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Nucicla
Nucicla, Hartman et al., 2019
Type species: Nucicla umbiliphora, Hartman et al., 2019
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Original description: [Hartman et al., 2019]:
Diagnosis:
Acavate, dorsoventrally compressed cyst with a rounded pentagonal outline, a hypocyst that is twice the size of the epicyst, an archaeopyle formed by the loss of three anterior intercalary plates, and a large sulcus with the posterior sulcal plate positioned at the antapex.
Affinities/Differential diagnosis:
This genus differs from all other peridinioid dinoflagellate cysts by its combination of (1) a consistent 3I archaeopyle, (2) a well-outlined cingulum and sulcus, (3) the absence of cavation, and (4) a large sulcus with a posterior sulcal plate at the antapex.
The Late Cretaceous to Early Palaeocene genus Trithyrodinium Drugg 1967 also has a 3I archaeopyle, but is cavate. Vozzhennikovia Lentin & Williams 1976 has an I or 3I archaeopyle, and is also cavate. Although the number of archaeopyle plates in Brigantedinium Reid 1977 is not determined and therefore can include species with a 3I archaeopyle, Brigantedinium is spherical/ovoidal and lacks tabulation other than the archaeopyle. Other genera with dorsoventral compression, a pentagonal outline and consisting of an autophragm include Votadinium Reid 1977, Lejeunecysta Artzner & Dörhöfer 1978, Trinovantedinium Reid 1977 and Leipokatium Bradford 1975. Like Brigantedinium, Votadinium and Leipokatium can have an archaeopyle consisting of any number of intercalary plates, but Votadinium differs from Nucicla in having a shallow or deep depression between the antapical lobes, and lacks a well-defined cingulum. Leipokatium has very distinct antapical horns and a hypocyst much smaller than the epicyst. Both Lejeunecysta and Trinovantedinium may have a sulcus and/ or cingulum, but have an I archaeopyle. In addition, Trinovantedinium has non-tabular proximochorate processes and Lejeunecysta has an epicyst and hypocyst of approximately equal size. For all of the above-mentioned genera the position of the posterior sulcal plate is either unclear or not as posterior as in Nucicla.
Type species: Nucicla umbiliphora, Hartman et al., 2019
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Original description: [Hartman et al., 2019]:
Diagnosis:
Acavate, dorsoventrally compressed cyst with a rounded pentagonal outline, a hypocyst that is twice the size of the epicyst, an archaeopyle formed by the loss of three anterior intercalary plates, and a large sulcus with the posterior sulcal plate positioned at the antapex.
Affinities/Differential diagnosis:
This genus differs from all other peridinioid dinoflagellate cysts by its combination of (1) a consistent 3I archaeopyle, (2) a well-outlined cingulum and sulcus, (3) the absence of cavation, and (4) a large sulcus with a posterior sulcal plate at the antapex.
The Late Cretaceous to Early Palaeocene genus Trithyrodinium Drugg 1967 also has a 3I archaeopyle, but is cavate. Vozzhennikovia Lentin & Williams 1976 has an I or 3I archaeopyle, and is also cavate. Although the number of archaeopyle plates in Brigantedinium Reid 1977 is not determined and therefore can include species with a 3I archaeopyle, Brigantedinium is spherical/ovoidal and lacks tabulation other than the archaeopyle. Other genera with dorsoventral compression, a pentagonal outline and consisting of an autophragm include Votadinium Reid 1977, Lejeunecysta Artzner & Dörhöfer 1978, Trinovantedinium Reid 1977 and Leipokatium Bradford 1975. Like Brigantedinium, Votadinium and Leipokatium can have an archaeopyle consisting of any number of intercalary plates, but Votadinium differs from Nucicla in having a shallow or deep depression between the antapical lobes, and lacks a well-defined cingulum. Leipokatium has very distinct antapical horns and a hypocyst much smaller than the epicyst. Both Lejeunecysta and Trinovantedinium may have a sulcus and/ or cingulum, but have an I archaeopyle. In addition, Trinovantedinium has non-tabular proximochorate processes and Lejeunecysta has an epicyst and hypocyst of approximately equal size. For all of the above-mentioned genera the position of the posterior sulcal plate is either unclear or not as posterior as in Nucicla.