopyle appears to be seven-sided, suggesting an affinity with the Family Heterocapsaceae. There are also two possible species of Subtilisphaera; S? inaffecta (Drugg 1978) Bujak & Davies 1983 and S? paeminosa (Drugg 1978) Bujak & Davies 1983, in the Late Jurassic (Kimmeridgian) of Europe. However, the peridiniacean affinities of these species are uncertain (Riding & Thomas, 1988). Aidelocysta is unusual among peridinioid genera in lacking polar horns and not being cavate.
Affinities:
Aidelocysta resembles several other small proximate genera, but is the only quadrilobate genus to have an anterior intercalary archaeopyle of peridiniacean type. Hexagonifera Cookson & Eisenack 1961 emend. Stover & Evitt 1978 resembles Aidelocysta in being an acavate peridiniineacean genus which lacks polar horns and has a subpolar type I archeopyle. However, Hexagonifera is subsphearical to ellipsoidal in outline, is not holocavate and lacks an equatorial constriction. Pycidiella Cookson & Eisenack 1958 differs from Aidelocysta in being elongate ellipsoidal, exclusively acavate, paratabulate and not constricted in the paracingular region. Members of the 'Parvocysta suite' of Riding (1984) resemble Aidelocysta in having lobate epicysts and hypocysts. This complex includes Parvocysta Bjaerke 1980, Reutlingia Drugg 1978 emend. Below 1987 and Susadinium Dörhöfer & Davies. However, members of the 'Parvocysta suite' usually have apical horns and therefore are subpentagonal is outline. Moreover, the anterior intercalary archaeopyles are longitudinally elongate and have geniculate anterior and posterior margins. Stenopyxinium Deflandre 1968 is a lobate genus, but is extremely small, spinose and probably has a epicystal rather than a intercalary archaeopyle. Of the genera with apical archaeopyles, the most similar to Aidelocysta are the quadrilobate forms Horologinella Cookson & Eisenack 1962 emend. Backhouse 1988. However, Horologinellahas an unusual paratabulation indicated by parasutural ridges and an apical archaeopyle with a subcircular principal archaeopyle suture (Blackhouse 1988). Tetrachacysta is small, quadrilobate, has no indications of paratabulation other than the angular, apical principal archaeopyle suture (Blackhouse, 1988, fig. 32) and accessory archaeopyle sutures. Ampulladinium gen. nov. varies from being acavate to holocavate and sometimes has a differentiated autophragm. However, Apulladiniumis trilobate and has an apical archaeopyle. Tringadinium Riding & Helby (this volume) and Woodinia Riding & Helby (this volume) are also somewhat similar to Aidelocysta. Tringadinium is lobate and has an equatorial constriction, but is exclusively acavate and has a gonyalacalean paratabulation indicated by intratabular protuberances. Woodinia is elongate, sometimes trilobate, has intratabular ornamentation and an extremely small epicyst. Both Tringadinium and Woodinia have apical archaeopyles.