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Odontochitina diducta
Odontochitina diducta Pearce, 2010, p.62,64, pl.6, fig.1.
Holotype: Pearce, 2010, pl.6, fig.1.
Type locality and horizon. Trunch borehole, Norfolk, UK; 279.9–280.0 m, Burnham–Flamborough Chalk (undifferentiated), high Offaster pilula Zone (mid-lower Campanian).
Age: middle Santonian–late Campanian.
Diagnosis. A species of Odontochitina with a widely divergent antapical and lateral horn separated by an angle equal to or greater than 80%.
Description. Large ceratioid, cavate dinoflagellate cyst with one apical, antapical and lateral horn of comparable length. The wall is two-layered, comprising a smooth endophragm and smooth, incompletely and faintly striate or distally perforate (although this may be due to corrosion) periphragm. The periphragm and endophragm are attached in the precingular region such that the species has a well-developed cavation connecting the lateral and antapical horns. The endocyst is sub-spherical, lacking obvious projections into the pericoel. The antapical and lateral horns are separated by an angle of greater than 80%. The paracingulum may be indicated by faint ridges on the periphragm. The archaeopyle is apical (Type tA, operculum detached), formed by the loss of all the apical paraplates.
Comparison. Differs from all other species of Odontochitina in the wide angle between the lateral and antapical horns that are also connected by the hypopericoel.
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Emended description: Pearce, M. A., 2018:
Emended diagnosis:
A cornucavate to hypocavate species of Odontochitina with a widely divergent antapical and
lateral horn separated by an angle equal to or greater than 80◦.
Emended description:
Large ceratioid, cavate dinoflagellate cyst with one apical, antapical and lateral horn of
comparable length.
Wall: two-layered, comprising a smooth endophragm and smooth, incompletely and faintly striate or distally perforate (although this may be due to corrosion) periphragm. The periphragm and endophragm are appressed in the precingular region with the lateral and antapical horns being either cornucavate or connected by a hypocavation.
Endocyst: sub-spherical, lacking obvious projections into the pericoel.
antapical and lateral horns are separated by an angle of greater than 80◦
Paracingulum: may be indicated by faint ridges on the periphragm
Archaeopyle: apical Type (tA)
Operculum: detached
Remarks:
In the original description of O. diducta, Pearce (2010:62) described the species as having “a well-developed cavation connecting the lateral and antapical horns”. However, this feature seems to be gradational to specimens from the same material that are cornucavate, and the diagnosis and description are emended here to account for this fact. The specimens referred to as Odontochitina sp. by Cookson and Eisenack (1968) and Costa and Davey (1992) are thus now considered synonymous with O. diducta.
Holotype: Pearce, 2010, pl.6, fig.1.
Type locality and horizon. Trunch borehole, Norfolk, UK; 279.9–280.0 m, Burnham–Flamborough Chalk (undifferentiated), high Offaster pilula Zone (mid-lower Campanian).
Age: middle Santonian–late Campanian.
Diagnosis. A species of Odontochitina with a widely divergent antapical and lateral horn separated by an angle equal to or greater than 80%.
Description. Large ceratioid, cavate dinoflagellate cyst with one apical, antapical and lateral horn of comparable length. The wall is two-layered, comprising a smooth endophragm and smooth, incompletely and faintly striate or distally perforate (although this may be due to corrosion) periphragm. The periphragm and endophragm are attached in the precingular region such that the species has a well-developed cavation connecting the lateral and antapical horns. The endocyst is sub-spherical, lacking obvious projections into the pericoel. The antapical and lateral horns are separated by an angle of greater than 80%. The paracingulum may be indicated by faint ridges on the periphragm. The archaeopyle is apical (Type tA, operculum detached), formed by the loss of all the apical paraplates.
Comparison. Differs from all other species of Odontochitina in the wide angle between the lateral and antapical horns that are also connected by the hypopericoel.
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Emended description: Pearce, M. A., 2018:
Emended diagnosis:
A cornucavate to hypocavate species of Odontochitina with a widely divergent antapical and
lateral horn separated by an angle equal to or greater than 80◦.
Emended description:
Large ceratioid, cavate dinoflagellate cyst with one apical, antapical and lateral horn of
comparable length.
Wall: two-layered, comprising a smooth endophragm and smooth, incompletely and faintly striate or distally perforate (although this may be due to corrosion) periphragm. The periphragm and endophragm are appressed in the precingular region with the lateral and antapical horns being either cornucavate or connected by a hypocavation.
Endocyst: sub-spherical, lacking obvious projections into the pericoel.
antapical and lateral horns are separated by an angle of greater than 80◦
Paracingulum: may be indicated by faint ridges on the periphragm
Archaeopyle: apical Type (tA)
Operculum: detached
Remarks:
In the original description of O. diducta, Pearce (2010:62) described the species as having “a well-developed cavation connecting the lateral and antapical horns”. However, this feature seems to be gradational to specimens from the same material that are cornucavate, and the diagnosis and description are emended here to account for this fact. The specimens referred to as Odontochitina sp. by Cookson and Eisenack (1968) and Costa and Davey (1992) are thus now considered synonymous with O. diducta.