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Pterocysta
From Williams et al., 2017:
[Pterocysta, Rochon in Rochon et al., 2003, p. 97.
Type species: Pterocysta cruciformis, Rochon et al., 2003 (pl.1, figs.1,4)]
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Original description: [Rochon et al., 2003]:
Diagnosis:
Camocavate cyst with an S-type gonyaulacacean tabulation and characterized by the separation of periphragm and endophragm on the ventral side, forming a wing-like structure. The cavity resulting from the separation of the two wall layers extends from apex to antapex along the sulcal area. The archeopyle is precingular and the paratabulation is marked on the ventral side by ridges on the wing-like structure, while on the dorsal side it is marked by ridges that gradually fade toward the cingular area, which is devoid of paratabulation. The hypotheca is also characterized by a slight dextral torsion.
Remarks:
The subfamily of our new genera is uncertain. The number and arrangement of the apical plates, together with the S-type tabulation, suggest an affinity with the Gonyaulacoideae. Conversely, the dextral torsion of the hypotheca suggests a possible affinity with the Cribroperidinioideae.
Affinities:
Pterocysta closely resembles Lophocysta Manum, 1979 in having a narrow wing-like structure from apex to antapex on the ventral side, and ridges that express the paratabulation. The main difference is that Lophocysta has an L-type ventral organization, whereas Pterocysta has an S-type organization. Pterocysta also closely resembles Galeacysta Corradini and Biffi, 1988 in having a crest, or separation, of periphragm and endophragm in the ventral region. The main difference is that Galeacysta lacks the crest in the sulcal area, and has paratabulation in the cingular region, which is absent in Pterocysta. Pterocysta differs from Thalassiphora Eisenack and Gocht, 1960 in having the cavation localized along the sulcal area, while in Thalassiphora it encompasses the entire ventral surface. Pterocysta differs from Seriliodinium Eaton, 1996 in having the paratabulation expressed by ridges at the surface of the periphragm, while in Seriliodinium it is expressed as a network of trabeculae joining adjacent processes. Pterocysta differs from Piccoladinium Versteegh and Zevenboom, 1995 by having the periphragm and endophragm connected ventrally instead of dorsally. Pterocysta differs from Dalella McMinn and Sun, 1994 in having the crest, or wing-like projection, outlining the paratabulation on the ventral area, while it is only present on the dorsal area in Dalella. Also, the free periphragm is trabeculate in Dalella, while it is cavate in Pterocysta.
[Pterocysta, Rochon in Rochon et al., 2003, p. 97.
Type species: Pterocysta cruciformis, Rochon et al., 2003 (pl.1, figs.1,4)]
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Original description: [Rochon et al., 2003]:
Diagnosis:
Camocavate cyst with an S-type gonyaulacacean tabulation and characterized by the separation of periphragm and endophragm on the ventral side, forming a wing-like structure. The cavity resulting from the separation of the two wall layers extends from apex to antapex along the sulcal area. The archeopyle is precingular and the paratabulation is marked on the ventral side by ridges on the wing-like structure, while on the dorsal side it is marked by ridges that gradually fade toward the cingular area, which is devoid of paratabulation. The hypotheca is also characterized by a slight dextral torsion.
Remarks:
The subfamily of our new genera is uncertain. The number and arrangement of the apical plates, together with the S-type tabulation, suggest an affinity with the Gonyaulacoideae. Conversely, the dextral torsion of the hypotheca suggests a possible affinity with the Cribroperidinioideae.
Affinities:
Pterocysta closely resembles Lophocysta Manum, 1979 in having a narrow wing-like structure from apex to antapex on the ventral side, and ridges that express the paratabulation. The main difference is that Lophocysta has an L-type ventral organization, whereas Pterocysta has an S-type organization. Pterocysta also closely resembles Galeacysta Corradini and Biffi, 1988 in having a crest, or separation, of periphragm and endophragm in the ventral region. The main difference is that Galeacysta lacks the crest in the sulcal area, and has paratabulation in the cingular region, which is absent in Pterocysta. Pterocysta differs from Thalassiphora Eisenack and Gocht, 1960 in having the cavation localized along the sulcal area, while in Thalassiphora it encompasses the entire ventral surface. Pterocysta differs from Seriliodinium Eaton, 1996 in having the paratabulation expressed by ridges at the surface of the periphragm, while in Seriliodinium it is expressed as a network of trabeculae joining adjacent processes. Pterocysta differs from Piccoladinium Versteegh and Zevenboom, 1995 by having the periphragm and endophragm connected ventrally instead of dorsally. Pterocysta differs from Dalella McMinn and Sun, 1994 in having the crest, or wing-like projection, outlining the paratabulation on the ventral area, while it is only present on the dorsal area in Dalella. Also, the free periphragm is trabeculate in Dalella, while it is cavate in Pterocysta.