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Scaldecysta
From Williams et al., 2017:
[Scaldecysta, De Schepper et al., 2004, p. 641.
Type species: Scaldecysta doelensis, De Schepper et al., 2004 (fig.12, nos.1–4)]
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Original description: [De Schepper et al., 2004]:
Diagnosis:
Thin and single-walled protoperidiniacean cysts, smooth or with low ornamentation, brown in color, with rhombic outline in dorsoventral view; sometimes with dorsoventral compression.
Five horns present: one apical, two lateral, two antapical. Apical horn ends in two divergent solid tips.
Archeopyle formed by loss of single anterior intercalary plate.
Comparison:
Stelladinium (Bradford, 1975) differs from Scaldecysta in its pentagonal rather than rhombic outline and by the presence of a single tip to the apical horn. Rhombodinium (Gocht, 1955) differs in having an internal body and a pale or colorless wall.
(Biological) Affinities:
Scaldecysta is classified as a protoperidinioidean based on its possession of an intercalary archeopyle, the brown pigmentation of the cyst wall, and its strong resemblance to the genus Stelladinium. The close similarity between Scaldecysta and Stelladinium is revealed through Scaldecysta sp. cf. S. doelensis n. gen. and sp. (Fig. 13.9–13.11), which has an outline approaching a pentagonal shape and divergent antapical horns as in Stelladinium, but an apical horn with two solid tips typical of Scaldecysta. Excystment studies of Stelladinium link this genus conclusively with the motile-defined genus Protoperidinium Bergh, 1881 (see Head, 1996a). Scaldecysta is known only from the Pliocene (this study), and we speculate that it represents an evolutionary precursor of Stelladinium, a genus not known from deposits older than Pleistocene.
[Scaldecysta, De Schepper et al., 2004, p. 641.
Type species: Scaldecysta doelensis, De Schepper et al., 2004 (fig.12, nos.1–4)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [De Schepper et al., 2004]:
Diagnosis:
Thin and single-walled protoperidiniacean cysts, smooth or with low ornamentation, brown in color, with rhombic outline in dorsoventral view; sometimes with dorsoventral compression.
Five horns present: one apical, two lateral, two antapical. Apical horn ends in two divergent solid tips.
Archeopyle formed by loss of single anterior intercalary plate.
Comparison:
Stelladinium (Bradford, 1975) differs from Scaldecysta in its pentagonal rather than rhombic outline and by the presence of a single tip to the apical horn. Rhombodinium (Gocht, 1955) differs in having an internal body and a pale or colorless wall.
(Biological) Affinities:
Scaldecysta is classified as a protoperidinioidean based on its possession of an intercalary archeopyle, the brown pigmentation of the cyst wall, and its strong resemblance to the genus Stelladinium. The close similarity between Scaldecysta and Stelladinium is revealed through Scaldecysta sp. cf. S. doelensis n. gen. and sp. (Fig. 13.9–13.11), which has an outline approaching a pentagonal shape and divergent antapical horns as in Stelladinium, but an apical horn with two solid tips typical of Scaldecysta. Excystment studies of Stelladinium link this genus conclusively with the motile-defined genus Protoperidinium Bergh, 1881 (see Head, 1996a). Scaldecysta is known only from the Pliocene (this study), and we speculate that it represents an evolutionary precursor of Stelladinium, a genus not known from deposits older than Pleistocene.