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Canningia duxburyi
From Fensome et al., 2019:
Canningia duxburyi Harding, 1990b, p.22–23, pl.5, figs.1–13; text-fig.8 ex Harding in Williams et al., 1998, p.88.
Holotype: Harding, 1990b, pl.5, fig.1; Fensome et al., 2019a, fig.12J.
This name was not validly published in Harding (1990b) since the lodgement of the holotype was not specified (ICN Article 40.7).
Age: late Hauterivian–early Barremian.
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Original description: [Harding, 1990, p. 22]:
Diagnosis:
Shape: Ambitus rounded, sub-pentagonal. Pronounced apical horn with lobate antapical region - often developed into two antapical horns of which the left is the most pronounced. Width greatest across paracingular reglon. Epicyst and hypocyst of approximately equal length. Strong dorso-ventral compression.
Phragma: Ectophragm very thin (ca. 0.3 µm thick), highly perforate and interrupted along parasutures, thus indicating paratabulation. Autophragm (1 µm thick) has pitted "orange-peel"-like surface sculpture. Ectophragm supported on processes and septa (up to 6 µm high) which form arcuate or linear process complexes. The processes and septa appear to be both intratabular and penitabular in nature depending on situation. Ectocoels are irregularly developed, reduced in dorsal areas and may be absent in ventral areas if ectophragm undeveloped.
Paratabulation: Sexiform gonyaulacoid, paratabulation: 4", 6", ?6c, 6""", 1"""", 1p, xs. Antapical lobes involve X/Y/Z and VI/Y/Z triple junctions.
Archaeopyle: Type (4A): loss of apicals as a simple polyplacoid operculum.
Paracingulum: Difficult to discern on many specimens as it is obscured by the disruption of the ectophragm. Individual paraplates are represented by narrow intratabular septa supporting narrow strips of ectophragm. On the ventral surface the septa become discontinuous and may be represented by processes.
Dimension:
Length, less operculum (94) 78.1 (66) µm. Width (120) 93.8 (80) µm. Length of operculum ca.35 µm. Specimens = 45 (42).
Affinities: (p. 23):
This new species differs from the species described by Helby (1987): it has an ectophragm which clearly breaks into paraplate related areas (unlike C. reticulata Cooksonand Eisenack 1960 and C. grandis Helby 1987), has a much more robust ectophragmal reticulum than C. pistica Helby 1987 and a much wider ectocoel than C. transitoria Stover and Helby 1987. It differs from C. senonica Clarke and Verdier 1967 by having a much more robust, angular autophragm and a much narrower ectocoel.
The adcingular margin of paraplate X, and the adsulcal margin of II, clearly show that Iu (which is not always indicated by ectophragmal development) lies outside the parasulcus. This indicates a gonyaulacoid affinity, rather than a ceratioid one, even though the first precingular paraplate is clearly planate.
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Comments Fensome et al., 2019a:
Harding (Citation1990, p. 22–23) differentiated Canningia duxburyi from Canningia reticulata in that ‘it has an ectophragm [outer wall layer] which clearly breaks into paraplate related areas …’. Harding illustrated Canningia duxburyi through scanning electron microscope (SEM) images. In our experience, some specimens of Canningia reticulata seen under the light microscope do show suggestions of tabulation, which might be more clearly seen in SEM images. Hence, we question whether separation of the two species is justified, but retain Canningia duxburyi as it is considered a useful biostratigraphic marker (Martin Pearce, personal communication).
Stratigraphical occurrence. Canningia duxburyi was originally described from the upper Hauterivian to lower Barremian of Norfolk, England.
Canningia duxburyi Harding, 1990b, p.22–23, pl.5, figs.1–13; text-fig.8 ex Harding in Williams et al., 1998, p.88.
Holotype: Harding, 1990b, pl.5, fig.1; Fensome et al., 2019a, fig.12J.
This name was not validly published in Harding (1990b) since the lodgement of the holotype was not specified (ICN Article 40.7).
Age: late Hauterivian–early Barremian.
---------------------------------------------------------------------------------------------------
Original description: [Harding, 1990, p. 22]:
Diagnosis:
Shape: Ambitus rounded, sub-pentagonal. Pronounced apical horn with lobate antapical region - often developed into two antapical horns of which the left is the most pronounced. Width greatest across paracingular reglon. Epicyst and hypocyst of approximately equal length. Strong dorso-ventral compression.
Phragma: Ectophragm very thin (ca. 0.3 µm thick), highly perforate and interrupted along parasutures, thus indicating paratabulation. Autophragm (1 µm thick) has pitted "orange-peel"-like surface sculpture. Ectophragm supported on processes and septa (up to 6 µm high) which form arcuate or linear process complexes. The processes and septa appear to be both intratabular and penitabular in nature depending on situation. Ectocoels are irregularly developed, reduced in dorsal areas and may be absent in ventral areas if ectophragm undeveloped.
Paratabulation: Sexiform gonyaulacoid, paratabulation: 4", 6", ?6c, 6""", 1"""", 1p, xs. Antapical lobes involve X/Y/Z and VI/Y/Z triple junctions.
Archaeopyle: Type (4A): loss of apicals as a simple polyplacoid operculum.
Paracingulum: Difficult to discern on many specimens as it is obscured by the disruption of the ectophragm. Individual paraplates are represented by narrow intratabular septa supporting narrow strips of ectophragm. On the ventral surface the septa become discontinuous and may be represented by processes.
Dimension:
Length, less operculum (94) 78.1 (66) µm. Width (120) 93.8 (80) µm. Length of operculum ca.35 µm. Specimens = 45 (42).
Affinities: (p. 23):
This new species differs from the species described by Helby (1987): it has an ectophragm which clearly breaks into paraplate related areas (unlike C. reticulata Cooksonand Eisenack 1960 and C. grandis Helby 1987), has a much more robust ectophragmal reticulum than C. pistica Helby 1987 and a much wider ectocoel than C. transitoria Stover and Helby 1987. It differs from C. senonica Clarke and Verdier 1967 by having a much more robust, angular autophragm and a much narrower ectocoel.
The adcingular margin of paraplate X, and the adsulcal margin of II, clearly show that Iu (which is not always indicated by ectophragmal development) lies outside the parasulcus. This indicates a gonyaulacoid affinity, rather than a ceratioid one, even though the first precingular paraplate is clearly planate.
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Comments Fensome et al., 2019a:
Harding (Citation1990, p. 22–23) differentiated Canningia duxburyi from Canningia reticulata in that ‘it has an ectophragm [outer wall layer] which clearly breaks into paraplate related areas …’. Harding illustrated Canningia duxburyi through scanning electron microscope (SEM) images. In our experience, some specimens of Canningia reticulata seen under the light microscope do show suggestions of tabulation, which might be more clearly seen in SEM images. Hence, we question whether separation of the two species is justified, but retain Canningia duxburyi as it is considered a useful biostratigraphic marker (Martin Pearce, personal communication).
Stratigraphical occurrence. Canningia duxburyi was originally described from the upper Hauterivian to lower Barremian of Norfolk, England.