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Ripea sussexensis
Ripea sussexensis Batten, 1985, p.431–432, text-figs.3A–C,4A–L,5A–F. Emendation: Batten and Lister, 1988, p.354.
Holotype: Batten, 1985, text-figs.3B, 5A
Age: ?Late Hauterivian
Emended diagnosis: Batten and Lister, 1988, p.354
Cyst generally slightly compressed dorsoventrally and triangular with rounded angles, two of which are weakly developed antapical lobes. Wall two-layered; total thickness 1 µm or less. Periphragm closely adherent to endophragm in apical region and adjacent to archeopyle, more loosely enveloping and crumpled against it elsewhere. Outer surface smooth, usually no evidence of a paracingulum but faint traces may rarely be discerned. Paratabulation generally expressed only by archeopyle; type either tI or tI + (tA). Principal excystment aperture formed by loss of 2 or ?3 intercalary paraplates, comprising a free, compound polyplacoid operculum, frequently accompanied by splitting of suture around apical series which may remain adherent but is occasionally completely detached. Accessory sutures sometimes developed between precingular paraplates. Overall size 30-36 µm.
Affinities and Remark:
Batten and Lister, 1988, p.354: We have emended R. sussexensis to allow for a more complex type of archeopyle than originally diagnosed. The apical portion of the operculum is commonly attached in the sulcal region when paraplate 1" remains fused laterally to precingular paraplates 1" and 7". When the suture around the apical series is completely developed, or nearly so, it either leaves the apical operculum adhering by a narrow isthmus (paraplate 1") within the sulcal notch or, more commonly, results in its complete dislodgement.
The marine peridiniacean cyst Umbodinium Bint, 1983 has a different shape and a combination intercalary/apical archeopyle (tA)a2I in which the apical portion of the operculum is ventrally adnate and the two intercalaries are free.
Holotype: Batten, 1985, text-figs.3B, 5A
Age: ?Late Hauterivian
Emended diagnosis: Batten and Lister, 1988, p.354
Cyst generally slightly compressed dorsoventrally and triangular with rounded angles, two of which are weakly developed antapical lobes. Wall two-layered; total thickness 1 µm or less. Periphragm closely adherent to endophragm in apical region and adjacent to archeopyle, more loosely enveloping and crumpled against it elsewhere. Outer surface smooth, usually no evidence of a paracingulum but faint traces may rarely be discerned. Paratabulation generally expressed only by archeopyle; type either tI or tI + (tA). Principal excystment aperture formed by loss of 2 or ?3 intercalary paraplates, comprising a free, compound polyplacoid operculum, frequently accompanied by splitting of suture around apical series which may remain adherent but is occasionally completely detached. Accessory sutures sometimes developed between precingular paraplates. Overall size 30-36 µm.
Affinities and Remark:
Batten and Lister, 1988, p.354: We have emended R. sussexensis to allow for a more complex type of archeopyle than originally diagnosed. The apical portion of the operculum is commonly attached in the sulcal region when paraplate 1" remains fused laterally to precingular paraplates 1" and 7". When the suture around the apical series is completely developed, or nearly so, it either leaves the apical operculum adhering by a narrow isthmus (paraplate 1") within the sulcal notch or, more commonly, results in its complete dislodgement.
The marine peridiniacean cyst Umbodinium Bint, 1983 has a different shape and a combination intercalary/apical archeopyle (tA)a2I in which the apical portion of the operculum is ventrally adnate and the two intercalaries are free.